# Questions tagged [frequency-spectrum]

The frequency spectrum of a time-domain signal is a representation of that signal in the frequency domain.

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### Transfer of the signal spectrum to zero frequency

There is a signal at a frequency of 6 kHz-6.5 kHz. Sample rate 40kHz. It is required to transfer it to zero frequency. I counted two arrays cos and sin: ...
1answer
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### Spectrum in real life with Spectrum in theory

as you know it is possible to measure the power spectral density ($|X(f)|^2$) of a certain voltage signal $x(t)$ through a Spectrum Analyzer. As far as I'm concerned, the simplest spectrum analyzer ...
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### Fast Sine Wave Recognition

I have a Sine wave at frequency F1. This signal changes and shifts to frequency F2. In frequency domain I like to find this shift as quickly as possible. (Signal has a lot of random noise and hard to ...
1answer
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### FFT Frequency-Spectrum has noise

I am plotting a Frequency-Amplitude Graph using openGL for the graph and Rosetta FFT implementation for the FFT calculations, I generated a 2 waveform, applied Hanning window, applied FFT and ...
1answer
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### Aliasing in Doppler Radar

my book about RADAR says that: If a Continuous wave radar sends a sine wave at frequency $f_T$ to a moving object (at speed V), a frequency $f_R$ is received. Their difference is called Doppler ...
2answers
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### The FFT of a sine wave with varying frequency and constant amplitude does not show a plateau, why?

I want to use python to see what the audio response of a speaker is. This would be done by comparing the output of the speaker measured with a microphone to the given input. That means that for both ...
3answers
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### Why would a time shifted signal have a higher maximum frequency than an unshifted one?

I´m reading the book Numerical Simulation of Optical Wave Propagation by Jason Schmidt. In section 2.1-2.2, the author performs the FFT of a centered and a shifted Gaussian pulse and makes the ...
4answers
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### Meaning of frequency and bandwidth of a signal, despite the fact that we do not know the signal

First of all, I am completely new to the domain of signal processing. As far as I know, a signal can be represented with an infinite integral of infinitesimal complex exponentials, which is known as a ...
1answer
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### Does the duration of a signal affect its frequency component's amplitude? Also, does the sampling frequency affect the power of a signal?

I have two questions that are bugging me: Does the duration of an audio signal affect the amplitude of frequency components of that same signal? For example, I am recording the sound of a fan using a ...
1answer
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### Performing root-music, how do i retrieve frequency and phase data of a signal?

I'm trying an alternative method to the classical fft to do signal analysis. I perform root-MUSIC on a certain known signal + noise in matlab with the function 'rootmusic'. This gives gives the signal ...
1answer
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### Brute forcing an aperiodic s-shaped signal to be periodic by mirroring it before performing FFT

I have an aperiodic signal of an s-shape in the time-domain that I would like to filter and calculate the derivative of using the FFT. The jump at the end of the s-shape has, of course, a strong ...
0answers
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### Periodogram/PSD from FFT amplitude

I have performed a STFT for signals and obtained the amplitude through ...
5answers
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### A DFT “periodic inputs” question

Why do people say that the fast Fourier transform (FFT) “views”, or “interprets”, or “assumes” its input sequence is periodic? I ask this question because the activities of viewing, interpreting, and ...
1answer
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### How to interpret a spectrum with FFT mirroring?

I have this code which interprets a few data points on magnetic field strength into a spectrum, as shown below: ...
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### Spectral peak location estimation using complex DFT

In this paper a simple method to estimate a spectral peak is proposed, by using quadratic interpolation between three samples of the DFT of the signal. Namely, the position of the peak relative to the ...
1answer
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### How does Music algorithm differ from simple DFT/FFT for frequency estimation?

I would like to know why would someone choose to use Music algorithm from frequency estimation when one can simply use DFT/FFT which are much simpler. What is the intuitive way for understanding Music ...
1answer
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### Why do I see a frequency shift of the peak between the S11 and impedance response?

I have a resonator I am trying to characterize, and the S11-Plot gives me a slightly different center (resonant) frequency than that of the Z-Plot. These measurements were taken simultaneously and ...
1answer
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### Why do I see a frequency shift from center when transmitting a QPSK via USRP with GNU Radio?

I am transmitting a QPSK signal via GRC and when I look at it on the spectrum analyzer, the signal is shifted away from my center frequency. This shift increases the higher the center frequency (i.e. ...
2answers
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### Difference in signal Spectrum

[ Here are two figures from the same signal, the 2nd one(B) is after digital predistortion at transmitter end. How can you describe it? What are the improvements and advantages of this technique? Much ...
0answers
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### Power Spectral Density vs Frequency Domain separation

I am just starting to learn about Power Spectral Density (PSD). What I'm reading is that it is possible to separate PSD masks if they are isolated, even if the frequencies do overlap. My understanding ...
1answer
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### Spectrogram without using stft

Can I use any kind of transform to make spectrogram, not just stft? Is it possible to get the spectrograms of a signal without using stft? What difference does it make if I calculate the frequency ...
1answer
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### What is the significance of the linear phase in the phase response of an M-point moving average filter?

I have plotted the magnitude and the phase responses of an M-point moving average filter, the following are the plots when M = 10: We can observe that corresponding to every lobe in the magnitude ...
1answer
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### Why Does ASK Modulation Create Fourier Sidebands?

I know why analog amplitude modulation has side bands, it is related to (fc+fd) and (fc-fd). But what about DAM? ASK(DAM) is a type of digital modulation, and there are only two state: carrier signal ...