Questions tagged [signal-analysis]

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2answers
10k views

How do I find the fundamental period of the given signal?

I am having a problem in finding the fundamental period of the signal $x(t)$ given below: \begin{align} x(t) &= 2\cos\left(\frac 45 \pi t\right)\sin^2\left(\frac{16}{3} t\right)\\ &= 2\cos\...
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4answers
3k views

What does the exponential term in the Fourier transform mean?

We know that Fourier transform $F(\omega)$ of function $f(t)$ is summation from $-\infty$ to $+\infty$ product of $f(t)$ and $e^{-j \omega t}$: $$ F(\omega) = \int\limits_{-\infty}^{+\infty} f(t) \ e^...
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2answers
181 views

Significance of modular arithmetic in DFT?

In what ways does modular arithmetic plays a part in DFT? Why is it a so integral part of DFT?
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2answers
448 views

relation between luminance and eigen values of an image

There are some research papers in the literature which apply Singular Value Decomposition (SVD) on an image to decompose the image matrix into U, ...
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1answer
61 views

Element-wise powering vs. discrete version of binomial theorem on a sum of Gaussians

I had recently posted a question on applying powers on a sum of Gaussians (here) to enhance signal resolution artificially. The discussion has given rise to another query. Consider this problem. We ...
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1answer
598 views

Hilbert transform properties

Here Its says Hilbert transform is a non-causal,linear,and time-invariant system How can I prove it mathematically? wikipedia says the input output relation like this $$\boxed{y(t)=\frac{1}{\pi}\...
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1answer
309 views

How to build a realtime simple audio spectogram? [closed]

I'm trying to build a spectogram view of history time of 4 seconds and I'm stuck at the part where you load/draw FFT vectors into the 2D bitmap. I just don't know how to do that, but i got the FFT in ...
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1answer
897 views

Create a third octave spectrum from a time signal

I have to create a third-octave spectrum from a time signal on Octave GNU. I found some code on the net to help me but I don't have all the parts of the algorithm. I have a .csv file which contains ...
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2answers
3k views

FFT of Square Wave and Sin Wave

When we have FFT of Square wave of a pure real signal with high frequency(close to f(max), less than half of sampling frequency) we see only 2 symmetric high peaks but when we decrease the frequency ...
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1answer
3k views

Why do we need to normalize a WAV file before calculating the FFT?

I am trying to calculate the FFT of a signal stored in a WAV file using SciPy. I found a solution here, but it seems like we need to perform this step before the FFT: ...
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0answers
72 views

Interpolation methods for radar and acoustic imaging and potential pitfalls

A) What are the most common methods used to remap data for current generation imaging radars and acoustic sensors? B) What are some of the pitfalls in these methods? For example, in the past, at ...
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0answers
222 views

How do I find amplitude modulation effects in natural signals

It is relatively easy to discover overlaid (additive) signals in natural phenomena using wavelet decomposition, Fourier Transforms, CEEMD, etc, because addition in the time domain is the same as ...
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0answers
86 views

Determining the probability of two signals, with added independent noise, being the same?

I have the first 100ms of two signals, each with a noise independent to that signal. I want to compare the two signals and determine the probability that these two signals are (minus noise) the same, ...
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2answers
675 views

Relationship between $E_b/N_0$ and $\rm SNR$ with channel coding

I would like to know what would be the relationship between $E_b/N_0$ and $\rm SNR$ when there is a coding rate of $R_c=K/N$. Normally when there is no channel coding according to this link. $$\...
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2answers
76 views

Applying a Power on a Sum of Gaussians to Enhance Resolution

There is so-called Power Transform technique in signal processing where the unresolved signal is sharpened by raising each data to a constant positive power. The example shown below is a sum of two ...
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3answers
1k views

How to get Instantaneous Magnitude for a Instantaneous Frequency From FFT?

My understanding if a frequency in my signal doesn't line up exactly with a bin, it is smeared over a few bins to the right and left. How can the instantaneous magnitude be determined? (do I have to ...
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1answer
656 views

Apply band pass filter (BPF) before calculating the power of a signal (PSD)?

From my understanding PSD tries to give a good estimation on the power each frequency attributes to the overall signal power. If I am only interested in a frequency range $(\omega_0 \leq \omega \leq ...
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1answer
764 views

GPS Coarse Acquisition PRN Codes

Are the actual 1023 bit sequences for each of the 32 GPS satellites available to consumers? I found the IS GPS 200 but it doesn't list the entire sequences. Are verified sequences available for ...
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0answers
30 views

Varying speed of shaft Spectral Kurtosis

I want to perform Spectral Kurtosis (Kurtogram) on 10-second vibration signal of 25.6 kHz sample rate, where the shaft is varying in speed. Will a preprocessing step of resampling the signal be ...
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1answer
49 views

Upsampling question- Aliasing/imaging problem

I'm trying to study vibrations in a non-stationary shaft by upsampling the original signal. The original sample rate is at 25.6kHz, and it is being upsampled to 36kHz. In the FFT of the upsampled ...
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1answer
131 views

CIC Filter implementation for Normalized Correlation

This is a follow-on to the original post ... I am trying to implement real-time correlation of two signals. I noticed the CIC Filter discussion here: How to find correlation/cross-correlation of two ...
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1answer
38 views

What's the point of using Morphological processing concerning images?

I dig deeper in internet to figure out what's the point of morphological processing on images, but i'd rather to hear the answer from people with experience, can you give me a hand with this? Thank ...
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3answers
73 views

Is there any algorithm to decompose a wave into a set of given frequencies?

I heard about Fast Fourier Transform can decompose any waves. But it seems like it was hitting for "all frequencies", namely, n HAVE TO be from 0 to N-1! What if I want to decompose the wave into ...
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0answers
43 views

Interpreting Auto correlation results

I used xcorr function in Matlab to compute the autocorrelation of my signal. I obtained a graph, which is shown below. How to interpret this? I read that autocorrelation helps in finding the patterns ...
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2answers
207 views

Is there any way to differentiate between impulses?

I have a set of signals consisting of impulses at different instant of time i.e. its not a continuous signal. What I want is a mathematically intuitive way to distinguish between any two such signals? ...
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1answer
64 views

Equalization : using the spectral or the temporal signal?

I'm trying to equalize a sound signal - using a JAVA program - and I'm using this process : 1/ Conversion of the temporal signal to a spectral signal, using a FFT 2/ Applying a coefficient to each ...
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2answers
466 views

Why look at power spectral density for stochastic processes?

I have been told that for deterministic signals, it makes sense to look at their respective Fourier transforms/spectra. For stochastic processes on the other hand, I am supposed to work with power ...
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2answers
594 views

Understanding the definition of signal's bandwidth

In class, we have defined bandwidth of a signal as the difference between the maximal and minimal frequency. Also, our tutor explained that the bandwidth indicates how fast the signal is changing. ...
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1answer
32 views

What is the effect of sampling time, sampling frequency and SNR on latency? [closed]

I believe that if we have two or more external sound cards, hence clock would vary for each device. How will this affect the latency? Will it increase or decrease? How will the factors like sampling ...
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1answer
49 views

Frequency estimates from three-dimensional data

I have a lot of three-dimensional positional data from patients with tremor, unevenly sampled at approx. 50 Hz, with timestamps. I am trying to find the dominant frequencies in the signal/tremor. ...
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0answers
27 views

Relationship of input-outputs in Hartley transformation based on few elements in a vector

This question is related also to that question HERE, but with further details and another issue I need to solve. Assuming we have a vector $X = [x_0,x_1,\ldots,x_N]$, its Hartley transformation is ...
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1answer
3k views

Why NRZ-L and NRZ-I line coding have DC component?

I can find the effect of having a DC component in the Internet which is "When the AC waveform has a DC component, the average voltage would be equal to the DC voltage instead". But in my text book, ...
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1answer
212 views

Estimating confidence intervals for the mean value

Say I conducted a numerical experiment -a time-dependent fluid simulation- and extracted a time-series of some variable. It looks like this: As a result of the simulation, I am supposed to report the ...
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1answer
251 views

FFT Frequency bin relationship

I guess this is a stupid question or it is not clear. I will try again I have a situation where I take the fft of a combined source, both at the same frequency but at different locations. I am ...
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1answer
36 views

What is the actual format of this audio file?

I am collecting some data from jotform .wav widget. All the audio files are in .wav format. But when I tried to open the file using python ...
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1answer
665 views

Daubechies wavelet transform

i have N samples obtained by sampling a signal with lot of frequency contents. How will i apply daubechies wavelet transform to obtain the frequency and its location? i need to write a program which ...
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3answers
808 views

Expectation of deterministic signals

Maybe this a stupid question, but I came along with this point and I would like to confirm that I am not wrong. I found some similar posts in StackExchange, like: Expectation and Auto-correlation of ...
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1answer
63 views
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1answer
135 views

Bandwidth of a trimmed sinus wave

I generate a sinus which duration is 15ms and frequeuncy of 13KHz. Is its bandwidth is (1/15ms) ? Or in other words, BW = 66.6Hz? I ask that because I have two freqs in my system: 13K & 13.1K. I ...
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0answers
21 views

Any recommendations for buying SINAD measuring equipment? [duplicate]

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 -> attenuator ->HackRF connected to PC with SDR# ...
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1answer
3k 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 ...
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2answers
471 views

Why are the basis functions for DFT so?

When you get a DFT of a signal, you use the basis functions as: $e^{-j2\pi kn/N}$ Why is it so? Why don't we use the conjugate, $e^{j2\pi kn/N}$, or any other function?
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1answer
78 views

Separate Complicated Signal into Exponential Components

This morning, I asked a similar question about separating simple signals - with constant frequency - into exponential components. User @AndreasH suggested that a hilbert transform can do this as ...
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1answer
90 views

Reduce the “glare” effect of a receiver within a system

I'm working this summer on a very interesting, albeit difficult to understand at 100 %, project and it turns around reducing the glare effect than could be applied on a receiver when he gets signals ...
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1answer
2k views

Calculate average mean FFT Magnitude in bins [duplicate]

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 ...
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1answer
58 views

Recommended literature to learn essential aspects of signals and its propagation [closed]

Where can I learn about signal's features. For instance mean, power, amplitude, frequency, energy, how they propagate in space or any other medium?. What power means its amplitude increases and ...
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1answer
1k 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 ...
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1answer
355 views

$N$ point moving average filters in state space

I am new to this filter, I did read about them, but could find out a state space notation of these: $$y(n)=\frac{1}{N}\sum_{m=0}^{N-1}x(n-m)$$ Are moving average filters an LTI systems? And how do ...
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2answers
1k views

How to recover frequency and damping coefficient from superposition of damped oscillators?

I have a signal which is (more or less) the superposition of multiple damped oscillators. There are relatively few oscillators involved, 2-3 would account for most of the signal. They have periods ...

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