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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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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
14 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
14 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
70 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
34 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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23 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
35 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
25 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
144 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
44 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
66 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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The diffrenance between spectogram, mel frequency, cepstrum, Mfcc, Mel frequency cepstrum

I was working on tts project a I come across the following concepts. Spectogram Mel frequency Mel frequency scale Cepstrum MFCC Mel frequency cepstrum Short-time Fourier transform(STFT) I've ...
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3answers
56 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
44 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
64 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
37 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
38 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
36 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. ...
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1answer
21 views

How do I generate sine waves with MATLAB’s max operator and the plot the resulting values in dB versus log frequency? [closed]

I just start learning about matlab. Im very confuse with this. Can anyone gives me such an example solution or any kind of help? HINT: Put the desired input frequencies in an array and use a for-loop ...
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1answer
22 views

How to make semilogx to get a plot gain against log frequency with several values? [beginner] [closed]

Gain: 20 log (Vout/Vin) with Vin = 1.0. I've been searching for gain values: a. -156.48 dB b. -80 dB c. -53.98 dB d. -13.98 dB e. 3.52 dB f. 10.32 dB g. 13 dB h. 13.93 dB i. 13.96 dB j. 13.98 dB I am ...
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1answer
65 views

Plotting Hilbert Spectrum from Hilbert Huang Transform

Before anyone calls it a repeat post from past posts. I'd like to point out I've read all of those; however, I have questions on making a hard coded version of the hilbert spectrum. I do indeed have ...
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2answers
37 views

Software to extract frequency spectrum data from an audio file

I've been trying to learn how computers recognize musical notes, and I found apps like spectrogram which shows the frequency spectrum of a sound, but what I need is the data which is plotted or the ...
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32 views

Converting IQ value to distance in FMCW radar

I'm working with a FMCW radar to measure the distance. I'm receiving IQ as the output. I wonder, how to translate this data to millimeter?I have s parameters (<...
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0answers
19 views

How to extract desired frequencies from a spectrum using e.g. a Parzen window?

Disclaimer: I am a geophysicist working with time-domain data which needs to be converted to the frequency domain evaluated at a specific set of logarithmically-spaced frequencies. The textbooks I am ...
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1answer
76 views

Frequency analysis to determine low-pass cut off frequency

I collected some data for a practical application, where the signal represents force data obtained from an impact of a punch against a force plate attached to a quasi-rigid rig (it moves once the ...
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2answers
41 views

Ultrasonic Interference with Electromagnetic Waves?

I am currently working on ultrasonic frequencies (20 kHz-60 kHz). According to a news snippet I found: The state government has also tried employing ultrasonic guns that can scare monkeys away and ...
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1answer
45 views

why transmitting a long pulse its spectrum gets spread?

I'm transmitting an RF signal with a CC1101 at 440 MHz. This signal is a constant of 1, so the spectrum should be a delta. Using a SDR dongle, I've checked the spectrum and it's wider than a delta ...
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1answer
40 views

Phase and Amplitude estimation

Context: I have used FFT many times, but for real, non-periodic signals I consider it a poor estimator. For most of my applications I am only interested on the power spectrum, so I use the Welch's ...
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50 views

Cosine Fourier Transform and Phase

If we do FT of cosine wave, then sine wave will be orthogonal. So, the imag parts of FT will be 0. This is my think. But, the result isn't show that. Like this. Figure 1. Real and Imag parts (Y label ...
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2answers
206 views

Bandwidth required to transmit a binary sequence

Does a digital binary number have any bandwidth? I explain suppose T want to express the number 10 in binary digits: 1 0 1 0 would that digital number have any BW in frequency domain? I would say ...
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1answer
30 views

Meaning of a formula about transient frequency bins

I'm trying to understand the following formula in this paper: Sadly, the paper does not define most of the symbols it is using, so my guesses so far are: $T_{tr}$ refers to the sampling interval i....
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11 views

Is there a criterion that says at what point you can distinguish 2 partially overlapping Lorentzian peaks?

If you have 2 Lorentzian peaks that partially overlap and you have some frequency resolution df (your points in frequency space are separated by df) and both Lorentzian peaks have FWHM $\Gamma$ is ...
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1answer
32 views

Detection of Troughs and Notches in a PPG Signal

I'm working a project which tries to determine Blood Pressure from PPG signals.I'm trying to extract the features as shown below... I'm having problem in finding the troughs and dicrotic notch for ...
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55 views

Simple tests for normalisation of power spectra

I am trying to compute power spectra of multidimensional (2d, 3d) arrays. In particular, I want to compute radially averaged power spectra $P(k) = P(|\mathbf{k}|)$ using FFTW, where $P(\mathbf{k}) = |\...
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1answer
52 views

How does works a bandpass filter?

My question is about the action of a bandpass filter. First, I have a temporal signal. I convert it in a spectral signal via a FFT. Now, I want to apply a bandpass filter on that spectral signal. But ...
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1answer
54 views

4th order butterworth filter using frequency response formula

I know this may be a kind of basic question, but I have my head wrapped over it for some time and hadn't found a solution. I want to generate the frequency response of a 4th order butterworth filter ...
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45 views

non-negative FFT spectrum, subtlety

definations $x(t)$ is a function of time. Physically, it can be voltage, displacement, magnetization and so on. It can be real, complex, vectors or more fancy numbers. $C(t)$ is the auto correlation ...
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1answer
60 views

The Instantaneous Frequencies from IMF Aren't Consistent with Its Spectrum

I'm trying to find the instantaneous frequencies for one of the Intrinsic Mode Functions (IMFs) I extracted from the original signal using Hilbert-Huang Transform. So, I got the following spectrum for ...
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23 views

How to Update Power Spectral Density Function Estimation of a Dataset in Moving Average Sense

Assume we have a dataset containing 1000 floating-point numbers. Its power spectral density function (PSD) can be estimated using various methods, e.g. Welch's method. Unlike above, please consider a ...
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26 views

how to plot log intensity of a 2D image wrt frequency?

I'm reading an article about frequency filtering and I came across this figure which represents log intensity of an image wrt frequency. I want to code this function with ...
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75 views

Graph signal processing

What's the intuition behind a ''Graph fourier transform'' ? I'm not so much interested in mathematical details or technical applications. I'm trying to grasp what a graph fourier transform actually ...
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1answer
89 views

How can I transform a time signal into a third octave spectrum?

I try to make a third-octave spectrum from a time signal and I have some troubles with the algorithm. I'm not an expert in signal processing so I don't know what is wrong. Here what my algorithm ...
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28 views

Detect pure sinewave in noisy signal by SIMULINK

To extract and detect two complex exponential signal in noise, I have problem to chose what kind of detection procedure that is also optimize. I think CFAR detector is only for 1D signals, but is that ...
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1answer
41 views

Play with a Gaussian random set in the frequency domain to obtain desired effect in the time-domain

Please assume we have a set of 100 random numbers obeying Gaussian PDF in time-domain. Let's index them 1-100. Within a time-accurate simulation, I apply four operations on this dynamic set every ...
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1answer
37 views

Accuracy of time domain signal when one frequency is absent

Suppose the known frequency spectrum of a signal is: $$ G(n\Delta f)=9,4,3,5,1,6,... $$ where $n=0,1,2...$ and $\Delta f=1$ Hz If, for some reason, we cannot sample $G$ at $n=0$ (i.e. $G(0)=9$ is not ...
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1answer
90 views

Scale FFT frequency range for a bars graph

I'm trying to show frequency spectrum for audio data as a bars graph using FFT. If I have data for a sine wave at 440 Hz and with sampling rate 44100 Hz and analyze its first 1024 samples I get an ...
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1answer
33 views

In a periodogram, why is the modulus squared of the DFT taken rather than the DFT itself? [duplicate]

Why can't you just take the DFT itself? And how accurate is this method in spectral density estimation? Are there cases in which it is very accurate?
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1answer
79 views

FFT - preferred way of tone detection

I am using FFT to detect certain frequencies (DTMF). I can clearly see the frequencies in the spectrum. Is there a preferred / optimal way to decide if a certain frequency is present or not by looking ...