Questions tagged [frequency]

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

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96 views

Why a DFT of two sinusoids is very noisy even with frequency sampling 5 times higher?

I've set up this case to try to understand DFT implementing a real case in Excel Frame Size $\;\color{blue}{(T = 5 \; s})$ Time Sampling $\;\color{blue}{(T_S = 0.1 \; s})$ Block Size $\;\color{blue}{(...
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Why is it called continuous-time frequency?

I'm just wondering about the CTFT. My lecturer refers to capital Omega $\Omega$ in the following as being the continuous-time frequency: Why is it called continuous-time frequency here but in the ...
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71 views

Break a signal into segments, add them together and then perform an FFT on the result

If you break a 4 second signal into 0.5 second segments, add them together and then perform an FFT on the resultant 0.5 second data. Will the FFT / frequency spectrum be the simlar to an FFT on the ...
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Frequency translation with FFT

I'm new to DSP and I would like to make an SDR receiver. For this I want to shift bins in the frequency domain in order to bring to 0Hz any portion of the base band spectrum (I know that there are ...
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254 views

Carrier Frequency Offset, Rotating Constellation and Correlator

I have been further reading up on carrier recovery methods and something is not clear to me: It's written that a carrier frequency offset results in a rotating constellation diagram but if you are ...
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581 views

What does it mean for a function to have frequencies?

In a lecture, my professor mentioned that $\cos$ has two frequencies. I see that using the inverse Euler's formula we can express $\cos$ as a some linear combination of complex exponentials, each with ...
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397 views

Why do frequencies of analog signals range from $-\infty$ to $\infty$ while frequencies of digital signals are restricted to $[0,2\pi]$?

In Fourier analysis while dealing with discrete-time signals, frequencies range from $0$ to $2\pi$ why? Intuitively how can i understand it?
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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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45 views

Intuitive understanding of frequency

I know that $f = \frac{\text{cycles}}{\text{unit of time}}$ and I know that period $T = \text{time it takes to complete one cycle}$. So if we take the definition $f = \frac{1}{T} = \frac{\text{1 ...
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I'm confused about the notion of frequency when it comes to arbitrary data

In signal processing class we keep learning about how it's so useful to bring things into the frequency domain instead of the time or space domain but I'm very confused about what the motivation is or ...
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99 views

How range of the signal increases when modulation is done? [closed]

I am very confused because we know by increasing frequency we decrease the wavelength hence the distance covered will be very less but when we modulate a signal we are basically increasing the signal ...
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351 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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How do I generate sine waves with MATLAB’s max operator and the plot the resulting values in dB versus log frequency? [closed]

I just start learning about matlab. Im very confuse with this. Can anyone gives me such an example solution or any kind of help? HINT: Put the desired input frequencies in an array and use a for-loop ...
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1answer
377 views

How can I determine the order of filter?

This is my first study about signal analysing. I'm very confused about filter order. My problem is how can I know whether its 12-th order, or 2nd order like the book says so? I already knew that slope ...
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35 views

Is there just a carrier in each frequency band in FDMA?

The figure is the FDMA,and i know that FDMA is that dividing the bandwidth into many blocks(frequency band),i want to ask Is there just a carrier in each frequency band in FDMA?i mean one carrier for ...
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Modulation of real-valued signal

I have one doubt according to modulation of a real signal. there are so many examples where the real signal was modulated with frequency bigger then 0. Why the signal could not be putted in f=0? is ...
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125 views

Estimation of Two Closely Spaced Frequencies?

What is the best frequency estimation algorithm for two closely spaced frequencies in term of the minimum frequency spacing achieved?
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133 views

Efficient calculation of exact frequency from a broad frequency range (1 Hz - 1000 Hz)

I have some input signal sampled at 1-10 MS/s. Let's assume that it contains one strong frequency component (with frequency anywhere in the range from 1 Hz to 1000 Hz or even higher, changing over ...
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281 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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149 views

How to compute impulse and frequency response of Flanger?

I have to the implementation of a Flanger effect on Matlab, buy previously I have to plot its frequency response and impulse response. The difference equation is $y[n]=x[n]+a\cdot x[n-d[n]]$ where $a$...
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The grid frequencies In the design of a digital filter

I want to find many difference 'h' with same group delay and length filter using this code : https://gist.github.com/mattdsp/17f508d2b368db61f47689e4622d8841/c1518f22a5aa451951601b56c5d9f72743868bfe ...
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213 views

how to calculate the maximum obtainable directivity for a microphone array?

Introduction The relationship between the maximum obtainable directivity and aperture of an antenna is described by: $$ D = \frac{4\pi A_e}{\lambda^2} $$ Where $D$ is the directivity, $A_e$ the ...
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1answer
1k views

Numpy fft2 frequency shift

I don't understand how to make frequency shift in fft2 or higher dimensions. Could anyone explain it, please? import numpy as np import matplotlib.pyplot as plt from mpl_toolkits.mplot3d import ...
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1answer
35 views

Non-decaying Harmonics in Vibration Signal

I am analyzing vibration data collected by an accelerometer positioned in a stamp press machine. The fundamental frequency is around 10 Hz. The problem here is that when I take the FFT of the data I ...
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1answer
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How to calculate wave length

Given that 30GHz to 300GHz is considered mm wave spectrum which can be used for high-speed wireless communication such as 5G. My question is how to calculate the wavelength if we know the frequency? I ...
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How can I design a PI controller for a closed loop system, which requires a bandwidth equal to the natural frequency and a set Phase Margin?

For a school project I have to hand in a small report on a this problem. I've been studying so much for it but right now I'm just mixing up everything I've seen and just don't know where to start. I'd ...
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84 views

Equalize Speaker using impulse response

So I have this school project where my aim is to improve a loudspeaker in general, my idea is to mesure the impulse response of the room using a mic, then use this mesure to conceive a loudspeaker ...
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285 views

The concept of normalized frequency

This question has already been asked and answered, but the motivation behind the use of normalized frequency units still evades me. The Discrete Time Fourier Transform $$X(\tilde{ \omega }) = \sum_{n=...
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Estimating frequency when there's little isolation between signal and noise frequencies

Say I have a signal which is guaranteed to have a frequency between 110-120 Hz but is corrupted by interference signals that're very close to this frequency range. For example, let the interference ...
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434 views

Instantaneous Frequency Estimation by Hilbert Transform - Theoretical Justification and Proof

I would like to better understand why the instantaneous frequency estimation by Hilbert transformation works (and especially why it doesn't work / lead to precise results in many cases). The ...
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1answer
212 views

Wavelet central frequency

What is the definition of the central frequency of a Wavelet and the bandwidth of a Wavelet? How do they affect the resultant waveform of the wavelet? Thanks.
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Evauating response to $x(n) = \sin{2\pi\frac{1}{4}n}$ given the system function

Let the input signal $x(n) = \sin{2\pi\frac{1}{4}n}$ go in to the system described by: $$y(n) - y(n-1)+\frac{3}{16}y(n-2) =x(n).$$ What is the output signal? I've calculated the system function $H(...
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Pitch perception - Why does our ear not directly detect the missing fundamental frequency?

My motivation for this question is related to biological phenomenon of our inner ear, so I initially posted in the biology community, but I suspect the answer has a DSP explanation, so I figured this ...
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Does anyone recognize this modulation?

I'm trying to extract the code of my garage remote, but i have some difficulty to find witch modulation has been used. At first I thought it was a simple digital modulation, but there is some strange ...
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83 views

How to connect $\omega$ in time domain to physical frequency?

I'm a noobie to DSP, and recently I'm learning DSP for an urgent assignment. There's a problem that has been confused me for days. I hope anybody could shed some light on it, although it might seem to ...
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209 views

How to see the amplitude of each frequency?

do you know software that exports spectrograms to images of 500x22000 pixels? all the spectrograms that I know show diffused frequencies and it does not look very good I just want to see the amplitude ...
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Frequency extracted from MATLAB's $\tt fft$ is not very accurate

As a test I made up a sine wave in MATLAB of this form y = 5*sin((2 * pi * freq).*x + 1.4) - 6; where freq is ...
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477 views

When listening in to an AM signals of various frequencies, how do we exactly tune in?

Alright, so I read on AM and Double Sideband AM, but I don't the more fundamental idea - the frequencies. Frequency is just: $ \frac{1}{T} $, where T is period So difference between 5 Hz and 30 Hz ...
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254 views

Phase of FMCW linear chirp

I'm doing a project involving FMCW linear chirp signals. Given the phase $\phi = 2\pi\frac{k}{2}t^{2} + 2\pi f_{c} t + \theta$ where $k$ is the frequency increase rate. When transmitting ...
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12kHz sine or square. I can hear the difference - why?

I can hear 12kHz sinewave but not 22kHz. A 12kHz squarewave has the fundamental and harmonics I think. But the first harmonic is outside my hearing range, so how come I can hear the difference ...
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Very basic question about how we define frequency in signal processing

When talking about general periodic continuous-time signals for which $$x(t + T_0) = x(t)$$ where $T_0$ is the fundamental period we define the fundamental frequency $\omega_0$ as $\omega_0 = 2\pi/T_0$...
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How do i select my frequency range to plot when fft is made on time domain

I have a vibration signal that i need to convert from time domain to frequency domain using fft in python. ...
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154 views

i want to mute a particular frequency in real time audio

i want to mute a particular frequency range in real time audio for eg: in audio signal frequency above 3 kHz should be muted for specific interval of time.
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Basic sampling excercise - unsure of rationale informing np.arange parameters for time array

I'm extremely new to DSP, so I apologise if it's a very basic question. I'm having issues understanding the following exercise: "Create an array of 201 samples containing a sin wave with a frequency ...
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107 views

Matlab produces two unknown spikes in custom FFT

I'm making a relatively small Cooley–Tukey FFT in Matlab and I'm noticing unusual spikes in the result compared with Matlab's own FFT. The figure below shows the signal flow of my program. It's a ...
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How to best separate my signal into frequency regions?

I have a signal with frequencies betwwen [0.5,500] Hz and i want to create a filter to best separate the signal in the following regions: [0.5-3]Hz [3-8]Hz [8-13]Hz [13-30]Hz [30-500]Hz My ...
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How to make bode plot when output signal changes amplitude?

When I do frequency analysis on my feedback controlled system and the controller is really tightly tuned, I get a frequency response that looks like this: Blue is excitation signal and green is ...
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Getting Frequencies Corresponding to Peaks In FFT Plot - MATLAB

So I'm currently working on a project where I need to find the frequencies for specific peaks in my FFT plot of an audio file. However, I'm not sure how to actually get the frequencies that correspond ...
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Why do we need to find the frequency response of FIR filter? [closed]

Sorry about my unscientific and informal question but i have an exam $3$ days later and i need to learn this. Can anyone explain clearly, shortly and without formula Why do we need to find the ...
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Highest frequency of collected force signal [closed]

I have collected force at the footrest during paddling at two occasions. During one occasion I accidently collected the force signals at 150 Hz instead of 1500 Hz. During the other time the data was ...