Questions tagged [signal-analysis]

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14
votes
2answers
13k 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{ ...
11
votes
1answer
21k 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, ...
59
votes
11answers
18k 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 ...
18
votes
1answer
25k 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 ...
3
votes
0answers
245 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 ...
44
votes
8answers
46k views

Meaning of Hilbert Transform

I understand the Fourier 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 ...
5
votes
3answers
8k 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....
10
votes
3answers
4k 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 ...
2
votes
1answer
1k 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 ...
3
votes
3answers
7k 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
2answers
219 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\;\;\;\...
12
votes
7answers
13k 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 ...
9
votes
2answers
769 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(\...
7
votes
1answer
3k 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 ...
4
votes
2answers
858 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
2answers
310 views

Sampled and aliasing signal

π‘₯(𝑑) = cos(200πœ‹π‘‘) + 2cos(320πœ‹π‘‘). π‘₯𝑝(𝑑), is produced by sampling π‘₯(𝑑) at sampling frequency $f = 300 Hz$. Is the signal sampled or aliased and why?
0
votes
1answer
453 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 ...
13
votes
2answers
13k 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 ...
7
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 ...
3
votes
2answers
2k views

Frequency Analysis (DFT / FFT) of a Signal Without a Constant Sampling Frequency (Non Uniform Sampling in Time Domain)

I'm a stack exchange user for some time and now I'm registering to ask a simple question (I think!). I have a vibration signal with an amplitude and time (sampling frequency not constant) in a $...
1
vote
3answers
4k 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
vote
1answer
1k views

Is convolution distributive over multiplication?

Is there any formula or expansion for $$a(t)*[b(t) \cdot c(t)]$$ $$a(t) \cdot[b(t)*c(t)]$$ where $*$ denotes the convolution? By expansion I mean something like $a(t)\cdot[b(t)+c(t)]=a(t)b(t)+a(t)...
0
votes
1answer
681 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 ...
4
votes
3answers
3k views

Why do we get ripples in the frequency spectrum of a chirp, and how do I remove it?

The ripples in the amplitude spectrum of a linear spectrum is undesirable. I desire to obtain a flat spectrum response. Hence, how can I remove these ripples? Also, which factors (like time bandwidth ...
3
votes
3answers
1k views

Dynamic convolution vs Volterra series

I'm trying to understand how a dynamic convolution model relates to something like a Volterra series, and what kinds of effects the latter can capture that the former can't (and vice versa). By ...
1
vote
1answer
65 views

Why does my sinusoid look “AM” in shape?

My code is : Fs=200e6; Ts=1/Fs; NFFT=2^14; Runtime=(NFFT-1)*Ts; t=0:Ts:Runtime; f_in=90*1e6; y_in=sin(2*pi *f_in *t); plot(t,y_in) ylim([-1.5 1.5]) Then why does ...
1
vote
1answer
4k views

What is the difference between undersampling and oversampling in analog to digital conversion ?

When converting a signal from analog to digital, we observe undersampling and oversampling. Does oversampling means that the sampling frequency is greater that the signal's frequency and does ...
1
vote
2answers
465 views

Significance of $ \lambda $ in Basis Pursuit

In basis Pursuit, L1 minimization is done to perform compressed sensing. In the literature there is a $ \lambda $ parameter used as a regularizer. What is its significance?
1
vote
1answer
116 views

Coefficients of the Fourier Series expansion of physical signals having finite power

Question 2.7. Show that for all periodic physical signals that have finite power, the coefficients of the Fourier series expansion $ x_n $ tends to 0 as $ n \to \infty $ I have computed $ |x_n|^2 $ ...
1
vote
5answers
68k 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|} $
4
votes
1answer
170 views

Signal Processing using Fourier Transform

How can I derive the fourier transform of ...
2
votes
3answers
2k views

Cyclic prefix vs. guard interval. Why use one over the other?

I'm currently studying some OFDM techniques, and have found that in order to avoid Inter-Symbol Interference (ISI), there needs to be some space in between symbols. Lets assume this length to be $\mu$....
1
vote
1answer
484 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
1answer
207 views

What is difference between outputs of Fourier transform and Fourier series of a periodic square waveform?

We can use Fourier transform of an aperiodic signal and Fourier series of periodic signal. But we can use Fourier transform formula for periodic function also. Now, let us consider a periodic square ...
1
vote
2answers
134 views

Eye pattern construction and interpretation

I have read some text about the eye pattern (or eye diagram), but I do not understand how should I read it. The wikipedia definition of it is this one: In telecommunication, an eye pattern, also ...
0
votes
2answers
5k views

Probability error for antipodal systems and orthogonal systems

I know that the error probability for antipodal systems is Q (√((2Fs)/No)) and for orthogonal systems it is Q (√(Fs/No)), however, can anybody give their derivation? Because I am finding different ...
0
votes
2answers
722 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
0
votes
0answers
79 views

IQ to RF conversion

I appreciate any help: I wanna convert IQ data to its RF data, representing an image. The centre frequency and sampling rate are available. What I do is: First I do up-sampling in MATLAB by ...
0
votes
2answers
45 views

How can I shape my time channel response, in order to have Gaussian shaped Doppler Spread?

I know how to generate a Rayleigh fading channel but I have no clue how I can shape the Doppler spectrum to be Gaussian. Any help will be really appreciated. ps: I am coding on matlab
0
votes
1answer
516 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
1answer
104 views

Recommendations for SINAD equipment

I am interested in buying a device that measures the SINAD of the audio signal(FM signal) that I receive from PC. Here is the setup: Signal generator (generating 1kHz FM signal ) $\rightarrow$ ...
15
votes
6answers
7k views

Is there any practical application for performing a double Fourier transform? …or an inverse Fourier transform on a time-domain input?

In mathematics you can take the double derivative, or double integral of a function. There are many cases where performing a double derivative models a practical real-world situation, like finding the ...
12
votes
2answers
14k 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 ...
20
votes
3answers
37k 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 ...
4
votes
3answers
3k 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 ...
12
votes
7answers
5k 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
5k 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 ...
5
votes
3answers
3k 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 ...
4
votes
4answers
13k views

Simple and efficient algorithm to detect frequency and phase of a sine signal

I need an algorithm to detect frequency and phase of a pure sine signal. The frequency of the input signal changes between 0 and 100 Hz. The value of the signal gets captured with a frequency of 20 ...