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

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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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18 views

Code for Generating Spectrum (MFCC) vs. Time Images

I am trying to do speech wake up (hot) word recognition by transforming it into an image recognition problem. The images are some kind of spectrum (MFCC) vs. time, made from a wave signal. I recall ...
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1answer
31 views

Confusion about frequency illustration of FMCW in matlab

I am currently working through the FMCW radar example in the Matlab Docs and have a question concerning the following plot Why is the frequency of the signal apparently decreasing if I have a linear ...
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1answer
23 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
28 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
37 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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2answers
73 views

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
39 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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34 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
67 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
40 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
40 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
31 views

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
42 views

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
92 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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0answers
24 views

Single frequency missing in time domain effect

How to explain effect of a missing frequency in time domain ? As we know it is simple task when we talk about frequency domain and missing a frequency component in there (in spectrum).What about time ...
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3answers
31 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
301 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
23 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
47 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
22 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
28 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
50 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
70 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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0answers
22 views

pulses: Power signals or Energy signals?

I am doing system Identification for a tracking task, and I want to determine in the frequency bounds where I can approximate a baseline model with the chosen signals. There are two channels, one is ...
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2answers
108 views

Z Transform - Do i always need 2 poles for every “peak”?

I am quite new to digital signal processing (and also Z transforms). I am reading about frequency response modelling and have some questions do we always need a pair of poles for each "peak" in the ...
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1answer
22 views

Linear Predictive Coding - Meaning of spectrally Flat

I am a student with very little background on signal processing and am studying the Linear Predictive Coding algorithm. I came across the term spectrally flat in ...
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0answers
10 views

What are some features that I can extract in order to identify the type of noise that is corrupting a signal?

I have a a frequency modulated PAM signal that is being corrupted by 1 of several sources of noise and I am trying to figure out which one it is. I have tried to use the spectral correlation but the ...
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0answers
15 views

Difference between power spectrum of NR signal as seen in Vector Signal Analyser and MATLAB pwelch method

My setup is as follows: I have an R&S SMW signal generator which generates a 100 MHz 5G New Radio signal. The signal is passed through a channel emulator which has components like Digital-To-...
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1answer
40 views

What is the proper way to implement a real time spectrogram?

I am trying to implement a real time spectrogram and I am not sure that I am implementing it the right way. First I decided to use Matlab, I was taking a short recording of lets say 0.1 seconds and ...
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1answer
37 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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42 views

Create a frequency spectrum from a sequence of event times

I have a sequence of event times with non-uniform intervals between events and I'd like to get a frequency spectrum from these data alone. I imagine I could create a waveform that peaks at these times ...
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1answer
26 views

Calculating Power of Sinusoidal Term and a Convolution expression

The following is an excerpt from the book Statistical Digital Signal Processing and Modelling (Monson Hayes) ...consider a random process consisting of a random phase sinusoid in white noise $$ x(...
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1answer
19 views

Defining frequency axis for periodogram

I am trying to simulate example 8.2.2 from Hayes, Statistical Digital Signal Processing and Modelling, on MATLAB. Let $x(n)$ be a WSS process consisting of random phase sinusoid in unit variance. $$ ...
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25 views

Kaiser Window Degree of Freedom

I intend to use Kaiser Window with alpha =5 and overlap of 70.5% to smooth a time series containing 1200 data points before calculating the power spectrum. The window length is 200 points. I know the ...
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1answer
92 views

Separate two sinusoids with very close frequencies (5 Hz difference) in a 44.1 Khz audio signal, with good time-domain resolution

Here is an audio signal which is a mix of (WAV file available here): a 2000 Hz sinusoid, beginning at 1.00 sec, without fade-in/fade-out a 2005 Hz sinusoid, beginning at 1.031 sec, with a slow fade-...
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1answer
36 views

Time signal FFT different for whole signal than half signal on high frequencies

I have a time signal of u from 0 to 1000 time units. If I chop the signal in two halves and compare the frequency spectrum of both it looks similar, as it should (...
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26 views

FFT phase spectrum not correlate with DSA

I am trying to use an USB DAQ to replace DSA 35670A (Keysight) as the instrument is going to be discontinued the end of this year. I am measuring target vibration response by driving chirp signals ...
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1answer
57 views

am I recording LTE uplink signals?

I have this app in my phone which tells me the LTE UL frequency and power: so I went with my SDR and measured the received signal at that frequency: Now, how can I be sure this is the transmitted ...
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1answer
48 views

Do energy of signal and power spectrum (in db/hz) indicate towards same signal property?

If I calculate energy of signal by squaring the magnitude of signal sample and power spectrum using spectrogram (db/hz) what kind of property of signal do they indicate and are they point towards same ...
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3answers
155 views

Harmonic distortion of sine signal. plotting resulting spectrum

I'm trying to learn about how the spectrum of a sine signal changes when fed into a waveshaper and i've learnt a great deal from you guys here on stackexchange. Specifically how a transfer function ...
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1answer
73 views

Spectrogram with square or non-square magnitude of STFT: power vs. magnitude

As seen in this question and answer, to do a spectrogram, it's common to plot either: the square magnitude $|\text{STFT}(\text{frame}, \text{bin})|^2$ ("power spectrum") the magnitude $|\text{STFT}(\...
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2answers
77 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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3answers
60 views

Using white noise to test filter freq. response?

If I want to test a digital filter, is using white noise a good way? I mean input white noise to the filter, and visualize the frequency out from the output. Is that procedure the same as testing a ...
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1answer
80 views

Calculating SNR from Frequency-time domain

I tried to analyse the time-frequency of specific appliances. As it shows in the following frequency-time graph I have High frequency noise from different appliances here. 4096 is the number of ...
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2answers
83 views

Square Wave with Random Edge Shifting

I took a square wave signal and individually shifted all the rising and falling edges by a random amount of time, within certain +/- bounds (a random time for each edge, not shifting all edges by the ...
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1answer
44 views

Are the frequencies a histogram in the frequency domain?

I'm new to signal processing, and was learning about wavelets from this site. In the graphs above, the time domain signal is obvious. The x axis shows the signal varying according to time. I don't ...
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4answers
44 views

Bandlimiting and OFDM spectrum - what is considered “bandlimited”?

I have been reading about OFDM modulation, it's not clear to me how you can have band-limited OFDM but given its prevalence in wireless communication there must be some designation of approximately ...
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1answer
37 views

Phase of a signal with multi delayed windowed (rectangular window) signal with different amplitudes

I have a signal $x(t)$ which is composed of multi delayed linear chirps with different amplitudes and phases but they share the same $w$ and $\alpha$, the signal can be expressed as follows: $$\...
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1answer
27 views

How to make sinewives with array input, for-loop functions and operate array with others [matlab]? [closed]

Thanks to previous question, I got some clues to resolve this one. But, I still get some problems here. ...