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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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how can I design Chebyshev filter with 5th-order polynomial and 0.001%-allowed ripples?

I'm very beginner in signal processing. I need to design a Chebyshev filter with 5th-order polynomial and 0.001%-allowed ripples by using matlab as I found in a paper. I'm filtering pressure data ...
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Is it possible to design a band-pass filter with fewer taps than a series HPF + LPF?

I am digitally filtering a signal that is streaming live. The goal is to reduce the filter delay as much as possible while maintaining the quality of some measurements based on the filtered signal. ...
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How to set sigmas and kernels for 3D-Laplacian of Gaussian filters to blob detection in Matlab?

I have written code according to a paper for Lung CT images, but its output wasn't correct. I think it is because of the setting of its parameters. The paper is about a multi-scale method using a ...
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How to filter low frequency signal from my correlation output [on hold]

my correlation output contain my useful low frequency signal. How to design a proper filter for that. I have used Fdatool and design a FIR filter, but that didn't work for me. code . ...
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What version of sinc function to use ? (With additional factor of $\pi$ or not.)

I have an exam tomorrow on Signal Processing and one of the questions can go two ways: Use a Hamming window to design an Nth th order (N+1 tap) band pass FIR filter with a pass-band between $f_0$-$...
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1answer
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How to filter an OFDM signal? [on hold]

Across the channel bandwidth there shoudd be 100 RBs (central 1200 sub carriers in a 2048 bin). Max power normalized to 0dB, the first OOB lobe should be -34dB. This 1st lobe on either side is at 5 ...
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43 views

Detecting phase difference between a clean and a noisy signal

I have a clean square-wave signal and a noisy signal from an accelerometer, perfectly synchronized to each-other but out of phase. I want to find the phase difference between them in real time, in ...
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1answer
93 views

Why shouldn't the magnitude of a practically realizable frequency selective filter be constant for a range of frequencies?

According to Paley-Wiener theorem, a practically realizable frequency selective filter shouldn't have a constant magnitude for a range of frequencies. Why is this so? How do we prove and understand it?...
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integral filter

Assume we have a time domain signal: s(i), i=1:N. To apply a derivative filter to it, i.e. D*s, where ...
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290 views

Why is it easier to design an IIR filter in the continuous time domain than in the discrete time domain?

Given that the goal is to approximate the ideal filter with an IIR filter, why would it be easier to design it in the continuous time domain than the discrete? This paper says: Discrete time ...
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38 views

What should be the cut off frequency of a Filter operating on an OFDM signal?

I have a time domain OFDM signal and to this I need to apply different linear filter however I am not sure on the cut off frequency. I am simulating for multiple symbols where each symbol has 1200 ...
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21 views

How to use the iircomb filter in matlab

I have a sound file that needs filtering which looks like this: Hence I think that I have noise spaced equally at 832Hz. i tried to use the iircomb filter taken from mathworks website and i managed ...
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1answer
22 views

Root raised cosine parameter

I try to create matched filter for receive BPSK signal. Sampling rate of the signal is 228000 Hz, data rate 1187.5 symbols/sec, signal was shaped using root raised cosine filter with rolloff factor = ...
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1answer
92 views

What exactly is Savitzky-Golay differentiation filter?

I could understand Savitzky-Golay filter as being smoothing filter, but then there also seems to be Savitzky-Golay differentiation filter, though for some reason, details do not seem to be clear. So ...
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Why do cutoff frequencies of a high-pass digital filter differ from the ones i used to transform it from a low-pass analog filter in MATLAB?

I need to transform an elliptic analog low-pass filter to a digital high-pass filter but i'm having a problem because the resulting filter has lower cutoff frequencies than the ones i set. Here is the ...
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1answer
24 views

Using Parks-Mcclellan (or others) for FIR differentiator?

I have never seen the use of Parks-Mcclellan for differentiator - most uses tend to be lowpass filters. Is this because Parks-Mcclellan implementation of FIR differentiator has numerical problems and ...
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10 views

Correspondence between spatial frequency and pixel position

I have a very basic image processing question for which I have not been able to find an answer so far: On several occasions I have encountered descriptions of image filters given in the frequency ...
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1answer
32 views

Determine poles and zeros of a specific filter design

I have a design question and need to determine poles-zeros of a IIR bandpass filter. Requirements are: 1-order should be 3 2-causal 3-real valued impulse response 4-stable 5-cutoff freq: pi/3-pi/...
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76 views

Compute time constant of discrete exponential decay pulses

I want to retrieve (within a FPGA) the time constant $\tau$ of incoming pulses of the form $$x[n]=Ae^{-n/\tau}u[n]+C$$ In addition to the offset, inputs are subject to noise. To measure the integral ...
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2answers
24 views

Relation between order and stability in IIR filter

What is the effect of increasing order of IIR filter? does it also effects stability? If we have an IIR filter of order 6, now we change its order to 7, will there be any change in its stability?
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time-frequency masking with shared properties between vector masks

I am working on a source separation problem and I have a logical mask that when applied to the STFT matrix, gives me expected results. The problem here, is that the mask is based on a spectral feature,...
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1answer
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What is Multi-band response?

What is meaning of multi band response? I have already tried reading filters texts but no help. How it is different from simple band pass or band stop
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Compute group delay of an audio file from STFT

I'd like to reproduce results from this paper in which the authors used Group Delay-grams as an input to the Machine Learning model. The Machine Learning side is not the one that I have problems with. ...
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2answers
82 views

How to graph magnitude plots for basic 4-pole filters?

I have developed magnitude plots for basic one-pole and two-pole filters derived from various Physics PDF's and tutorials I have found online and calculated from: https://www.desmos.com/calculator/...
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Signal Processing

My question is related to the attached picture What is the effect of the system on the input. For example if I have a simple function x[n] = A , then I would expect y[n]= { [ B^(-n) x[n] ] * p[n] ...
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Low pass filter implementation in real-time

I wanted to get to the bottom of something that I thought I had a grip on. We have a real-time target machine that runs a model at 100 Hz (low frequency model dynamics), and an external Inertial ...
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The Definition of Q Factor by an Equation and How to Graph

I am currently building an EQ in an music app, and it's relatively simple: 6 bands of fixed center frequency, and a Q knob to control the Q of all bands, because we do not currently have space for ...
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1answer
113 views

Why does my low pass filter diverge below 7000 Hz?

I'm trying to create a LPF, using language JAVA. My first aim is to understand how filters design is working and the second one is to create a "home made" equalizer with "home made" filters. To help ...
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1answer
41 views

Image Processing/ Computer Vision: How is separability of filters implemented?

I am trying to convince myself that a separable 2D filter can be implemented via two 1D filters. So, I took the example of following Sobel filter: $1/8\begin{bmatrix}-1&0&1\\-2&0&2\\-...
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0answers
28 views

Phase shift of multitone sinusoids

How to apply phase shift for a multitone complex signal? Say we have the following signal $$x(t) = \sum_{i=1}^Me^{j(2\pi f_it+\theta_i)}.$$ I want to apply an arbitrary phase shift $\phi_i$ for each ...
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23 views

Butterworth filters and power spectral density

I am trying to get power spectral density estimates of an hour time series, sampled at 1Hz. The only frequencies that I am interested are between 1-20 mHz. I was wondering which is the more accurate ...
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what is the type of filter that has values ones? [closed]

I used the filter with values ones but i don't know what kind of type is? p=ones(1,L) where L is the length of the filter in ...
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1D and 2D Image Filters: how to calculate composite filter and its Fourier transform

Suppose the below 1D image filter as: $\begin{matrix}h[-1] = 1,&h[0] = 2,& h[1] = 1\end{matrix}$ Apply this filter to an image first vertically then horizantally, so i get this: $h_1 = \...
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Choosing settings on my Butterworth filter

I've been using a Butterworth filter with the code shown below, however I do not know how to find the cutoff frequency. The data I'm passing into the filter are discrete time-series based displacement ...
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How to filter a discrete waveform by having continuous domain poles and zeros

Let's consider we want to model a continuous time filter that has one zero at 30GH and two poles at 35GHz. I also have a sampled waveform with sampling frequency of $f_s$, so the time interval ...
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2answers
29 views

Inverse z-transform of a modulus square

Suppose we have the z-transform of $x[n]$ is $X(z)$ and that of $y[n]$ is $Y(z)$. Then we know that the inverse z-transform of $G(z)=X(z)Y(z)$ is $g[n]=x[n]*y[n]$, where $*$ is convolution. What will ...
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1answer
38 views

How to implement Discrete time FIR Hilbert transformer filter?

I want to implement FIR Hilbert transformer filter in Matlab.
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Are there any applications using absolute Savitzky-Golay filter to smooth data and preserve non-negative properties?

I want to smooth peaks for non-negative matrix factorization (NMF). Since Savitzky-Golay has polynomial smoothing, I think it is good for narrow peak shape in my signal profile. But NMF needs to be ...
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1answer
43 views

Block diagram of filter

Can you help me with this question. Can you explain where i should start to solve the problem.
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How does cascading low pass modules affect pass band ripples?

This question 10.21 is taken from GATE IN paper 2015. I don't understand the answer given, I mean why is the frequency response at the pass band frequency considered to be $(1-\delta)$, isn't the ...
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20 views

Octave's decimate — adequate filter order as a function of downsampling factor?

The documentation for decimate in Octave (I believe also in Matlab) indicates fixed default filter lengths (Chebyshev order 8 if IIR, and order 30 if FIR). The Python documentation for the equivalent ...
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1answer
52 views

Recursive filter with repeated poles

This post follows this previous resolved post where I was trying to find the inverse Z-transform of a more simple filter output (that I used as an example to get the methodology). The present filter ...
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0answers
38 views

Savitzky–Golay on real-time data

I'm trying to use the Savitzky–Golay smoothing on real-time data in R. The R documentation page for the sgolay function says this: "Normally, you would apply the first (n-1)/2 rows to the first k ...
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1answer
91 views

Kalman Filter : How measurement noise covariance matrix and process noise helps in working of kalman filter , explain intuitively please?

How noise covariance matrix and process covariance matrix helps in improving the state estimate, can some one explain intuitively without mathematics ?
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1answer
36 views

Is CMA equalization applicable for OFDM

I have a question regarding the constant modulus algorithm (CMA), as you know it's one of the known algorithms used for blind equalization. The cost function of the CMA is build blindly, it means ...
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1answer
43 views

How to calculate the Fourier transform of a mean filter in Matlab?

In Matlab, how can I calculate the discrete-space Fourier transform of a mean which takes the average of 4 adjacent points, with this kernel $$\begin{pmatrix} 0 &1& 0\\ 1 &0&...
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88 views

How to find the impulse response of a filter, given the difference equation?

What is the impulse response of the system: $$ y[n]= \frac{16}{26T} \left(-\frac{1}{16} x[n] + x[n-2] - x[n-4] + \frac{1}{16} x[n-6] \right)? $$
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Band Limited White Noise

How do I create in simulink a true white noise? The block 'Band Limited White Noise' asks for power, step and seed. The power must be choosed accordingly to the step time. As a reverse proof I've ...
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2answers
27 views

Finding Signals when the baseline varies greatly by signal set

I have milliwatt consumption data from home appliances. I'm collecting this data in hundreds of households. Based on the machine model, the baseline value for a given household can vary from 0 to ...
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Octave filtfilt converted to R code

R has a function called filtfilt that performs zero-phase digital filtering by processing the input data in both the forward and reverse directions. But it suffers from having steep transition bands....