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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348 views

Help with my first (simple) Z-transform

I need to transform this Laplace function to the z-domain: From the answer I received: $s=(1-z^{−1})/T$ Then substitution into my Laplace function would give: $t(z) = 2R/(m*(1-z^{−1})/T + 2R)$ Is ...
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59 views

Meaningful output of FIR filter output

I have implemented FIR filter using tapped delay line method. I start getting output as soon as first input sample is passed to it, I am wondering from which sample I will get the proper output(...
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1answer
39 views

Extra frequencies after applying low pass filter

I used Python/scipy to create an input data (sinewave with frequencies {600,1200,1800,2400,...,9000}) and sampling at 10000Hz. A lowpass filter is created using butter(10, 4000/(10000/2), 10000, btype=...
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49 views

Python resampling and filtering question

Intro Hi I'm looking for someone with some experience to walk me through some questions I have regarding resampling (downsampling) in Python. Here is my problem: I have accelerometer data that comes ...
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1answer
68 views

Why is my filter unstable and self-oscillating in this case?

I am using resonant bandpasses to simulate modes of guitar/piano strings for audio synthesis. While attempting to introduce coupling effects I have encountered a problem. I will illustrate with some ...
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2answers
63 views

How do I convert this simple Laplace equation to Z-domain?

A basic model of coupled strings (eg. piano) is provided here as: The principle is that it has two identical string simulations each formed by a delay line and LPF. The outputs of these are summed at ...
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2answers
38 views

How is time or sampling rate accounted for in this model?

A basic model of coupled strings (eg. piano) is provided here as: The principle is that it has two identical string simulations each formed by a delay line and LPF. The outputs of these are summed at ...
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0answers
39 views

Creating a combination of extrusion to a point, and motion blur

I am attempting to generate a effect that allows me to use original color of image, but also mimic a pinched extruded 3d surface from orthographic view. To do this, I used the G'MIC-QT scripting ...
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2answers
353 views

downsample signal to a specific number of samples in Python

The Python Scipy library provides several functions to downsample signals, but they all have limitations: The resample function is based on Fourier method, which means it assumes periodic signals. ...
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3answers
104 views

How to use a FIR on a signal with a drifting central frequency?

I have been working on this subject for a while and I couldn't get a proper answer. I am trying to estimate the phase of the input signal : $x(t)=Ae^{j(at^2+bt+c)}+n(t)+i(t)$ Where $n(t)$ is a ...
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1answer
35 views

Applying a 2D band pass filter (Butterworth ?) to an array with NaNs

I am trying to filter out the low frequencies of an array looking like this : For now, I am taking transects of this array and applying a 1D - butterworth band pass filter : ...
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17 views

Is there a way to get output in second order sections (SOS) format from Scipy's signal.firwin

I am using Scipy's signal.firwin to implement a lowpass filter. Using the rule of thumb formula(s) to estimate the order of the filter, I am getting a very high number. I looked into this question, ...
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72 views

how a signal for which calculate RMS can be filtered and have a fast settling time?

i designed a sinusoidal pwm amplifier (3KHz to 20KHz) that regulates its output voltage reading the RMS value of output current. The RMS is obtained squaring the signal sampled by AD converter @...
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529 views

2D convolution of image with filter as successive 1D convolutions

I want to prove (or more precisely experiment with) the idea that a 2D convoltion as produced by the Matlab conv2() function between an image I (2D matrix) and a kernel (smaller 2D matrix) can be ...
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1answer
37 views

Detect playback position in swept sine sweep

I am wondering what the most precise method is to detect the playback sample position of a sine sweep? The real playback sample position is unknown and an DSP with constraint computing capabilities ...
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19 views

DFT of a function and array convolution

I saw some questions (and answers) on this subject, but they were all about a specific example and I'm not sure I understood. I'm trying to understand the meaning of computing the DFT of an array ...
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1answer
130 views

Generating Kawase Blur Kernels to Approximate a Gaussian Blur on an Image

Is there an algorithm to generate the Kawase Blur Kernels to approximate the actual Gaussian Blur (of a specific kernel size, and if possible, a sigma)?
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1answer
586 views

Number of taps needed in an FIR filter to remove DC

An FIR filter is being used to remove the DC of an ECG. The sampling rate is 500Hz. How many taps would said FIR filter require (theoretically and practically) to filter out the DC. P.S. the filter ...
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1answer
98 views

SciPy Lfilter issue

For one of my DSP projects, I decided to use python to perform signal processing. While I am new to python, I understand that it is a very powerful and versatile language. For my processing, I opted ...
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1answer
41 views

Phase response in a filter for an Audio Application

Should I be concerned with the group phase delay which a filter produces? Especially in an audio application? Should I aim at using a linear phase delay filter for example?
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2answers
146 views

Understanding the Bilateral Filter - Neighbors and Sigma

I have been reading about the Bilateral Filter in - Fast Bilateral Filtering for the Display of High Dynamic- Range Images and have felt crippled and confused while understanding its working and the ...
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3answers
163 views

How to reliably compute the group delay of a comb filter

I applied the following FIR comb filter in real-time: y[n]=x[n]-x[n-40] Since this is an FIR, the group delay is D=(N-1)/2=20 samples. After applying the filter ...
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21 views

decouple signal from environmental effect

Sensor signal depends on environmental factors such as temperature, relative humidity. Temperature compensation is relatively straightforward. But I am not entirely sure how to model the effect of ...
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2answers
65 views

Preloading an IIR Filter

Is there a mathematical approach to initializing an IIR filter so that turn-on transients are minimized? Background: I have a high pass Butterworth design that overloads at the start of a sine wave ...
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1answer
79 views

FIR filter format - Brutefir - Volumio

I am trying to compensate for the high frequency droop of a TDA1543 based nos DAC. One straightforward method is described here. Having played the resulting .wav, ...
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26 views

Using an IMU for gravimetry and calculation of gravity anomalies

I am currently working on a project which seeks to utilize a tri-axial IMU to measure gravity anomalies caused by density variations in planetary crusts. The instrument will be attached to a Helikite ...
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1answer
63 views

Is there any difference in Implementing sigma delta modulator using filters and state space model in FPGA?

Sigma delta modulation is extensively used in quantization to reduce quantization noise. In the literature one can see different architecture for example python-deltasigma to implement a modulator. ...
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2answers
97 views

why do directional derivatives work better with a gaussian filter?

I've been working on image segmentation and computing the directional derivatives of a grey-scaled image, with the objective of detecting contours and edges. I have realised that if I apply a gaussian ...
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1answer
53 views

Fuse two sources of linear acceleration with a Kalman filter

How would I fuse two different sources of linear acceleration with a Kalman filter (perhaps linear acceleration readings from an IMU and from a dedicated accelerometer)? My state is defined by ...
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1answer
28 views

What exactly is stored in “output” variable in the FIR Filter code below? [duplicate]

What exactly is stored in "output" variable in the FIR Filter code below? ...
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2answers
246 views

Why ideal filter cannot realised practically?

I know the difference between ideal and practical filterI just wanted to know why it not realisable?
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50 views

How to filter power line noise from ECG?

currently i'am trying to get rid off power line noise (50/60 Hz) from an ecg. Specification: Bandwidth of the ecg 0.05 - 150 (achieving this with a butterworth second order bandpass) sampling rate ...
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1answer
90 views

What are the limitations of FIR filters?

I know that for type II FIR filter it adds a zero at $z=-1$ so it cannot design a high-pass filter. My question: what type of limitations the other types have (type I, III, IV)?
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1answer
36 views

What exactly is stored in the buffer array in the code below? Is it the values of x[n-k] or something else?

What exactly is stored in the buffer array in the FIR Filter code below? Is it the values of x[n-k] or something else? ...
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0answers
50 views

Coupling two resonant bandpass filters? (To simulate guitar/piano string effects)

A major part of the sound of a guitar or piano string comes from the coupling of the horizontal and vertical string vibrations. This concept is described in terms of transfer functions here. This ...
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1answer
64 views

Reconstruction of sampled band-pass signal

I am pretty new to signal processing. I am currently trying to reconstruct a sampled band-pass signal created with the filtfilt and ...
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1answer
64 views

Magnitude and phase response and cut-off frequency of a moving average filter

The frequency response of a typical moving average filter of length $N$ is given by $H(\omega)=\frac{1}{N}\frac{\sin(\omega N/2) e^{-j \omega ((N-1)/2)}}{\sin(\omega/2)}$. Firstly, isn't the cut off ...
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23 views

Is there a way to filter out low volume content in an audio sample?

Imagine you are listening to a digital file that contains some random speech. Now, while you are listening to it, you also hear in the background (spatially) some low volume content, either noise, ...
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1answer
100 views

Use recursive least square as an “actual” filter?

I am currently studying recursive least square (RLS) and as far as I understand, the setup is (for example) that we are given a process with uncertain parameters/noise and we want to adapt parameters ...
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2answers
58 views

Impulse response of an infinite-length system

I have a system which is expressed as following: y[n] + $\alpha$ y[n-N] = x[n] where y is the output and x is the input. When I take the z-transform of both sides, I've found the transfer function ...
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1answer
101 views

Kalman Filter EM Estimation of Covariances

The question might be very simple, but I get a strange result from Kalman Filter. Let us consider the simplest state-space model, the random walk plus noise: $$ y_{t} = x_{t} + \varepsilon_{t}\\ x_{t} ...
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1answer
236 views

How to filter a white noise or random noise in Matlab Simulink?

I am working on a sun-synchronous satellite Simulink model wich determines its attitude from a Sun sensor and a star sensor whom measure the sun and star direction in the satellite body reference ...
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1answer
34 views

behavioral model of an electronic device

I have an assignment for the course entitled "Nonlinear System Identification," and I appreciate any help. The below figure shows the model that I need to extract its parameters. we have been ...
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1answer
48 views

How to make signal smooth using filter?

I have measured the output of a mechanical system and obtained the signal shown at the attached image. I want to make it smoother by removing the chattering (I think it is called chattering). In order ...
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4answers
149 views

Layman Description of the Kalman Filter

I want to know about Kalman Filter but i tried searching different links including Electrical Engineering StackExchange but the information available there was hardly digestible. All I am able to ...
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1answer
36 views

Sampling a signal with varying frequency

Question I'm trying to figure out the sampling rate for my ADC to sample essentially signal essentially of the form: $$y(t) = \sin(\max(t, \omega_{max})\times t) + n$$ where $n$ is noise. Context ...
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1answer
39 views

Why does a strange frequency appear in this image?

Here is an image of a filter bank spectrograph, where the main signal is at 2.5kHz and the high signal is at 21.5khz, What is the high frequency signal? I doubt that birds can make frequencies above ...
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1answer
175 views

Scaling Function in Wavelet Analysis

I was watching a YouTube tutorial on wavelets https://www.youtube.com/watch?v=wgRgodvU_Ms, where the presenter showed that if we multiply a Gaussian with a sine wave (and follow some other conditions),...
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1answer
59 views

Is gradient vector of pole zero carry usful information?

Consider a transfer function (TF) with $n$ number of poles $(p_1,..p_n)$ and $m$ number of zeros $(z_1,..z_n)$. One can write the magnitude of the frequency responce of the TF in terms of poles and ...
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37 views

Require explanation for Matlab freqz2

Question I browsed the code of the Matlab freqz2 function (to find out how it is different to simple fft2.) First of all it ...

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