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Questions tagged [phase]

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How does phase relate to motions in an image?

There is lots of research based on exaggerating motions by decomposing an image into complex sub-bands using pyramid representations such as the complex steerable pyramid and manipulating phase ...
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23 views

Preamble detection using cross-correlation

I am generating a preamble with a sequence of [1 -1 1 -1 1 -1....] and spread with a barker-11 sequence. Now, the transmitted signal becomes [B(Barker), -B(Inverse of Barker), B, -B,....]. In channel, ...
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30 views

How does a Costas Loop lock to one of multiple BPSK signals

I've been looking into how GPS receivers work in terms of signal processing. When a GPS receiver tracks the received signal, it often uses a Costas loop to synchronize the carrier. How that works ...
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11 views

Signal delay in phase interferometry?

I want to write program for phase interferometry to understand how its work. For the beginning I generate signal, which arrives on two antennas with delay. Matlab code: ...
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46 views

90 Degree Phase Shift / Rotation Algorithm for SDR

I'm working on a library to preform frequency demodulation from an SDR signal. I'm using https://github.com/sysrun/rtl-sdr/blob/master/src/rtl_fm.c as a crib for this. The algorithm starts by taking ...
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31 views

how to detrend a carrier phase with butterworth filter?

I am new with detrending techniques, I have a carrier phase measurements and I want to detrend it by 6th order butterworth digital filter. After creating the digital filter I get its numerator (...
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1answer
50 views

Detecting phase difference between a clean and a noisy signal

I have a clean square-wave signal and a noisy signal from an accelerometer, perfectly synchronized to each-other but out of phase. I want to find the phase difference between them in real time, in ...
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2answers
31 views

Is there such a thing as a continuous phase BPSK?

My knowledge of signals and signal processing is limited, so I apologize in advance for my naïve and possibly confusing question. In the case of BFSK, the frequencies are altered to represent the ...
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1answer
56 views

How to uniquely identify phase difference between harmonics?

Let's say I have a multi-frequencies signal of 440Hz and 880Hz, slightly out of phase. I can take a chunk of the signal and calculate phase difference of the two frequencies with FFT bins. However, ...
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2answers
74 views

How to efficiently control an FIR's magnitude response by altering its phase spectrum

Question: Extensively searching the space of all possible vectors of length $n$ to satisfy a (non-overdetermined) requirement is possible in principle. Hence, there is a way to calculate a complex ...
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1answer
48 views

what happens If I change the phase and magnitude of a signal

I have a speech signal. I want to know what happens when I make some changes on the phase of its frequency reaponse. When I set its phase to zero I observed that the new signal is even and the ...
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2answers
61 views

Phase shift of all-pass bi-quadratic filter

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. But nobody mentions that at normalized frequency 0....
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1answer
21 views

Shifting and phase difference

Assume we have a series v[k] of length M=16. It's shifted to the right in a circular manner by k0=2 samples. Which phase difference between the DFT spectrum of the original signal and that of the ...
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2answers
35 views

How to make sure that a sinusoid wave with different subsequent frequencies matches up?

A very basic formula to transform a sequence of notes into a signal would be: $$ x(t) = A\cos( 2 \pi (2^{current\_note}/12) t) $$ where $current\_note$ is $notes[\lfloor t / period\_per\_note\...
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1answer
43 views

Given a plot of both the magnitude $|H(\omega)|$ and its angle, How can you find the $H(\omega)$?

I'm specifically trying to use an inverse Fourier Transform to find $h(t)$, but I'm finding it difficult to get $H(\omega)$ in the first place. I'm under the impression from my textbook that $H(\...
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1answer
49 views

Frequency Hopping Spread Spectrum Synchronization Methods

Frequency-hopping spread spectrum waveforms change the carrier frequency at some interval. I can see if the frequency is constant for the duration of an entire packet, the pilot symbols could be used ...
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1answer
26 views

Equalizing a temporal sound signal with a convolution

This question is more or less the following of a previous question. The aim is to equalize some sounds signals. By equalizing, I mean increasing or decreasing some frequency ranges, a bit like an ...
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2answers
82 views

Why is my DFT/FFT always 90° out of phase?

I'm doing an FFT using Python and Numpy on one machine, and C# on another. I'm using some dummy data that mimics how I'll eventually be gathering data from sensors in the C#/UWP application. The two ...
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22 views

Confidence measure for GPS CA Code Acquistion

As a follow-on to this question, how do GPS receivers decide if they've successfully acquired the coarse acquisition (CA) code for a GPS satellite? If it's based on post correlation SNR, what's the ...
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32 views

Can Reassigned-STFT be an invertible transform? Algorithm for “Signal => Reassigned-STFT => masking => Reassigned-ISTFT => Output signal”

It is well known in DSP that this is a successful method to modify audio signals: Signal => STFT => masking => ISTFT => Output signal For example, ...
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2answers
829 views

What exactly is a 90 degree phase shift of a digital signal in FM demodulation appraoches?

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. My sampling frequency ...
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1answer
131 views

Phase shift problem in Fast Fourier Transform

I try to make graph/print for magnitudes and phase shifts for impulse response calculated by FFT. For magnitude everything works perfect, but for phase shift I get some strange curve for higher ...
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1answer
103 views

OFDM: How to do the carrier recovery of the quadrature(I/Q) demodulation

For an OFDM system, after the OFDM modulation, the quadrature modulation is used to move the signal from the baseband to the pass-band. But when it comes to the receivers, I can't find any way to make ...
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2answers
71 views

Relating phase difference in a signal with its frequency

I have a 134 point complex signal. Using MATLAB, I have observed that the phase difference between any two adjacent samples of this signal is 2 radians i.e. the phase increases linearly from 0 to 268 ...
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1answer
31 views

Is the phase difference between recorded sounds from left and right ear the same as the phase difference between their HRTF?

Pardon my ignorance if my question is silly. Lets say I did a binaural recording and found the phase difference between right and left channel. If the recording was done in anechoic chamber, where ...
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1answer
73 views

Phase wrap when computing impulse response from frequency response [closed]

Short: I have the frequency response of a system as a set of complex numbers. I want the impulse response for that system. Problem: The phase of my frequency response wraps around 2pi multiple times....
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2answers
219 views

Can the instantaneous frequency be always derived from an analytic signal?

Instantaneous frequency can be defined as a derivative of an instantaneous phase of an analytic signal which can be nicely seen in practice in this example from Scipy's documentation. But it seems ...
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1answer
40 views

Phase of a signal with multi delayed windowed (rectangular window) signal with different amplitudes

I have a signal $x(t)$ which is composed of multi delayed linear chirps with different amplitudes and phases but they share the same $w$ and $\alpha$, the signal can be expressed as follows: $$\...
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203 views

Simulating Phase Noise: How to do it?

I have a system that I am simulating, and I want to add phase noise to the process. I didn't know how to do it, so I have been conducting an literature review. I found a good reference with an "easy ...
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1answer
84 views

About phase unwrapping

I am not too familiar with phase-related problems so I need some suggestions or corrections in a problem that might be an old but easy one. Here is my problem: given a complex signal: $$y(t) = e^{j\...
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3answers
104 views

Phase response of a FIR Hilbert transformer

The graph below shows a linear phase response of FIR Hilbert transformer with a constant diff of -0.06135923. I am not sure if I understand the concept of the phase response correctly, but as the ...
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0answers
82 views

How to know whether numerical roundoff error or not in MATLAB?

This is result of real and imaginary parts of cos fft. I think e-13 number is numerical error but, I don't know how to know they are real numerical error. If I have to try change primitive types, ...
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1answer
69 views

Phase and Amplitude estimation

Context: I have used FFT many times, but for real, non-periodic signals I consider it a poor estimator. For most of my applications I am only interested on the power spectrum, so I use the Welch's ...
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1answer
205 views

Why MATLAB fft cos makes imaginary parts?

The cos fourier transform has no imaginary parts, but in this code it has imaginary parts that little big. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% figure(7); fs=128; t=-4*pi:1/fs:4*pi-1/fs;...
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44 views

Passband filter before Hilbert transform

I have a .wav file of human speech sampled at 48kHz. Before making the analytic signal with: hilbert(s_real) lets say in range 200 - 3,500 Hz, I probably need to do pass-band filtering, say 300 - 3,...
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1answer
65 views

Converting Time Shift to Phase Shift

I have just started taking signal & systems lessons and here is my question: If we say that x0(t) = A.cos(w0t). (a cosine signal with zero phase shift, w0 ...
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3answers
198 views

Phase change rate of human speech

I have a .wav file of human speech, sampled at 48kHz, with useful signal up to 5kHz, and almost no noise. If I do Hilbert transform in MatLab, I get the Analytic signal: $$ s_\mathrm{a}[n] = s_\...
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254 views

Cosine Fourier Transform and Phase

If we do FT of cosine wave, then sine wave will be orthogonal. So, the imag parts of FT will be 0. This is my think. But, the result isn't show that. Like this. Figure 1. Real and Imag parts (Y label ...
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60 views

Bandpass Fractional Delay Filter

I am designing a fractional delay filter, I found this code for lagrange FIR fractional delay filter, The fractional delay filter acts as a low pass filter, it passes low frequencies from 0 to 0.25*fs....
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1answer
227 views

Discrepancies between FFT-based Hilbert Transform and FIR filter results

I compared the results of Hilbert Transform as provided in scipy.signal.hilbert() (which is uses I/FFT as you can see in the source code) with its approximation implemented as FIR filter using coeffs ...
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2answers
92 views

Phase ambiguity in QAM modulation

I'm currently studying a decision directed carrier recovery scheme. Basically a PLL try to estimate the phase error in the current received symbol, the phase detector compensate the incoming symbol's ...
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2answers
46 views

Why the angle of a real signal in frequency is continuous?

This original signal is shown below (time domain): It is a real signal. According to the signal processing theory, the form part of the angle is conjugate to that of the latter part. That is, $\...
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1answer
259 views

extracting ultra accurate phase and frequency with FFT with real world data

I was doing some experiments in Matlab, and write this code to experiment with it. I want to know if it's possible to extract accurate within -+0.01° phase info from samples of an ADC, the matlab FFT ...
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29 views

How does the M-law Synchronizer work?

Relatively new to DSP, I've came across the approach for phase-estimation of PSK-Signals x(k): My question is: What do we get by exponentiating the Baseband-Signal?
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2answers
465 views

QAM constellation slicer with unknown carrier phase

As shown in the image, I have a 16QAM constellation that is misaligned due to a phase rotation. In this case you can see that rotation amount is approximately $\theta = \pi/4$, but this won't be the ...
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0answers
158 views

Phase Noise in OFDM simulation

I am trying to simulate phase noise in OFDM and in search of a mathematically tractable model. So far, I have managed to get phase noise by multiplicating $e^{j\phi(n)}$ in frequency domain where $\...
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1answer
126 views

Measuring acoustic phase difference between two receivers

I am trying to measure the acoustic phase difference between two sensors 30cm apart each other. The sampling frequency is 20kHz, and my interest frequency is about 1700 Hz. The below is how I ...
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1answer
65 views

Adaptive filter to scale and phase shift two sensors output

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 ...
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1answer
135 views

Phase Modulation and Intermodulation Anomaly ? (Spectrum plots inside - **Updated**)

I have a MATLAB script for modelling a two tone signal (a sum of two sinusoids) going through a non linear transfer function (such as an amplifier). The amplitude of a signal is amplified non linearly,...
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2answers
128 views

Adding phase to a signal that has multiple frequencies

An amplifier changes the phase at different amplitudes of asignal. I am using amplifier data in a MATLAB model. I have constructed a signal that is a sum of sinusoids of different frequencies with ...