Questions tagged [frequency]
Frequency in signal processing is the number of cycles (of the signal) per second.
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What is the physical significance of negative frequencies?
This has been one of the holes in my cheddar cheese block of understanding DSP, so what is the physical interpretation of having a negative frequency?
If you have a physical tone at some frequency ...
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Amplitude modulation vs sampling rate?
As a sampled tone's frequency nears $f_s / 2$, amplitude modulation grows apparent:
("Actual" curve in grey; blue is what we get if taking samples (dots) "at face value"). This is ...
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What is meant by a system's "impulse response" and "frequency response?"
Can anyone state the difference between frequency response and impulse response in simple English?
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Which time-frequency coefficients does the Wavelet transform compute?
The Fast Fourier Transform takes $\mathcal O(N \log N)$ operations, while the Fast Wavelet Transform takes $\mathcal O(N)$. But what, specifically, does the FWT compute?
Although they are often ...
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Estimate Sine Frequency under White Noise — simple and effective method
Given a sinusoidal signal in white noise, how can one efficiently determine its frequency?
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Estimation of Amplitude, Frequency and Phase of Linear Combination of Harmonic Signal Beyond the Leakage Resolution of DFT
How can I find a rough ( as accurate as possible) Amplitude of each frequency when there is spectral leakage.
Currently, I am dealing with a system that contains special leakage which seems ...
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How can I get the power of a specific frequency band after FFT?
I need help with my matlab code. I have recorded EEG data and now I want to analyse it in matlab. I want to find the mean power of specific frequency ranges (theta: 4-8 Hz,alpha: 8-12Hz etc.). For ...
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Image Reconstruction:Phase vs. Magnitude
Figure 1.(c) shows the Test image reconstructed from MAGNITUDE spectrum only. We can say that the intensity values of LOW frequency pixels are comparatively more than HIGH frequency pixels.
Figure 1.(...
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FFT frequency resolution
I'm having some problems understanding the FFT. Is the frequency resolution in the spectrum calculated as
$\frac{\textrm{sampling rate}}{\textrm{number of FFT points}}$ or $\frac{\textrm{sampling ...
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Is there an algorithm for finding a frequency without DFT or FFT?
I was looking in the Android app store for a guitar tuner. I found a tuner app that claimed it was faster than other apps. It claimed it could find the frequency without using the DFT (I wish I still ...
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Detecting drum bpm in a noisy .wav file
I am looking for algorithm(s) to solve the following problem:
Given a noisy .wav sound capture (some wind + friction noise on the microphone), how to detect the BPM of a soft drum beat?
I have ...
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Calculate and interpret the instantaneous frequency
I'm new to the principle of calculating the instantaneous frequency, and came up with a lot of questions on it. You find them all in a bullet-point list at the end of this text. The text might be a ...
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Lock-in amplifier
From what I have studied so far I have understood that the benefit of a lock in amp is its ability to resolve the amplitude of a signal which is deep into noise.
I was wondering if the same concept ...
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What can be meant by "bandlimited"?
This question was a source of disagreement on whether "amplitude aliasing" can occur for a signal bandlimited to below half the sampling frequency. The question was closed before the ...
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FFT for a specific frequency range.
I would like to convert a signal to frequency domain. The desired frequency range is 0.1 Hz to 1 Hz and the frequency resolution ...
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Why does a wave continuously decreasing in frequency start increasing its frequency past the half of its length?
I'm trying to programmatically generate a wave (sine or square) with a continuously decreasing frequency.
To do so, I simply multiply the starting frequency for a decreasing value, that linearly goes ...
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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 $...
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Bandpass filter equivalent for amplitude
I have a signal where I am using a bandpass filter to limit the frequency range. I am also interested in filtering the remaining frequencies (after bandpass filtering) within the signal by their ...
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PLL for Phase Demodulation and Carrier Tracking
I've been playing around with using a PLL for phase demodulation and it's working pretty well. The PLL locks to the carrier and the error term is the demodulated message signal. However, depending on ...
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Upsample data using FFTs. How is this exactly done?
I am basing my question on this post here, because I would like additional details on it, as I have not had any success in re-creating it.
I would like to simply learn, in no uncertain terms, how to ...
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What Is the Bilateral Filter Category: LPF, HPF, BPF or BSF?
I`m reading about Bilateral filter with images, I knew that it uses Gaussian filter (which is a LPF) as a domain filter plus a range filter and it is used to preserve edges(high freq component).
Can ...
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Designing High Pass Filter to Remove DC Offset from a Signal
I want to design a high pass filter (f0*S/1+f0*S) in order to remove the dc offset from a signal ? (i.e. how to choose the frequency f0).
Thanks,
Hacene
Ps : the filter is for MATLAB implementation, ...
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Signal Processing/FFT gives very high magnitudes for low frequencies
The script essentially pulls PCM data from the sound card and stores them in a buffer. Then I apply fft and graph it. I am looking through this blog post for some examples and ideas on how to ...
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Is there other basis possible for DFT?
As I understand, the DFT of a signal $x$ is a representation of this signal in the basis
$$ \{ e^{j2\pi kn/N} \}_{k = 0, 1, \dots, N-1}$$
Is it possible to form a base of such discrete complex ...
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Determine fundamental period from zero crossing signal
I have got a signal which consists of zero crossings over discrete time and I would like to estimate the fundamental frequency (period) from this signal in order to remove noisy samples.
The signal ...
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instantaneous frequency for a sum
In the literature, the instantaneous frequency for a signal $s(t)=e^{-j \phi(t)}$ is given by: $$f(t)=\tfrac{1}{2\pi}\frac{d\phi(t)}{dt}$$
This my problem: I have a signal $$u(t)=e^{-j \alpha_1 \phi(...
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Difference between Fine and Coarse Frequency Offset in OFDM
I need to explain for a project the difference between Fine and Coarse Frequency Offset in OFDM signals. I know what the frequency offset is and what it does to the carrier frequencies but I cannot ...
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Magnitude value of filter frequency response
Can someone help me with this problem:
Suppose we filter signals with the below pre-emphasis filter:
$$y[n]=x[n]-0.8x[n-1]$$
I have to calculate the impulse response of the filter (ok easy) and ...
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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 ...
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OFDM sampling frequency offset
how the 4G LTE Or 5G NR OFDM measures and corrects the sampling frequency offset? if there is an algorithm using matlab please help
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Does negative frequency actually exist or it is just theoretical?
This below questions gives good explanation regarding negative frequency
What is the physical significance of negative frequencies?
But I have one query
Does negative frequency only exist ...
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Extracting different frequency bands (alpha, beta, gamma) from MEG source estimated data
I have a dataset that consists of source estimated data of MEG brain signals.
I need to extract the different frequency band features (i.e., alpha, beta, gamma, etc) from them.
What steps/procedure ...
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Symbol timing recovery in Python
My objective is to demodulate QPSK signal. At the receiver I apply RRC filter and interpolate the signal to get the values of the signal (approximately) at the sampling instances. Then I am concerned ...
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What is the Gabor filter? And what are its main uses?
I'm doing research on the Gabor filter. When I Googled it, I found very long and complicated articles. Can anyone help me to find a simple explanation about it, or recommend a website or article to ...
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How can I plot frequency vs magnitude of wavelet transform?
I am running Morlet continuous wavelet transform. I have got wscalogram of signal and now I want to plot freq-magnitude like the following picture., but I don't ...
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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 ...
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What is the bandwidth of a (real) sinusoidal tone, and pulse?
I would like to know how to go about calculating the bandwidth of:
A constant (real) sinusoidal tone
A (real) sinusoidal pulse.
The question is as simple as that, but I am having a hard time with ...
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How is it possible to Filter out a person's voice out of 100 of other voices?
So, I've just learned that the human voice is not a single sine wave its a bunch of unlimited Sine waves each having a different frequencies,
According to Wikipedia,
The voice consists of sound ...
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Discrete Time Signal Property
Property:
The frequency of oscillation of discrete time sinusoids sequence increases as $\omega$ increases from $0$ to $\pi$. If $\omega$ is increased from $\pi$ to $2\pi$ then frequency of ...
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Why should one use windowing functions for FFT?
So I just revised my pitch calculation algorithm using a harmonic product spectrum algorithm. I was just curious about why this explanation of Harmonic Product Spectrum states that you need to ...
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Amplitude of the Signal in Frequency Domain different from Time Domain
How does the Amplitude of the Signal is changed when taking the FFT of a Signal,
Have a look,
The amplitude had changed from 2 to 30,
and Here is my code for generating the above output,
...
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What is the difference between phase noise and frequency noise?
I'm reading Audoin and Guinot's The Measurement of Time: Time, Frequency and the Atomic Clock, and ran across a confusing an interesting passage (Section 5.2.5, pp 72-73):
The physical origins of ...
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Why can Quadrature Demodulation demod a Frequency Modulated Signal?
I use a Quadrature Demodulator in my SDR application, which is defined as:
$\angle (S_n, S_{n+1})=arctan(S_{n+1}*\overline{S_{n}})$
So practically its amplitude is the angle between two Samples $S_n$...
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Doppler shift in time domain?
I have some clarifications required in this topic
So initially I know that to shift a signal $X(f)$ by $f_0$ we need to take its inverse fourier transform and multiply it with a factor of $\exp(−j2\pi ...
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Setup frequency array properly
I've just stepped into the FFT's world since the last weeks, therefore I still don't have an clear overall idea of how to setup the frequency array.
In case of even...
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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 ...
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Removing noise from audio using Fourier transform in Matlab
I'm trying to remove noise from an audio file. This audio file contains speech as well as constant pink noise. I know that I have to use the Fourier transform to convert to the frequency domain then ...
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Calculate the magnitude and phase of a signal at a particular frequency in python
I have a signal for which I need to calculate the magnitude and phase at 200 Hz frequency only. I would like to use Fourier transform for it. I am very new to signal processing. And this is my first ...
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How to find period/envelope that is larger than sample size?
Mercury's distance from the solar system's barycenter (in kilometers)
can be approximated as:
...
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Understanding the $\mathcal Z$-transform
I was studying $\mathcal Z$-transforms and found pretty good material on the topic, though I feel I do not have a proper understanding of the concept. Could someone help me clarify this?
I know that ...
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