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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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What is an “innovation filter”?

I'm a math postgrad student working through a paper on eigenvalue decompositions of matrices of FIR filters (used for stuff like total decorrelation, convolutive mixing, MIMO). Towards the beginning, ...
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1answer
38 views

Manual filter or digital filter first for EEG?

I am getting conflicting advise regarding how to clean my EEG data: 1) Manually remove artefacts first and then apply digital filters OR 2) Apply digital filters first and then manually remove ...
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21 views

Make an envelope smoother but keep the sharp attack

I have a signal x for which I would like the envelope. I have taken the Hilbert transform (like in this question): ...
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0answers
11 views

In what what way is the DoG more tunable than the LoG?

I was reading through this post "What is the difference between Difference of Gaussian, Laplace of Gaussian, and Mexican Hat wavelet?" and noted in Chris Luengo's answer that he mentioned that the ...
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17 views

Practical filter output [on hold]

If practical filter output is not ideal then other unwanted frequency can also pass through that then how can we use that distorted output for useful signal generation?
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2answers
43 views

Realization of a filter based on its transfer function

How can we check whether the filter is realizable given its transfer function and What are the parameters the realization depends on? Here is an example: Show that a filter with transfer function ...
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21 views

Plot Bit-Error-rate (BER) vs Eb_N0 of a discrete BPSK signal passed through integrator in MATLAB [on hold]

I am a novice to communication systems but I am in need to solve this question. I would appreciate inputs in this regard. Apologies if you my question lengthy. I have a BPSK signal such that the ...
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12 views

Changing BCJR algorithm to work on all trellis states

I am using the BCJR algorithm for channel equalization (simple ISI channel + AWGN). The algorithm assumes that zeros are transmitted in the beginning and in the end, but I would like to change it not ...
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1answer
54 views

Transfer function intuition

What is the meaning of the transfer function of a filter? Please explain intuitively with an example if possible.
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1answer
19 views

How Is Laplacian of Gaussian (LoG) Implemented as Four 1D Convolutions?

I am trying to understand the four 1D convolution operations involved in implementation of Laplacian of Gaussian(LoG). I have read this answer and I am also reading ...
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4answers
57 views

Baby Cry recognition robust against the distance [on hold]

I am building a baby cry detection system using deep learning algorithm, Raspberry Pi and a microphone as the sound sensor. When the baby starts crying then the system should detect the cry. It is ...
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0answers
29 views

How far can numerical differentiation be accurate for sinusoids?

Suppose you have samples of uniform interval of a sinusoidal signal that is some sum of sinusoids. Forget about aliasing, as the signal is bandlimited. If we have infinite number of samples at ...
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0answers
21 views

Rocketry : Combine two accelerometers to reduce noise?

I am designing an IMU for an experimental rocket. I'll be using the BN055 9DOF that has sensor fusion - orientation quaternion - and gravity compensation. My main goal is speed computation, and I was ...
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1answer
57 views

How to reduce latency under mean filter for high noise?

We have a position sensor that under some conditions receives some high frequency noise. We can eliminate that very well with a simple mean filtering. Unfortunately this causes too much lag when ...
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1answer
40 views

Transfer function of resonant filter with 2 poles, peak at $f_0 = 500\text{ Hz}$, and $\Delta f = 32\text{ Hz}$

This a contest question. I'd like some help because I can't find any materials related to this topic. https://www.qconcursos.com/questoes-de-concursos/questao/ecd6c966-51 My english translation: ...
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2answers
77 views

Fundamental misunderstanding of windowing

I believe I have a fundamental misunderstanding of windowing. I thought that windowing is applied to a signal with pointwise multiplication, then some sort of filtering is then done to it (say using ...
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0answers
29 views

What would be an appropriate method to filter the noise from the following data?

I have a paralleled potentiometer and capacitor connected to the digital pin of a micro controller. I am using the micro controller to discharge the cap and then measure the time it takes for it to ...
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0answers
30 views

Do you know this 1D filter?

I'm looking for a bibliography or some kind of information for this filter; goes like this, on a 3 point moving window: $$y_{-1}=\frac{1}{3}\sum_{i=-1}^{1} y_i-0.5(y_1-y_{-1})$$ $$y_{0}=\frac{1}{3}\...
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1answer
24 views

Wiener Filter in Frequency Domain: What it does to a specific Frequency?

As I understand Wiener filter in time domain tries to estimate a signal as close as possible to its (original) non-degraded signal using the degraded signal by white noise. $$H(\omega)=\frac{\Phi_{...
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43 views

What happens to a rectangular signal filtered with an Exponential Smoothing filter?

Filter given; $y[n] = \alpha x[n] + (1-\alpha) y[n-1]$. In principle all samples before the present one influence What happens to a rect-signal? How would it look like?
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1answer
22 views

Denoising before or after Geometric Transform?

I am working on a image which needs denoising (bilateral filter) and a geometric transformation. I am not sure in which order these filters should be applied. Personally I think it is better to use ...
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1answer
59 views

How does a digital filter work?

To introduce my situation: I'm developing a digital synthesizer in a form of a C++ library, working with low level APIs like WASAPI, ASIO, ALSA etc. It's probably not very practical and I'm mostly "...
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0answers
26 views

Accounting for Mechanical Vibration in Accelerometer Readings

I am very new to DSP so please forgive any ignorance within this post. I am working on a device which has a 6-axis IMU measuring acceleration and rotation. The device itself is attached to a ...
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0answers
34 views

Removing noise from time series with known sigma?

I have an instrument producing time series data with significant noise (the noise is about 3x larger than the signal). Here is an example plot of simulated data and noise (data here): I want to ...
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3answers
57 views

Question on Wiener Filtering

I have read that a Wiener filter is a filter used to produce an estimate of a desired or target random process by linear time-invariant (LTI) filtering of an observed noisy process. Now, my doubt ...
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0answers
18 views

How to transmit beamform without explicit phase shifting at RF frequency

I would like to perform beamforming from an array of antennas when transmitting. I know the difference between analog and digital beamforming when receiving a signal from an array (there is a lot of ...
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2answers
197 views

Alias-free digital nonlinear filter design

@Jazzmaniac has a good answer to the question of how to design an alias-free digital nonlinear time-invariant filter here: https://dsp.stackexchange.com/a/28787/18276 Basically, according to that ...
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1answer
40 views

What are the advantages and disadvantages separability of Gaussian 2D filter?

I know separability of a Gaussian filter enhances the computational complexity from $\mathcal{O}(L^2*N*M) \to \mathcal{O}((L*N*M)$. How this really reflect on my program? I suppose the number of for ...
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1answer
37 views

FIR filter delay and window length

How long does it take for FIR filter to produce first output sample for given window / kernel / impulse (not sure what is best name) length? Does it differ between minimum phase and linear phase ...
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1answer
53 views

digital IIR filter delay and oversampling

Can oversampling decrease the delay of digital IIR filter? Imagine there is some digital signal going into processor that applies low pass filter.Lets say its 1 KHz sample rate and the filter is ...
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1answer
22 views

how to extract 45 cycles from bunch of waveforms

I want to extract 45 number of cycles from the bunch of cycle which is similar to sine wave of varying amplitude. please help me to do so. in this picture i have capture only 45 cycles but i have ...
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1answer
53 views

A general conceptual understanding of moving average

I have a conceptual question here. I understood how to calculate a Moving Average(MA). For example : x(n) = 0, 1, 2, 3, 4, 5 MA = 0, 1/2, 3/2, 5/2,7/2, 9/2, where for calculation of the MA we only ...
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1answer
27 views

How to make sinewives with array input, for-loop functions and operate array with others [matlab]? [closed]

Thanks to previous question, I got some clues to resolve this one. But, I still get some problems here. ...
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1answer
26 views

Detect gradual increase then decrease in slightly noisy data

I have data thats not too noisy and I am trying to detect a pattern where it gradually increases then decreases in a short period of time (20 ticks? it should be roughly similar per session but can ...
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1answer
56 views

How can I determine the order of filter?

This is my first study about signal analysing. I'm very confused about filter order. My problem is how can I know whether its 12-th order, or 2nd order like the book says so? I already knew that slope ...
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1answer
42 views

Recursive Least Square Adaptive Linear Equalizer

For the adaptive filter to work properly, a desired signal d(n) needs to be provided. The output from the equalizer y(n) is subtracted from d(n) to produce an error signal, which is used to adjust the ...
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26 views

Estimating a discrete summer with constrained input bandwidth

I have a discrete-time system which can be described as: $$ Y_m = \sum_{r=-N_g}^{R-1+N_g} c_r x[R(m-1) + r] $$ The unknowns are $c_k$ but I know that they have the following approximate behavior: $$...
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42 views

How can I manually find the coefficients, poles and zeros of Butterworth low pass filter in MATLAB instead of using the built-in functions?

Actually I need to filter a raw ECG signal using low pass Butterworth filter at 70 hertz. And j need to implement the Butterworth filter first for that. Please any help since I'm very new to this ...
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1answer
44 views

How to understand the relationship between the filter time constant and the half-power cutoff frequency

I learned that the time constant can be computed as $\frac{1}{2 \pi f_0}$, where $f_0$ is the half-power cutoff frequency of a high-pass filter. However, I was wondering how the time constant and the ...
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1answer
36 views

FIR filter design and implementation meaning [closed]

What is the output of the convolution meaning which is used in the FIR filter? how can conclude the output of the FIR filter in the output according to the input $x[n]$?
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2answers
54 views

A question about Gibbs phenomenon example in Richard Lyons book

If anyone has a copy of this book could you please shed some light here: I was trying to reproduce the example shown in Chapter 5, section 5.3.1 Window Design Method's Figure 5-19 which illustrates ...
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2answers
35 views

How do you initialize the output of a second-order-section filter?

I've got a 4 stage second-order-section filter. When I turn this filter on, it assumes it is starting from zero and takes forever to converge on the actual signal. For example, let's say I have a ...
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26 views

Convolution Filter Size

I am reading a paper on dilated convolutions, and I have come across this piece of mathematics. It makes sense for the most part, except when the author says that the filter size is $(2r + 1)^2$. ...
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32 views

Is the behaviour of the following filter plausible?

I've designed a filter based on this equation $$ E(u) = \frac{1}{2}\int_{\Omega} \left[(u-f)^2 + g(\lVert \nabla u \rVert)\right]dxdy $$ Euler-Lagrange equations in this case are (should be) given ...
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1answer
41 views

Band pass filter (digital resonance)

Q1:  Consider a discrete-time band-pass filter (BPF) that uses only two poles as $$ H(z) = G \frac{1}{\big(1-r \, e^{j \omega_0} z^{-1}\big)\big(1-r \, e^{-j \omega_0} z^{-1}\big)} $$ where this ...
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2answers
34 views

multiplying the received signal by carrier, in OFDM system

Sorry for this question, I'm still new in signal processing area. In OFDM system, let $x$ be the received signal, what do we call the process of multiplying the received signal $x$ by $e^{-j2\pi F_c ...
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1answer
46 views

Damped Harmonic Oscillation as an LTI

The goal is to create an LTI filter which is exactly, or approximates, damping of harmonic modes. The equation of course is: $$\frac{d^2 x}{dt^2} + 2 \xi \omega \frac{dx}{dt}+\omega^2x=0$$ This can ...
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1answer
47 views

Question of Digital filter; stability and order

Below 1~6 are my question. Shortcomings of IIR filter. Mean of unstable. (Things that will happen when system is unstable.) How to select the best order(n). What happens when I raise order too much. ...
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0answers
21 views

Backgroun noise in voltage vs time graph

I am analyzing a voltage vs time graph and I am coming across sinusoidal background noise in the cathode. I was wondering what the best method of getting rid of this noise would be on python. So far I ...
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3answers
49 views

Usefulness of Practical filter ouptput

If a practical filter can't remove all unwanted frequency components like ideal filter, does that mean unwanted frequency component are still present after filtering? how can we use such distorted ...