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

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56 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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24 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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31 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
38 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
52 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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32 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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2answers
80 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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14 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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1answer
69 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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52 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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21 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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10 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
34 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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28 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
43 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
38 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
65 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
116 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
186 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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18 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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17 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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48 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
39 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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49 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
17 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
45 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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50 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 ...
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55 views

Short VHF pulse detection from SDR

I need to detect a short (10ms) VHF pulse that occurs every 1.5s at a specific frequency (e.g., 150.20 MHz). I have an SDR that support IQ sample rates up to 10MSPS but due to computing constraints ...
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1answer
54 views

What is the relation between the domain of Fractional Fourier transform and time and frequency?

This refers to the link where it clearly writes that: The FrFT argument $u$ is neither a spatial one $x$ nor a frequency $\xi$. We will see why it can be interpreted as linear combination of ...
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38 views

GNU Radio - QT GUI Frequency Sink block - field Bandwidth and signal frequency spectrum

I am simulating QPSK modulation in GNU Radio. The flowgraph is here: File Source is a binary file. Unpacked to packed is packing bits densely so that one incoming byte contains 4 QPSK symbols. ...
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131 views

Phase spectrum of the DTFT of a rect pulse using FFT

I'm trying to use the FFT to plot the phase spectrum of the DTFT of a sampled rect impulse function. Here's the Matlab code I've written. ...
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1answer
34 views

Has there been any research on time-windowed spectral estimation using more than one window function at the same time?

In the Welch's method, a signal is divided into overlapping segments, multiplied with a window function, and transformed to frequency domain via fourier transform. Why does the method use only one ...
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12 views

What spectral estimation technique to use for finding sharp spectral lines?

At the moment, I am using the Welch's averaged modified periogram method for spectral estimation, which has the frequency resolution $f_s/N$ where $f_s$ is the sampling frequency and $N$ the window ...
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1answer
62 views

Why do we use sinc interpolation rather than just multiply the frequency domain signal by rect?

I know if we have a continuous-time bandlimited signal $x_{ct}(t)$ that is sampled frequently enough we get a signal that we can call $x_s(t)$. If we take the Fourier transform of $x_s(t)$ to get ...
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2answers
109 views

How does the Magnitude of an FFT relate back to the Time Series wave it was created from?

Alright, to start out I am a mechanical engineer with very little circuits and digital signal processing background. So please excuse my ignorance as this is far out of my usual territory. When ...
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1answer
127 views

An explanation of parts of the MUSIC Algorithm for someone without a background in signal processing?

I've been looking at every tutorial and paper I can find, but I keep losing the intuition behind what's going on when they get into the matrix operations. There is a step in which the signal vector ...
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2answers
54 views

How to represent ratio between harmonics in audio spectrum

I was provided a report where the amplitudes of spectral harmonics have been extracted from several audio files. The amplitudes have been extracted using Audacity's spectrum visualizer, where the ...
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2answers
70 views

Spectral Analysis vs. Spectral Line Analysis

We usually talk about "spectral analysis" but some resources (this paper or this doc) talk about "spectral line analysis". Does this make sense to you, i.e. are the 2 fields actually different or the ...
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3answers
160 views

Large sample rate or large number of cycles when estimating frequency?

I wish to determine the frequency, amplitude and phase of a sine wave with some noise and I can only have a fixed number of samples. Should I go for many cycles and a small sample rate or a few cycles ...
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19 views

Distinguish between two vocals by their timbre

Right now I'm working on a signal processing project, I'm not quite to the point where I'm implementing the DSP algorithms yet (still working on the low level hardware) although I'd like to get an ...
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2answers
75 views

How can I accurately represent an mp3's wave form in respects to time?

I'm trying to programmatically plot a sound wave that I have placed in a 2d array, however, I cannot consistently get the sound wave to reach the end of the window. For example, when you load a sound ...
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1answer
88 views

Eliminating inertia effect from the acceleration signal

I am struggling with a problem, and would be happy if you could assist me. I put an accelerometer sensor inside a spherical enclosure, and release it to the water. While it was translating in the ...
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votes
1answer
61 views

Hamming window for filtering unwanted terms

I am trying to filter off two unwanted terms in this frequency spectrum (the spectrum on top). First, I used a convolution between a rectangular window to make the unwanted terms equal to zero. ...
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1answer
62 views

Convolution reverb using a frequently updated frequency dependant impulse response

I am implementing a software to auralize a virtual scene but am kind of a newbie to DSP. The focus should be the calculation of the IR which is frequency dependant. But this means that the renderer of ...
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0answers
34 views

Replicating a visual audio spectrum

I've been developing a web app as a hobby over the past few months which is essentially a real-time Javascript clone of the audio visualizer used by Monstercat. While it looks kind of close to the ...
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0answers
28 views

Memory and bookkeeping for realtime window-overlap-add (WOLA)?

Given a realtime embedded system with input samples x(n) coming from an ADC, what is the pipeline to output y(n) if ...
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3answers
123 views

Extreme audio stretching

This tool (Paul's Extreme Sound Stretch) is able to produce extreme timestrech (50x, or even 100000x). Any song can become an interesting sound texture or ambient music (listen to this example). The ...
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2answers
155 views

Frequency Spectrum with c++

I have written a script to plot the frequency spectrum of a sinusoidal signal with c++. Here are the steps 1-Applying Hanning window 2-Apply FFT using fftw3 library I have three graphs: Signal, Signal ...
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1answer
120 views

Spectrogram, time vs frequency localization, and length of signal

So I'm having some trouble conceptually and am hoping somebody can clear something up for me. This is long and I apologize for that but I want to provide as much information as possible so that the ...
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1answer
124 views

What is the spectrum of modulated noise?

I use a white-noise generator in an rf bridge to measure antenna impedance. The receiver is an ordinary AM/CW/SSB communications type, nothing fancy, nothing 'coherent'. As I approach the null of the ...