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Questions tagged [signal-analysis]

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9
votes
1answer
19k views

I and Q components and the difference between QPSK and 4QAM

Both 4QAM and QPSK apparently produce the same waveform, but are they the same mathematically? In a QPSK constellation, are the mapping points at 45, 135, 225 and 315 degrees while the 4QAM is at 0, ...
12
votes
2answers
8k views

What are advantages of having higher sampling rate of a signal?

Being a non signal processing science student I have limited understanding of the concepts. I have a continuous periodic bearing faulty signal (with time amplitudes) which are sampled at $12\textrm{ ...
15
votes
1answer
23k views

Help calculating / understanding the MFCCs: Mel-Frequency Cepstrum Coefficients

I've been reading bits and pieces online but I just can't piece it all together. I have some background knowledge of signals / DSP stuff which should be enough prerequisites for this. I'm interested ...
9
votes
2answers
2k views

Shift a signal by fraction of a sample

I have a signal with a sample time of 0.5 micro seconds and I would like to shift this signal by a fraction of the sample time, say by 3 nano seconds. I have read a few online resources about ...
3
votes
0answers
211 views

Segment/Idenfication of signal from a spectrogram

I have the following Spectrogram of a signal: Essentially, in this signal, I know there is one point of interest (between 60-80) and between the the particular frequencies. I could, potentially ...
49
votes
10answers
14k views

Is deep learning killing image processing/computer vision?

I'm looking forward to enroll in an MSc in Signal and Image processing, or maybe Computer Vision (I have not decided yet), and this question emerged. My concern is, since deep learning doesn't need ...
1
vote
2answers
204 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 1T\int_{-T/2}^{T/2}y(t)e^{-i\omega_kt}\;dt\;\;\;\...
33
votes
8answers
32k views

Meaning of Hilbert Transform

I understand the Fourrier Transform which is a mathematical operation that lets you see the frequency content of a given signal. But now, in my comm. course, the professor introduced the Hilbert ...
8
votes
7answers
9k views

Why Does the DFT Assume the Transformed Signal Is Periodic?

In many signal processing books, it is claimed that the DFT assumes the transformed signal to be periodic (and that this is the reason why spectral leakage for example may occur). Now, if you look at ...
5
votes
3answers
7k views

Generalized Cross Correlation

What is the definition of Generalized Cross Correlation? I need it for estimating the delay (time offset) between two audio signals. The time offset between the two signals might be as large as 500ms....
4
votes
2answers
536 views

Does “keying on” a sine wave at a zero-crossing reduce its bandwidth?

I understand that a pure sine wave of infinite duration occupies no bandwidth, i.e. it is only the modulation of a carrier that gives it sidebands. Does the exact timing of a sudden modulation make ...
0
votes
1answer
331 views

understanding discrete-time convolution in LTI systems

I'm trying to understand the discrete-time convolution for LTIs and its graphical representation. standard explanations (like: this one) start with the idea of decomposing an input signal $x[t]$ into ...
0
votes
1answer
638 views

How channel state information is calculated from Sounding Packet

What I understand is for Explicit Transmit Beamforming scenario, the Transmitter sends an NDP packet(aka HT Sounding) which consist of OFDM training symbols in packet preamble (HT-LTF) which are ...
11
votes
2answers
10k views

Why do we say that “zero-padding doesn't really increase frequency resolution”

Here is a sinusoid of frequency f = 236.4 Hz (it is 10 milliseconds long; it has N=441 points at sampling rate ...
6
votes
1answer
3k views

Magnitude-squared Coherence calculation inconsistence

I have to calculate the magnitude-squared coherence (MSC) between two signal. However, using a routine that uses only one taper (or no tapers at all) my result is always 1, despite the signals are ...
4
votes
2answers
2k views

Audio Signal Separation - Identifying Interest points

I asked this question here: Audio Separation of .wav signal but it wasn't clear, so, here is my second attempt: First off, assume that I have a .wav file containing a sentence as follows: "My name ...
7
votes
1answer
2k views

Random sampling vs uniform sampling

In this paper of Lustig, he speaks about a something which appears unintuitive: sampling at random may exhibit better performance than sampling uniformly. I tried to understand this starting from page ...
1
vote
3answers
3k views

What are the advantages of LTI ( Linear Time Invariant ) systems over other systems? [duplicate]

In our engineering academics, there is one subject named "signals and systems". In this subject only LTI system is discussed. I want to know what are the advantages of LTI systems over other ...
-1
votes
1answer
407 views

How to detect and remove ringback-tone and ivrs voice etc from the beginning of an audio call recording

In an audio recording (say a telephone conv. b/w two people), how would I programatically detect and remove the dial-tone at the beginning of a call using python. Ex : As you can see the first 15 ...
3
votes
3answers
5k views

How condition for existence of Fourier transform is valid?

The condition for Discrete time Fourier transform to exist for function $f(n)$ is given as $$\sum_{-\infty}^\infty |f(n)| < \infty.$$ In case of continuous Fourier transform the difference is ...
1
vote
1answer
712 views

GPS signal acquisition

I have a set of GPS satellite signal data, the set is 1 ms long and has the information of two satellites (satellite number, code phase and frequency) buried in noise. This data has a carrier ...
4
votes
1answer
162 views

Signal Processing using Fourier Transform

How can I derive the fourier transform of ...
2
votes
1answer
244 views

Cross-correlation, sharp peak at 0?

First of all, I have to stress that I am not a professional of coding, no more than a professional of signal processing. I am a chemist that happen to be working on a project involving both. So in ...
2
votes
2answers
178 views

GPS CA Signal Acquisition

The coarse acquisition C/A GPS signal has a symbol rate or chip rate of 1.023 Mcps with code period of 1 ms. The code bandwidth is +/-1.023MHz (to 1st sinc nulls). I'd like to record this signal using ...
1
vote
1answer
392 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 ...
1
vote
4answers
48k views

How to check if a signal is power signal or energy signal?

What is the procedure to check the signal type? example: $ x(t) = A \sin (\omega t) $ $ y(t) = A e^ {-\lambda |t|} $
0
votes
1answer
287 views

Average FFT Magnitude in bins

I am analyzing sounds of daily activities recorded by a smartphone. For example walking, getting up from bed, falling, running etc.. (one at the time). Let’s take one them. My goal is to convert from ...
0
votes
2answers
512 views

IIR Lattice Filter in C programming

I would like to implement Lattice IIR filter in c, i can't defined the value of gN, i know that x(n) = fN(n), but how to initialize gN ?. you can find the algorithm here : n
12
votes
2answers
11k views

How do I determine if a discrete signal is periodic or not?

I want to know how I can determine whether a series of data is periodic or not. I want to use Fourier transform/series. My data looks either aperiodic [111100001111000110010101010000101] or ...
14
votes
3answers
30k views

What is the difference between linear and non-linear filters?

How a mean filter is called as linear filter and a median filter is called as non linear filter? I understand how a mean and median filter operates, but I was not able to relate with the term linear ...
3
votes
3answers
2k views

Filtering with STFT

I have sucessfully implemented a STFT (+inverseSTFT with perfect reconstruction of original signal, with overlap add, etc.) in order to work on audio files. Using this STFT / iSTFT framework, I have ...
11
votes
7answers
4k views

Obtain a signal's peak value if it's frequency lies between two bin centers

Please suppose the following: The frequency of a signal's fundamental has been estimated using FFT and some frequency estimation methods and is lying between two bin centers The sampling frequency is ...
5
votes
1answer
3k views

Signal filtering using Python

I'm trying to create an application using python that is capable of recording an audio signal and detecting short glitches in the signal. For example, I could be recording a 1000Hz sine wave and ...
4
votes
2answers
3k views

infomation about Stockwell Transform

I need some information about Stockwell transform (also known as the S-transform): How can I implement it in MATLAB? *Does it give you the damping ratio $\zeta$ of a signal like the complex Morlet ...
4
votes
2answers
6k views

Feature extraction from spectrum to aid categorisation

i have two sets of signals whose spectrum looks like shown in the figure. The first column of signals belongs to category 1 and the second belongs to category 2. Looking at the spectrums I want to ...
2
votes
1answer
7k views

Use Butterworth and Chebychev filters

I need to calculate frequency response, phase response and apply to signals the Butterworth, Chebychev1 and Chebychev2 band-pass filters. I'm developing in C++ with Qt, and I'm looking for algorithms ...
7
votes
2answers
548 views

Duration of unknown rectangular pulse with additive white Gaussian noise

Problem. There is a discrete signal $f[i]$ (example below). It is known, that $f[i]$ have a form of rectangular pulse with additive white Gaussian noise. $f[i] = s[i] + n[i]$, $s[i] = \alpha(\...
2
votes
2answers
1k views

Morlet wavelet time and frequency resolution

I want to calculate Morlet time and frequency resolution. the Morlet wavelet function is define as : $\psi(t)=\frac{1}{\sqrt{\pi f_b}}e^{j2\pi f_c}e^{-t^2/f_b}$ Note: I know the answers, but I don't ...
6
votes
3answers
330 views

Acoustic Scenarios With Negative SNR

For all the practicing engineers out there: Where have you encountered a negative SNR? How negative, in dB, was it or estimated to be? Where would you expect to encounter a negative SNR? Note: I ...
3
votes
1answer
5k views

How do I generate sound using MATLAB?

I want to generate and play sound for tones with frequency 100 Hz and 200 Hz for 10 sec and 5 sec respectively using MATLAB with sampling frequency equal to 20500 Hz. Also I want to plot their ...
3
votes
1answer
708 views

How moving part pixel intensity values of video frames becomes dominant compared to stationary part intensities in reconstructed frames?

Hello everyone i want to do dynamic texture video sementation using the Fourier transform in MATLAB. I am applying 3-D fft on dynamic texture video frames (using matlab function 'fftn') and ...
3
votes
1answer
174 views

Noise rejection / feature extraction

I'm hoping someone could point me in the direction of some signal processing methods to clean up my data. I'm collecting physiological data from human muscle (lower leg; gastrocnemius) during walking/...
3
votes
3answers
1k views

Need a better step detection algorithm

I have a time series with lots of steps/jumps (data file here). A plot is given below. I would like to subtract an appropriate value for each of these square wave features to bring them back down to ...
3
votes
2answers
3k views

detect to rising, stable and falling point in non-smooth rectangular wave

I am working on basic signal processing problems in MATLAB. I have found a signal from the internet (i don't remember the site exactly). The data is organized in column wise. 1st and 2nd column is ...
1
vote
1answer
912 views

Sampling signal after root raised cosine

I am generating series of 1 and 0. then pulse shaped them with root raised cosine and after than deciding to do match filtering and recovering the bits however it turns out that I am not getting the ...
0
votes
1answer
6k views

how to apply Short-time fourier transform to code in matlab

Please Help, I have a white noise signal that I created and need help to apply the Short-time fourier transform to my code so that it can do the bandpass filtering. I am trying to put it in the code ...
0
votes
3answers
614 views

Is the system represented by the equation $y(t) = x(2t)$ time invariant?

I came across this problem in the text book Signals and Systems - Oppenheim (Example-1.16). To solve this, I followed the following algorithm (described in the book earlier for a separate problem): $...
0
votes
1answer
13k views

System Properties; Linear, Causal, Time-Invariant, Stable?

I know the answers of the below question but I dont know why, except linear, could you explain the rest? Small tick: correct, small tick with dash incorrect answer.
4
votes
3answers
6k views

How to remove the periodic oscillations from a signal

The task that I have is to remove the annual and semiannual oscillation from a set of temperature measurements, taken over several years, by means of least squares method. I found the method ...
4
votes
3answers
2k views

Compressive Sensing Incoherence Principle

As people acquainted with Compressive Sensing would know, incoherence and sparsity are two main principles. I've been reading about compressive sampling and developed an interest into the topic. What ...