Questions tagged [phase]

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20 views

How to compute correct phase in FFT even after applying phase unwrap and zeroing round off error?

I am converting a time-domain synthetic 1D signal to frequency domain using MATLAB fft. In the frequency domain, the amplitude vs frequency plot is coming reasonable which means it is showing the ...
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23 views

Power spectrum is phase blind

I came accros the phrase " It is well known that the autocorrelation and power spectrum are phase blind". Is there an analytical way to prove this, so I can understand why this is correct.
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37 views

Breaking down sin wave to frequency domain causing weirdness in phase

I have tried many many different things and I cannot figure out why my phase is messed up. Here is what I am trying to do. I create a simple signal with a known wavelength, phase, and amplitude like ...
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1answer
54 views

Creating Bode Plot from Experimental Data

I have a blackbox system in which I can input a function and obtain the output signal (in MATLAB). I'm attempting to reconstruct a Bode diagram and have had success with the Magnitude plot, however, I'...
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1answer
96 views

Phase correction algorithm: minimisation phase error

Thank you for your participation in my discussion in advance. I am working on the implementation of a phase correction. Currently, I have finished the algorithm. I think it is a standard algorithm ...
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1answer
53 views

Why does Phase-locking value show spurious effects at the beginning & end of a signal?

I am trying to understand the behaviour of the phase-locking-value, as e.g. defined here, by some simple examples. Basically, I am creating two signals with the same frequency & amplitude, where ...
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2answers
100 views

How can I experimentally find the bandwidth of my PLL?

I recently designed a phase-locked loop. I would like to quantify its bandwidth so that I can better understand it. However, I made this bandwidth in an informal manner due to my lack of formal ...
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1answer
39 views

Beyond “mid-side”: decompose an audio stereo recording (coincident microphones) into Mid + 45° + 90°

Context: I have done in the past stereo recordings in XY position (coincident microphones): from a source far from at least 20 meters (example: piano in a big reverberant building). Since the ...
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25 views

Reconstruct phase while preserving magnitude

I was wondering if anyone could help me with this problem, I'm fairly new to audio signal processing so please bear with me. My ultimate goal is to, given a magnitude, reconstruct an audio clip from ...
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2answers
81 views

Fringe movement analysis to extract displacement

I am using a Michelson interferometer with the interferogram recorded on a CMOS sensor. I have taken a video of the fringes moving when a displacement of 50 $\mu m$ is imposed to one of the mirrors. ...
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1answer
28 views

Compression of Multivariate Phase Signals

I have a data matrix $X$ whose columns are composed of instantaneous phases of recordings from different electrodes. In other words, each column keeps a periodic sawtooth signal with a range from $[-\...
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2answers
125 views

CORDIC, What is it?

I am reading about CORDIC (Coordinate Rotation Digital Computer) and I have t implement it. Honestly, I am reading and don't understand the difference between phase detection algorithm ( PLL, Costas ...
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1answer
26 views

Pointers for digital FM synthesis

I am working on a digital synthesis project, in python and c currently. I have made a Sine and Saw wave generator and have now been working on FM between the two wave types. I have successfully made ...
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18 views

Instantaneous Phase Synchrony with Multiple Signals

I've recently been looking at phase synchrony to measure the Phase Synchronization between signals (following tutorial at jinhyuncheong signal processing tutorial). I.e. for two signals, retrieve the ...
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34 views

Can an unwrapped phase lag diagram have values beyond $-\pi$ to $\pi$?

I have a PLL that tracks the phase lag of a resonance system. When unwrapped, my system's phase lag has values beyond $-\pi$ to $\pi$. After unwrapping phase lag, are there any bounds on the phase ...
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2answers
56 views

Strange results with all pass compensation

I am new to DSP and, as a learning exercise, I am trying to design an all-pass filter in order to compensate the phase of an input impulse response (heqm.mat, which you can download from here). The ...
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1answer
75 views

What is the relationship between group delay and propagation delay for a filter? [duplicate]

I was trying to design a filter for a system and I was able to obtain the group delay plot in matlab using grpdelay. The group delay output is in samples. However, I was not able to relate that data ...
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1answer
79 views

Phase rotation without Fourier Transform

Is there any known math equation or other method to perform phase rotation on signal without decomposing it to frequency domain? In frequency domain it is obvious. You just need to perform phase shift ...
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78 views

Order one FIR Filter with complex coefficient

I am trying to learn about the behavior of the FIR filter however with complex coefficients. The filter I am trying to analyze is the following: $$H(z)=a+jbz^{-1}\quad\text{where the variable}\quad j =...
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1answer
110 views

All-pass phase compensation only in a specific frequency range

I am trying to design an all-pass filter in order to compensate the phase distortion at the output of an equalizer. To do so, I take the phase vector of the output, compute the real and imaginary part ...
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1answer
79 views

Why is my resonance phase lag discontinous?

I am programming a phase-locked loop to track the resonance of a tuning fork so that the tuning fork is always on resonance. This will be used in condensed matter physics through atomic force ...
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1answer
53 views

minimum-phase phase via Hilbert transform returned values

Following my previous question: HRIR Minimum phase I managed to compute the minimum-phase phase of a FIR filter (in my particular case, HRTF filters). However I am not sure of the phase values ...
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1answer
47 views

Finding the maximum phase and the maximum frequency deviation of an angle-modulated signal

I have an angle-modulated signal: $$ s(t)=10\left[\cos\left(10^8\pi · t + 5\sin\left(2\pi\cdot10^3·t\right)\right)\right] $$ How would I go about finding the maximum phase and the maximum frequency ...
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1answer
21 views

Spectral properties of QPSK modulation

From what I've read, the spectral properties of the modulation largely depend on the rate of change of the signal phase - "a signal in which the phase changes stepwise has a broad spectrum, well ...
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0answers
26 views

Why do we not encode frequency in 3 dimensions in MRI?

If I understand correctly, to select a particular slice (of an object, during an MRI scan) that is orthogonal to the direction of the main magnetic field applied, we apply a magnetic field that varies ...
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32 views

Artifacts reduction during filter cutoff change: is it possible?

I am designing a digital sound synthesizer and prototyping it using Max. The synth in question includes a dedicated filtering module, including a bi-quadratic filter whose cutoff frequency is ...
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42 views

Why the transfer function is equal to the output in this case

In this description of transfer functions on the z-plane (image linked), I'm confused by equation 1.49, which says that $H(f)=v_{out}(f)$ when $v_{in}(f)= 1 * e^{j 2 \pi (f/f_s)}$. (For another matter ...
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37 views

Stability of filters with negative phase delay, group delay, and positive phase

Lets assume I have an IIR filter with : bz = [1.0195 0 0]; az = [1 0.0166 0.0020]; fvtool(bz,az) The filter is stable as i can see. If you check the phase delay ...
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1answer
37 views

Filter design for an unusual EEG experiment

I'm designing a quite unusual (in terms of signal analysis) EEG experiment, which forces me to design my own filter. I have never done this before, so kindly please check my work and suggest ...
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18 views

Interpreting FFT Phase - why phase of a cosine?

I understand how to interpret the magnitude result from the FFT, but why is the phase that we obtain, arctan(Im(x)/Re(x)) indicative of the phase shift of a cosine graph, and not a sine graph?
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1answer
50 views

Convert measured spectrum to impulse response

I am still learning, so please bear with me: My audio measurement tool exports the measured spectrum of the DUT in the following format: Frequency [Hz] Magnitude [dB] Phase [degree] It is stored in ...
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2answers
111 views

Non-zero DFT components where zero is expected?

I am implementing DFT in Octave. Here's my code: ...
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0answers
29 views

Getting the “phase” in a streaming way?

The context is a supervised learning problem. I have a dataset with features X and a target y. Among that dataset there is the date of the day encoded as an integer starting at 1. I have around 10k ...
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13 views

How to get the phase/angle from an Alglib complex variable

It is easy to get the magnitude using alglib.abscomplex function (https://radfiz.org.ua/files/temp/Lab1_16/alglib-3.4.0.csharp/csharp/manual.csharp.html#gs_stdfunctions), but I would like to know, how ...
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2answers
97 views

Inaccurate phase returned by np.angle

I am generating 2 sine waves, first one has fundamental frequency = 50 Hz, amplitude=10, phase=0, the second one has fundamental frequency = 100 Hz, amplitude = 5 and phase = np.pi/6 (which is ...
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2answers
100 views

Correcting phase response of a signal

I have a sensor that applies a frequency dependant phase alteration to my signals. I'm trying to find a way to correct these phase responses using an FIR filter. Essentially, I'm looking for methods ...
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0answers
39 views

How can I implement a phase detection algorithm with my amplitude detection?

I have been recently working on a signal detection problem in Matlab. At the minute I am detecting signals based on their amplitude, using an m-of-n detector. I am interested in improving the false ...
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0answers
36 views

Something like Hilbert Transform to obtain arbitrary Phase Shift? [duplicate]

I was wondering if there is something like a Hilbert Transform but that can implement an arbitrary phase shift to every frequency component. I mean, I know that the magnitude response of a "...
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1answer
855 views

Calculate the magnitude and phase of a signal at a particular frequency in python

I have a signal for which I need to calculate the magnitude and phase at 200 Hz frequency only. I would like to use Fourier transform for it. I am very new to signal processing. And this is my first ...
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1answer
38 views

Estimating a phase for a frequency band

I'm looking for a way (preferably already implemented in eg. python) of estimating a phase for a specified freq band. When I'm performing FFT on the signal, I can determine components frequencies as ...
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3answers
87 views

Does converting an FIR filter from causal to non-causal remove phase delay?

Let's say I have a causal 3-tap FIR filter: $$y[n] = ax[n] + bx[n-1] + cx[n-2]$$ Assuming I have access to all the data prior to filtering and generate a similar non-causal filter: $$y[n] = ax[n+1] + ...
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1answer
49 views

What does nonnegative zero-phase response mean?

I am not exactly sure what nonnegative zero-phase response means. If a filter is zero-phase (i.e. symmetric and non-causal), then what does nonnegative imply? And what are the conditions to satisfy it?...
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1answer
50 views

Design of discrete time second order all pass filter

I want to design a second order digital all pass filter with the transfer function given by $$H(z)=\frac{a_2 +a_1 z^{-1}+z^{-2}}{1+a_1 z^{-1}+a_2 z^{-2}}$$ The input to this filter has frequencies ...
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1answer
25 views

Mathematical relationship between phase modulated (PM) signal and the complex phase/magnitude of the frequency component at the carrier frequency?

What is the mathematical relationship between phase modulated (PM) signal and the complex phase/magnitude of the frequency component at the carrier frequency used? This is partially related to the ...
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2answers
96 views

Why should the last point be excluded when performing a least-squares fit of a periodic discrete time signal?

I fitted the function: f(t)=A_o+A_1 cos(wt)+B_1 sin(wt) to the following periodic discrete signal: ...
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0answers
112 views

Understanding Phase noise of a Hard Limited Sine Wave

I need help in understanding the frequency spectrum of a sine wave with phase noise that has been hard limited. Background: Typically, textbooks define phase noise for a sinewave, however in many ...
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1answer
60 views

Distortion in phase difference measurement using FFT

I am doing distance measurements by transmitting a 100 kHz tone and receiving it and measuring the phase difference.The distance is simulated by a delay simulator which is very precise (around 10 psec)...
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1answer
40 views

Modulate Bipolar(?) signal

I want to modulate this signal if possible with an Arduino, but have no idea what circuit can help me here. Let's ignore the timing and the measurements from the image for a moment, my problem is more ...
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2answers
80 views

find phase greater than 2*pi in MATLAB

I'm working on extracting the phase information in a given signal in MATLAB. I've the following vector; ...
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1answer
56 views

Terminology for instantaneous phase of magnitude component of complex signal

In my field, we deal with data that are originally complex-valued. Typically, researchers convert their data from real + imaginary to magnitude + phase, and then discard the phase data (i.e., we ...

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