# Tagged Questions

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### Why does QAM use two cycles instead of one per byte?

If you look at this image, you can see that you have 256 possible binary values by modulating the amplitude (the radius of the trigonometric circle) and the phase (the degrees) of the carrier. ...
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### Calculating Phase Response for 2 microphones given the input

I want to measure and compare the phase response of two identical microphones. To do this, I have a pressure chamber, which allows to apply the same pressure to both microphones. I apply a sweeped ...
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### Decomposition of $H(z)$ as maximum-phase, minimum-phase

The frequency response is: $$H(z) = 2-7z^{-1}+7z^{-2}-2z^{-3}$$ I see that it has $3$ zeros: $z_{01} = \frac 12$, $z_{02} = 2$, and $z_{03} = 1$; and $3$ poles in: $$z_x = 0$$ Now, I have to write ...
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### Maximum phase with the same magnitude response

I'm trying to solve an exercise in a general way and I can't find if my answer is correct. Given this frequency response: $$H(z) = 4 + 2\sqrt2 z^{-1} + z^{-2}$$ I need to find a frequency response ...
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Say I have 2 signals: A = 1kHz Sine B = 1kHz Sine, 30° lagging the first one. If I plot the FFT-Phase of these 2 waveforms, and get the Phase values at 1kHz, I would get: A = -90° B = -120° ...
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### Signals cross-correlation

I am trying to measure phase difference between two received waves which are recorded by two separate PC's (microphones). The two PC's starts recording at the same time, then I make a sine wave sound ...
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### Phase invariant detection of low frequency spikes

I am a physics graduate student studying a new physical device via simulations. Thanks to SE DSP, reading Lyon's Understanding DSP as suggested (not all the way through it yet though), and a bunch of ...
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### Best way to implement variable phase shift on FPGA?

I have an incoming digitally sampled sine wave pulse, so my FPGA has the ADC level from an I and Q channel. I want to be able to shift the phase by some arbitrary amount. What's the most efficient ...
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### Relating phase shift to the ROL/ROR operations

Is phase-shifting in continuous-time analogous to the rotate-left (ROL) and rotate-right (ROR) operations in discrete-time?
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### How would Fourier and Cosine Transforms responds to summation of cosines with same frequency but different phases?

For example, if I have two signals, $\cos(2\pi ft+\frac\pi4)+\cos(2\pi ft+\frac\pi3)$, what would be different in both transforms (Fourier and cosine) how would the spectrum changes? And What would ...
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### Finding phase of fundamental from autocorrelation

I have some code, shown below that I have been using to find the fundamental of a guitar string. After this function is called, I go thru the real buffer and find the peak, whose location gives me ...
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### How to plot magnitude and phase response by hand if I have the Transfer Function?

I have the transfer function of the system, which is: $$H(z) = \frac{1-z^{-1}}{5(1+2z^{-1})}$$ How do I sketch the magnitude and phase response? I'm sorry for the bad formatting, it's my first time ...
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### Code for a wavelet based hilbert transform? [closed]

I normally implement the Hilbert transform using the Fourier transform. I have noise related issues I want to solve. Does anybody have an (apodized) implementation of the Hilbert transform handy, ...
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### How to shift a signal to the center of the frequency domain?

Let's assume I have a 1024 x 1024 matrix that represents the spatial domain. After I perform a FFT and center the frequencies, I get the a signal that looks like the following in the frequency domain....
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### Reasoning Behind Additional Phase Shift in DPSK

In MATLAB's Comm System Toolbox there is an option for 'Phase Rotation', defined as the phase difference between previous and current modulated symbols when the input is zero. This is the first time I'...
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### Reducing standing waves with phase randomization

Will constantly randomizing the phase of an audio signal, say a speaker in the corner of a square room, reduce standing waves (i.e. room modes) in the room? For example if you wanted to create a ...
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### How to remove 50 Hz frequency noise from a PCM file?

Are you kind to tell me the odds or the means by which should I grab a clean signal with the $~50 \mathrm{Hz}$ carrier removed using just programming? I managed to make a program in Visual-C that ...
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### Strange step response

In the figure there is represented a step response of a mechanical system. I created a step variation in the excitation of a DC generator. This lead to a step variation in the torque developed by that ...
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### Continuous phase for phase delay calculus in FIR filters

I would like to estimate the phase delay accurately for any random FIR filter. The definition of the phase delay is the continuous phase divided by the angular frequency (with a sign change). That ...
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### What is the absolute phase and the relative phase, of a signal?

I need to know what is the absolute phase and the relative phase, of a signal? and why these phases are important in the signal processing?
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### Amplitude/phase recovery on noisy signal

I have a noisy signal that has an ac component of fixed frequency but variable amplitude and phase. I'd like to recover the ac component. The signal (blue trace) is mostly smooth, but has a few ...
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### Phase shifting a noisy signal

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. I can only read the signal+noise and thus can not separate them. I want to phase shift ...
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### Obtaining a frequency response from other frequency responses

I have loaded six impulses responses (1024 samples each in length) into Matlab, zero-padded the end of each with 1024 zeroes and taken 2048 point DFTs of each using Matlab’s built in ...
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### Why does this reconstruction produce a phase shift from the original signal?

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. Using the magnitude and phase data of each frequency, it's reconstructed, ...
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### Help Understanding Time of Flight Phase Sanitization Algorithm

I'm implementing the technique found in this paper: http://front.sjtu.edu.cn/~jinyh/gradCourse/Paper/Wireless/SpotFi%20Decimeter%20Level%20Localization%20Using%20WiFi.pdf to perform localization. I'...
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### Extracting accurate phase and amplitude information from FFT with an arbitrary number of samples

This is a followup question to one I asked earlier based on the chat after the answer given by @hotpaw2, and cross-posted from stackoverflow since it was suggested it is more relevant to DSP. I have a ...
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### Ideas to implement phase shifter on 4DSP FPGA FC6301

I have an FPGA FC6301 and I need to implement a simple phase shifter using StellarIP. At the moment i'm using Fpga FC6301 with carrier FMC144 by 4DSP and I'm using the provided design named: ...
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### Will decorrelating an audio signal help reduce interference patterns at low frequencies?

In live sound it is common to have a left/right sub-speaker configuration, which will produce an strong interference pattern in the audience area based on listener/sub-speaker locations. If the left/...
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### Average Asynchronous Resample Latency

Given a sample frequence of 1 Hz and periodic events. The latency of an event is the time difference to the next sampling point. What is the average latency over infinitely many events? Events are ...
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### Estimate gain and phase from measured input and output

I have a measured output from a closed loop controlled complex system with a simple sinusoidal command input. How can I estimate the gain and phase between input and measured output?
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### DAPSK bit assignment for the amplitude difference

I am studying DAPSK(Differential amplitude phase shift keying) at the moment. I have a 64-DAPSK. We are using 4 concentric rings and 6 bits per symbol. The first two bits contain the information of ...
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### How do I find the phase response of a filter from the filter equation?

I am new to this forum. I have been teaching myself DSP for the last two years, so my experience and knowledge has a long way to go. I am trying to find the phase response of a specific filter that I ...
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### Minimum Phase & maximum phase

i have 2 questions: 1-If zeros on the unite circle that will be min or max phase?and this system has low-pass frequency response or not ? 2-Is the min phase has the shortest impulse response?
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### The need for phase wrapping?

I understand the need for phase unwrapping and the complexity behind it. But, I'm struggling to understand why the phase information gets wrapped between $-\pi$ to $\pi$ in the first place?
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### How is the Leslie speaker simulated?

What are Leslie speaker / "rotary" style of digital audio processors doing? I think a simple one would model: Delay between speaker and a pair (stereo) of microphones. The tonal change when the ...
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### Filter Design for Phase Response

How can I design an all pass filter to have a constant phase shift over a bandwidth centered around a carrier? I don't care about phase shift outside the band. I would like to have the filter in ...
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### Get phase information from bursty time series with amplitude variability and sharp edges

I have time series like this one, and I am trying to get the phase information from it. If it matters why, because I need to compute the precision of the cycles and amplitude variability is ...
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### Why is the name “Phase vocoder”?

I've read that phase vocoder is the STFT, but done in windows (i.e. using windowing). Why is it called "phase vocoder"?
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### Overlap/Chunk processing possible with Zero-phase?

I'm relatively new to DSP and I'm currently investigating FIR filter and IIR filters. From what I've found FIR filters can be implemented efficiently using the overlap-save method, but I was wondering ...
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### Design Hilbert filter at matlab (pure 90 phase and magnitude 0db)

I need to design a filter able to take a measurement of alternate current and shift the phase of the input by 90°. The filter should work between 40 and 60Hz and at this range should have unity ...
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### Would subtracting the phases of two images be a superior difference metric than subtracting the images directly?

I'm hoping someone can sanity check this idea as I am admittedly a bit of a noob when it comes to working with FFT's. Say I have two (registered) images of two of the same object and want to use one ...
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### Phase measurement

I have a problem with phase measuring. I'm acquiring two signal with a USRP (complex signals) with a coherent generator and I want to measure the phase different between them.. One is at 150Mhz and ...
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### Phase spectrum of the DTFT of a rect pulse using FFT

I'm trying to use the FFT to plot the phase spectrum of the DTFT of a sampled rect impulse function. Here's the Matlab code I've written. ...
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### At what amplitude does spectral leakage start to be noticeable in the phase spectrum?

I understand that discontinuities at the boundaries of a finite signal may introduce spectral leakage, that alter both the amplitude and phase spectra of the FFT, specially at low amplitudes. That is ...
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### Amplitude, Phase via DHT

How can I find out Amplitude & Phase of an audio signal via Discrete Hartley Transform? Isn't it like finding via DFT, as I know DHT is similar to DFT except imaginary part?
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### Is there any way of retrieving phase information with only access to real part of successive FFT frames?

Due to a limitation of the WebAudio specification the FFT available in JavaScript only makes available the real part (1st half) of the calculated frequency data. Is there any way of recreating the ...