# Questions tagged [filters]

In signal processing, a filter is a device or process that transforms a signal by selectively choosing specific frequencies and leaving others with appropriate gain or as it is.

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### Pre-Warping is not working on bilinear transform

New here and I just wanna ask the question of what happens when your pre warping doesnt work on your bilinear transform? I am assuming my isnt working as part of my research I have read that the ...
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### Can digital filters actually separate signals?

I've come to realize what appears to be a hard limit in convolution theorem: to avoid time-domain aliasing, we must pad the signal/filter, but the padding distorts the spectrum. Consider a ...
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### Accelerometer Inference from power spectrum

I have 3d accelerometer data sampled as 60hz. When I am looking at the power spectrum in all three accelerations (x,y,z). I am noticing a trend with a negative slope. I trying to figure a few things ...
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### Is there really no perfect digital filter?

In context of transition width vs. stopband attenuation, different windows (Blackman, Hamming, etc) are compared in terms of tradeoffs between the two, always noting that one cannot perfect both. Why ...
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### What is meant by “information encoded in time domain”?

Author on pg 292 claims the windowed-sinc "is not a filter for signals with information encoded in time domain", because its "step response has overshoot and ringing". That phrase, ...
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### reconstructing a frequency response function from a factor

I am looking at a stationary monopole source with a frequency of 80 Hz with the driving data $1+0i$. It creates an output $-0.191714-0.786113i$ at a certain point $p$. I calculate the "transfer ...
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### Convolution and Cross Correlation Blackbox

Suppose I was handed a blackbox that I know is either a Convolution filter or Cross-Correlation filter, and my job is to find out which it is. My idea is to pretend that it's Cross-Correlation and ...
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### Complex signal low pass filter

I'm trying to implement a low pass filter in python for a complex signal but the output doesn't look right. I've created a simple example below where I've mixed a 15Hz complex sine wave and a 30Hz ...
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### Correlation in Image Processing vs Correlation of statistics

I am new to image processing. Please forgive me if you find this question naive or meaningless. I was studying about correlation filtering in images to smoothen the image. I want to know if ...
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### How Come the Low Pass Filter in Sobel Operator Isn't Normalized?

I am relatively new to the field of computer vision and I have just learnt about the sobel operator. The sobel operator in the x direction is a convolution of the finite difference kernel $[1,0,-1]$ ...
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### Variable Window Size of Blackman FIR filter

I am trying to implement an FIR filter with a Blackman window function. The solution I got for my signal filtering problem is to have different window sizes for certain characteristics of the input ...
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### Apply “non-causal” filter buffer-wise, a.k.a “soft real-time filtering”

I am dealing with digital filtering of signals, both offline and in real-time. Typical filtering purposes are highpass filter or bandpass filter. So far I worked on prerecorded signals (e.g. ...
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### half-band fixed-point decimate-by-2 fir filter with matlab

I would like to apply a half-band fixed-point decimate-by-2 symmetrical coefficients fir filter to a stream of 15 bit ADC output with matlab and see its effect done to the data. I already have ...
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### How to determine windows size of moving average filter

I've recorded acceleration signal data using an accelerometer attached to vehicle , and I want to calculate the displacement of signal data using double integration or any other methods. I read many ...
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### Differences between the mean filter, trend(mean) removal, and baseline correction filter?

I've recorded acceleration signal data using an accelerometer attached to vehicle and I want to know what the differences between the mean filter, trend(mean) removal, baseline correction filter, and ...
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### Are IIR filters (and specifically Butterworth filter) causal?

I am new to signal processing. I am learning now about filtering and I am trying to implement high pass filter (HPF),and later band-pass filter (BPF). I implement the filters in ...
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### Filtering a square signal with a median filtering to preserve the edges

If needed, you can find my first post for this problem here. I am trying to clean the following signal: As proposed in the comment, I tried to use this post proposing 2 methods: median filtering and ...
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### Applying a lowpass filter to a noisy square signal leads to a shift of the signal

My knowledge of analog and digital signal analysis is behind me.. thus I do not have enough confidence in my procedure to analyze my signal, and I do not know which direction to pursue to improve. I'm ...
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### Design RRC filter [closed]

I have designed a RRC filter, as below : ...
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### Roll off rate vs filter order?

The concept of "increasing roll off rate with increasing filter order" applies only to butter worth or also chebyshev and other filter types?
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### DSP system toolbox buffer boundary conditions with filters such as dsp.HampelFilter

I have started using DSP system toolbox. It seems to be very efficient for designing simple routines with hardware restrictions. A good example is the simulation of the Biquad Filter with buffer ...
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### Is it applicable to implement a cascaded moving average filter with variable window on real-time?

I am using a 3-pass cascaded moving average filter for smoothing noisy data. I applied some optimization algorithms to determine the optimal length of the MAF window. For different amplitudes of data ...
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### Sweep through a resonance simulated with FM+AM

I'm working on a hobby project involving music synthesis with parallel processing on my dekstop computer's GPU. The technique is that for a sound that has some time-varying spectrum of partials, I ...
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### Modulation upsampling method

I try to implement a qpsk modulator in Octave. The chain is the state of the art I guess: Mapper -> Upsampling x4 -> Root raised cosine filter. My main question is about the upsampling. I try to ...
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### How does window length influence cut-off frequency of filter and group delay?

I'm attempting to interpret the following function. To my understanding, this aims to implement an FIR low-pass filter with a Nuttall window. Then, it filters the signal by a simple application of the ...
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### What is sampling frequency in this case?

I am using Matlab fdatool to implement highpass IIR butterworth filter But 'Fs' value cell is gray and i am not able to change sampling frequency, what is the actual value in this case of attached ...
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### Advice on designing a digital filter that doesn't have phase-sensitive edge artifacts?

I'm pretty well versed in statistics, but not really digital signal filtering. I have a data scenario where I expected to be able to pretty easily filter out some noise (human pulse) that's at a known ...
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### How does this represent a low-pass filter?

I am faced with the following code snippet to get an understanding of a F0 estimation algorithm (DIO). Have a quick look below: ...
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Following shows the discrete time Fourier transform of an ideal low pass filter with cutoff frequency $\omega_c$: H\left(e^{j\omega}\right) = \begin{cases} 1, & \text{if $|\omega| \le \omega_c$...
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### Filtering a noise of F[sig] frequency [Example 20Khz] in measurement system

I am developing a system where there is inherent noise of F[sig] frequency. This is a DC measurement system and want to get rid of the noise by sampling at F[samp] samples per rate and taking multiple ...
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### How to filter, in real-time, a quasi periodic signal

I have a signal affected by a rather complex quasi-periodic noise. I must filter this signal in real-time to remove this noise. The noise is not really "high frequency" and its main ...
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### Reconstructing a signal from multiple filtered copies using overlapping tapered windows

I have an audio signal that I need to process and analyse in blocks. I've now decided to process it using overlapping non-symetric Hanning windows of length M = 9600 and a hopsize of R= M/2. I zero ...
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### IIR to FIR, is a best fit polynomial usually necessary?

I'm messing around with IIR/FIR filters and want to convert the former to the latter. I set up a classic impulse response calculation. X[4] = 1.0 Y[0] = 0.0 Y[1] = 0.0 ...
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### Which one can be accompanied by linear filters?

I have a matrix : \begin{bmatrix} 1 & 2 & 3\\ 1 & 4 & 5\\ 2 & 6 & 7 \end{bmatrix} After doing operation 1 , I get \begin{bmatrix} 0 & 0 & 0\\ 1 & 2 & 3\\ 1 &...