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

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Comparing vibration frequencies

I have two iron pipes, one bent and cracked, and one whole. On one end Ive attached a vibration motor (200hz) and on the other end Ive attached a vibration sensor. I do a fft and then get out the ...
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1answer
40 views

FFT analysis of binned data of different length

I am conducting experiments to collect wind speed data from wind anemometers placed on a moving platform. Closely, there is a fixed wind mast holding a wind vane. Prior to analysing the wind data from ...
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47 views

Fundamental frequency extraction

I fail to determine the fundamental frequency of an engine sound recorded from the microphone to MATLAB. I am using the user defined code in frequency domain. My code is enclosed below: ...
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1answer
72 views

Determine spectrum amplitudes for half-wave rectified sine

I am trying to learn how to solve a bunch of digital signal problems and I have trouble understanding the solutions provided by this book I'm using. Basically, this problem asks me to determine ...
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2answers
69 views

Why are window functions used when calculating spectral estimates, really?

Having just read the rather long article on Wikipedia about window functions, I still do not see the mathematical point in using window functions when calculating spectral estimates (using e.g. ...
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1answer
23 views

Signal Plus Weakly Stationary Noise

I was reading the book "Spectral Analysis of Time Series" By Herman Koopmans. On Page 55, he explains that a specific type of non-stationary signal which is the result of adding weakly stationary ...
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26 views

How to draw discrete specturm of a signal

Before I begin this is not an assignment or a homework problem just something I'm practicing for my test next week. I need to draw discrete spectrum of a signal. How do I do that? Here is the actual ...
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1answer
30 views

Do Spread Spectrum technologies combat time-selective fading of a channel?

The Spread Spectrum technologies such as DSSS and FHSS are successful against frequency-selective fading because the original signal is spread to a larger bandwidth and different frequencies are used ...
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26 views

Measuring spectral tilt

I have quite a few noisy signals and I want to calculate their spectral tilt over time, preferably using a method from literature. So far, I can only come up with the slope of the line between the F0 ...
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1answer
45 views

What Information does the phase of a cross power spectra give me?

I obtain the cross power spectra by the following steps: compute the FFT of signal A and B Multiply A with the conjugate of B store it in C (cross power spectra) Now looking at the Phase of this ...
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28 views

Constant Q transform and time synchronisation

I'm looking to use the constant Q transform for onset detection and am having a bit of trouble aligning the time axis of the transform with actual note events. I'm using the CQT transform toolbox ...
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1answer
26 views

Demodulation with matlab

I am trying to listen VLF radio signals. I have a recorded wave file (download) and here is the frequency spectrum: I have produced this spectrum using this matlab code: ...
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1answer
81 views

Power Spectrum: Defnition

I am new to the study of time series. Recently I have asked a question about the covariance of real and imaginary part of a real(in time domain) stochastic time series and I have received an answer ...
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1answer
64 views

Determine frequency content of variable rate signal

What is the proper way to calculate the frequency content or spectrum of a signal with a variable (but measured) sample rate? I.e. get similar results as you would from an FFT, but for data not ...
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33 views

UWB radar to find heartbeat

I have a UWB radar that Im playing with. The problem is that my algorithms at the moment can clearly, reliably and validly pick up 1-2mm movements of a pendulum i've set up. However, when I use it on ...
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1answer
69 views

Frequency spectrum analysis

How do you find the phase and inverse Fourier transform of this frequency spectrum?
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2answers
61 views

Frequency spectrum of a sinc function

I am doing one example from my book as a preparation for exam. The assignment is: It is given that: $$\mathbb{rect}(t)=pf(t) \leftrightarrow PF(f)=2AT_0 \cdot \mathbb{sinc}(2\pi fT_0)$$ you ...
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1answer
77 views

Uncertainty, time-bandwidth product, harmonics

For a signal that is not corrupted with noise, how is the time-bandwidth product affecting the uncertainty or error introduced when extracting the fundamental frequency ? I mean, instead of choosing ...
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1answer
34 views

How are phase values able to capture motion from video?

I know that the phase spectrum contains most of the structural information about the image importance of phase. But I want to know more about importance of phase spectrum related to video signals. I ...
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0answers
41 views

Is it possible to decompose an image into basis images using MATLAB?

I have read that: Using Fourier decomposition any arbitrary image can be represented as summation of orthogonal basis images. I want to see the basis images for any image say Lena or ...
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1answer
60 views

Inverse DTFT of $e^{-j\omega}$

I've been trying to solve the following problem, but I noticed that I get two different answers by means of two different techniques: Find the impulse response, $h(n)$, of the following system, ...
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1answer
32 views

frequency response of a signal in which two signal added in

Here goes the problem I faced: Sig1= A*sin(w*n) Sig2= B*sin(w*n+phi) Length of both signal is L. Then, I put them in ...
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1answer
117 views

Under what condition is the available bandwidth $f_s$ instead of $\frac{f_s}{2}$?

Can someone help me with this interview question? It is about the sampling frequency rate. Under what condition the available bandwidth is $f_s$ instead of $\frac{f_s}{2}$?
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1answer
43 views

Dimensions of a spectral representation [closed]

I'm currently trying to perform analysis of a spectrogram, with the use of PCA. I'm confused about what the dimensions of the result should therefore be. Currently, the dimensions are: ...
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2answers
57 views

Interpreting Cepstrum of plucked string

in my attempts to synthesize a plucked electric guitar string (using supercollider's digital waveguide, which is based on the Karplus-Strong algorithm) I came to a dead end and decided to look that ...
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1answer
38 views

Deep zeros in the spectrum of the input data?

I wanted to know the meaning of "deep zeros" in the spectrum of the input data. I came across this terminology while going through the introduction of chapter 2 (Bussgang techniques for blind ...
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0answers
49 views

Spectral estimation from noisy time-series data

This is the first time I'm posting a question on here so I hope I'm doing it right. I've tried searching on here for an answer but haven't found anything particularly relevant. I have some data ...
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1answer
152 views

1/3 Octave Analysis

Good Morning! I am new in signal processing and I am trying to do a work in noise control of an electronic steering lock device (ESL). My aim is to calculate the loudness (Zwicker Method- ISO 532 B) ...
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2answers
63 views

Comb-like peaks in frequency spectrum

I am currently working on a project which involves measuring the sound produced by the onset of a vapour bubble in boiling water. All the experiments went perfectly well and I'm now trying to obtain a ...
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72 views

Obtaining power spectrum from ACF, FFT using Matlab and FFTW

I am using Matlab R2012b 64-bit on Windows 7 in order to estimate the power spectrum of a simple signal that is: $$cos(10t) + sin(20t) $$defined in the time interval from 0.0 to 10.0 Here is what I ...
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76 views

Autocorrelation Function and Power Spectrum

My aim is to determine the power spectrum of a signal of finite duration using Its autocorrelation function Performing FFT directly on the time-domain data The function is defined as follows in ...
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2answers
181 views

fft(x) different from fft(ifft(fft(x))?

I normalized the spectrum of a time series and windowed the spectrum, then something strange happened. The code below can run in MATLAB or Octave. ...
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1answer
45 views

Analyzing Spectrum of a signal?

my_signal = 8192*cos(2*pi*6*(0:7)/8) + 1i* 8192*sin(2*pi*6*(0:7)/8); my_signal_fft = fft(my_signal); plot(abs(my_signal_fft)); This is matlab code. What do you ...
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2answers
104 views

Magnitude Spectrum, different magnitudes same amplitude

When the following code is written,the resulting magnitude spectrum shows magnitude values represented by two peaks is different even though they have the same amplitude. why is that? a fast reply ...
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0answers
104 views

A problem about whitening of a signal

You guys are correct. I tested the code again. It's OK. ...
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1answer
86 views

Rate of fall of sidelobe level

Anyone can explain me about how measure side lobe roll-off rate of kaiser window from Spectrum in matlab where side lobe roll-off rate is the asymptotic decay rate, in decibels per octave of ...
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55 views

Doppler shift using PLL

I am trying to apply phase lock loop to calculate phase shift due to doppler effect and finally calculate the doppler frequency($\Delta f$). I am assuming that the received wave is of the form, $r(t) ...
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2answers
74 views

Sin wave spectrum shows multiple frequency

I am very new to DSP, so excuse my ignorance. Using Audacity, I generated a sine wave of: frequency 440Hz amplitude: 0.8 duration: 1 minute Now when i plot the spectrum for this sine wave, I ...
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37 views

it it possible that absorption appears in the power spectrum of a non man-made system? [closed]

I mean some kind of system may dislike some special frequencies and there may be absorption lines. Can somebody give some example? You can lots of emission lines below. But is it possible the PSD is ...
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2answers
98 views

FFT for bearing fault analysis

Why is FFT a good method for detection of bearing faults? Why can't we do the analysis in time-domain?
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1answer
59 views

How to get spectrum of an image?

I have an image : img = imread('pic.jpg'); Now, How can I get spectrum of that image?
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2answers
56 views

Extra energy when altering frequency amplitudes

How can I convert a time signal (audio) into the frequency domain, multiply frequency amplitudes by a vector of scalars, and convert it back into the time domain, without messing up timing information ...
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1answer
69 views

Order analysis or order tracking

Last week I've been trying to implement the Order Analysis in MATLAB in vain. I've read a lot of docs about it like this one , but I still can't figure it out. This will be my last shot. Say I have ...
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1answer
105 views

Amplitude Spectrum, Nyquist Frequency, mixed/min/max wavelets

The problem is here. Now I know the definition of mixed/max/min phase wavelets, whether the roots lie within the unit circle or not. Starting from n = 1, let $$ x_t = ( 5, 6) $$ $$ X(z) = 5 + 6z $$ ...
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2answers
142 views

PSD estimate using FFT - scaling and units

I know that similar questions have already been asked – I have read the answers, yet I am still not sure if I understand the topic properly at some points. I want to use FFT to calculate PSD ...
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1answer
124 views

use prony method for damped exponentials

let us consider represented of damping exponential model by prony method,there is source code ...
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0answers
50 views

Why the radar (moving) target return is not centered at zero frequency

In Radar signal processing, one has to separate clutter(unwanted signals) from moving target signals. The picture given below is an example of Radar Signal Power Spectum(taken from the book Radar ...
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1answer
152 views

use chirp z transform for spectral resolution

let us suppose that we some signal $x(t)$,which consist of sinusoidal components and white noise,i would like to know how to use chirp z transform for improving spectral resolution?i found this ...
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1answer
158 views

Convert normalized frequency to real frequency in AR model

Let us suppose that we have modeled signal using AR model, and suppose we have following model: I used spectral estimation function from MATLAB pyulear Now ...
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0answers
105 views

Yet Another Peak Detection Request

I looked over the other entries regarding peak detection and none seem to answer my question. I'm working with Fourier spectra of digitized audio that can't be measured again. There are no ...