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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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how to obtain the throughput expression for NOMA system

For a NOMA system of three users(i) with respect to 5 subcarriers(j) form a cluster on the same frequency the how to form the throughput expression inorder to calculate the performance. similarly for ...
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What does “same spectrum resource” mean in a NOMA system

In a NOMA system, multiple users are multiplexed into transmission power domain and then non orthogonally scheduled for transmission on the same spectrum resource. With respect to the statement what ...
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2answers
42 views

why is my FFT magnitude of real time recording so volatile?

My goal is to do spectrum analysis of a gear motor. I used Python with the Pyaudio package and made a crude spectrum analyzer that displays the FFT as the sound is being recorded. I recorded 10 ...
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4answers
44 views

Spectrum estimation

When calculating the spectrum estimation of a signal $x(t)$ with random noise, why do we use ($E$ for expectation) $$E[|X(\omega)|^2]$$ but not $$E[|X(\omega)|] $$ If it is because the random ...
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How does discrete spectral moment relate to continuous spectral moment?

It is said in discrete/digital signal processing that $r$th spectral moment of signal $x[n]$ is defined as: $$\sum_{n=-\infty}^{\infty}n^r x[n]$$ But how does this relate to usual continuous $r$th ...
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35 views

Real time spectrum analyzer display problem

In real time spectrum analyzers, it is said that data is captured without any loss in time domain and user can see any event that happend in the captured time. In case of high bandwidth and low ...
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1answer
31 views

Can spectral density be a complex quantity?

I have a signal ($S(t)$) which is product of a Gaussian ($G(t)$) and a random phase function ($e^{i\theta(t)}$, here $\theta(t)$ is a random function), as shown below $S(t)=G(t).e^{i\theta(t)}$ If I ...
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1answer
39 views

Fourier like spectral analysis with uneven intervals and redesigned DFT matrix

I intended to use a discrete Fourier transform (DFT) on a time series sampled at uneven intervals. What I did was to calculate a DFT matrix where the elements are the values at the uneven locations ...
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33 views

Sampling: How should I sketch a signal spectrum?

As revision, I am going through Signals and Systems, and in Section 7.1the authors are sketching representative spectra for x(t) and ...
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How to plot noise shaped spectrum of First order Incremental Sigma Delta ADC's output?

A little background: This question is about viewing the output spectrum of incremental delta sigma modulators (IDSM). IDSM is a subcategory of general delta sigma modulators where the integrators are ...
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1answer
34 views

Will noise cancellation with playstation eye improve my spectral analysis?

Im doing some beginners spectral analysis for a homemade reactive RGB LED project and was thinking of ways to improve the accuracy of the audio analysis. Im using a Playstation eye with a Raspberry Pi ...
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system identification: MATLAB tfestimate gives different results for different Fs

So I have an experimental data; A is a chirp signal (sweep sine wave) and B is the response of the system. I identify the system as follows in MATLAB: ...
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1answer
24 views

Frequency spectra of a sampled process

I have a process $X$ with frequency spectra I sample this process with sampling frequency $f_s = 2$. What will the frequency spectra $R_z(f)$ of the sampled process $Z$ look like? I realize that ...
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1answer
25 views

What's the right scale to represent a frequency spectrum?

To represent a 16 bits temporal spectrum, it's "easy" : my scale is going from -32000 to +32000. But What's the scale for a frequency spectrum ? I made that try : I calculated a pure single frequency ...
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18 views

Removing outlier data points from frequency-domain signal

Hello signal processing stack exchange, I have a complex frequency-domain signal representing the impulse response of a physical system over some range of frequency space. As an artifact of the ...
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2answers
76 views

How to increase resolution of FFT?

I have an input signal in the ( 0 - 20 kHz ) frequency range . When i sample this signal maximum sampling frequency is around 40 kHz . When i calculate the FFT using 1024 points i got resolution of ...
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Best Way to Extract Frequency from Signal [closed]

I want to send signal that compound from 16 different frequency over GSM. The problem is the GSM network is very noisy and I have only 400-3400 hz frequency available for use. I try using fft ...
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how a non-constant FPS affects the spectral analysis of RGB signals

I am doing low-level research of remote plethysmography imaging (without a concrete target application, it could be heart rate monitoring, emotion recognition). I would like to study the effect of the ...
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Proof that the Lomb-Scargle periodogram reduces to the classical periodogram when the sample is equally spaced

If we have a equally spaced sample, we can use the conventionally used periodogram: $$P_x(\omega) = \frac{1}{N_0}\left[\left(\sum_j X_j\cos \omega t_j\right)^2+\left(\sum_j X_j\sin \omega t_j\right)^...
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56 views

Frequency resolution - resolution BW relation for different window functions

I am working on FFT based spectrum analyser and I am not sure how to proceed calculating the RBW. According to the document (page 20) in the link, RBW described as $k \frac{f_s}N$ where $f_s$ ...
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1answer
55 views

How to estimate the frequency characteristics of a nonlinear chirp?

Given a partial time-domain recording of a noise-corrupted chirp that asymptotically approaches a frequency, and the function that determines the non-linearity, how can I accurately estimate the final ...
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0answers
25 views

Determine 3 most dominant frequencies in a signal, PSD or just the absolute value of a Fourier transform?

I have a noisy ECG signal recorded for 5 minutes. My goal is to determine heart rate every 2 seconds. To find out 3 most dominant heart rates (Beats per minute) in a 2s-signal should I calculate its ...
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25 views

Power spectrum of a signal time-shifted by a stochastic delay

I'm trying to analytically compute the power spectral density (PSD) of a stochastic noise, say $p(t)$, which is time-shifted by a delay which is the sum of a constant delay $dT$ and a stochastic part $...
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1answer
45 views

Power spectrum RMS or peak

I’m a newbie and wondering if I calculate the power spectrum from the peak amplitude or from the amplitude rms ? This is my matlab script so far: ...
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0answers
20 views

Finding sampling rate of signal using reference signal with same characteristics and known sampling rate

I have two (fairly long - about 100k samples) signals $A$ and $B$ where $A$ has a known sampling rate. $B$'s sampling rate is unknown but it is coming from a source with same or very similar (spectral)...
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46 views

Frequency Modulation to arbitrary Audio signals [closed]

I understand how FM synthesis works, but I was wondering how to FM arbitrary samples or part of samples. I.E any frame of audio samples. Further more the modulator can itself be an arbitrary frame of ...
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1answer
45 views

Spectral averaging without phase information

In the context of signal averaging to reduce uncorrelated noise: Is it possible to perform signal averaging from just the magnitude spectrum of certain signals? Or that would only work if we know ...
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1answer
79 views

What is the difference between Spectrogram and Scalogram?

Could someone please explain the difference between the two? Spectrogram: A visual representation of the spectrum of a sound changing through time. Scalogram: (signal processing) A visual ...
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47 views

Matching two signals with small time drift

I have two time-domain signals sampled at 100 Hz that were measured using two different oscillators and therefore have a time drift between them. I have two synchronization points, one at the start ...
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1answer
33 views

Advantage of using DFT and IDFT hardware for modulation

I am doing a course in communications and while discussing multicaruer modulation to break down a signal into smaller bandwidths (for BW to be less than coherence bandwidth), there was mention of ...
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1answer
52 views

Calculating SFDR from FFT of ADC output

A few months ago, as part of my summer internship, I had performed interfacing of an ADC with FPGA (Zynq-7000). The goal was to take an analog signal from a signal generator, feed it to the ADC and ...
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2answers
46 views

Accurate description of the spectrum of sinusoid waveform added with WGN?

The transmitting signal is $$ s(t) = \sin(20\pi t)+\sin(40\pi t)+\sin(60\pi t) $$ The received signal after AWGN channel is $$ r(t) = s(t)+n(t) $$ where the variance of noise $n(t)$ is $\sigma^2$. ...
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Plot the spectrum and n-point DFT

$x_a(t) = \cos(2\pi f_a t)$ was sampled with sampling period $T_s$. Plot the { spectrum | $N$-point DFT } of $x[n]$ ($f_a$, $T_s$ or $f_s$ given, $N$ given - whole number of periods or not). Anyone ...
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2answers
58 views

How to plot and normalize a spectrum in matlab

I am given the coefficients of an FIR filter. I have created its impulse response through a convolution with a unit pulse. Now I want to plot the frequency spectrum. I perform zero-padding and ...
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0answers
37 views

Frequency bins too powerful at the start and at the end of each sample computed DFT data

I've taken the following link http://coding-geek.com/how-shazam-works/#comments as a project to start practising and learning signal processing and python programming for me to get started in speech ...
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1answer
75 views

Spectrogram of 493 signals at a time [closed]

I have been working with some seismic data and recently submitted a paper to a journal. My seismic data has 493 traces: each trace are 8300 seconds long with sampling frequency of 2000 Hz. One of ...
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1answer
53 views

How can I get the power of a specific frequency band after FFT?

I need help with my matlab code. I have recorded EEG data and now I want to analyse it in matlab. I want to find the mean power of specific frequency ranges (theta: 4-8 Hz,alpha: 8-12Hz etc.). For ...
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1answer
65 views

Spectrogram Interpretation

I collected vibration data (amplitude and time) on a component that was attached to an engine. Using MATLAB I plotted a spectrogram to see what frequencies it vibrated at. The code: ...
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2answers
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difficulty in understanding amplitude, frequency and period

I have difficulty in understanding of some fundamental terms as amplitude. Can be there more than one amplitude for a signal? The following expression is combination of 3 sinusoidal signal, so are ...
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0answers
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Can I have some feedback on this research paper on vibration diagnostics?

I have submitted this paper "Detecting a Valve Spring Failure of a Piston Compressor with the Help of the Vibration Monitoring" to figshare.com. I would like to get some feedback on the methodology ...
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1answer
99 views

Spectrum of Cosine in Complex Form

The complex exponential form of cosine $$\cos(k \omega t) = \tfrac{1}{2} e^{i k \omega t} + \tfrac{1}{2} e^{-i k \omega t}$$ The trigonometric spectrum of $\cos(k \omega t)$ is single amplitude of ...
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3answers
35 views

Ideal sampling of audio signals-Periodic spectrum [duplicate]

When applying ideal sampling on audio singals, why is the spectrum periodic ?
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1answer
314 views

Practical book in C [duplicate]

Is there any practical “go to” book that demonstrates the main dsp methods for time series written in C for practical applications? (Doesn’t have to be for hardware, but for any raw data such as ...
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1answer
26 views

Equalizing a temporal sound signal with a convolution

This question is more or less the following of a previous question. The aim is to equalize some sounds signals. By equalizing, I mean increasing or decreasing some frequency ranges, a bit like an ...
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0answers
49 views

How to calculate the Fourier Transform of a solvable chaos waveform?

Recently I am stucking in frequency estimation of a solvable chaos waveform. Its local analytic expression in time domain is $$ z(t)=s_m(u_m-s_m)e^{\beta(t-mT)}\cos(\omega_0 t+\varphi),mT\leq t<(m+...
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1answer
54 views

Signal in frequency domain with OpenCV dft

I am experimenting with cv::dft: a 1HZ sinus signal is generated, and displayed in the frequency domain. But for some reason it hasn't got the maximum component at ...
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1answer
33 views

Equalization : using the spectral or the temporal signal?

I'm trying to equalize a sound signal - using a JAVA program - and I'm using this process : 1/ Conversion of the temporal signal to a spectral signal, using a FFT 2/ Applying a coefficient to each ...
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1answer
56 views

FFT of a $N$-length real sequence via FFT of a N/2-length complex sequence

I would like to optimise FFT algorithm by only using a FFT of size $N/2$ to transform a real sequence of length $N$. There are already many questions and many excellent answers on the matter (here for ...
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1answer
73 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}{(...