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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174 views

Calculating filter coefficients of a Moving average with error correction

I have an oversampling ADC where I need to correct Gain/offset errors 'during' each conversion. This also links to my previous question - Moving average and linearization of two piecewise linear ...
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Consistency check of Kalman Filter

I am interested doing the consistency check of the Kalman filter. There are several measures like Posterior Cramer Rao Lower Bound (PCRLB), NIS (Normalised Innovation Squared), NEES(Normalized ...
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Bessel filter vs other prototypes(especially butterworth) [closed]

What is main difference between bessel filter and other filters(elliptic, chebyshev and specially butterworth) As apparently both butterworth and bessel have flat response
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How to filter very low amplitude staircase signal from a background noise

I have a staircase signal of a specific pattern that is drowned in a background noise. The ratio of signal to noise amplitude is nearly $10^{-4}$. I have attached the image of both with this post. I ...
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Laplacian of Gaussian operator

This might be a silly question. I was reading about the Laplacian of Gaussian (LoG) operator and got confused about the alternative equivelant ways we can make use of it. Let's assume we have a 2D ...
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Reconstruct $x(t)$ from $y(t)$ and $z(t)$

Let $x(t)$ be band-limited signal with $X(j\omega) = 0$ for $|\omega|\gt \omega_M$. We use $$s(t) = \sum_{k =-\infty}^{+\infty}(-1)^k\delta(t - \frac{kT}{2})$$ for sampling. So we have $z(t) = x(t)s(t)...
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The Stability of the RLS Algorithm for Equalization

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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Filter a negative SNR signal whose frequency spectrum lies inside the noise frequency spectrum

I am a newbie in Signal Processing and need your suggestion in the following problem. My signal amplitude is 10 times weaker than the noise. Furthermore, the frequency spectrum of the noise and the ...
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1answer
41 views

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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Resources for learning about filters from scratch?

Topic of filters is very important in signal processing So i want to learn about filters from scratch and then eventually reaching FIR and IIR filters I have some idea about low pass,high pass,band ...
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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 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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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 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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467 views

Attempting to use the trapezoidal rule to form a difference equation representing a circuit

I have a differential equation that has been proven to be correct. The transfer function obtained by Laplace domain analysis and Matlab freqs match up and all is well. The problem is somewhere in ...
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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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217 views

How to perform spectral inversion in the frequency domain to convert a low-pass filter into a high-pass filter?

To convert a linear-phase FIR low-pass filter into a high-pass filter with the same cut-off frequency, we can invert the sign of the low-pass filter's impulse response $h(n)$ and then add one to the ...
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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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2answers
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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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1answer
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Decimating Non-Uniform large time-series data

I'm working with accelerometer data that is sampled at a non-uniform rate. There are major gaps in the data. Below is a scatter plot of the data I can also give a sense of the frquencies at which ...
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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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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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how many things Can they be done with a spectrogram?

I found some things that can be done with a spectrogram. filter frequencies by setting the bins to zero observe what frequencies make up the signal. observe the energy or amplitude of each frequency, ...
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1answer
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Low pass filter output showing instability

I am fairly new to DSP, and I'm trying to implement the Pan Tompkins algorithm for QRS detection of ECG signals in MATLAB. The first stage of the algorithm consists of a second-order 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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1answer
34 views

linear-expansion filter for image (2D array)

I am working in python analyzing 2D arrays and I am looking for a filter or some other routine that would provide a linear expansion of an region boundaries in a 2D array with binary regions (i.e. a ...
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Why is a linear phase important?

If symmetry conditions are met, FIR filters have a linear phase. This is not true for IIR filters. However, for what applications is it bad to apply filters that do not have this property and what ...
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207 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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When are MLSE (with Viterbi algorithm) equalizer used in real life (only for equalization)? [closed]

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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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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How to Extract High Frequency and Low Frequency Component Using Bilateral Filter?

What does High frequency and low frequency component signify in an image. How to separate out the high frequency as well as low frequency component of an image using Bilateral filter.
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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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Which filter is best for noise removal from audio, Butterworth, Chebyshev, or Elliptic? [closed]

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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1answer
100 views

Distort voice to hide talker identity as much as possible

I need to develop an app which makes speech recognition. Because I need to be able to constantly improve the recognition capability, I would like to train the engine with real recordings and match the ...
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1answer
155 views

How does a bandpass filter work?

My question is about the action of a bandpass filter. First, I have a temporal signal. I convert it in a spectral signal via a FFT. Now, I want to apply a bandpass filter on that spectral signal. But ...
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2answers
57 views

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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1answer
29 views

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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Average image over $N$ frames with one frame buffer

Can you give some filter that is averaging an image over $N$ samples in a recursive way that only needs one frame buffer? $\frac{1}{N} \sum_{k=1}^{N} y_{k}(m,n)$ I can only imagine filters that need ...
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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
79 views

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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How to design a filter that can filter out noise accurately, after setting the parameters of the filter using standard signal?

I meet a problem with designing a filter. I have two different instruments that could measure the same AC signal (usually ~200hz, always <1kHz), A and B. A can carry out signal measurement during ...
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1answer
28 views

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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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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1answer
35 views

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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1answer
93 views

Sample-rate, filtering, digital-filtering and aliasing

I am strugling with a question that I hope someone can help me with. I am recording single molecule events which I detect is picoampere square deflections. I wish to use as gentle low-pass bessel ...
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1answer
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The notation to express a datum filtered by arbitray number of one-dimensional filters?

I'm a pure novice in signal processing but I'm writing a paper that needs to be expressed in the SP way. The question is, I want to express an N-dimensional datum goes through N one-dimensional ...

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