Questions tagged [fft]

The fast Fourier transform is an efficient algorithm to compute the discrete Fourier transform (DFT) and its inverse.

Filter by
Sorted by
Tagged with
0
votes
1answer
14 views

How to extract the dominant frequency from the audio WAV file using numpy

So, I recorded this audio on my phone while I was running a tone generator on my PC at a frequency of 13Khz, now I want to extract this frequency which is dominant from the recorded ...
0
votes
1answer
28 views

FFT for Arbitrary time history

I have two Time-Speed histories one is real ( real measurements) the other is synthetically generated using formula. I need to compare both in the frequency domain using FFT given that: the time step ...
1
vote
0answers
39 views

3dFFT to compute angle of arrival in FCMW radars

I hope I am not asking any already-answered question. I have a simulated doppler-range map of a 1Tx - 4Tx (azimuthally displaced) FMCW radar and I am doing something wrong to calculate the angle of ...
0
votes
1answer
38 views

Audio, estimate codec's compression ratio only by content

I am about music audios. These can be compressed by different formats with different degree. (I.e. I don't mean the dynamic compression). After being compressed by a large degree (say 96kbps mp3) the ...
1
vote
1answer
45 views

Help generating non-Gaussian noise

I'm trying to add non-Gaussian noise to an image. The purpose is to synthesize realistic camera noise. I am doing the following: Obtain a noisy image sample by subtracting a low ISO photo from a high ...
0
votes
1answer
52 views

Periodic signal detection algorithms?

I am currently working on pulsar signal periodicity detection. Most of the literature which i studied used traditional FFT (Fast Fourier Transform) or (Epoch Folding) techniques to find the ...
0
votes
0answers
26 views

How to smooth wiener deconvolution result in Python?

I'm wondering if it is possible to smooth the estimated response from a Wiener deconvolution in order to have a better representation of the original signal and to remove the side lobes. (Here an ...
0
votes
1answer
27 views

Matching short tones

I have a series of tones, that are no more than a second long each (around 0.6/7 seconds each), I am recording them through a soundcard and want to be able to match which tone has been played. I am ...
0
votes
1answer
89 views

Motion detection with FMCW radar

I am studying the work of a microwave rangefinder and faced such a problem, but before that, a preface: I have a microwave module that operates at 24GHz. I use a 1kHz triangle waveform as the ...
1
vote
1answer
27 views

Frequency mixer shows 2 FFT spikes

I'm attempting to use a frequency mixer to shift one frequency range to another. Right now, I have a complex sine wave at $43\ \rm kHz$. My imaginary value on the complex object is 0. If I output a ...
0
votes
1answer
35 views

FFT gain after Zero Padding

I am trying to compare signals in the spectrum domain. The signals have a different number of samples, N samples of signal1 and M samples of signal2. To compare the powers, I am doing an FFT of N ...
0
votes
1answer
46 views

How to separate real and imaginary part of a complex FFT?

I have an exercise where I have to calculate the FFT of a complex signal $x=l+j\cdot r$ using only one single call to a complex FFT algorithm. $l$ is the left, $r$ the right real valued vector of a ...
0
votes
1answer
27 views

Fast fourirer transform - Even and odd numbered elements

I'm trying to understand some optimizations on DFT. So in this step, there is a note like the following: The next step involves the mathematical observation that the even-numbered elements can be ...
0
votes
2answers
37 views

Calculating Hann WIndow

Hey I have this CSV file which contains 8 chunks of 256 samples of a sine wave with different frequencies (each chunk has different frequency starting from 8 to 64Hz). The total samples of this file ...
0
votes
0answers
25 views

Power spectrum of a signal in negative frequency domain

I have a signal with fc = 308 kHz and B = 30 kHz and some white noise added. The signal is sampled at samplFreq = 4fc. ...
0
votes
2answers
36 views

"Mirror" look when computing FFT on samples

I'm trying to plot a frequency-magnitude spectrum, I have 2048 samples of a complex sine wave where the imaginary part is always 0, this results a "mirrored" look, so if I have one sine wave ...
0
votes
1answer
43 views

Alg for identifying any temporal interfering signal

I'm a little bit on a loss at my search for an algorithm due to audio signals. I'm a sw-engineer with some basis knowledge in math here and there, know how to build and use FFT etc. but with no prof ...
0
votes
2answers
24 views

Interpolation from discrete time fourier transform in python

I have a function that I sample from over one period. I want to use the Fourier Transform to learn the function and then predict unsampled values. Please see the code below: ...
0
votes
1answer
33 views

scipy.signal.stft temporal resolution

Using the STFT function from scipy.signal has produced unexpected results for me. I am performing an STFT on 10 seconds of data, sampled at 25,000 Hz. I am using STFT settings of nperseg=256 and ...
1
vote
0answers
48 views

Introductory DSP Texts [duplicate]

I have an interview for a communication theory position and part of the interview requires basic knowledge of signal processing. What are good introductory texts that cover the basics of signal ...
0
votes
1answer
36 views

Extracting "frequency domain features" from signal for classification

I have a real signal with only nonnegative values (actigraph measurements). Many papers say they use "frequency domain features" for classification, such as mean, variance etc. But I'm ...
1
vote
0answers
69 views

Wrong amplitude in the FFT for 10 seconds measured signal

I measured a signal with the Osziliscope that I generated with a signal generator. The signal is a pure sine wave with a frequency of 1 kHz and a peak amplitude of 2.5 V, I measured the signal for ...
0
votes
1answer
83 views

Calculating an N point FFT by calculating 4X N/4 point FFTs in parallel

I have an FPGA based application where I need to perform 4096 point FFTs in real time on a 1GS/s data stream. Data comes to the FFT from an A/D converter as 4 samples in parallel at 250Mhz. My data ...
0
votes
1answer
55 views

When to zero-mean a signal?

I have two sets of signals. The first is a noisy sinewave, which I zero-mean before taking the FFT since I need to find the amplitude. The other is essentially noise with a gaussian distribution. I'm ...
1
vote
1answer
70 views

Shifting frequency in Fourier domain

Assume I have a continuous function $f(x)$. Its spectral representation is $F(X)=\mathbb{F}(f)$. I need to calculate another function $f'(x)$ which has a spectral representation of $F'(X)=g(F(x))$, so ...
1
vote
1answer
35 views

EEG peaks do not get identified at the correct frequencies

For my thesis I am re-analyzing a dataset where subjects were visually stimulated with 5.45, 8.57, 12 or 15 Hz. This well-known technique (steady state visual evoked potential) should elicit EEG peaks ...
0
votes
0answers
13 views

Reasonable Methodology for Breathing Data Analysis

I am currently analyzing breathing data taken from nostril exhalation over a microphone over a period of 1 minute, and wanted to figure out the best way to tell which nostril is 'dominant'. Currently, ...
1
vote
1answer
35 views

Reduce signal length while maintaining properties?

I am new to DSP. So I have a noisy signal with some high-frequency components. I was able to characterize the statistical properties of this signal through a gaussian distribution. My aim is to run a ...
0
votes
1answer
43 views

FFT on impulse response: phase doesn't look right, Python

I want to analyze an arbitrary impulse response. Basically, a list of tap coefficient. In general, "tap1" will give me a BW limitation. I want to add more taps and see what it does to the ...
1
vote
1answer
27 views

Minimum discernible frequency in power spectral analysis

Say I have a signal of length 20s that contains signal from various (unknown) biological sources, e.g. heartbeat (~0.2Hz), respiration (~1Hz), and possibly som very-...
0
votes
0answers
51 views

How to get the phase of a 2D sine wave?

I am trying to find the phase of a generic 2D sine wave with the 2D FFT. The formula for the phase is arctan(im/re). So I made 22 sine waves with phases ranging from 0 to 2 pi (by cropping the ...
1
vote
1answer
105 views

Radar MIMO Virtual Antenna Array Formation

Referring to the figure attached above, is the ordering of the virtual antenna arrays (shown on the right) to measure azimuth and elevation angles of arrival correct? In my understanding, the ordering ...
0
votes
0answers
38 views

Problem with the output self implemented “ Iterative FFT DIT Radix2 ” algorithm matlab

I´m trying to implement my own FFT with the iterative Radix2 algorithm (I even thought about using the recursive one but it seems Simulink doesn´t allow me to). I tried all of the possible variations ...
1
vote
0answers
15 views

Properties of the Frequency Domain to Ensure a Periodic Inverse Discrete Fourier Transform

I've been working on a project to send data via sound waves. The way I've carried this out is by encoding the data in pulses in the frequency domain, and then creating a unique sound wave containing ...
1
vote
2answers
64 views

What is the advantage of overlapping windows while evaluating Spectrogram?

I've seen many documents that refer to calculate spectrogram through overlapping windows but haven't found clear documents on why this is done and how to calculate the number of points that need to be ...
2
votes
1answer
47 views

Why the frequency response is similar for different inputs?

I am new to DSP, learning some stuff, and looking for some advice from experts here. I am using the CMSIS DSP lib to get the frequency response of a dummy input signal that's a combination of 10 Hz + ...
0
votes
1answer
77 views

Why does a wave composed of two waves have an FFT with only one peak?

I am trying to find a value from a given mathematical function whose input is supposed to be derived from FFT components. Essentially, I follow the procedure from [1] which assumes that a given sine ...
0
votes
0answers
29 views

Reflected wave in FFT?

I'm trying to determine the reflective coefficient of sine wave. This one paper suggests a method using Fourier analysis. Here, it suggests Incident Wave = a cos(kx + Constant1), Reflected Wave = a ...
0
votes
1answer
38 views

FFT behaving weirdly for frequencies below 100Hz

I've written a simple program to take an audio file, and calculate the most prominent frequency for every 0.1s interval. My audio file has a sampling rate of 48000, and am taking datapoint windows of ...
0
votes
0answers
14 views

compressed sensing versus Lomb-Scargle

Say I have a signal that's the sum of only a few sine/cosine waves, and some noise, which has been measured at random times. I would like to find the frequencies of the waves. With this goal in-mind, ...
2
votes
0answers
50 views

Multiple 1D gaussian filter

Given $$ \begin{cases} &f_0(x)=1 \\ &f_{n+1}(x)= (\varphi*(f\mathbb{I}_{[a_n,b_n]}))(x)=\int_{-\infty}^{+\infty}\varphi(x-t)f_n(t)\mathbb{I}_{[a_n,b_n]}(t)dt = \int_{a_n}^{b_n}\varphi(x-t)f_n(...
0
votes
0answers
12 views

How to find the number of vectors to sample in Compressed Sensing?

When comparing my MATLAB code to a previously written one, I come across the following formula for the number of vectors to sample: ...
2
votes
1answer
48 views

excluding the value of some frequency in a Fourier Transform

I have a variable in time and I calculated its mean which is 9.5. I have done the Fourier Transform of this variable, using the FFT in matlab. I would like to consider only a range of frequencies, so ...
0
votes
0answers
17 views

Setting required FFT spectrum bandwidth w.r.t the Sampling rate

I am working on an accelerometer with sampling rate of 26.7 kHz using which I intend to calculate FFT. Hence the FMax = (26.7/2.56 = 10.4kHz). As I am performing this on a microcontroller, I have a ...
1
vote
1answer
41 views

Analog Signal Treatment for FFT with Padding

My education and career has been focused in mechanical and materials science; sorry if the following is well known, but I haven't been able to find the appropriate SEO terms. Wanting input to further ...
0
votes
0answers
33 views

Matrix multiplication computational complexity based on radix 2

I am wondering, can we use Radix 2 based computational-complexity calculation for any matrix multiplication whose size is $N$ x $N$ ?? where $N$ = $2^K$ and $K > 1$ is an integer ?? Or it can only ...
2
votes
0answers
55 views

How do large tap counts effect FIR Filters for block data?

I am using the ARM CMSIS DSP library for a signal processing application. I find good filter performance when using tap counts that are in excess of 10% of the length of my data block. I understand ...
0
votes
0answers
37 views

Output of sliding FFT with a white noise input

I'm currently in the process of porting a customer's algorithm for Matlab/Simulink to a DSP. In their algorithm, they perform a sliding DFT on a sinusoid and they use bin 1 to estimate the frequency. ...
0
votes
1answer
38 views

OFDM IFFT/FFT processing

After the serial-to-parallel to break input bitstream into groupings we do the constellation mapping into values of phase/amplitude (or I, Q). For 64 sub-carriers this gives us 64 pairs of amplitude(n)...
0
votes
2answers
73 views

Is there a way to convert audio to a list of frequencies preserving the temporal position?

I want to convert an audio file to a list of frequencies. We can apply an FFT on the audio to gain analysis of all the frequencies in a given audio sample, however, I want a list of frequencies as a ...

1
2 3 4 5
53