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

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How to validate an estimated model in case of output-only data (in frequency domain)?

Before moving to the actual question, I would like to emphasize on the following points (maybe they are obvious to some of you, but I still would like to list them, since they make the difference): ...
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25 views

Why do aperiodic signals have continuous frequency spectrum? [closed]

I cannot get the intuition why aperiodic signals have continuous frequency spectrum. As for periodic signals, it is easy for me to imagine because one thing I know is that the fundamental period is ...
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44 views

How to shift a signal to the center of the frequency domain?

Let's assume I have a 1024 x 1024 matrix that represents the spatial domain. After I perform a FFT and center the frequencies, I get the a signal that looks like the following in the frequency ...
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2answers
76 views

Explaining / Communicating spectra: Generating Visualizations

I'm very often in the situation that I need to explain / visualize spectrum of signals or frequency behaviour of systems (esp. filters). My favourite, very "textbook" styled way of communicating these ...
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2answers
44 views

What is the difference between a'mixer' and a ' multiplier' used in modulation process?

I am not sure if it is valid to conclude that a mixer produces a difference/sum of frequencies at output ,while multiplier produces multiples of frequency at its output. I am keen to know how far I ...
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60 views

Two-Sided Frequency Spectrum

I am trying to make FFT simulation in Matlab by generating noise added two sinus waves in 60Hz and 100Hz. After adding the noise into these signals then I have applied the FFT as I put my Matlab code ...
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2answers
94 views

Fourier transform of a Fourier transform

I generate a Gaussian noise and then I filter it with a passband FIR Kaiser window filter. When I perform the Fourier transform of the output of the filter and plot its magnitude spectrum, it is ...
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2answers
37 views

Multipath resistance of spread spectrum systems

I have been reading about various telecommunications technologies and one thing keeps being repeated many times without a clear explanation - that spread spectrum is not only resistant to multipath ...
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1answer
69 views

Reduce the number of frequencies after FFT

I have a long signal (1 day sampled at 500 Hz), which results in many frequencies if I calculate the amplitude spectrum (see e.g. here). However, I am only interested in the "big picture", let's say ...
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1answer
34 views

Calculating spectral coherence coefficient (scc) - implementation help

I am trying to calculate the SCC of a cyclostationary signal. I have estimated the Spectral Correlation Function (scf) of the signal using FFT Accumulation Method (FAM). I implemented the following ...
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42 views

Unable to generate and verify a sound wave of frequency 200 Hz

I am trying to generate a sound that contains low frequency in the range 100-500 Hz. I then record the sound using a microphone and generate a spectrum for the recorded signal using ...
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1answer
54 views

$\mathrm{FFT}$ generates non-linear noise

I followed the tutorial for generating the frequency spectrum of a signal here, and for testing I generated a sine signal with the frequency of $440 \textrm{ Hz}$. That resulted in the time domain in ...
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1answer
21 views

How to determine the central frequency from a vectorial spectrum analyzer?

I have taken measures of an antenna with a vectorial spectrum analyzer. I need to obtain the central frequency at which the antenna works. In order to do so, I have selected S11 (reflection) and I ...
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3answers
83 views

Band-pass filter doubles the frequency

I ran into a strange bug while implementing a complex band-pass filter. The filter design process is based on the windowing method and seems to be working well, but when i apply the coefs of the ...
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0answers
84 views

How to design an interpolated notch filter in Python to filter powerline harmonics

I have a a time domain data set that records the magnetic field vs time, which must be processed to reveal an embedded signal. This data also contains power line harmonics (i.e. multiples of 60 Hz) ...
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2answers
113 views

Relation between the DTFT and the spectrum of a sampled signal

In the $\rm DTFT$ (Discrete Time Fourier Transform) the spectrum is periodic with period of $2\pi$ . A continuous signal when sampled has a spectrum which is a repeated version of its original ...
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3answers
103 views

How to interpret spectrogram correctly?

I have a pressure transducer signal from a reacting mixture available here, which has a sampling frequency of 50kHZ. I have also obtained the spectrogram of the signal with NFFT=256, noverlap=4 as ...
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1answer
55 views

Order Analysis Signal Processing

I'm currently working on vibration detection machine used to detect unbalance from a rotating shaft, rotating from 300-2500 Hz. I have both the tacho signal ( 1 PPR ) and the vibration from ...
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1answer
42 views

Fourier Transform of triangle function $x(t)=\Delta\left(\frac{t-1}{2}\right)$

Can you please tell me if my working is right for the Fourier Transform of this function: $$x(t)=\Delta\left(\frac{t-1}{2}\right)$$ My workings are: I have used the fourier transform standard ...
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2answers
157 views

why is moving towards higher frequencies so important in frequency spectrum?

As we know, as frequencies becomes higher, bandwidth becomes higher.And, according to channel capacity theorem, channel capacity increases with higher bandwidth. Also, energy is directly ...
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2answers
77 views

Why Fourier Transform doesn't show obvious periodicity?

I have a clearly 4Hz periodic signal (see image below). However when I apply a fourier transform, there is no peak at 4Hz. Also, when I do a power spectrum density (using Matlab's pwelch algorithm), ...
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6 views

What is frequency warping in regards to vocal tract adjustments?

When we do spectrum smoothing using a filter-bank how can we adjust to different vocal tracts? We do vocal tract length normalization: frequency warping. Can you explain what is frequency warping?
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13 views

Digital filtering - Just set values to 0? [duplicate]

Let's say we want to digitally filter a signal to preserve only relevant frequencies. We calculate the frequency response $F(\omega)$ of the time series data $x(t)$ using the FFT. Imagine that we ...
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1answer
72 views

Recovering phase from spectrogram

In this answer, an iterative algorithm is given for recovering a signal from its spectrogram, assuming overlapping windows: $$ x_{n+1} = \operatorname{istft}(S \cdot \exp(i \cdot ...
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51 views

FSK audio spectrum for demodulation

I am working on Python script to demodulate FSK audio signals. The audio signal contains GPS NMEA strings. I am a beginner in DSP, but trying to work my way through this problem. I think this is a ...
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32 views

Error in summation of spectral components

The error associated with a given estimated spectral component $f(w)$ ($w$ is the frequency) of a Gaussian signal follows a Chi-squared distribution with $\nu=2$ degrees of freedom. For instance the ...
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1answer
81 views

Relationship between the Real and Imaginary parts of a LTI causal system

Prelude I am writing an elaborate text on the relationship between the real and imaginary parts of a LTI causal system and how stability, causality and analyticity imposes various constraints on its ...
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2answers
69 views

Matlab fast fourier transform (FFT) function and time in hours frequency : hertz or millihertz?

I have a function of type $$C(t)=0.31 \left(e^{-0.267t}-e^{-1.72t}\right)$$ Where $t$ is in hours The function represents the evolution in a window of 24 hours of a drug blood concentration, after ...
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45 views

Single/ Double sided spectrum plot

After performing the fft transform there are 2 options to plot the spectrum the complex (Real and imaginair) spectrum and the ...
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106 views

Minimum Sampling Rate of Bandpass signal

Consider a DSBSC signal s(t) = m(t).cos(2.pi.20k.t) where say m(t) is multi-tone signal with frequencies less than 5 kHz. The ...
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17 views

SISO model? white noise excitation

I'm now trying to do this problem. I have data set including input and output for both 600 gal and 800 gal, and 3 white noise excitations. But i don't understand the model of this problem. 3 White ...
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197 views

Is R suitable for digital signal processing

While asking a question about representing large time series in R I was discouraged from using R for digital signal processing. I understand that R is geared towards statistics. However, a signal is ...
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3answers
61 views

Logaritmic amplitude squarewave

This morning i was experimenting with GNU Octave. I created several signals(Sine, Saw tooth, square wave and noise). After this i used the periodogram. in the periodogram the square wave weren't ...
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24 views

Shifting Signal Components of all Harmonics to a particular Harmonics

I have a Time-Domain signal. After performing the FFT, the signal component I'm interested in lies in 60Hz and it's Integer Multiple. The FFT of the signal is here: I want to shift the component of ...
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12 views

Wireless Resource Allocation Problem: How to acquire channel state information for different frequencies?

I am trying to understand frequency allocation in Dual Hop Relaying S-->R-->D. I have questions about Channel State Information. I am assuming the whole transmission occurs in two time slots and ...
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1answer
35 views

Phase spectrum: $\mathrm{arg}\mathcal{F}(\omega)$ or $\mathrm{-arg}\mathcal{F}(\omega)$?

Do we need minus or not? I need to extract phase spectrum from that thing $$f(x) = \frac{1}{2\pi}\int_{-\infty}^{\infty} e^{i\omega x}d\omega\int_{-\infty}^{\infty}f(t)e^{-i\omega t}dt$$ I can do it ...
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30 views

Find unknown broadcast frequency

I'm very new to this stuff, so please excuse the dumb sounding terminology. I'm trying to capture the data from my elster smart hydro meter. How can I find its frequency (I know its between 902 and ...
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1answer
47 views

Partitioning the frequency axis with shifting resolution

I am calculating the sum of the signal energy in different frequency bands for music in Matlab. At the moment I have calculated the FFT for a music signal and then split this frequency vector in N ...
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1answer
42 views

Frequency spectrum of an amplitude modulated signal

I am talking about a DSB- Suppressed Carrier amplitude modulation. Let message signal be $m(t)=A_m \cos{\omega_c t}$ and carrier signal be $c(t)=A_c \cos{\omega_m t}$ Then the amplitude modulated ...
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2answers
102 views

How do I get the Time information after STFT?

I'm tring to code a STFT program in Matlab. I got results but I'm confused a bit. I have a audio signal of 900000 pts sampled at 1000Hz (15 min signal). I've taken fft with following parameters => ...
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1answer
141 views

How to reverse frequency spectrum of a 2D image?

Reversing spectrum of an audio signal is said to be often used in DSP – i.e. applying a low-pass filter is quite a simple operation, compared to a high-pass. So they shift the specrtum by multiplying ...
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4answers
233 views

Why audio clipping produces harmonics?

Today I was talking to my collegue about clipping and he said that clipping produces harmonics in frequency domain as he showed me the clipped signal frequency response. However when I asked him why ...
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20 views

Power estimation using eigenvalues

There are many different method to estimate power of a signal at a particular frequency or direction of arrival. As an example root music(Matlab rootmusic.m). The question is: do we have a bias when ...
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21 views

Temporal Interpolation of Spectra

The signal of interest to me is the ocean wave height as a function of time at a particular location. Its power or variance spectrum is estimated by buoys at regular time intervals. Specifically, ...
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111 views

Implementing a 2d butterworth filter for image processing?

I am at the moment trying to implement a bandpass butter worth filter which i then can use to apply on my original image. Problem is though My implementation of it using OpenCV doesn't seem to be ...
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1answer
45 views

Voss algorithm and pink noise

the voss' algorithm generated a 1/f series. What does the series mean? For example, we use three dice and the result sequence length is 8. Let's set the sequence is 8,15,6,9,14,10,9,7. Then what does ...
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58 views

1/f noise generation

Recently I was reading a paper about the pink noise generation. But I don't have any background of this field. I am confused with some part in the paper. First, the Voss's algorithm generated a ...
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0answers
19 views

Difference of spectral estimation procedure for narrow-band and broad-band

One of the important application of signal processing is spectral estimation. By spectral estimation I mean estimating the frequencies in a given signal. Fourier transform is fundamental, but there ...
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1answer
54 views

Obtaining power spectral density without having knowledge about frequency bandwidth or sampling frequency of the signal in Matlab?

Is there a way to plot PSD of a signal which show true frequency amounts ( not normalized one) without having knowledge about frequency bandwidth or sampling frequency of the signal in matlab ?
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63 views

Frequency response and impulse response of black box

I am trying to find out the transfer function of a real life continuous-time black box. First thought is of course to input a delta and get the impulse response as the books have taught us but I ...