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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52 views

Why Cramér spectral representation and not DTFT for stochastic process

In a lot of time-series analysis references I find (written by mathematicians or statisticians rather than engineers), I find the following signal decomposition for a stochastic process, termed the &...
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30 views

Can largest-triangle-three-buckets downsampling method used with fourier transformed signal?

I've been reading on the largest-triangle-three-buckets downsampling method for downsampling. Though it was originally published in the thesis "Downsampling Time Series for Visual Representation&...
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Spectral Inversion in Zero IF Receivers

Is spectral inversion possible in zero IF receivers? If yes, then can somebody explain with an example how that happens and what can be done to correct it. The following problem can be taken as ...
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1answer
118 views

A-weighted Digital Filter for 1/3rd Octave Band Analysis

I want to do a 1/3rd Octave band analysis on a noise signal. But the sound pressure levels should be in dB(A), i.e., and it should be A-weighted. For this, I am using the A-weight function from this ...
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1answer
80 views

Generating spectrum of a spectrum / identifying frequencies of ripples present in a spectrum

I have a spectrum as shown. The x-axis is frequency in GHz. The spectrum shows ripples that we can visually quantify as ~50 MHz ripples. I am looking for a method to calculate the frequency of these ...
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29 views

Match an Equalizer Curve

I’ve passed a sine sweep wave file into an equalizer plugin I have, now I want to model it in matlab so that I can ‘copy’ the equalizer setting sound. I’ve both in.wav and out.wav audio files and ...
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1answer
55 views

Why use PSD to analyze a signal instead of its Fourier Transform?

Let's imagine I have a perfectly known signal $s(t)$ and I want to analyze its frequency components. I noticed that mostly everyone would use the PSD of $s(t)$ to do that, instead of simply use the ...
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1answer
47 views

Steady state variance of a stochastic differential equation - relation between the frequency and time domains

Consider a stochastic differential equation: $$ dx(t) = a x(t)dt + b y(t)dt \quad (1) $$ where $y(t)$ is a stochastic process satisfying $\langle y(t)y(t')\rangle = \delta(t-t')$. We will assume that ...
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28 views

What is the “Energy” equivalent of the Magnitude Spectrum

I have a semantic issue regarding the discrete spectrum $X[k]$ of a time domain signal with limited length $x[n]$, so we're talking about the FFT. Now, when I what to compare the bandwidth and ...
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1answer
78 views

Auto Tune Shifting

So i have an algorithm that gets the fundamental frequency of windows, and can shift the pitch of each window as well (by a factor of x). For example. if x is 2 and the f0 is 440, the resulting f0 ...
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1answer
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About the orthogonality of columns in Zadoff-Chu matrix

As we know that Zadoff-Chu matrix is similar to Walsh-Hadamard matrix where every columns in those matrices is orthogonal with the any other column. For Walsh-Hadmard matrix, the orthogonality is ...
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PSD Accelerometer and Gyroscope

I used Xsens IMU and collected 1 Hour static data for accelerometer and gyroscope. I used the pwelch analysis in matlab to calculate the onsided PSD. The plots looks the following: How do I ...
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56 views

Wavelets vs Fourier Transforms

It's supposed that computing a spectrogram for a signal is faster using wavelets. However, wavelets need to be applied to the signal for every time step and frequency, giving the implementation a time ...
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44 views

Why does the frequency in fft plot of the baseband modulated signal isn't changing at the receiver

I have designed a transceiver system for cellular frequencies(800MHz). On the receiver side, I have converted the band signal to baseband signal through digital mixing. I have added the Inphase and Q ...
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26 views

log spectral distance interpretation

I am using the log spectral distance (LSD) as a metric to evaluate signals. I have 2 completely different signals pairs I compared. Pair (A,B) : signal A as pretty similar to B. There are only very ...
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1answer
56 views

Pitch shifting with bins creating large feedback

I am attempting to create a pitch correction algorithm. I started by performing a test. The test goes as such: Get WAV file Split it into bins of size n (512 in my case) Shift each bin by 2 semitones ...
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1answer
22 views

bandwidth vs. bandwidth range

As known, Bandwidth is the difference between the upper and lower frequencies in a continuous band of frequencies. OK, what means when saying that bandwidth range is 15 ~ 20 KHz ? Does that mean that ...
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1answer
40 views

Smoothing PSD plot

I am currently working with a signal, and I am interested in plotting its spectra. I have used python, I have computed the signal values, and I have an array that has the time-series values of the ...
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31 views

How to determine number of observations based on measurement frequency?

So I'm working on a problem where I'm measuring a signal with two different instruments -- one is a low frequency measurement system (1 Hz), and the other is a high frequency measurement system (200 ...
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1answer
25 views

RF Downconversion using Heterodyne Principle

after a RF down-conversion using heterodyning principle, will there be an information loss? If we translate to a fixed IF frequency, is there is an intuitive way of explain that the information can be ...
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35 views

How to take the inverse FFT of Welch's power spectral density in Python?

I have calculated the power spectral density of a weakly-stationary signal using Welch's method (as implemented by scipy.signal.welch in Python), and am looking to take the inverse Fourier transform ...
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1answer
37 views

Carrier frequency offset estimation for QPSK and asymmetrical spectrum

I am working on estimation of carrier frequency offset for QPSK data from a satellite. From my understanding, there are two main approaches: either remove data from the carrier (by taking the fourth ...
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2answers
32 views

Digital filtering based on frequency component amplitude… why not?

I've got a very general question. I've just implemented a filter working in frequency domain that simply cuts every frequency component whose modulus amplitude falls below a certain threshold value. ...
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1answer
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What is role of BW and frequency in internet speeds?

First the bandwidth (BW): It is the amount of data that can be transferred simultaneously.just like more no. of highway lanes so that many cars can travel side by side simultaneously. Frequency It ...
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1answer
50 views

Blackman-Tukey Autopower equation

I am looking over Blackman-Tukey method for Autopower. It uses the DFT after a window is applied on a autocorrelation. $$ Power Spectrum = \frac1{2\pi} \ \sum_{(k=-(N-1))}^{N-1} w[k] R[k] e^{-i\...
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1answer
47 views

Why there is a peak at zero frequency?

I have a very simple code for ploting frequency spectrum of a signal in MATLAB. My center frequency is at 5e6 but I see a much higher peak at zero frequency despite the fact that I remove DC component ...
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3answers
68 views

How do you sub-sample an FFT?

I'm currently trying to understand this paper on a Sparse Fourier Transform. On page four, there is a section on a sub-sampled FFT. The purpose of this section is to show that you can compute a sub-...
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33 views

frequencies in frequency spectrum with no correlation together

I have a lack of understanding of the following questions: If I have a signal from a motor that is recorded with an accelerometer. And the rotating speed of the motor is 150Hz(rpm 9000 ), I can see in ...
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2answers
85 views

How to properly smooth the phase of a spectrum (or any unit-complex function)

I want to smooth the phase of a measured (transfer) spectrum without destroying unit-complexity of the phase factor. Suppose $$f:\mathbb{R}\to \mathbb{C}\qquad , \qquad f(\omega)=r(\omega)\cdot {\rm e}...
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1answer
16 views

Is the power or root-power scale correct for FFT analysis of an audio file?

I wrote Python scripts to create a spectrum analysis of audio files. The goal is to compare multiple spectrums to get the dB difference at certain frequencies. When I started using the Sonic ...
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1answer
24 views

What is spectrum permutation?

This paper refers to the concept of "spectrum perumutation" on page 4. I'm having a difficult time understanding what it means to permuate a signal. This is mainly due to the fact I don't understand ...
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1answer
46 views

how many things Can they be done with a spectrogram?

I found some things that can be done with a spectrogram. filter frequencies by setting the bins to zero observe what frequencies make up the signal. observe the energy or amplitude of each frequency, ...
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What is the origin of the line shape in a Marginal Hilbert Spectrum

When calculating the marginal Hilbert spectrum of a discretely sampled harmonic oscillation (sine wave), I have found that the peak in the spectrum has a roughly Lorentzian line shape, albeit ...
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Why does the Marginal Hilbert Spectrum of an anharmonic oscillator have two peaks?

I've been looking at the marginal Hilbert Spectra of both the simple harmonic oscillator and the anharmonic Morse oscillator. I have found that while the SHO has a marginal spectrum with a single and ...
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31 views

Why is there a difference in the spectrum of an audio file between Sonic Visualizer and my Python script?

I am working on a script which is creating a spectrum analysis from an audio file using SciPy and NumPy. Before I started, I analyzed the file using Sonic Visualizer, which got me the following result:...
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1answer
32 views

How to convert my transfer function to the frequency domain

I have the following transfer function in the time domain: $h\left(t\right) = B x\left(t\right) + a x^2\left(t\right) + b x^3\left(t\right)$. My simulation is in the frequency domain, so I would ...
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2answers
39 views

difference in spectrum

First I defined 5 signals with same length (40 samples) with different frequency and sampling frequencies, then I've put them together like [X1 X2...] and took it's fourier transform and the result is ...
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43 views

What is the best way to detect rectangular pulse for AFSK demodulation?

I've got a WAV file with a rectangular pulses coding zeros and ones. By specification, a 1 bit is a 320 microseconds wide rectangle, and a 0 bit is a 640 microseconds. So basically the idea is to ...
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3answers
837 views

Understanding FFTs for simple Sin / Cos

this is my first question in this forum, and although I read several threads on this side and googled a lot I could not find the answer to my question (maybe it is too basic)? For anyone reading this ...
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Linear Kernel seems to be only Kernel to predict Class from Spectral Data in Support Vector Machine

I made a Support Vector Machine in Python using the sklearn library. The data I am using is Amplitude vs Frequency for 200-520 kHz with a 0.33 kHz step. My input data is the amplitude value for my n-...
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GPS Acquisition Graphs [closed]

I am trying to generate GPS Acquisition signals using frequency code phase search acquisition. I generated C/A gold codes and digitised at 16.368e6 MHz(sampling frequency) I generated carrier signals ...
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19 views

Noise floor flatness in IQ FFT window

I am doing a simple $P_{in}$ - $P_{out}$ linearity test for my RF generator/receiver system. The generator provides an IQ modulated CW single tone with $P = - 80dBm$ at 1 GHz. If we look at the RF ...
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1answer
17 views

Difference in frequency spectrum of continuous time signal and discrete time signal?

I am studying chapter 4 of book signal processing first There i came across a concept which says that(what i have understood)the spectrum of continuous time signal has limited number of lines while ...
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1answer
47 views

How to difference a loud sound (playing notes), from a soft noise in spectrum. (Pitch detection with bass)

I'm trying a program that outputs the bass line that you are playing. I have some arrays from a big one with the sound in time domain, that are splited (Hann window). Later, I do the FFT, then I get ...
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1answer
44 views

Why does my digital upconversion result in two tones?

I am using Xilinx's RFSoC in I/Q mode. The important point is that in the digital space I have real and complex samples. I take the incoming data and multiply it by a complex sinusoid. In my test ...
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1answer
33 views

Confusing regarding triangular wave vs square wave?

I am reading signal processing first by Mcclellan. In chapter 3, I came across the term "discontinous" as shown underlined in attached photo. Apparently "discontinuous" means having a gap/break but ...
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2answers
64 views

Confused in Smoothing a signal in the Frequency domain

First of all i am new in DSP, so i have no solid education in the field. I have convert my time domain acceleration-seismic data to frequency using DFT and i am trying to smooth the DFT data, in ...
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1answer
72 views

What is issue in square wave reconstruction?

As shown in attached photo: What is the reason that the approximate square wave $$x_N (t)$$ at right side is not like the original $$x(t)$$ at left side .? Is the only reason is that number of ...
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1answer
45 views

Is it true that each and every signal has multiple frequency components?

Usually when we observe spectrum of a signal,we see multiple frequency components, each having different contribution to amplitude But is it true that each and every signal has multiple frequency ...

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