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

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18 views

Determining the point in a temporal signal when a periodic behavior begins to occur

I'm a newcomer to digital signal processing, so I'm looking for some general advice and direction on this problem I have. I have a signal like that shown below. Starting around x=40000, you can see a ...
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0answers
9 views

Extract features from video based on temporal frequency

Situation is as following: there is a video, 2d sequence of frames, each of which contains still picture of beating heart, or some other oscillating object. Also each picture contains some features, ...
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1answer
39 views

Measuring frequency response range of piezoelectric disc

How can I measure the frequency response range of a piezoelectric disc below. I don't have an oscilloscope but I do know how to program in matlab / octave I was thinking of creating a swept signal ...
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4answers
275 views

Difference between DC component and zero frequency component of signal

We know that Fourier Transform of a signal exists if it is absolutely integrable and it exists for periodic signals if impulse functions are allowed. If we consider the fourier transform of ...
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1answer
39 views

How to find transfer function looking bode plot

I have some Bode plot (only in amplitude) as these: Now, I must to find their transfer functions, in particular the exact value of their zeros and poles. It is clear that their are a low pass ...
5
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3answers
136 views

How can I automatically identify and remove a fundamental frequency and all of its harmonics?

I have some microscopy data that is contaminated by a heartbeat artifact that I'd like to remove. The data consists of a large time series of images captured at ~60Hz. Here's a small example clip in ...
2
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2answers
75 views

How to know if a audio file is real lossless using its spectrogram?

I need to know if a certain audio file is real lossless and not a transcode (i.e. lossy converted in lossless, but lossy at the end). I was told there was a way to do this by creating a spectrogram of ...
0
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0answers
33 views

How to plot Full spectrum with negative frequencies

I'm trying to do frequency analysis on signal of a rotating shaft. The signal is generated in two measurement planes i,e X-position and Y-Position. I was able to use fft and transform into frequency ...
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2answers
97 views

What is meant by *sampling* in terms of the *sampling theorem*?

Let $y:\left(-\frac T2,\frac T2\right)\to\mathbb{C}$ be a square integrable function. The Fourier coefficients of $y$ are $$\underline{Y}(k):=\frac ...
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3answers
60 views

Sampling theorem and signals explained to a mathematician

Let $f:\left(-\frac T2,\frac T2\right)\to\mathbb{R}$ for some $T>0$. The Fourier coefficients of $f$ are $$\left\{\begin{matrix}a_0&=&\displaystyle\frac ...
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1answer
50 views

Strange phase spectrum from stft

I've tried to implement STFT in functional way in Python. I've got code such as below: ...
0
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0answers
27 views

Square signal: from a period histogram to a frequency analysis

I have a dataset of square waves (with periods slightly varying from the nominal one) and I read the times between edges with a PIC microcontroler, so I can obtain a histogram of periods. The data ...
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0answers
31 views

Applying a custom filter to FFT results?

I think I am missing something here and I do not quite understand why. Background: I am collecting quadrature signals from a software defined radio. There are two signals, the I, and the Q which is ...
0
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1answer
65 views

Removing periodic noise from image using Fourier transform

I'm trying to get rid of some periodic flicker noise through post-processing of the recorded images. The reason for these artifacts is that the electronic rolling shutter of the camera reads each line ...
0
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1answer
51 views

Formulas to plot Frequency Impulse Response Coefficients

I made this question newbie:Plotting FFT and Impulse Response Coefficients, using Java I have the IRC: Impulse Response Coefficients: $h(k), k = 0, 1,.., N-1$ Low Pass: ...
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1answer
19 views

Is a negative Es/No for an SCPC RF signal possible, and what would such a value signify?

I apologize if this isn't the correct Stack on which to ask this question, but it seemed like the best fit. I've tried to Google an answer, but I haven't been able to find anything that applies ...
0
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0answers
51 views

How to plot the amplitude spectrum of the Ricker wavelet in MATLAB?

I have the following MATLAB code and I would like to plot the Ricker wavelet both in time domain and frequency domain. I would like some help because I am getting amplitude greater than one for the ...
1
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2answers
74 views

Using only positive frequencies in fourier domain, How will it affect the ifft?

I am going to do some kind of transformation and transform a data to another domain, and again back to the first domain. For this, I take a fourier transform of the data and separate the positive part ...
0
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0answers
26 views

How to transform one graph to a spectrum?

Recently, I studied a paper called "What Does Your Chair Know About Your Stress Level? It can be download at the link below. ...
0
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0answers
17 views

How to measure spectrum envelope in matlab

I would like to measure the energy change of the spectrum envelope of a wav file like 20hz - 40 hz and plot a graph like this in matlab: Sorry I have no knowledge about signal and would like someone ...
0
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0answers
20 views

What does it mean compute spectra of Center of Press?

Recently, I studied a paper called "What Does Your Chair Know About Your Stress Level? It can be download at the link below. ...
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2answers
70 views

Normalization purpose in signal processing

What is the purpose of normalizing the signal? If we have two signals on hand, how is it used when comparing these two signals?
1
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1answer
48 views

For a standard second order transfer function, what is the equivalent time domain significance of $\zeta>0.707$?

In frequency domain $\zeta>0.707$ implies no resonant peak in frequency response. But I am unable to correlate what is the exact time domain effect of this? If $\zeta=0.707$ acts like an ...
0
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2answers
37 views

fundamental question regarding bandwidth

What I've learnt so far is that, if we change a time-domain signal into frequency domain, its bandwidth shows the range of frequency of radio waves that required to generate such signal. However, for ...
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1answer
40 views

What is the distance metric in dynamic time warping?

I am reading the lecture slides from this site http://luthuli.cs.uiuc.edu/~daf/courses/CS-498-DAF-P/Lecture%2018%20-%20Time%20series,%20DTW.pdf In slide 24, the lecture suggest using metric of the ...
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0answers
53 views

Confusion in the spectrum of FSK modulated signal by using matlab fskmod module

I want to do a comparison of power spectral density of BFSK, 4FSK and 8FSK by using matlab baseband module "fskmod".Following is ...
0
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0answers
49 views

How to, efficiently, identify telephone number from the key pressed data audio file?

A very common homework question. You are given an audio file(.wav) which has the recording of the keys pressed during a telephone call. You have to identify the telephone number from this audio file ...
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0answers
128 views

Detect Frequency of Incoming Audio on Raspberry Pi

I've been lurking around these forums for a while and they've been a great help to me in the past. However, I've been researching this problem for the past 2 days or so and can't seem to find a ...
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1answer
58 views

Downsampling fft results to a graphics display

I'm new to dsp. I've got a complex signal that was sampled at 192kHz then an fft of 16384 bins created. This now needs to be plotted on a graph for a real time spectrum display. The problem is if ...
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1answer
74 views

Help on implementing an IIR filter

I am new to signal processing and and having difficulty understanding how to implement an IIR filter. The reference is athttp://www.dxatlas.com/rocky/Advanced.asp in the Band scope section. It ...
0
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0answers
13 views

Suppose we have the following data. How can we calculate the channel capacity and R?

A channel has a bandwith of 5MHz. If signal strength to spectral noise density S/N0 is 107 Hz, calculate the channel capacity C and R. The problem is that I can use Shannon-Hartley theorem because ...
0
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1answer
25 views

Is there any tool to anlyze audio specturm of a song and give the average visually ?

I have a lot of songs I made over the 20 years and was thinking it would be interesting to see how the overall EQ changed on the various songs I made. Any tool out there to help me with something ...
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1answer
60 views

why upsampling contracts the spectrum?

I'm trying to understand why Matlab function upsample causes contraction in the spectrum, like the following figure shows. Also showed in mathwork online document. enter link description here ...
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1answer
86 views

Detecting a frequency swept sinusoid and its parameters?

Given a (FFT-sized) frame of data, and detection of a spectral component statistically above the noise floor in the FFT of this window, what characteristics or signal analysis could be used to ...
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1answer
92 views

FFT on Hamming Window Function [duplicate]

I want to apply Hamming window function the Audio sample then find out its fft.. ...
0
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1answer
40 views

Developing a classifier for a periodic music

I am trying to develop a classifier for Indian Taals, for which I would be focusing only on the Tabla. Now once a extract a period of the Tala(a repetitive pattern), I want to develop some feature ...
0
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3answers
76 views

Choosing the best measure for machine learning on a Spectrogram

I am working on an application to classify Talas(a piece of music with onsets). For that, I have the spectrogram of a Tala, which I want to compare with the test Tala, or compare 2 Talas. For this I ...
0
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0answers
67 views

How to remove modulation frequency and its harmonics

I have amplitude modulated sound file signal and after demodulation using FFT I got fundamental frequency and its harmonics and of course noise. How to remove that fundamental modulation frequency ...
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2answers
53 views

Signal corrupted using peak (biquad) filter at low frequencies

I'm trying to process an audio stream through a series of peak filters at static frequencies that range from 0 to nyquist. If I start the range from anything below about 25Hz, the audio gets corrupted ...
0
votes
1answer
93 views

Spectral effects of multiplying a signal by itself?

This has to do with creating the synchronization circuit for MSK in a DSP as described in "Minimum Shift Keying" by Subbarayan Pasupathy published in IEEE Communications Magazine. At the beginning of ...
-1
votes
1answer
59 views

Can all pass filers have a pole/zero at the origin of the root locus

I came across this root locus diagram in my DSP class. It has a pole at the origin, another pole within the unit circle and a zero just outside the unit circle. I understand that the poles and zeros ...
0
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0answers
50 views

Simplest approach to classify signal based on its 'smoothness'?

First of all, I have no experience with signal processing whatsoever and I may not even use proper terms so please bare with me. I am just humble software developer trying to find the simplest and the ...
0
votes
2answers
70 views

What is a translation property in DFT

Hi someone please explain me the translation property of DFT. I am not able to understand it neither from Gonzalez nor from internet. I have done extensive study on this but not able to get it. Really ...
1
vote
1answer
84 views

How to learn MUSIC algorithm?

I was actually preparing for my semester project and decided to take up Frequecncy estimation.I ll directly come to the point that I want to know how should I learn MUSIC algorithm. How do I start it? ...
0
votes
2answers
36 views

Spectral Content of two waveforms

I have found this interesting question here: Which of these two waveforms has a richer spectral content, and why? Intuitively speaking, I think that the first one is richer, but I cant really ...
0
votes
0answers
47 views

Python module request: Spectral density estimation for multivariate time series

I have worked with scipy.signal.welch and spectrum.pptm to calculate power spectral density with Welch and Multitaper methods. However as far as I can see these functions are meant for one dimensional ...
0
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0answers
179 views

fft magnitude scaling

I use the following code to calculate the fft of 1024 samples of a 200 Hz windowed sinusoid (code taken from aurio touch apple example app): ...
2
votes
2answers
170 views

Calculation of sampling rate and its effect on an Image?

I know that for a given signal, the sampling frequency $F_s$ must be twice or more than maximum frequency of the signal $F_m$. It is easy to understand the concept for a 1D signal. But I don't know ...
0
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0answers
111 views

Get Mirrored FFT Results in Real part

Ok, I'm new to the whole Dsp thing, so sorry if the question is a lame one I'm trying to extract frequencies from a signal provided by a radio Device (Win Radio G31DDC- IFstream). The radio provides ...
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0answers
95 views

Why is level of power spectrum dependent on FFT resolution?

I created a sinusoidal wave in some noise, and plotted the power spectrum of the signal using two periodogram estimates (welch procedure). One estimate is 'high resolution' - i.e. it uses a longer ...