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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Calculating IIR Filter gain at given frequency

Let's consider an IIR filter with transfer function: $H(z)$. Given the sampling frequency $F_s$ how can I calculate gain at say $F$ ? When I was dealing with analog systems when I wanted to calculate ...
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How to Improve the Kalman Filter for Tracking the Periodic Motion of a Car?

I have a quite typical Kalman filter to design. I really read a lot of articles about the design of this filter but the performances of my filter are still quite bad. Here is my situation. I have a ...
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In what circumstance can an RLS algorithm for equalization be unstable?

I am reading in the litterature that LMS is more stable than RLS. But RLS is far more faster in convergence. So my concern is how to be sure that my RLS algorithm will be stable when I am doing ...
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How to remap center frequencies of a mel filter bank?

I'm trying to implement vocal tract length peturbation in python (Vocal Tract Length Perturbation (VTLP) improves speech recognition. Navdeep Jaitly, E. S. Hinton, Published 2013, Computer Science) by ...
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How to correctly pass filter states from one processing block to the next

I'm processing a 4 channel audio signal and due to memory requirements need to process the signal in an arbritrary number of blocks. To ensure consistent filtering between blocks I've been told I need ...
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How to deal with different audio formats for audio classification?

I am working on an audio classification problem statement to classify between two audio classes. I have collected samples from jotform, they are providing audio widget to collect .wav audio but it ...
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What is the actual format of this audio file?

I am collecting some data from jotform .wav widget. All the audio files are in .wav format. But when I tried to open the file using python ...
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22 views

Direct form 1 filter equation for a biquad filter

In general, we all know that the direct form 1 equation for a biquad filter is given by $$y(n) = b_0x(n) + b_1x(n-1) + b_2x(n-2) - a_1y(n-1) - a_2y(n-2)$$ But when it comes to practical applications ...
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3 dB cut-off frequency of first-order IIR high-pass filter

As descipbed in this great answer (thank you Matt L.), the suggested exact formula was very precise. I need a first order high-pass with similar precision. EDIT: (clarification) The low-pass filter ...
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Phase correction using second order all pass filters/LMS with Wiener-Hopf equations

I am working on phase correction algorithms. Can anyone help me understand how can the following diagram be used for phase correction: Additionally, for a channel function suggested How determine the ...
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What Is an Oriented Gaussian Second Derivative Filter

In the paper: Detecting and Localizing Edges Composed of Steps, Peaks and Roofs, the authors refer to an image filter as an oriented second-derivative Gaussian filter. I'm trying to figure out what ...
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When are MLSE (with Viterbi algorithm) equalizer used in real life (only for equalization)?

The complexity of a MLSE decoder (with Viterbi Algorithm) is in the order of $M^L$, where $L$ is the length of the channel and $M$ is the order of modulation. My question is in what circonstances, it ...
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Phase of matched filter for chirp signals

I am using the following system: Ultrasonic chirp signals with central frequency 100kHz are being transmitted using ultrasonic sensor. After the transmission through the medium(air/solid/liquid/...
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Image Processing Terminology Question: Even/Odd Quadrature Pairs and Center Surround Filter

I am reading the paper Learning to Detect Natural Image Boundaries Using Local Brightness, Color, and Texture Cues available here. In section 2.2.2, page 5, slightly after halfway done the page on the ...
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Matched filter correct peak detection [duplicate]

I am working with ultrasound signals with frequency 100 kHz. Chirp signals with bandwidth 16 kHz are being modulated with 100 kHz and then transmitted via one ultrasonic sensor. With another ...
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Which filter is best for noise removal from audio, Butterworth, Chebyshev, or Elliptic?

I am writing a Matlab code to check which filter from Butterworth, Chebyshev type 1 and Elliptic is better to reduce noise added to the signal but I could not figure it out as all filters give the ...
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Coefficient Scaling of IIR filter to obtain unity gain response

I am designing a 2nd order IIR digital filter : My tf equation with coefficients is ...
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How to apply band-pass filter and get the filtered back from frequency to time domain in python?

I know this is basic for signal processing, but, I am not sure what is wrong about my approach. I have a signal that behaves as damped sine signal with a sampling frequency of 5076Hz and 15,000 number ...
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Why does the filtered signal amplitude increase exponentially?

I am new to signal processing. I am having a problem applying a filter to a test signal. I am working with MatLab. My test signal is a chirp up to Nyquist frequency and my filter is in zeros and poles ...
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2answers
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Calculating the 3dB frequency of an nth order low pass filter and nth order high pass filter

I am using the 6th order high pass filter in the C code. And the cut-off frequency selected for it is 150 Hz and the sampling frequency being used is 32000Hz. Now, I want to calculate the 3 dB ...
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Plotting Frequency Response Magnitude and Phase for first order all pass filter

Having trouble plotting the frequency response characteristics for first order all pass filter. The Magnitude is expected to be constant across entire freq and Phase is expected to be only decreasing (...
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Why filtic function does not work for a specific use?

And how can I solve this issue? I designed a filter via bilinear transformation in order to obtein a high-pass filter of Butterworth. When I want to set initial conditions with filtic function, it ...
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Question about Linear Time Invariant (LTI) Systems [closed]

Suppose $x[n]$ is a discrete signal and transformation $H$ is defined as follow: $$H\{x[n]\} = nx[n]$$ Does $H$ define an LTI system?
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Lifting scheme versus filter banks

I am having some trouble understanding the intuitive connection between the two. I worked through all the theory and learned that Sweldens showed how to derive lifting steps when having admissible ...
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What is the phase response of SRRC/NRZ/RZ pulse shapping filters and does it matter?

So I would like to know if filters usually used for pulse shaping (like SRRC) have a linear phase response, and if not, what this response looks like and does it matters in any circumstances?
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Fourier transform of an integrator filter

I have to find the Fourier transform , and $y(t)$ of an $ x(t) = e^{- \frac {t}{T} } u(t) $ that passes into a integrator filter. I know that $ Y(f) = X(f) H(f) $ so I first calculate the Fourier ...
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Butterworth band-pass filter transfer function

I have some complex data in the frequency domain and want to multiply by an appropriate function to get complex data in the frequency domain that is appopriately filtered. I think such a function ...
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2answers
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Calculating the true values of biquad filter coefficients from normalized form

I have a C code in which the IIR filter(BiQuad) uses only 4 (normalized) coefficients per stage (a2/a0,a1/a0,b2/b0,b1/b0) instead of 6 coefficients (a0,a1,a2,b0,b1,b2). I know that the value of a0 is ...
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Which part does the filter in CNN drop to have the same size as input image?

In CNN (Convolutional Neural Networks), we have an image by size $N\times N$ and a filter by size $H\times H$ which usually $H < N$. When we want to find the transform of the image and the filter ...
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A question about the Commutativity Property in discrete signals block diagrams

According to the Commutativity Property of block diagrams, we can place b0 at the entrance or at the exit of the block diagram, it wouldn't matter. My question is, if we placed it at the entrance, we ...
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Can I use a filter design to optimize the preconditioning of an optimizer?

Consider a noisy time series y_i and that I have waited until end of experiment. I now want to fit a nonlinear parameterized function F(A,d,k; t) to determine A,d,k. So I can happily Newton-Raphson ...
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How to make noise power estimation on a single tone transmission?

Suppose we have a single tone transmission over a Single Input, Single Output (SISO) channel impaired by Inter-symbol Interference and Additive White Gaussian Noise (AWGN). How to compute the noise ...
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How should we read FIR filter phase response graph?

What should we see from the FIR phase response graph, as an example for a linear phase? And what does this straight line at $0.5\pi$ mean?
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How FIR filters provide a linear phase?

I know that we can design a linear phase FIR filter by choosing filter coefficients symmetric or antisymmetric, what is the intuitive idea behind that?
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Remove background, keep black characters

I use ID scanner machine (link) to remove the background. The result is the gray image below. It seems that the scanner uses IR to do that. Is there any algorithms to obtain the same result? Thanks in ...
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Discretize process noise in Kalman filter

Reading P. Andrews et al. I see that it is very common to do the following approximation of the process noise covariance matrix: $$Q_{k} = G_{k-1}QG_{k-1}^{T}\Delta t$$ so that the propagation ...
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Why FIR uses often direct-form instead of transposed-form?

Even though tranposed-form has less computational burden and memory requirements, why FIR uses mostly direct-form?
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how to do smoothing a linear noise adc signal to a exponencial curve to increase and logarithmic to decrease

I am studying methods of signal smoothing obtained in an Analog Digital converter that is operated by a common potentiometer that generates a certain noise, such potentiometer is linear and I cannot ...
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Remove AC component from the mixed signal using an elliptic filter

I have a signal like this: $s(t) = C + a \cdot sin(2 \cdot \pi \cdot f \cdot t)$ where $C$ - arbitrary constant, $f$ - frequency of AC component (Hz) and $a$ - amplitude of AC component. Parameters:...
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Comparison of results with Direct form1 and Direct form2 implementation of IIR filters

The results obtained from Direct form1 and Direct form2 implementations (in C language) of IIR (BiQuad) filters are a little different. In the implementation, i have made the b0 coefficient as 1. So, ...
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What is the difference of windowing functions for FIR filtering?

What is the difference of window types such as Hann, Rectangular, Hamming in the application. Is there such a thing that the one is better than the other? There will be an oral exam for DSP course ...
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Why a pair of complex-conjugate zeros provide a nulling filter? (FIR filter case)

FIR filter having a pair of complex-conjugate zeros that lie on the unit circle, with zeros of the form: $$ z_1 = e^{j\omega_i}\qquad\text{and}\qquad z_2 = e^{-j\omega_i} $$ And transfer function: $$ ...
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What is the intuitive idea behind FIR filter order and filter parameters? [duplicate]

I know that if we decrease stop-band and pass-band attenuation, and also decreasing the transition band, the filter order will increase as well as filter performance. But what is the intuitive idea ...
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Understanding zero-phase filters

I'm reading the book "Digital Image Processing" by Gonzalez and Woods and I'm wondering how their definition of zero-phase-shift filter is equivalent to the one given here. "Digital Image Processing" ...
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Do we need Channel estimation prior to (time domain DFE or linear) adaptative equalization in single tone transmission?

If we are to transmit a single tone signal over a channel impaired by inter symbol interference and awgn, and if the equalization is adaptative (LMS/RLS track) and is done in time domain by LE (linear ...
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How to remove the bump from the signal using filters?

I want to have only the slope of the signal. How can I do? I have tried to apply some filters but so far I have not been able to hit the nail on the head. I use Matlab.
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Extracting the DC component of a signal, that proportional to the displacement about the y-axis

I’m not sure that I clearly enough reflected the essence of a small problem in the title of the topic, but I’ll try to reveal its essence in the question itself. https://www.wolframalpha.com/input/......
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How to determine SNR required for adding AWGN noise to clean IQ samples?

I'm doing an experiment w.r.t PSD output. I have generated some 11a IQ samples and checking its PSD output in MATLAB using pwelch and comparing with the PSD output obtained using hardware. Here are ...
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Zero-phase-shift filters must be symmetric about the origin

In reading Rafael Gonzalez Digital Image Processing, second edition, section 4.10.2, the author writes: Notch filters are the most useful of the selective filters. A notch filter rejects (or passes)...
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Order of filters

on the 24th page of this pdf file for Slaney's Gammatone filter bank this sentence is written: The result is returned as an array of filter coefficients. Each row of the filter arrays contains ...

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