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phase shift | Phase shift of all-pass bi-quadratic filter | https://dsp.stackexchange.com/questions/53777/phase-shift-of-all-pass-bi-quadratic-filter | <p>Does anybody know how to derive this phase function for that all-pass filter structure? Many papers re-print them, and corresponding chart as well. </p>
<p><a href="https://i.sstatic.net/xo8bQ.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/xo8bQ.png" alt="enter image description here"></a></p>
<p>B... | <p>First of all, that formula for the phase has a sign error, at least if <span class="math-container">$\alpha$</span> is defined as in the diagram of the filter structure. Second, your phase plot shows a jump from <span class="math-container">$-\pi$</span> to <span class="math-container">$\pi$</span>, which is no jump... | 1,134 |
phase shift | Time shift and Phase Examples | https://dsp.stackexchange.com/questions/82329/time-shift-and-phase-examples | <p>Given are two cosines according to the following formula
<span class="math-container">$x_i(t) = cos(2\pi f_i t)$</span>
with <span class="math-container">$f_1 = 1Hz$</span> , <span class="math-container">$f_2 = 2Hz$</span> and <span class="math-container">$f_3 = 3Hz$</span> .</p>
<p>The two cosines are delayed by <s... | <p>Any signal <span class="math-container">$x(t)$</span> can be time-shifted: simply calculate <span class="math-container">$x(t + \Delta t)$</span>.</p>
<p>A sinusoid can also be phase-shifted. Consider the cosine signal with phase <span class="math-container">$\phi$</span>: <span class="math-container">$$x(t) = \cos(... | 1,135 |
phase shift | resilient codes to phase shift | https://dsp.stackexchange.com/questions/36228/resilient-codes-to-phase-shift | <p>I need to define an encoding to beacon IDs. The codes are going to be periodic but in the receiver side I can have phase shifts so I' wondering the best way to decode:
- 8 bits code groups that represent the same ID: </p>
<pre><code>Group1: 00000001, 00000010, 00000100 ..... 10000000
Group2: 00000011, 00000110, ..... | <blockquote>
<p>How can I verify that a code belongs to a group?</p>
</blockquote>
<p>Assuming these are really just sub-words that are common to all elements in a group, simply trying out all 8 possible (cyclic) bitshifts of the received sequence to see whether you can match any group representative (e.g. the first... | 1,136 |
phase shift | Accounting for phase shift in time-dependent signals | https://dsp.stackexchange.com/questions/82456/accounting-for-phase-shift-in-time-dependent-signals | <p><strong>Background:</strong></p>
<p>I am using a vibration sensor and arduino to record signals and log them with timestamps, where the signals need to be time accurate so that I can glean information about which frequencies are present.</p>
<p>To eliminate aliasing I am connecting a low-pass Butterworth filter betw... | <p>All filters will introduce delay; the sharper the roll-off the more delay is required since the two are directly related. It is the variation in group delay specifically that can cause distortion in the signal when we are concerned about the time alignment of signals that occupy different frequencies. Group delay i... | 1,137 |
phase shift | Does resampling cause phase shifts? | https://dsp.stackexchange.com/questions/66961/does-resampling-cause-phase-shifts | <p>I have a signal sampled at 40MHz, I would like to resample it to 37MHz. The signal is <em>not periodic</em>, I did resampling with Matalb resample function and it doesn't cause phase shift (as far as I understood). Matlab applies an anti-aliasing FIR filter and compensate for the delay introduced by the process.</p>... | <p>Unfortunately, although <code>scipy.signal.decimate</code> has a zero phase shift argument, the decimation factor can only be an integer so you won't be able to downsample from 40KHz to 37kHz.</p>
<p><code>scipy.signal.resample</code>, on the other hand, can do the resampling you want but may (and most likely will)... | 1,138 |
phase shift | Nyquist Frequency Phase Shift | https://dsp.stackexchange.com/questions/14125/nyquist-frequency-phase-shift | <p>The figure below shows in dashed lines sinusoidal signals of the same frequency at three different phase shifts. The signals are then sampled such that the sinusoidal frequency is exactly a half of the sampling frequency, i.e. the frequency of all the sinusoids is the Nyquist frequency. The samples taken from this... | <p>The sample rate needs to be GREATER than (NOT just equal to) twice the highest non-zero frequency content of the signal being sampled. Just a little bit greater might work, but the closer the sample rate is to twice the signal frequency, the longer in time you may need to sample to raise the signal above the noise ... | 1,139 |
phase shift | Zero-phase-shift filters must be symmetric about the origin | https://dsp.stackexchange.com/questions/68063/zero-phase-shift-filters-must-be-symmetric-about-the-origin | <p>In reading Rafael Gonzalez Digital Image Processing, second edition, section 4.10.2,
the author writes:</p>
<blockquote>
<p>Notch filters are the most useful of the selective filters. A notch filter rejects (or passes) frequencies in a predefined neighborhood about the center of the frequency rectangle. Zero-phas... | <p>Consider the Inverse Fourier Transform as the impulse response of the filter. In the case of an ideal brick-wall filter with zero-phase, the impulse response would be a Sinc function centered about zero in time (given by the Inverse Fourier Transform).</p>
<p><a href="https://i.sstatic.net/VbI44.png" rel="nofollow ... | 1,140 |
phase shift | How to correct for inperfect 90 degree phase shift before doing IQ demodulation? | https://dsp.stackexchange.com/questions/9377/how-to-correct-for-inperfect-90-degree-phase-shift-before-doing-iq-demodulation | <p>I want to sample two signals, S and R and later do IQ demodulation on these.</p>
<p>I am multiplying S with R and I also want to multiply S with a 90 degree phase shifted version of R by shifting the samples in R so I get a 90 degree phase shift.
The problem I encounter with this is that unless I have a sampling ra... | 1,141 | |
phase shift | Adaptive filter to scale and phase shift two sensors output | https://dsp.stackexchange.com/questions/49221/adaptive-filter-to-scale-and-phase-shift-two-sensors-output | <p>One way of separating downgoing and upgoing wavefields in offshore seimic processing is to add signals from hydrophone and vertical component of the geophone (they are co-located). Hydrophone only registers a change in the pressure whereas geohphone as well as registering a change in seismic field also reacts to the... | <p>It seems that you want to equalize one time series to the other or vice versa or some combination. The general problem is then (in shorthand)
$$
h_1{\Large *}y_1 \approx h_2{\Large *}y_2
$$
where $\Large *$ denotes convolution, $h_i$ are filters, and $y_i$ are your time series. If you simply equalize one time series... | 1,142 |
phase shift | Phase shifting a noisy signal | https://dsp.stackexchange.com/questions/29671/phase-shifting-a-noisy-signal | <p>I have a signal of the form $s(t)=A(t) \sum \cos(\omega_i(t)t +\phi_0) + n(t)$, where $n$ is gaussian noise.</p>
<p>I can only read the <em>signal+noise</em> and thus can not separate them.</p>
<p>I want to phase shift the signal to $A(t) \sum\cos(\omega_i(t)t)+n'(t)$ and I am at a loss on how to do this. During l... | <p>With a real cosine a phase shift is equivalent to a time delay. If you delay the signal by $\phi_0$ then you will get the result you want.</p>
<p>The number of samples that you will need to delay by will likely not be an integer number. You can delay by a non-integer number of samples via a <a href="https://dsp.s... | 1,143 |
phase shift | Does FFT filtering preserve the phase shift of a PSK signal? | https://dsp.stackexchange.com/questions/94842/does-fft-filtering-preserve-the-phase-shift-of-a-psk-signal | <p>I'm working with the wonderful Direwolf sound card TNC software, and am attempting to use the OpenCL clFFT GPGPU acceleration library to do FFT on the signal to replace the bandpass and lowpass filters with a much more efficient GPGPU accelerated FFT filter.</p>
<p>In PSK (phase key shifting) the signal waveform is ... | <p>"FFT filtering" is just filtering (if not buggy); it's the actual filter that defines the signal properties of that. In other words, it's the filter coefficients, and not the algorithmic shortcuts you take.</p>
<p>In communications we typically use linear-phase filters, since they have constant group delay... | 1,144 |
phase shift | $360^\circ$ Phase shift between Bode plots of two similar systems | https://dsp.stackexchange.com/questions/96533/360-circ-phase-shift-between-bode-plots-of-two-similar-systems | <p>I am trying to identify the characteristics of an FIR filter in an ideal case as a sanity check. I observe that there is no strange behaviour, but there is an unexplainable issue in the phase plot of the original and identified filters. To make it simple, I've provided the transfer function coefficients below:</p>
<... | <blockquote>
<p>but I would like to understand why this happens with the bode function in MATLAB.</p>
</blockquote>
<p>That's difficult to answer since you basically asking about the inner workings of a commercial piece of software.</p>
<blockquote>
<p>Also, it would be great if you could tell me how to correct this wh... | 1,145 |
phase shift | Phase shifting in frequency domain | https://dsp.stackexchange.com/questions/63568/phase-shifting-in-frequency-domain | <p>I am aware this topic has already been addressed in at least one question here, but despite that I could not find the solution to my problem.
Also bear patience with me since I am not a mathematics guru but a coder, so I am not really able to explain my problem with formulas but I will try to expose it to my best an... | 1,146 | |
phase shift | What is the minimum phase shift for Quadrature Amplitude Modulation (QAM)? | https://dsp.stackexchange.com/questions/58258/what-is-the-minimum-phase-shift-for-quadrature-amplitude-modulation-qam | <p>I'm a bit of a noob here, looking for a simple formula or just a table which can tell me the absolute <em>minimum</em> phase shift angle possible for different variations of QAM. Particularly QAM 16, 64, 256 and 1024. If the answer is zero (is it?), then what is the minimum phase shift possible in each case other th... | <p>The minimum phase shift in 16-QAM, 64-QAM, 256-QAM etc is 0 (same value regardless of whether you are using degrees or radians!) and occurs when the symbol transition is from one constellation point on some radius vector to another constellation point on the same radius vector. If we take the constellation points a... | 1,147 |
phase shift | help to calculate phase shift in certain frequency(identified from FFT) | https://dsp.stackexchange.com/questions/64555/help-to-calculate-phase-shift-in-certain-frequencyidentified-from-fft | <p>I am designing a 24ghz doppler radar, with 1TX 2RX. Four adc channel are recording at 25khz, applying 256point FFT on adc of both of RX I and Q, I could identify the target in certain doppler frequency(speed) . The next step is to calculate the phase shift to get the angle of the target, that's where I stuck. Since ... | <p>Phase shift in time domain translates to frequency shift in the Fourier transform. </p>
<p><span class="math-container">$FT of exp(j2πf0t)x(t) = X(f−f0).$</span></p>
<p>If there is a phase shift in time, the Fourier transform that you take is already shifted in frequency. Find the shift in frequency f0 and you sho... | 1,148 |
phase shift | why do low pass and high pass filters generate a phase shift? | https://dsp.stackexchange.com/questions/28750/why-do-low-pass-and-high-pass-filters-generate-a-phase-shift | <p>I just learned following notation for a sine wave:</p>
<p>$A e^{j\phi t}$</p>
<p>A low passfilter and a highpass filter respectively generate a phase shift in the complex plane of the sine wave as follows:</p>
<p>$A e^{-j\phi t}$ and $A e^{+j\phi t}$</p>
<p>I don't understand what phase shifting has to do with l... | <blockquote>
<p>I just learned following notation for a sine wave: $Ae^{j\phi t}$</p>
</blockquote>
<p>well, that's not really a sine wave; that's a complex sinusoid. The real and imaginary parts of that are cosine and sine, respectively.</p>
<blockquote>
<p>A low passfilter and a highpass filter respectively gen... | 1,149 |
phase shift | Phase shift in higher order filters | https://dsp.stackexchange.com/questions/35055/phase-shift-in-higher-order-filters | <p>I was doing some research on filters, So I designed butterworth filter based on pole locations. I applied to a simple sine signal to check for the outputs. I cannot find the reason for what I noticed.</p>
<p><a href="https://i.sstatic.net/A7t6h.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/A7t6h.pn... | <p>Discrete filters are divided in two major classes: <a href="https://en.wikipedia.org/wiki/Finite_impulse_response" rel="nofollow">Finite Impulse Response (FIR)</a> filters and <a href="https://en.wikipedia.org/wiki/Infinite_impulse_response" rel="nofollow">Infinite Impulse Response Filters (IIR)</a>.</p>
<p>Both ty... | 1,150 |
phase shift | What are the drawbacks of using the phase shift method (Hilbert Transformer) for SSB modulation? | https://dsp.stackexchange.com/questions/95548/what-are-the-drawbacks-of-using-the-phase-shift-method-hilbert-transformer-for | <p>The phase shift method (Hilbert Transformer) can be used for single sideband (SSB) generation. The box marked (−𝝅)/𝟐 is a 𝝅/𝟐 phase shifter, which delays the phase of every spectral component by 𝝅/𝟐. Hence, it is a Hilbert Transformer.
An ideal phase shifter is also unrealizable. It is easy to build a circu... | <p>An example of common signals that cannot be used with this circuit as the modulator itself is any complex baseband modulation where the quadrature component is independent of the in-phase component. This includes most modern waveforms including QPSK, QAM, etc. This is because the “Q” or quadrature component is compl... | 1,151 |
phase shift | Calculating the phase shift between two signals based on samples | https://dsp.stackexchange.com/questions/41291/calculating-the-phase-shift-between-two-signals-based-on-samples | <p>I am comparing two signals in MATLAB Simulink for finding the phase between them. To do this I am inspired by using the code found <a href="https://www.researchgate.net/post/How_can_one_find_the_angle_between_voltage_and_current_sinusoidal_waves_in_MATLAB_SIMULINK_environment" rel="nofollow noreferrer">here</a>.</p>... | <p>It's an <strong>approximation</strong> as also admitted by your statement "satisfactory performance". Here is why.</p>
<p>Let $a[n]=\cos(w_0 n)$ and $b[n]=\cos(w_0 n + \theta)$ be two <strong>sequences</strong> of size $N$, represented by $1 \times N$ row <strong>matrices</strong> $\bar{a}$ and $\bar{b}$ in a progr... | 1,152 |
phase shift | How can I apply a phase shift to an LFM pulse? | https://dsp.stackexchange.com/questions/88933/how-can-i-apply-a-phase-shift-to-an-lfm-pulse | <p>I am modelling radar scenarios in python and am trying to make a model which retains phase information. To do so, I'm envisioning something which works like this:</p>
<ol>
<li>Generate samples of an LFM waveform at RF in a numpy array</li>
<li>Calculate the distance to the target (two way)</li>
<li>Divide the time t... | <p>You are off in your approach. First things first, however:</p>
<blockquote>
<p>For example: say the delay corresponds to 37.465 samples. I can't shift the elements by this much, but I can shift them by 38 samples and say that, in each element, the point of the waveform at which the sample is measured is offset by a ... | 1,153 |
phase shift | Relating phase shift to the ROL/ROR operations | https://dsp.stackexchange.com/questions/31074/relating-phase-shift-to-the-rol-ror-operations | <p>Is phase-shifting in continuous-time analogous to the rotate-left (ROL) and rotate-right (ROR) operations in discrete-time? </p>
| <p>If you mean phase shift of a sinusoid, then yes, a phase shift is equivalent to a translation. </p>
| 1,154 |
phase shift | Does filtering by wavelet decomposition and reconstruction introduce a phase shift in the filtered signal? | https://dsp.stackexchange.com/questions/88953/does-filtering-by-wavelet-decomposition-and-reconstruction-introduce-a-phase-shi | <p>I am removing low frequency noise from a signal using Matlab using the DWT and then reconstruction at a specific level:</p>
<p>I am removing the approximation signal at level 10 which approximates the low frequency noise</p>
<pre><code>signal sampled at 500 hz
[a,b] = wavedec(signal,13,'db8'); % DWT to max level... | 1,155 | |
phase shift | How can I extract a sinusoid from a very noisy signal for computing the phase shift? | https://dsp.stackexchange.com/questions/24941/how-can-i-extract-a-sinusoid-from-a-very-noisy-signal-for-computing-the-phase-sh | <p>I have done some measurements and I got two very noisy signals. I want to extract a certain sinusoid from the signals and I want to compute the phase shift between them.</p>
<p>I made some simulations and I saw that the noise modifies a lot the value of the phase shift.</p>
<p>How can I get a trustful value for th... | <p>You are correct. Estimating the instantaneous phase of a noisy sinusoid is NOT easy. I suggest you design a narrow bandpass filter such that your sinusoid-of-interest is in the filter's passband. (The better the filter the more noise that will be eliminated.) Pass your two signals through the bandpass filter to ge... | 1,156 |
phase shift | How to find phase shift and process I/Q channel | https://dsp.stackexchange.com/questions/24161/how-to-find-phase-shift-and-process-i-q-channel | <p>I am currently working of 24GHz FMCW radar signal processing. The Module I'm using has 2 receiving antennas and each has 2 outputs (I and Q channel). So overall I've 4 channels. I'm using combination of harware and software for the processing in frequency domain. Range and velocity is fine, if I sample any one chann... | <p>The way to do it is to correlate the received signal with the signal you sent out- likely a chirp or something. You correlate it with the signal from antenna 1, which will give you a time (location of the cross correlation peak) and phase (phase of the complex value of the peak). You do the same with the signal fr... | 1,157 |
phase shift | Bode plot phase shift equation when poles and zeros are not at the origin | https://dsp.stackexchange.com/questions/89778/bode-plot-phase-shift-equation-when-poles-and-zeros-are-not-at-the-origin | <p>Let <span class="math-container">$$H(s)=\frac{s^{n}}{s^{m}}$$</span>
For <span class="math-container">$n \ne m$</span> the phase shift between output and input will be
<span class="math-container">$\frac{\pi}{2}(n-m)$</span>.</p>
<p>For situations where the poles and zeros are not at the origin, I could find the pha... | 1,158 | |
phase shift | Why doesn't this complex multiplication in the frequency domain produce my expected phase shift? | https://dsp.stackexchange.com/questions/47063/why-doesnt-this-complex-multiplication-in-the-frequency-domain-produce-my-expec | <p>I know how to change the phase of a complex number by multiplying by $\cos \theta + i \sin \theta$. And I understand that the phase of a sine wave is reflected in its Fourier transform. So, I am trying to phase-shift a signal by changing the phase of its Fourier transform..</p>
<p>This works for "synthetic" Fouri... | <p>If you want a phase-shifted strictly-real result, then you have to make sure the data you feed to the IFFT is conjugate symmetric. So make sure to reflect the complex conjugate of any phase changes you make. e.g. Make the upper or negative half of your IFFT input vector mirror the complex conjugate of the bottom o... | 1,159 |
phase shift | Playrate change based on sinc interpolation generating phase shift? | https://dsp.stackexchange.com/questions/46043/playrate-change-based-on-sinc-interpolation-generating-phase-shift | <p>I want to simulate the play-rate change function of a modern digital sampler. For the purpose I have constructed a sinc-resampling based algorithm of my own which changes the play-rate of a digital audio signal.</p>
<p>There is some issue with the algorithm, as the output of the algorithm is far from nulling with t... | 1,160 | |
phase shift | Nyquist Theorem adding two same frequency near to Nyquist Frequency with phase shift | https://dsp.stackexchange.com/questions/53605/nyquist-theorem-adding-two-same-frequency-near-to-nyquist-frequency-with-phase-s | <p>This is my first question on this platform. Sorry if I made mistakes.</p>
<p>What happens if we add two or more same frequency signals near to Nyquist Frequency with phase shift and sample them?</p>
<p>For example, assume that we have a signal of 18000Hz. And add another signal with same frequency, but having 180 ... | <p>When you add 2 or more sinusoids at the same frequency <span class="math-container">$f_o$</span> but with different phase shifts you get a sinusoid at same frequency but an additional attenuation term. Mathematically, you will have following:
<span class="math-container">$$cos(2\pi f_ot + \phi)+cos(2\pi f_ot + \thet... | 1,161 |
phase shift | Calculating phase shift between two sines of equal, unknown, amplitude and frequency | https://dsp.stackexchange.com/questions/63904/calculating-phase-shift-between-two-sines-of-equal-unknown-amplitude-and-frequ | <p>I've got a source signal <span class="math-container">$s_1(t)$</span> and a system affecting that, yielding a phase-shifted version <span class="math-container">$s_2(t)$</span>;</p>
<p><span class="math-container">\begin{align}
\color{blue}{s_1(t)} &= A\sin(t+\phi_1)\\
\color{red}{s_2(t)} &= A\sin(t+\phi_2)... | <p>Two samples is sufficient and we can determine if the phase difference is indeed <span class="math-container">$\frac{3\pi}{2}$</span> as follows:</p>
<p>Start with the hypothesis that the phase difference <span class="math-container">$\phi_1-\phi_2$</span> is <span class="math-container">$\frac{3\pi}{2}$</span>, wh... | 1,162 |
phase shift | Best method to extract phase shift between 2 sinosoids, from data provided | https://dsp.stackexchange.com/questions/8673/best-method-to-extract-phase-shift-between-2-sinosoids-from-data-provided | <p>I have been asking around if the way I was extracting phase shift (lag) was correct, and I ran into some trouble.</p>
<p>So in general, given 2 arrays of data of the same length, representing:</p>
<ol>
<li>the input sinusoid and</li>
<li>the response, also a sinusoid. </li>
</ol>
<p>So not knowing the functions t... | <p>You can use the <a href="http://en.wikipedia.org/wiki/Cross_correlation">cross-correlation</a> function to determine the lag between the two signals.</p>
| 1,163 |
phase shift | Moving Average Filter. General Form of a Filtered Signal. How to Determine the Phase Shift? | https://dsp.stackexchange.com/questions/95436/moving-average-filter-general-form-of-a-filtered-signal-how-to-determine-the-p | <p>Let's consider the following filter <span class="math-container">$$y[n]=\frac{1}{3}(u[n-2]+u[n-1]+u[n])$$</span> and <span class="math-container">$M=3$</span>, <span class="math-container">$k=\overline{0,2}$</span> with <span class="math-container">$$u[n]=\sin\left(\frac{\pi}{10}n\right)+\sin\left(\frac{\pi}{4}n\rig... | <p>You correctly computed the frequency response, but your output signal isn't correct (as you already suspected), because you didn't take the phase shift into account.</p>
<p>The response of an LTI system with frequency response</p>
<p><span class="math-container">$$H(\omega)=\big|H(\omega)\big|e^{j\phi(\omega)}\tag{1... | 1,164 |
phase shift | Phase-shift filter design | https://dsp.stackexchange.com/questions/2934/phase-shift-filter-design | <p>If a time-domain signal has sharp corners, its frequency spectrum will contain high-frequency components. Truncating the spectrum results in Gibbs' phenomenon. So if you're trying to design an FIR, you really want the target frequency response to be nice and smooth so that windowing the impulse response down to a fi... | <p>This would be an allpass filter. Except for the trivial case of unity and integer-sample delays, these can't be done as FIR filters and in general an IIR filter is required. However, they are easy to make. The zeroes of an allpass are simply the inverse of the poles (and vice versa). If you have the poles in polynom... | 1,165 |
phase shift | Is the magnitude of the phase shift independent of the volume of the sound? | https://dsp.stackexchange.com/questions/84054/is-the-magnitude-of-the-phase-shift-independent-of-the-volume-of-the-sound | <p>Sound waves can cause vibration of the particles/objects that are scattering/reflecting/emitting the light. Since vibration is spatial displacement, it causes a phase shift by affecting the value of "<span class="math-container">$x$</span>" from the light (electromagnetic wave) phase formula: <span class=... | <p>In most cases the answer will be "no". Talking about a "phase" of light implies a mono-chromatic coherent light wave. Most scattering, diffusion or reflecting processes will destroy the coherence and there is no way to define the phase of the reflected light. It doesn't matter if the reflecting/s... | 1,166 |
phase shift | Phase shifts of QPSK | https://dsp.stackexchange.com/questions/60159/phase-shifts-of-qpsk | <p>I'm honestly lost on creating timing diagrams for bit sequences. I understand for QPSK there are symbols 00, 01, 10, 11 with phase shifts of 45,135,225 and 315. </p>
<p><a href="https://i.sstatic.net/ztioA.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ztioA.png" alt="enter image description here"><... | <p>In QPSK, the bit information is embedded in the phase of the carrier signal. For example, for bits 00, the phase shift is 45degree. This means the carrier signal <span class="math-container">$x(t) = cos(2\pi f_c t + \phi) 0 \lt t \lt T$</span>, the phase shift <span class="math-container">$\phi = \pi / 4$</span>. S... | 1,167 |
phase shift | I can't understand why there is a phase shift in phase modulation of a sawtooth wave | https://dsp.stackexchange.com/questions/73601/i-cant-understand-why-there-is-a-phase-shift-in-phase-modulation-of-a-sawtooth | <p>This is regarding question 5.1-2 (see picture attached) from <em>Modern digital and analog communications, Lathi & Zhi Ding (2010)</em>.</p>
<p><a href="https://i.sstatic.net/ZG49j.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ZG49j.png" alt="Question" /></a></p>
<p>I do not understand what the ... | 1,168 | |
phase shift | Confusion understanding phase shift/delay? | https://dsp.stackexchange.com/questions/75059/confusion-understanding-phase-shift-delay | <p>I am reading proakis, as shown highlighted in attached snap shot,there is '-'sign along with j,but still it is written (underlined red) implies shift in positive n direction,why and how positive?when we have negative sign with j?</p>
<p><a href="https://i.sstatic.net/kMsb7.jpg" rel="nofollow noreferrer"><img src="ht... | <p>Delay is the negative derivative of phase with respect to frequency. Phase that increases linearly negative as frequency increases will result in a positive (later) delay in time. This is given by the Fourier Transform property of time delay:</p>
<p><span class="math-container">$$\mathscr{F} \{f(t-\tau)\} = e^{-j\ta... | 1,169 |
phase shift | How to calculate the phase shift AND time delay of non-periodic signals | https://dsp.stackexchange.com/questions/44057/how-to-calculate-the-phase-shift-and-time-delay-of-non-periodic-signals | <p>Say I have two non-periodic signals, $f_1(t)$ and $f_2(t)$, with Fourier transforms $F_1(\omega)$ and $F_2(\omega)$. Basically, I need to line up $f_1(t)$ and $f_2(t)$ as close as possible, and I am allowed to shift the signals in time and multiply their Fourier transforms by a constant phase.</p>
<p>What is the mo... | <p>A pure time delay could be determined by looking for a peak in the cross correlation. But in your case $f2$ might also have an overall phase offset.</p>
<p>You could try to compute two cross correlations:</p>
<p>$$
\begin{align}
x &= cross(f1,f2) \\
y &= cross(f1,hilbert(f2)) \\
\end{align}
$$</p>
<p>wher... | 1,170 |
phase shift | How do I perform a time domain phase shift in the frequency domain? | https://dsp.stackexchange.com/questions/64389/how-do-i-perform-a-time-domain-phase-shift-in-the-frequency-domain | <p>I've seen some information on this topic around, but I don't quite understand it.</p>
<p>I have a time domain signal. I understand that if I want to time shift this signal, I can do so by multiplying its Fourier transform by <span class="math-container">$\exp(-j\omega\delta t)$</span>, where <span class="math-conta... | <p>Let’s be clear on what we will refer to as time delay and phase shift. Due to the common association of individual frequencies as sinusoids many confuse delay and phase shift as being equivalent. However a phase shift in time is simply multiplying a time sample by <span class="math-container">$e^{j\phi}$</span> whil... | 1,171 |
phase shift | Behavior at DC and Nyquist of an ideal phase shifter | https://dsp.stackexchange.com/questions/84914/behavior-at-dc-and-nyquist-of-an-ideal-phase-shifter | <p>In Matt L's <a href="https://dsp.stackexchange.com/a/31616/59893">answer</a> he states that an ideal phase shifter with a phase shift <span class="math-container">$\theta$</span> has a frequency response</p>
<p><span class="math-container">$$
H(\omega)=
\begin{cases}
e^{-j\theta},&\omega>0 \\
e^{j\theta},&... | <p>The frequency response of the ideal phase shifter can be written as</p>
<p><span class="math-container">$$H(\omega)=\cos(\theta)-j\,\textrm{sgn}(\omega)\sin(\theta)\tag{1}$$</span></p>
<p>where <span class="math-container">$\textrm{sgn}(\omega)$</span> is the <a href="https://en.wikipedia.org/wiki/Sign_function" rel... | 1,172 |
phase shift | How do you relate imaginary numbers with phase shift? How to imagine this? | https://dsp.stackexchange.com/questions/11173/how-do-you-relate-imaginary-numbers-with-phase-shift-how-to-imagine-this | <p><img src="https://i.sstatic.net/eCpbp.gif" alt="enter image description here">
So I found this answer on one of the questions. I wanted to ask how the complex part can be related with the phase shift. I wanted to ask this on the same question but it didn't allow me. Could anyone please help me understand this concep... | <p>Paint a red dot on the blue complex spiral at t=0, where the value is 1.0. Now roll the spiral upside-down until the red dot is at -1.0, still at t=0. This roll would be equivalent to a phase shift of Pi. Note that the real part no longer corresponds to a cosine wave that starts at t=0. </p>
<p>But the real par... | 1,173 |
phase shift | Does phase shift introduce high frequencies? | https://dsp.stackexchange.com/questions/89358/does-phase-shift-introduce-high-frequencies | <p>In PSK phase modulation scheme, the signal phase is shifted, hence it looks something like this:
<a href="https://i.sstatic.net/jU5bj.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/jU5bj.png" alt="enter image description here" /></a></p>
<p>I cannot understand why this doesn't introduce a set of unwa... | <p>The steps in the time domain for unshaped PSK refer to a rectangular baseband modulation waveform. The frequency response of this is a Sinc function which does indeed contain high frequency components, compared to a pulse shaped version where the time domain transitions are tapered rather than stepped.</p>
<p>When m... | 1,174 |
phase shift | Why would someone need a Spatial Light Modulator with a maximum phase shift $> 2\pi$ | https://dsp.stackexchange.com/questions/35092/why-would-someone-need-a-spatial-light-modulator-with-a-maximum-phase-shift-2 | <p>I am working with <a href="http://holoeye.com/spatial-light-modulators/slm-pluto-phase-only/" rel="nofollow">Spatial Light Modulators</a> for a project and I was wondering why does the producer think someone would need a maximum phase shift $>2 \pi$ since the device works as a monitor and every phase-element moni... | <p>That will be useful at least for pulse shaping, because then it is not just a single wavelength that you are dealing with, and as modulo $2\pi$ is actually implemented as modulo of displacement, it would work only for a single wavelength, creating jumps in the phase for nearby frequencies.</p>
| 1,175 |
phase shift | What exactly is a 90 degree phase shift of a digital signal in FM demodulation appraoches? | https://dsp.stackexchange.com/questions/51889/what-exactly-is-a-90-degree-phase-shift-of-a-digital-signal-in-fm-demodulation-a | <p>I am working on an FSK demodulator (1200/2200Hz, 1200 baud) featuring a 90 degree phase shift operation. I don't exactly understand what 360 degrees mean for a digital signal.</p>
<p>My sampling frequency is 8 kHz. Is a 90 degree shift a delay by 8000/4 samples, or is it a delay by 4000/4 samples?</p>
| <p>The OP asked about a phase shift specifically but from the written details without seeing the actual demodulator implementation, I suspect he may possibly be asking how to implement the delay that is used for some simple FM demodulation approaches. I want to mention the possibility that this may actually be a delay ... | 1,176 |
phase shift | DSP based phase shifting in Phased Array systems | https://dsp.stackexchange.com/questions/82231/dsp-based-phase-shifting-in-phased-array-systems | <p>Is there a downside to doing phase shifting at basedband in the DSP section of phased Array systems?</p>
<p>I suppose you trade off analog components for digital which may be more costly but I suspect modern systems give each antenna it's own ADC and DAC regardless.</p>
| <p>The downside is power consumption due to the combination of more data converters and additional digital processing required for each antenna, in comparison to phase shifters and gain control implemented at RF together with analog combining- which can then be done with a single ADC (for receiver) and DAC (for transmi... | 1,177 |
phase shift | Relation between Normal Phase Shift of a wave and Phase Modulation | https://dsp.stackexchange.com/questions/42803/relation-between-normal-phase-shift-of-a-wave-and-phase-modulation | <p>I am little confused with the Phase Modulation and the phase of a sine wave. I get the phase modulated wave from the google images as below:</p>
<p><a href="https://i.sstatic.net/QE7Uv.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/QE7Uv.jpg" alt="enter image description here" /></a></p>
<p>Phase mod... | <ul>
<li><p>When adding a constant time shift, the equation is then $\cos(2\pi f (t + t_1))$ (note the parentheses around the time values).</p></li>
<li><p>$(xA_m)$ should really be $xm(t)$ in your phase modulation equation - it is a time varying quantity.</p></li>
<li><p>$xm(t)$ has units of radians.</p></li>
<li><p>I... | 1,178 |
phase shift | Depth estimation using phase shifted sine waves | https://dsp.stackexchange.com/questions/86606/depth-estimation-using-phase-shifted-sine-waves | <p>For 3 phase shifted sine waves using the projected pattern: I = sin(x + δi) where δ ∈ [-2pi/3, 0, +2pi/3] which is then projected onto a scene. The resulting image is captured with a camera. I am using the method mentioned below as <em>Robust sine patterns</em>:
<a href="https://i.sstatic.net/d7Fdx.png" rel="nofollo... | 1,179 | |
phase shift | How to estimate the delay in time domain when knowing the phase shift in frequency domain | https://dsp.stackexchange.com/questions/83225/how-to-estimate-the-delay-in-time-domain-when-knowing-the-phase-shift-in-frequen | <p>I am strugling with how to compute the exact value of delay in time-doamin when knowing phase shift in frequency domain.
I have a analog circuit, I sweeped about 30 single tones frequency ranging from 250 MHz to 8 GHz, and achieved amplitude (A) and phase (<span class="math-container">$\phi$</span>) response of the ... | <p>Group delay is the negative derivative of phase with respect to frequency:</p>
<p><span class="math-container">$$GD = \frac{-d\phi}{d\omega} \tag{1} \label{1}$$</span></p>
<p>When the delay in time is fixed, the phase in frequency will be linear versus frequency, increasing at a constant rate in the negative directi... | 1,180 |
phase shift | Can a causal filter without phase shifts exist? | https://dsp.stackexchange.com/questions/13970/can-a-causal-filter-without-phase-shifts-exist | <p>When I was studying dispersion of refraction index in semiconductors and dielectrics, my professor tried to explain that if a filter (like a dielectric absorbing some light frequencies, or an electric RC-filter) removes some frequencies, then the remaining ones must be phase shifted to compensate for those frequenci... | <p>Suppose that a linear filter has impulse response <span class="math-container">$h(t)$</span> and frequency response/transfer function <span class="math-container">$H(f) = \mathcal F [h(t)]$</span>, where <span class="math-container">$H(f)$</span> has the property that <span class="math-container">$H(-f) = H^*(f)$</s... | 1,181 |
phase shift | Estimates sub-pixel shift directly in phase region | https://dsp.stackexchange.com/questions/38312/estimates-sub-pixel-shift-directly-in-phase-region | <p>I try to estimates shift estimation directly in phase region, by following the proposed method in this <em>Sub-pixel Shift Estimation of Image based on
the Least Squares Approximation in Phase Region</em> by Fujimoto, Fujisawa and Ikehara (<em>Proceedings of 26th European Signal Processing Conference, EUSIPCO '16</e... | <p>I am unable to comment on your Matlab code, but eq. (14) seems straightforward to me. You have a phase difference field $\theta$ which depends on the two spatial wavenumber components $k_1$ and $k_2$, and which formes a wrapped plane. The shift you seek is the slope of this plane, expressed as two scalar component... | 1,182 |
phase shift | How does time shift correspond to phase change in a discrete signal? | https://dsp.stackexchange.com/questions/15807/how-does-time-shift-correspond-to-phase-change-in-a-discrete-signal | <p>I was watching <a href="https://www.youtube.com/watch?v=6xaaeop7gJ8#t=1030" rel="nofollow">this</a> video where the presenter remarks: </p>
<blockquote>
<p>For a discrete signal, time shift corresponds to phase change in a discrete signal but not vice versa.</p>
</blockquote>
<p>I was trying to figure out how t... | <p>If you have a signal</p>
<p>$$f[n]=\cos(\Omega_0n)$$</p>
<p>and you apply a time shift of $n_0$ you get</p>
<p>$$f[n+n_0]=\cos(\Omega_0(n+n_0))=\cos(\Omega_0n+\Omega_0n_0)=\cos(\Omega_0n+\phi)$$</p>
<p>where $\phi=\Omega_0n_0$ is the phase shift.</p>
<p>The other way around, if you have a phase shift of $\phi$,... | 1,183 |
phase shift | Is it possible to find precise peak frequency using FFT phase shifts? | https://dsp.stackexchange.com/questions/61922/is-it-possible-to-find-precise-peak-frequency-using-fft-phase-shifts | <p>Been experimenting with FFT on a generated sinusoid and found something strange that doesn't seem to be described anywhere (though I may be missing something of course).</p>
<p>A sinusoid that exactly corresponds to a bin gives what we all know: an amplitude and a phase shift of the sinusoid in that bin.</p>
<p>Ho... | <p>For a set of exact equations that describe how a pure real tone works in a DFT check out equations (23)-(25) in my blog article:</p>
<ul>
<li><a href="https://www.dsprelated.com/showarticle/771.php" rel="nofollow noreferrer">DFT Bin Value Formulas for Pure Real Tones</a></li>
</ul>
<p>The phenomenon you have found... | 1,184 |
phase shift | Obtaining the phase component of an integer shift using phase only correlation | https://dsp.stackexchange.com/questions/81648/obtaining-the-phase-component-of-an-integer-shift-using-phase-only-correlation | <p>I'm trying to implement a sub-pixel estimation approach for my stereo matching project that I'm working on, by using the proposed method in the following paper "<em><a href="https://ieeexplore.ieee.org/document/7760216" rel="nofollow noreferrer">Sub-pixel Shift Estimation of Image based on the Least Squares App... | 1,185 | |
phase shift | Shifting phase with boolean logic gate | https://dsp.stackexchange.com/questions/95591/shifting-phase-with-boolean-logic-gate | <p>Given 4 foundational identical square wave with different phases:</p>
<ol>
<li>Yellow: (Ground/Phase Reference)</li>
<li>Cyan: 45 degree relative to Yellow</li>
<li>Purple: 90 degree relative to Yellow (a.k.a. the quadrature version of Yellow)</li>
<li>Green: 135 degree relative to Yellow</li>
</ol>
<p><a href="http... | <p>Using these conventions:</p>
<blockquote>
<ol>
<li>the frequency of the input signal is "1", "2", "3" or "4", where the frequency of the yellow wave is "1". and</li>
<li>The phase of the input signal is one of 0⋅,1⋅,2⋅,…,7⋅π/2, where the yellow signal has phase 0</li... | 1,186 |
phase shift | Why dont sin and phase shifted cosine overlap? | https://dsp.stackexchange.com/questions/15798/why-dont-sin-and-phase-shifted-cosine-overlap | <p>I plotted a sine wave(blue) and a 90 degrees phase shifted cosine wave (red) expecting them to overlap each other. </p>
<pre><code>x = 0:0.001:1;
%ploting sine
y = sin(2*pi*x);
plot(x, y);
hold('on');
%ploting cosine
z = cos(2*pi*x-90);
plot(x, z);
</code></pre>
<p><img src="https://i.sstatic.net/muXzq.png" al... | <p>You're confusing degrees and radians.</p>
<p>$$\sin(x)=\cos(x-\pi/2)$$</p>
<p>$\pi/2$ radians corresponds to 90 degrees.</p>
| 1,187 |
phase shift | OFDM complex symbols have dynamic phase shift after the fft-block & before the BPSK demodulator at the receiver , | https://dsp.stackexchange.com/questions/89491/ofdm-complex-symbols-have-dynamic-phase-shift-after-the-fft-block-before-the-b | <p><a href="https://i.sstatic.net/e1pVG.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/e1pVG.jpg" alt="enter image description here" /></a><a href="https://i.sstatic.net/OWhKc.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/OWhKc.jpg" alt="enter image description here" /></a>I have transm... | 1,188 | |
phase shift | How to minimize peak-to-peak amplitude of periodic waveform through FFT phase shifts? | https://dsp.stackexchange.com/questions/46706/how-to-minimize-peak-to-peak-amplitude-of-periodic-waveform-through-fft-phase-sh | <p>For one of my music projects, I'm playing back periodic audio signals (by looping single periods). Unfortunately, one of my waveforms sounds too quiet (even at maximum volume).</p>
<p>I'm trying to use FFT to obtain harmonic strengths, then phase-shift each harmonic to minimize the peak-to-peak amplitude, and then ... | <p>There are algorithms for determining low-peak-factor signals, for example:</p>
<blockquote>
<p>"Synthesis of low-peak-factor signals and binary sequences with low
autocorrelation (Corresp.)", M. Schroeder, 1970</p>
</blockquote>
<p>I have used this for flat-spectra signals to minimise peak to peak amplitude.</... | 1,189 |
phase shift | How to remove phase shift for a baseband signal given an estimated CFO (Bluetooth) | https://dsp.stackexchange.com/questions/88505/how-to-remove-phase-shift-for-a-baseband-signal-given-an-estimated-cfo-bluetoot | <p>I am working with Bluetooth specification 5.1 where the advertisement packets can send a constant tone extension (CTE) over the baseband signal to estimate the angle of arrival with an antenna array.</p>
<p>Due to inaccuracy of transciever and reciever clocks for bluetooth devices, the CTE is not exact.. This leads ... | <p>Such carrier frequency offsets are typically compensated for digitally by using a numerically controlled oscillator (NCO)- the complex signal at or near baseband is multiplied by the complex NCO output with a full complex multiplier, consisting of 4 real multipliers and 2 adders according to;</p>
<p><span class="mat... | 1,190 |
phase shift | What's the difference between frequency shift, frequency offset, phase offset, and phase noise? | https://dsp.stackexchange.com/questions/86997/whats-the-difference-between-frequency-shift-frequency-offset-phase-offset-a | <p>I'm confused about these terms: frequency shift, frequency offset, phase offset, and phase noise. My understanding that frequency shift and frequency offset are the same and caused by Doppler shift. Phase noise is caused by the instability of the local oscillator, and it changes per symbol. However, some books say t... | <p>Frequency shift and frequency offset could reasonably refer to the same thing, but a shift suggests something that has moved (from one frequency to the next as would occur in a changing Doppler) while a frequency offset suggests something more static such as a difference in frequency from a frequency reference after... | 1,191 |
phase shift | What exactly is a frequency component, and what is the phase shift from the argument of the Fourier Transform relative to? | https://dsp.stackexchange.com/questions/91503/what-exactly-is-a-frequency-component-and-what-is-the-phase-shift-from-the-argu | <p>I'm an EE undergrad that struggles heavily with the intuition behind the Fourier Transform (most likely due to a shoddy mathematical foundation). Specifically:</p>
<ol>
<li><p>From what I understand, the real part of the Fourier Transform is the Fourier Transform of the even part of the function in time domain, and ... | <p>Granted a precise answer to your question would (and has) fill(ed) a multitude of books, here is a stripped down answer.</p>
<ol>
<li><p>In the context of Fourier analysis, when we refer to a "frequency
component" of a function <span class="math-container">$f(t)$</span>, we are typically talking about the
... | 1,192 |
phase shift | Why is there a phase shift when taking the average of the Hilbert transformed signal for all trials, but not in individual trials? | https://dsp.stackexchange.com/questions/96234/why-is-there-a-phase-shift-when-taking-the-average-of-the-hilbert-transformed-si | <p>As you can see in the figure attaches below, for individual trials (which is the first row), the bandpass filtering using complex morlet wavelet convolution is in phase with the result of the real part of the hilbert transform applied after filtering the signal. However, when I take the average across all trials (wh... | 1,193 | |
phase shift | Phase shift between X and Y components of the same wave | https://dsp.stackexchange.com/questions/94170/phase-shift-between-x-and-y-components-of-the-same-wave | <p>I was told to post this question here, originally posted on Overflow.</p>
<p>I have two signals, I1 and I2, which were acquired from a white light source in a spectrally resolved interferometer with a waveplate and a polarizer in one arm, such that they are the X and Y components of the original wave after introduci... | <p>These are narrow band signals. The phase at most frequencies that are outside of the band are undefined or dominated by noise.</p>
<p>You need to evaluate the phase difference at the exact center frequency of the signal: at any other frequency the phase will be mostly garbage. A quick way to get started is to find t... | 1,194 |
phase shift | Analyzing a signal that contains frequency content at Fs/2 doesn't seem to work unless there is a phase shift | https://dsp.stackexchange.com/questions/59804/analyzing-a-signal-that-contains-frequency-content-at-fs-2-doesnt-seem-to-work | <p>I am trying to write a basic program that samples a 4 kHz sinewave at a sampling rate of 8 kHz and takes the FFT of the signal and plots it.</p>
<p>From everything I have read, as long as the signal you are sampling has frequency content that is less than or equal to Fs/2 no aliasing will occur and the results will... | <p>the discrete function <span class="math-container">$$x_q[n]=\sin(\pi n)$$</span> is always zero for all of the integers <span class="math-container">$n$</span>.</p>
<p>the discrete function <span class="math-container">$$x_i[n]=\cos(\pi n)$$</span> is always <span class="math-container">$(-1)^n$</span> for integer ... | 1,195 |
phase shift | How to calculate the total signal strength and phase shift of multiple signals in a reciever | https://dsp.stackexchange.com/questions/67139/how-to-calculate-the-total-signal-strength-and-phase-shift-of-multiple-signals-i | <p>I have a simulation to make where I have an array of transmitters that transmit the same signal. At a random point, which I have to consider as a receiver I have to measure the phase shift of the signals and also measure the total signal strength. The requirement is that the transmitter emits the same signal but wit... | <p>This is simplified assuming there is not multipath occurring in the transmission (where the receiver would typically receive multiple copies of the same transmit signal at different delays resulting in multipath distortion which are typically addressed using channel estimation and equalization).</p>
<p>The OP's pha... | 1,196 |
phase shift | Why does this reconstruction produce a phase shift from the original signal? | https://dsp.stackexchange.com/questions/29545/why-does-this-reconstruction-produce-a-phase-shift-from-the-original-signal | <p>After an FFT of a signal is done, it is plotted as in the image below, with the original signal is on the first subplot.</p>
<p><a href="https://i.sstatic.net/Wf23i.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Wf23i.jpg" alt="No Ballast"></a></p>
<p>Using the magnitude and phase data of each freq... | <p>The shift is due to using an FFT with a different length than the length of the data, and likely using a non-symmetric arrangement of zero-padding to increase that original length to the zero-padded length.</p>
<p>Non-symmetric zero-padding rotates the phase results of an FFT, spiraling across result bins.</p>
| 1,197 |
phase shift | How to process/generate a phase shifted frequency varying sine wave? | https://dsp.stackexchange.com/questions/7988/how-to-process-generate-a-phase-shifted-frequency-varying-sine-wave | <p>I want to phase shift an incoming sine wave with varying frequency but I am unsure how to go about doing so in practical terms.</p>
<p>A little more info regarding the requirements:
I have an encoder producing a sine/cosine pair with a fixed Peak to Peak but as the speed changes so obviously does the frequency. I w... | <p>Indeed, as Jason R sais, that's how all sine oscillators are designed for synthesizers, they must change frequency without changing phase, so you have to control them only using a counter, and you vary the counter increment speed to change the sine/cosine frequency, in that way the sine is always one count onwards f... | 1,198 |
phase shift | Approximate using DFT phase shifting property | https://dsp.stackexchange.com/questions/72828/approximate-using-dft-phase-shifting-property | <p>I have a discrete signal <span class="math-container">$x(n)$</span> having <span class="math-container">$N$</span> samples with DFT <span class="math-container">$X(n)$</span>. Here <span class="math-container">$N$</span> is <em><strong>large</strong></em> say <span class="math-container">$N=600$</span>. Let the samp... | 1,199 | |
gene expression | Average number of gene products in (a) eukaryote(s) | https://biology.stackexchange.com/questions/3780/average-number-of-gene-products-in-a-eukaryotes | <p>Due to alternative RNA splicing, it isn't uncommon to ultimately find multiple gene products expressed from one gene in eukaryotes. I'm looking for a reference value for <em>the average number of final gene products expressed per gene</em> for:</p>
<ul>
<li>... <strong>a particular eukaryote (preferably humans)</st... | <p>One answer can be found in the UniProt FAQ:</p>
<blockquote>
<p>What is the human complete proteome?</p>
<p>In 2008, a draft of the complete human proteome was released from
UniProtKB/Swiss-Prot: the approximately 20,000 putative human
protein-coding genes were represented by one UniProtKB/Swiss-Prot
e... | 0 |
gene expression | What is meant by "alien" probe in a microarray? | https://biology.stackexchange.com/questions/8210/what-is-meant-by-alien-probe-in-a-microarray | <p>In my lab we did a microarray to analyze differential gene expression in S. cerevisiae treated with UV irradiation. We are now analyzing the results and one of the up-regulated genes is labeled "Alien4_60." I believe this is some kind of control, but I am having trouble understanding what it is. </p>
<p>I would thi... | <p>It's a probe to detect external 'Alien' RNA standard, a synthetic mRNA commercialized by Stratagene/Agilent.</p>
<blockquote>
<p>The Alien RNA transcript is a ~500-nt, polyadenylated RNA molecule that
is synthesized by in vitro transcription. The Alien RNA transcript is
nonhomologous to all known nucleic ac... | 1 |
gene expression | 2 blue eyed children | https://biology.stackexchange.com/questions/15025/2-blue-eyed-children | <p>My husband had light brown eyes. His father had hazel and his mother, light brown as well. His younger brother however, has blue eyes. Both my children have blue eyes. Is this possible? I thought once the recessive gene was used in my first child, his dominant brown gene would take over?</p>
| <p>There is some chance for that. Look at this chart with some probabilities:</p>
<p><img src="https://i.sstatic.net/guIuv.jpg" alt="enter image description here"></p>
<p>Its from this <a href="http://www.dnaexaminers.com/lib/ckeditor/eye-color-paternity-test.html" rel="nofollow noreferrer">webpage</a>, which also gi... | 2 |
gene expression | Why is polysome loading affected by double stranded structure? | https://biology.stackexchange.com/questions/35500/why-is-polysome-loading-affected-by-double-stranded-structure | <p>Why polysomes are not able to load properly onto a transcript if a transcript has a double-stranded structure in it?</p>
| 3 | |
gene expression | Is the increased/decreased enzyme activity (tyrosinase) caused by an environmental factor (UV radiation) considered to be gene expression? | https://biology.stackexchange.com/questions/44704/is-the-increased-decreased-enzyme-activity-tyrosinase-caused-by-an-environment | <p>My AP Bio assignment asks that I research the effects of UV radiation on melanin production, but the directions and questions suggest that UV radiation influences gene expression. From what I could find, such as on <a href="http://enhs.umn.edu/current/5103/uv/harmful.html" rel="nofollow">this</a> university site or ... | <p>Since @anongoodnurse already nicely covery the effects of UV radiation on the cellular level, I will only have a look on the molecular level.</p>
<p>UV radiation of the skin causes increased DNA damage and thus activity of p53 in the keratinocytes of the skin. This causes (amongst others) the production of Kitl (Ki... | 4 |
gene expression | What is the role of TATA box in transcriptional regulation? | https://biology.stackexchange.com/questions/45783/what-is-the-role-of-tata-box-in-transcriptional-regulation | <p>I know what is the TATA box, but I wish to know whether it has specific roles in transcriptional regulation.</p>
| <p>TATA box serves as a binding site for the <a href="https://en.wikipedia.org/wiki/TATA-binding_protein" rel="nofollow">TATA-binding protein</a> (TBP; and its associated factors, together comprising the <a href="https://en.wikipedia.org/wiki/Transcription_factor_II_D" rel="nofollow">TFIID</a>). </p>
<p>TATA-box is on... | 5 |
gene expression | What is the difference between differentially expressed genes and deregulated genes? | https://biology.stackexchange.com/questions/59131/what-is-the-difference-between-differentially-expressed-genes-and-deregulated-ge | <p>Can anyone explain clearly what is the difference between differentially expressed genes and deregulated genes?</p>
| <p>Any gene whose gene expression differs significantly from some reference is considered to be differentially expressed. I think the most common representation of differential expression is the volcano plot, where you're plotting the fold change or log2 fold change against the -log10 p value assigned that gene. </p>
... | 6 |
gene expression | Cell type that expresses 90% of the genome | https://biology.stackexchange.com/questions/60568/cell-type-that-expresses-90-of-the-genome | <p>Cells that are differentiated express the genes that are necessary for their own usage. I've heard that some cell type expresses about 90% of 30,000 proteins that are encoded in the genome. Can anybody tell me what this cell type is?</p>
| <p>Well, I found this paper:</p>
<p><a href="https://genomebiology.biomedcentral.com/articles/10.1186/s13059-016-1079-9" rel="nofollow noreferrer">Danan-Gotthold M, Guyon C, Giraud M, Levanin EY, Abramson J. 2016. Extensive RNA editing and splicing increase immune self-representation diversity in medullary thymic epith... | 7 |
gene expression | qPCR: Huge variation in fold change of genes between biological replicates | https://biology.stackexchange.com/questions/74310/qpcr-huge-variation-in-fold-change-of-genes-between-biological-replicates | <p>I am trying to validate my RNAseq data by doing qpcr for which I am looking at the fold change of few genes across various timepoints of treatment conditions. I am getting huge amount of variation (in thousand folds ) in my biological replicates. I thought may be it is due to genomic DNA contamination so thats why I... | 8 | |
gene expression | Element of promoter responsible for expression power of gene | https://biology.stackexchange.com/questions/80737/element-of-promoter-responsible-for-expression-power-of-gene | <p>I know that there is a classification of promoters like: strong, medium and weak. This shows how a promoter affects gene expression levels. So my question is: what part of the promoter affects it? </p>
<p>For example I want to raise or lower the expression of some gene, so, what part of promoter I need to edit or m... | <p>Tldr; In an <em>in vivo</em> context the answer is going to be dependent on DNA sequence and context.</p>
<p>Simplistically, Eukaryotic genes promoters can be segmented in to several parts. The first, a core promoter region where RNA pol II will bind. This isn't capable of a robust transcriptional response on its o... | 9 |
gene expression | How do substances for gene expression work? | https://biology.stackexchange.com/questions/90948/how-do-substances-for-gene-expression-work | <p>How does amplification of gene expression work?
I often find in various articles expressions like "Using substance X or peptide X, we enhanced the expression of gene Z, which led to a certain therapeutic effect.</p>
<p>How to find out which substance enhances the expression of a particular gene? Is there a law, a p... | 10 | |
gene expression | Why do Alu repeats form secondary structures? | https://biology.stackexchange.com/questions/35385/why-do-alu-repeats-form-secondary-structures | <p>I've been doing a lot of research on Alu repeats and how they mediate the gene expression. I read the following article <a href="http://link.springer.com/article/10.1007%2Fs00018-007-7084-0" rel="nofollow">"Useful junk: Alu RNAs in the human transcriptome"</a>.</p>
<p>And it says that alu repeats embedded in 5'UTR ... | <p>Single-stranded RNA can easily form secondary structures, a very important example of this are tRNAs. </p>
<p>From a quick look at the article you read it seems that these Alu repeats work similar to riboswitches in the 5'-UTR. They can form secondary structures that block translation initiation, riboswitches commo... | 11 |
gene expression | Which is more important for protein expression mRNA structure or codon optimization? | https://biology.stackexchange.com/questions/1152/which-is-more-important-for-protein-expression-mrna-structure-or-codon-optimizat | <p>The field seems extremely divided on the debate. On one hand, artificial experiments have suggested that synonymous mutations don't correlate with gene expression but rather, the mRNA 5' structure is the most important <a href="http://www.ncbi.nlm.nih.gov/pubmed/19359587">1</a>. On the other hand, genome wide analys... | <p>This is an excellent question! To my knowledge, there hasn't been a definite answer yet. Recently, I did tons of research on which factors influence protein expression and you should definitely check out the following questions which I asked: </p>
<ol>
<li><p><a href="https://biology.stackexchange.com/q/1/28">What ... | 12 |
gene expression | Determining potential protease sites within a recombinant protein | https://biology.stackexchange.com/questions/1176/determining-potential-protease-sites-within-a-recombinant-protein | <p>My expressed proteins are frequently truncated and I'm trying to figure out which bands are which. The first thing to come to mind is using PeptideCutter from ExPASy but there is just a data deluge of potential sites. I was curious what other strategies exists for determining the potential breaks asides using LC-MS.... | <p>LC-MS is certainly quantitative and will give you a definitive answer, but it is costly and requires access to such a machine.</p>
<p>I presume you're analyzing your protein based on western blotting.</p>
<p>The first thing you should always do is verify your DNA sequence is coding for the protein product you want... | 13 |
gene expression | Time from stimulus to gene expression | https://biology.stackexchange.com/questions/291/time-from-stimulus-to-gene-expression | <p>My understanding is that gene expression, in response to some stimulus, generally occurs on the order of minutes. I'm curious about the extremes...the quickest and the slowest cases.</p>
<p>What is(are) the fastest time(s) recorded for genes being expressed in response to a stimulus? What are the slowest times?</p>... | <p>The fastest I know of is the heat shock locus in <em>Drosophila</em>. The transcription factor (HSF) accumulates within about 30 seconds, and RNA Polymerase can be seen to start accumulating within 3 minutes.</p>
<p>Katie L. Zobeck, Martin S. Buckley, Warren R. Zipfel, John T. Lis. 2010. <a href="http://www.scien... | 14 |
gene expression | Random X-Inactivation and Duchenne | https://biology.stackexchange.com/questions/111596/random-x-inactivation-and-duchenne | <p>I'm reading about X-inactivation and I can't reconcile some things with it being truly random. In only a small percentage of female carriers Duchenne's will be expressed. But if this was truly random, wouldn't 50% of female carriers expressing the disease?
As one of the X-chromosomes is silenced at random, this seem... | <p>Duchenne muscular dystrophy (DMD) is caused by the body's inability to make the protein dystrophin, which is needed for proper muscle function (<a href="https://www.genome.gov/Genetic-Disorders/Duchenne-Muscular-Dystrophy#:%7E:text=A%20woman%20who%20has%20a%20genetic%20change%20in,genetic%20material%20unless%20they%... | 15 |
gene expression | Why are protein-coding regions rich in GC? | https://biology.stackexchange.com/questions/88062/why-are-protein-coding-regions-rich-in-gc | <p>I have been searching for an answer for this question and have some possible solutions, but I am not sure. GC regions are more stable as there are 3 hydrogen bonds instead of 2 with AT, however I am not sure if this would influence the number of protein-coding genes in GC regions? Protein-coding regions would have t... | <p>Transcription factors generally bind to promoters, enhancers, silencers, and other regulatory regions that lie outside coding regions, through there are "duons" which code for amino acids and also bind TFs to regulatory effect. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3967546/" rel="nofollow n... | 16 |
gene expression | Why can a gene lack of a binding site be expressed in skin cells? | https://biology.stackexchange.com/questions/100244/why-can-a-gene-lack-of-a-binding-site-be-expressed-in-skin-cells | <blockquote>
<p><a href="https://i.sstatic.net/I4WtA.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/I4WtA.png" alt="enter image description here" /></a>
In order for a specific gene to be expressed in the mammal’s cells, all of the gene’s binding sites must be bound by transcriptional activators. The ma... | <p>You understand this wrong: All <strong>present</strong> enhancers of a gene must be bound by a enhancing factor, not all factors of a certain cell types have to be bound. So when skin cells contain activators for B, D and E they can activate gene 2 and 4 of your example, but not gene 3 since the activators for A and... | 17 |
gene expression | How does a gene "know" what to change to? | https://biology.stackexchange.com/questions/66019/how-does-a-gene-know-what-to-change-to | <p>Excuse my ignorance but I've always been curious about this...</p>
<p>For example, a frog is red, but it starts living in a green forest. Over time the frog becomes green to camouflage. But a gene can't see and I'm sure there's no mechanism for color info to be transmitted to individual genes from the brain. So how... | <p>Using your example, the gene doesn't know anything. Mutations cause some of the offspring of the red frog to turn green, some to turn blue, some to turn fluorescent yellow, and some stay red. Birds can't see the green ones as well as the others, so more green frogs survive and make more green frogs. The red frogs, t... | 18 |
gene expression | Will a nucleic acid sequence deduced from a protein sequence be expressed from a plasmid? | https://biology.stackexchange.com/questions/94967/will-a-nucleic-acid-sequence-deduced-from-a-protein-sequence-be-expressed-from-a | <p>I have a fasta file containing the amino acid sequence of glycogenin-1: <a href="https://www.rcsb.org/fasta/entry/6EQJ" rel="nofollow noreferrer">https://www.rcsb.org/fasta/entry/6EQJ</a></p>
<p>I want to create a plasmid that produces glycogenin-1.</p>
<p>Is it possible to use the glycogenin-1 amino acid sequence t... | <p>I lack the knowledge to fully answer your question but I can give some potentially useful pieces of information:</p>
<ul>
<li><p>In theory you can easily in-silico reverse translate a peptide
sequence to an unambiguous nucleotide sequence using the GMOs
optimized codon usage. I can share a Python script for that.</p... | 19 |
gene expression | Do housekeeping genes vary between tissues | https://biology.stackexchange.com/questions/51800/do-housekeeping-genes-vary-between-tissues | <p>I am working on an RNA-Seq project, and I am aware that some researchers use housekeeping genes as a method of normalization. My project has several different tissues, and I was wondering if housekeeping gene expression is generally invariant across tissue type?</p>
| <p>My experience is: Yes they can vary quite a lot (according to differences in the genetic profile of the cells) and you have to test this. As a primer I can recommend reading the articles listed below. These are mostly looking into this in the context of realtime PCR, but this should be valid for RNAseq as well. For ... | 20 |
gene expression | How many copies of RNA per cell are usually reached through overexpression in human cell-lines? (any technique) | https://biology.stackexchange.com/questions/96820/how-many-copies-of-rna-per-cell-are-usually-reached-through-overexpression-in-hu | <p>After 8 hours of online-research I was unable to find any info at all..</p>
<p>I was able to get some concrete copy numbers of DNA (e.g. plasmid) per cell after transfection of diverse transfection techniques, but I was unable to get any concrete copy numbers of RNAs that correspond to the transgene (of any overexpr... | 21 | |
gene expression | How are the various classes of E coli genes determined? | https://biology.stackexchange.com/questions/1758/how-are-the-various-classes-of-e-coli-genes-determined | <p>Looking at some more detailed <a href="http://www.faculty.ucr.edu/~mmaduro/codonusage/codontable.htm">codon usage tables</a>, genes may be further clustered into three gene classes: Metabolic genes, highly expressed genes during exponential growth, and horizontal gene transfer. Looking at the original <a href="http:... | <p>I read through the paper. The author starts by stating that as of the time of writing, two different classes of codon usage profiles were known (or at least putatively so). All 782 unique CDS sequences used were subjected to a two-step classification method. In step one, each CDSs was broken down into a 61-dimension... | 22 |
gene expression | How extensive is CD47? | https://biology.stackexchange.com/questions/1901/how-extensive-is-cd47 | <p>CD47 aka the "don't eat me" signal has recently been claimed <a href="http://www.pnas.org/content/early/2012/03/20/1121623109.short">to be expressed on all tumor cells</a>. This doesn't seem to corroborate with other cell-biology experiments. On what other cells is CD47 expressed?</p>
| <p>I don't know how extensive. Let's run a simple data query and find out: Go to <a href="http://www.ncbi.nlm.nih.gov/geo/" rel="nofollow">GEO</a> at NCBI. In the "Gene profiles" window, type CD47, and hit enter to launch the query. At the top of the resulting page, use the link labeled "Limits" to restrict the 7000+ r... | 23 |
gene expression | What exactly is meant by the expression "differentially expressed"? | https://biology.stackexchange.com/questions/2176/what-exactly-is-meant-by-the-expression-differentially-expressed | <p>As far as I've seen, this expression is almost always used in relation to gene expression profiling. Unfortunately, I have no background in this area. Can someone please explain this in layman terms?</p>
| <p>Although each cell of your body essentially contains the same DNA and the same genes, cells in different tissues express (turn on) different genes under different conditions. Measuring differential gene expression involves looking at the amount of expression for a gene (or set of genes) in two contrasting scenarios.... | 24 |
gene expression | T7 promoter leakiness | https://biology.stackexchange.com/questions/2758/t7-promoter-leakiness | <p>Can a gene be expressed under the T7 promoter in an E. coli strain (e.g. DH5 alpha), which does not have the T7 polymerase gene encoded in its genome? In other words, is T7 promoter leaky? </p>
<p>To be more specific, how is it possible that a regular E. coli strain, which does not encode for the T7 polymerase, can... | <p>Apparently not, <a href="http://openwetware.org/wiki/E._coli_genotypes#High-Control.28tm.29_BL21.28DE3.29_.28Lucigen.29" rel="nofollow">leakiness can be controlled by tightly regulating the T7 polymerase with a tight promoter (in this case lacUV5)</a>. </p>
| 25 |
gene expression | A mathematician's confusion regarding parametric $t$ tests for gene expression data | https://biology.stackexchange.com/questions/5010/a-mathematicians-confusion-regarding-parametric-t-tests-for-gene-expression-d | <p>I'm a mathematician trying to test some things on gene expression data, and I'm thus skimming over various articles such as <a href="http://www.ncbi.nlm.nih.gov/pubmed?term=Sotiriou%20et.%20al.%2C%20Breast%20cancer%20classification%20and%20prognosis%20based%20on%20gene%20%20expression%20profiles%20from%20a%20populat... | <p>I understand this in the following way:</p>
<p>For each probe you have two sets of measurements, one for ER+ and one for ER-. What you do is a T-test (to my understanding is that the "parametric" just emphasizes that T-test is a parametric test) on these two sets, testing if their mean is significantly different (t... | 26 |
gene expression | Confusion related to the DAVID tool | https://biology.stackexchange.com/questions/7299/confusion-related-to-the-david-tool | <p>I am trying to use the DAVID tool to do some gene analysis. I have some probe set intensities for some cancer cell lines. I found this link in the DAVID tool <a href="http://david.abcc.ncifcrf.gov/tools.jsp" rel="nofollow">http://david.abcc.ncifcrf.gov/tools.jsp</a>. I am a bit confused with the terminology introduc... | <p>Its a bit confusing, but DAVID uses the term Gene List as a generic term. </p>
<p>Looking at Step 2, you can submit many kinds of lists to DAVID, including actual gene symbols, Ensembl or RefSeq Accessions, etc... actually nearly 30 kinds of terms including 'not sure' which probably looks at your list and tries to... | 27 |
gene expression | What is benjamini | https://biology.stackexchange.com/questions/7354/what-is-benjamini | <p>I was doing some gene expression analysis using this tool <a href="http://david.abcc.ncifcrf.gov/summary.jsp" rel="nofollow">http://david.abcc.ncifcrf.gov/summary.jsp</a>. However, I have a confusion about what benjamini is. I fed it some gene list and it gave me some potential pathways the genes belong to(KEGG path... | <p>It is a <a href="http://udel.edu/~mcdonald/statmultcomp.html" rel="nofollow">Benjamini-Hochberg q-value,</a> similar to a p-value corrected for multiple hypothesis testing using the false discovery rate.</p>
| 28 |
gene expression | Complexity in creating transgenic animals (e.g., mice) | https://biology.stackexchange.com/questions/7619/complexity-in-creating-transgenic-animals-e-g-mice | <p>Many papers I have seen describing transgenic rodent models (and presumably applicable to other model organisms) involve the knock-in, or modification to, a single gene, possibly two genes. With respect to recombineering techniques, what prevents targeting multiple genes in a single organism? For instance, if I want... | <p>One reason is the low likelihood of success. Modifying a gene almost always involves a recombination event of plasmid DNA with a target site in the genome (and I say almost just because there may be some method that I don't know about, but all the ones I'm familiar with do). The likelihood of that decreases <strong>... | 29 |
gene expression | Known MicroRNA - Gene Systems? | https://biology.stackexchange.com/questions/9703/known-microrna-gene-systems | <p>Have there been any experimentally-verified systems of microRNAs targeting a gene set (e.g., in cancer, perhaps)?</p>
| <p>Yes. Below is a link to a review of ncRNA (non-coding RNAs) and their role in disease. There are many examples in this review in all sorts of diseases, one of which is miR-200, which is thought to play a role in some cancers. </p>
<p>There are also some tables in the paper that list the miRNA and the disease they a... | 30 |
gene expression | Expression of bidirectional promoters | https://biology.stackexchange.com/questions/9783/expression-of-bidirectional-promoters | <p>How are bidirectional promoters expressed ? (Won't RNA Pol have to go in 3'-5' direction?)
Why are they more commonly found in eukaryotes than prokaryotes?</p>
| <p>Genes controlled by bidirectionl promoters are in head-to-head configurations, meaning that their 5' ends are facing one-another. Remember that DNA is double stranded, so this means one gene is on the 'top' strand and one gene is on the 'bottom' strand. Check out the diagram below, genes are in capitals, bidirecti... | 31 |
gene expression | The reason why researchers usually use cell lines from "blast cells"? | https://biology.stackexchange.com/questions/13740/the-reason-why-researchers-usually-use-cell-lines-from-blast-cells | <p>What's the reason why researchers usually use cell lines from "blast cells" (so, immature, like lymphoblastoid cells) for measuring gene expression data? Is that they are growing up, which would make their expression data higher and more significant?</p>
| <p>Some of the reasons why immature blast cells are studied:</p>
<ol>
<li>They have self renewal ability </li>
<li>Can be differentiated to different types of cells</li>
<li>Serve as model for studying development: this is quite pertinent to the gene expression studies. Because it is important to know what changes tak... | 32 |
gene expression | Punnett Square Help | https://biology.stackexchange.com/questions/13825/punnett-square-help | <p>In fruit flies, red eyes are dominant over white eyes. Show a cross between two white-eye fruit flies. </p>
<p>My question is...</p>
<p>How do I know if the white-eye fruit flies are homozygous or heterozygous?</p>
| <p>Just to add an extended perspective to all of the answers submitted so far. </p>
<p>The classic white-eye phenotype in <em>Drosophila</em> is associated with a gene, <em>white</em> (or <em>w</em>) that is carried on the X chromosome (females XX, males XY) i.e. it is a sex-linked phenotype. Male white-eyed flies are... | 33 |
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