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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Filter characteristic frequencies of one time series signal dataset and paste/add them into another

I have two categories of a time series signal dataset in the time domain - one "good" and one "bad" category. My goal is to create "fake" bad data by filtering out the ...
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How important or interesting to increase the spatial resolution of linear array for narrow band or broadband radar for SONAR or other areas?

May I request your comments, please? Consider we have a linear array (radar) to detect some targets. The system may be narrowband or broadband. Using broadband we may get better time resolution but ...
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Why is taking the inverse Fourier transform the same as taking the Fourier transform when computing the cepstrum?

Usually, the cepstrum of a signal is introduced as the result of taking the logarithm of its power spectrum, then applying the inverse Fourier transform: $$C_p = |F^{-1}\{\log(|F\{f(t)\}|^2)\}|^2$$ It ...
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Telecommunication with same frequencies

If signal is transmitted with same frequencies they interfers, but why can't we use the technique of encryption and decryption to stop from interfering signals with same frequencies?
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What is the result of taking the real part and imaginary part of a complex signal in the frequency domain?

Suppose that $g(t)$ is a lowpass complex signal with magnitude (solid line) and phase (dashed line) To modulate $g(t)$ into a bandpass equivalent signal $f(t)$ with center frequency $f_c$, we compute ...
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Spectral function value of a frequency above the nyqist limit

this was the question on my today's exam on signals and systems: *We have a continuous function $f(t)$. Its value of the spectral function at an angular frequency of $8000\pi\ rad/s$ is $\frac{1}{...
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52 views

Identifying Instruments within a music file

Say I have a file that contains a few musical instruments, how can Identify the name of each one (ultimate goal) or at least the category they belong to, like wind instruments? For example, if I load ...
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Classifying 2 Classes of Ultrasound Signal Using Machine Learning by Frequency Domain

I have two samples which, when exposed to ultrasound, emit their unique frequency responses. As can be seen in the attached figure, where the exciting frequency is 2.25 MHz, sample 1 emits a strong ...
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How to select parameters suitable parameters for a spectrogram

I have a limited background in DSP but I need to generate a spectrogram of an electrocardiography (ECG). I am using the scipy.signal.spectrogram and I need to set ...
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How to visualize frequency domain of signal with multiples of $f_s$?

Is it possible to visualize signal in frequency domain for frequencies bigger than $f_s$? I'd like to get the plot of some example signal like that: I tried to create some signals in ...
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Recovering phase of harmonics in an arbitrary pulse train

I want to recover the phase of the harmonic components of a pulse train. There's a lot of cool resources out there that talk about recovering power spectra from signals in several ideal and non-ideal ...
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How to use inverse 2D Fourier transform to reconstruct the original image?

I have managed to get the forward Fourier transform of an image to the frequency space like so: But I cannot for the life of me reconstruct the original image from the inverse Fourier transform of ...
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FFT on Pulse Trains with Varying Periodicity

I am looking at FFT on events over the course of a year (~365 days). My data is the number of events in a day. I assign occurrence as a pulse with the amplitude reflecting the number of events. I ...
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Is this an appropriate way to calculate power and relative power for individual spectral bands (EEG, MATLAB)?

I apologize in advance if this is a dumb question, I'm really new to this kind of analysis. Essentially I have my EEG signal (EEG1) and I'd like to calculate the power and the relative power in each ...
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Measuring the frequency and impulse response of an audio recorder

I would like to test the frequency and transient/step response of the Zoom H5 recorder preamps. If possible, I'd also like to test the preamps for the built-in (exchangeable) XY capsule module, but I'...
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Are the sparsity of transform coefficients comparable when their frequency ranges are different?

I have obtained a graph-based Fourier transform from an optimization problem, and for evaluating the sparsity of transform coefficients, I was going to compare it with other transform coefficients ...
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Creating the frequency-spectrum with VC-curves for Building Vibrations measurement

I'm very new to signal processing and can't get ahead: I'm using an Accelerometer to measure the acceleration of i.e. the building vibrations or elements/machinery etc. For creating the spectrum, I ...
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Frequencies calculation of discrete signal in frequency domain

I have some misunderstanding in definition of frequency resolution of the signal. Here it is assumed that the resolution is: $$\hat{f_k}=f_{signal}\cdot T_{sampling}$$ (which is just relation of ...
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Unexpected Sidebands on the Frequency Spectrum

I am working on an alternative approach for a specific signal processing sequence which involves a kind of a test that I am using for justify the mathematical background of the design. The test is ...
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51 views

Under which conditions will windowing with a rectangular window intime always lead oscillations in the spectrum?

I'm going through some conceptual questions about windowing signals. I came across the following: Assume a sinusoidal signal - under which conditions will windowing with a rectangular window ...
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Parameterization of a Idempotent Filter

I'm interested in if there has been research into how to parameterize filters so they are idempotent. I'm looking for the property shown below: $$ h \circledast h = h $$ I searched around and found &...
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misunderstanding of spectral leakage

I want to understand spectral leakage. I understand that whenever we feed $N$ time-samples of a periodic, continuous, signal into a FFT algorithm we are multiplying in time-domain the true periodic, ...
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How to increase the low frequency resolution of spectrum of music signal

I know normal FFT with a fixed window size will introduce leakage and rectangular window function will give me the best main lobe width. For example, with 44100Hz sample rate, 2048 window size, a 64Hz ...
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Why is the error of the frequency estimation dependent on SNR?

Last time, I asked how to estimate the error of the frequency estimation (1) (I want to determine the error as in $f=0.92 \pm 0.013 \; Hz$). I'm analyzing a sample of a continuous signal that was ...
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56 views

The scaling of FFT magnitude and phase

In Matlab, I simulated and graphed out the FFT of a signal composed of three pure sinusoids of distinct magnitudes and phases. Figuring out the scaling of the frequency axis is fairly straightforward ...
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Expression of the sampled spectrum - how to check the writing of a spectral expression?

I'm trying to sample the three voltages below with a period $T=1ms$ $e1(t)=Esin(2πF1t);F1=0,2kHz$ $e2(t)=Esin(2πF2t);F2=1,2kHz$ $e3(t)=Esin(2πF3t);F3=0,8kHz,E=1Volt$ the expression of the sampled ...
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Phasor diagram of Phase modulated signal

While studying the phasor diagrams of Amplitude modulation and Frequency modulation, I am stuck at a problem involving the phasor diagram of an angle modulated signal whose equation is given by $$s(t) ...
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Effect of inserting a single sample on the spectrum

I have read about interpolating 0s uniformly in a time domain sequence and its effect on the resulting spectrum. I am wondering what happens to the spectrum when you insert just one sample (say a 0 or ...
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113 views

Error estimation for frequency

I want to estimate the error my frequency estimation has. I used FFT with a window on a series with 3954 samples, sampled at 40 Hz. I know I can calculate the frequency resolution after Rayleigh's ...
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66 views

How to increase the frequency resolution in FFT?

I'm still learning. I have checked many questions on here similar to mine, but have not found an answer. I'm analyzing the oscillation of a train catenary system. Due to bad sampling frequency and ...
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Finite Precision DFT looks broken

I calculate the FFT of a sine wave. In Matlab I get the result as I would expect with a nice real and imaginary part. (blue is real, red is imaginary) Now I also calculate a FFT on a FPGA with fixed ...
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Python FIR Notch filter applied on both + and - frequency but only need + frequency

I have posted a summary of what I am seeing, I just made a pulse train and testing a notch filter on it as an example only. I also have a complex baseband signal centered on 0 Hz, this complex ...
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Multiplying complex signal with its own complex conjugate transposed copy? [closed]

Let input be a real (audio) signal, and let X be its complex frequency domain representation. What does the output represent when the frequency domain signal is ...
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If either of the 2 signals analyzed did have a DC offset?

If either of the 2 signals analyzed did have a DC offset? A generally speaking, what changes would you see in the analysis?, My answer-If either of the 2 signals analyzed did have a DC offset the ...
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When if an FFT more efficient than Goertzel?

Given a block, $x[n]$, of M samples. Calculating abs(fft(x)).^2 returns the power spectrum of that block through the use of a $M$-point FFT. I can calculate the same using Goertzel's algorithm. At ...
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Get Hilbert marginal spectrum with emd package in python

I want to get the Marginal Hilbert Spectrum in Python using the emd package. You can estimate the Marginal Hilbert Spectrum as where, and A(ω,t) is the time-dependent amplitude modulation and ω ...
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Why does adding a high-pass or low-pass EQ increase volume?

The following three screenshots show the max volume levels (indicated above the VU meter) of Cuckoo by Tipper if played with: No EQ: -0.5db Headroom High Pass EQ: +2.5dB over Low Pass EQ: +0.4dB ...
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how make an equation of a procedure?

Good day to everyone, i have frequency spectrum i selected top 10 peaks of that spectrum i give weightage from 1 to 10 to top 10 frequencies by multiplying the corresponding amplitude by weightage ...
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Units of a Fourier Transform (FFT) and Spectrogram [closed]

I am very interested in analyzing signals in the frequency domain. Units of a Fourier Transform (FFT) when doing Spectral Analysis of a Signal 1.In the previous question, answer the unit for the ...
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Mapping STFT magnitude to sound intensity level

I have a signal for which I have computed my STFT magnitude spectrum in dB. The plot is the following: This is my magnitude spectrum in dB computed with ...
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Power spectrum of a signal in negative frequency domain

I have a signal with fc = 308 kHz and B = 30 kHz and some white noise added. The signal is sampled at samplFreq = 4fc. ...
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84 views

Phase Noise and Multi-carrier Frequency conversion

I have a oscillator with a phase noise mask that was represented in dBc at specific offsets from a carrier. Two options for a multicarrier signal going into a converter, apply the phase noise mask (...
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Limiting Bandwidth for QAM and OFDM signal in MATLAB Simulink

currently im creating an application capable of generating QAM and OFDM signal to be transmitted using SDR. The whole application is implemented in MATLAB Simulink using only code generateable ...
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I have two signals, recorded from the same device. How do I standardize/normalise them?

I essentially have two signals X and Y, recorded with PPG devices. These have been filtered already. I want to standardize(z-score) or min-max scale them but I don't know if I should do this on each ...
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Problem with the output self implemented “ Iterative FFT DIT Radix2 ” algorithm matlab

I´m trying to implement my own FFT with the iterative Radix2 algorithm (I even thought about using the recursive one but it seems Simulink doesn´t allow me to). I tried all of the possible variations ...
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Extract signals with certain frequenceis from a data sample using python

I did not major in signal processing, and I do not know a lot about some possibly very basic facts, so although SE has some questions related to this, I still have some confusion. I am given a data ...
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57 views

dB octave band spectrum

When I was at the University I did some courses about Acoustic. I always seen the dB octave band spectra, as the Fourier Transform of the dB in time. Now looking at some reference in Matlab, I noticed ...
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How to Frequency Modulate an Audio Signal

I've started to learn about FM and I followed this guide to FM a sine wave. I have managed to do it and here is the result: And the code: ...
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Self Quadratic Phase Coupling || What does it really tell us?

I am working on a beginner kind of project, and after processing some data and plotting a lot of bispectrum plots, I found out that a lot of them had peaks on the diagonal fx = fy (where fi denotes ...
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How to extract noise from a signal in order to get both noise power and signal power

I have to implement a function to get an accurate SNR value. For that, I would need a separate noise signal to get the signal power and noise power but I have only one noisy signal (a .wav file.) ...

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