# Questions tagged [frequency]

Frequency in signal processing is the number of cycles (of the signal) per second.

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### Costas assisted by Frequency Locked Loop (FLL)

Carrier synchronization for M-PSK signals can be accomplished with the Costas loop. Typically, this loop consists of an error detector, a second-order loop filter and an NCO. Error detector is being ...
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1 vote
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### What is the analogy of frequency sampling of a 1D signal in a 2D signal (image)?

I made model to remove noise using deep learning for 1D ECG signal (time-amplitude domain). The model was trained on 360 Hz frequency sampling ECG data on millivolts unit. I stated to my professor ...
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### Amplitude scaling for the FFT of a logarithmic frequency sweep

I have performed a logarithmic frequency sweep on a system from 1 Hz - 5000 Hz at constant amplitude and acquired the data at a linear acquisition rate of 10000 Hz. The frequency sweep reference ...
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### very basic confusion about the bandwidth of constant signal function

I have a very basic question about bandwidth of constant function $f(t) = K$. As the Fourier transform of a constant pulse is a delta-function centered at zero frequency, the bandwidth (maximum value ...
1 vote
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### How to measure the vibration of an object on a video shot at high speed camera?

I have a video fragment which I split into frames (pictures). I use them in pairs (1 frame with 2, 2 with 3, etc.) to find shifts on x and y axes (i.e. how much I need to shift 1 frame to make it like ...
1k views

### Why is sampling frequency/rate typically abbreviated Fs and not Sf in English?

This is not a technical question, it is rather a question about the implicit notation used in MATLAB and multiple digital signal processing books to refer to sampling frequency/sampling rate. Why is ...
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### How does the shape of a frequency domain function (Fourier Transformed time domain function) change when a time shift is applied in the time domain?

When there is a time shift (or delay) in the time domain on a function, the Fourier transform gets multiplied by an exponential which corresponds to a phase shift on the original frequency domain ...
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### Are integer multiples of a frequency in an FFT necessarily in phase?

I performed a FFT on a signal and the most prominent frequency at about 0.5 cycles/time only makes up about 6% of the total frequency distribution, which is pretty low for my purposes, so I was ...
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### What's Nyquist frequency in DFT?

I'm currently studying digital signal processing at university but I can't figure out what the Nyquist frequency means in the DFT coefficients, I know what the Nyquist frequency is in the sampling ...
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### How do you properly cut out negative frequencies from FFT of a real signal if it reduces sample size?

If a real time signal has $N$ samples, then the magnitude of its FFT will also have $N$ samples--half of which will have positive frequencies and half of which will have negative frequencies. The ...
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### Result of complex exponential fourier series approximation and trignometric fourier series approximation are not exactly same in MATLAB?

I have a signal and i am trying to observe its approximations using complex exponential fourier series and trignometric fourier series but i am not getting exactly same result(graph of trignometirc ...
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### Since harmonics only generate at multiples of the center freq, is it for this reason that the left part of a FT (like sinc) has no physical meaning?

If we have a rectangular pulse function, we know that after a Fourier transform we obtain a sinc: We know that the left part (negative frequencies) has no physical meaning and it's just specular. It'...
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### Doppler radar. Signal to noise ratio

I'm trying to figure out how a continuous wave Doppler radar works. When moving towards the radar, the Doppler frequency should increase, and when moving away from the radar, the frequency should ...
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### Frequency Modulation - Demodulation - Distorted frequency shape

I am interested in the effect frequency modulation has on the signal. I am using an acousto-optic deflector to steer a laser beam. The deflector receives a Radio-frequency (RF) signal (~100 MHz, sine-...
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### Interpolation of STFT between time and frequency bins

I am trying to identify and remove airplanes in a time series obtained at a radio meteor receiver. Here we have a spectrogram which displays the power content of my signal as a function of frequency ...
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### How to show that these two factors are related to frequency interpolation and extrapolation respectively

Consider two sequences $x[n]$ and $y[n]$ being simultaneously sampled from a real-world signal. Let $x[n]$ be a sequence of length $N$ sampled for duration of $T_x$ at rate $f_x$ $n = 0, ..., N-1$ ...
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### (graphic) Relation between FFT and complex signal

I have a complex signal with a frequency between 0 and 16 (16 not included). I have made four plots (in python) to show four examples. For each example I provide the signal, its FFT in both real, imag ...
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### Finding oscillation frequency in a harmonic polluted signal [duplicate]

I would like to find periodicity and the oscillation frequency in a signal. I used this simple MATLAB code which works find for some signals, but for a harmonic polluted signal like the one given ...
356 views

### Identifying incorrectly sampled recordings and finding their actual sampling rate

I have a dataset that contains a lot of recordings sampled incorrectly. This incorrect resampling could be explained in two ways: A recording S, which was recorded with a sampling rate of 16kHz, was ...
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1 vote
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### What is the effect of carrier frequency offset (CFO) on the zeros of the z-transform?

Suppose I have a discrete-time signal vector, for example, x(n)=[1,a1,a2,…,aN]. The signal is then transmitted by using the single carrier pulses, constituting a single-carrier communication over a ...
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### I need help deciphering an audio file .mp3 file to get an answer. From a game

I was given a .mp3 audio file needed to be deciphered however I don't know how. I found the spectrogram which outlines the words "youtube", so I suspect the final answer might have a youtube ...
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### Plot amplitude vs freqency in DB

I have C++ App which wich plot 3 plot amplituede vs sample amplitude vs frequncey(used FFT for calculation) amplitude(in dB) vs frequncey I want plot 2 with y axis lable represent in DB, without ...
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### How to convert the phase noise spectrum density to frequency spectrum density?

Following the answer in this post: Phase noise and frequency noise relationship, I can calculate the phase noise spectrum density with the unit from $\frac{dB_{c}}{Hz}$ to $\frac{rad}{\sqrt{Hz}}$. ...
1 vote
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### Real part of signal

A little story. At the university, I did laboratory work on expanding functions into the Fourier series. I have this drawing. My teacher told me he is faithful. But he asked me this question: "...
1 vote
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### Collecting average frequency data of a song/audio recording

I'm a university student, and for one of our classes we have to use TouchDesigner to make some sort of dynamic visualizers. I know how to do this already, but to make the process more scientific I ...
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### How to find Gain when i have frequency of input and output signal

I need to find the bandwidth of an filter, for this im generating frequency of 1Hz to 200 hz in step of 1hz from a function generator Im expecting -3db point anywhere between 1 and 200 The output of ...
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### How to extract the oscillation frequency from the following signals?

Signals contain both transient and stabilizing processes. In the transient process, the signal exhibits oscillatory behavior with damping. Is there some efficient algorithms to extract the frequency? ...
915 views

### Does analytic signal have positive instantaneous frequency?

The Analytic representation of a signal has no negative frequencies. Does this mean that everywhere, it's instantaneous frequency is positive?
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### Why does FFTPack 5.1 not give the same complex numbers as Matlab's FFT2 command does?

I'm doing FFT2 with FFTPack 5.1 and it's working great. But it does not give the same result as Matlab's FFT2 command. Turning Time domain -> Frequency domain -> Time Domain give the same result ...
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### How to do FFT with complex numbers - Ansi C code

I have a small issue. I'm going to do FFT2 onto a matrix $X$, and the only library I have is FFTPack. FFTPack is the oldest FFT library, but it's one of the fastest and 100% portable too. The problem ...
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### Separating an audio file into "N" frequencies

I'm working on an audio visualizer using Blender, and I'm wanting to separate input audio files into their respective frequencies to allow my models to react based on the amplitude at different ...
1 vote
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### Separating an audio file into "N" frequencies

I'm working on an audio visualizer using Blender, and I'm wanting to separate input audio files into their respective frequencies to allow my models to react based on the amplitude at different ...
118 views

### Sampling a pulse train with a controllable square wave

I have an issue regarding a sampling process of a pulse train in an image sensor based on events. Basically, these are a family of image sensors in which each pixel outputs a train of pulses, and the ...
1 vote
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### Replicating SDR transmitter and receiver (shifting of a quadrature signal)

I am trying to implement an SDR transmitter and receiver based on the description here. ...
204 views

### Central frequencies of band filters with cut-offs at 0 and the sampling rate

I'm trying to configure AutoEq for SuperEQ. The latter was originally a Winamp DSP, but now it's used in foobar2000 and DeaDBeeF. AutoEq requires a list of central frequencies and Q-factors for ...
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### Paul Kellet Resonant Filter: freq from/to hz?

I was working/studing a basic Resonant Filter, using the Paul Kellet one as test case: https://www.musicdsp.org/en/latest/Filters/29-resonant-filter.html The freq is feed in normalized value 0..1. So ...
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### Frequency response measurements by audio signal FFT

I am trying to measure the frequency response of different audio canals, e.g. tubes, hollow pipes etc. My experimental setup looks like this: I generate an audio signal with a loudspeaker (Visaton WS ...
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### How to remove phase shift for a baseband signal given an estimated CFO (Bluetooth)

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. ...
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### Does subtracting a phase from the frequency components of a DFT output result in rotation?

I'm currently reading a paper (Page 23 of the PDF) about the application of the Fourier transform to standardize some climatic data to easily compare them. I have the following text : 2.3 ...
795 views

### Why does spectrum magnitude decay away from DC for positive signals?

I would like to understand why the second frequency component usually has the greater magnitude within the range [1, (N/2)], i.e why (I remove the DC component and ...
107 views

### How to modulate a signal to a certain frequency in time domain

I have a root-raised cosine pulse signal of bandwidth $500$ MHz. If the signal is modulated at the frequency $6$ GHz, the result should apparently look like this : If I understand well, to modulate ...
1 vote
95 views

### Is there a way to get this reverb effect working on something else than 44.1 kHz?

I have successfully implemented the Sony PlayStation 1 reverb effect, until I realized that it strictly works at a sample of 44.1 kHz. A quick web search shown that (as far as I understand), an IIR ...
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### FFT of complex signal (I/Q), what do the bins N/2..N-1 represent?

I know it's a very basic question, but I've spent almost a full work day researching and still can't find a clear (or even just usable) answer. For the DFT of a real-valued signal the second half of ...
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### Block Diagram 2nd Butterworth Low-pass

I would like to represent a second-order butterworth low-pass filter in a block diagram, how can I get started? As per the attached image
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### What is the symbol for angular frequency?

I am reading the book Signals and Systems Laboratory with Matlab Book by Alex Palamides and Anastasia Veloni I was going through chapter 6 (Fourier transform) and I came across a confusing thing ...
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### Sampling Frequency of a Rotational Sensor

In the picture above you can see a sensor I've been dealing with, called a "Caliper". This sensor arm simply passes over the pits or bumps on a disk rotating with a constant angular velocity ...
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### How to find sampling frequency in aperiodic signal?

I have a signal that is $x(t)=e^{-3/t^2}+2\cos(3\pi t^3)$ and I'm trying to find its proper value for fs. But I couldn't find a way on how to do it. I'm working on an interval $0<=t<=2$ and \$x(t)...
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### Aliasing problem with pressure data

I have done some pressure measurements of flowing air with transducers that had a frequency response of 5 kHz. The data from these transducer was sampled also with 5 kHz and this is where my problem ...