# 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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### Transform lowpass filter to highpass filter, what happened to unit sample response and difference equation?

I know that multiple a lowpass filter signal by $(-1)^n$ can transform it to a highpass filter. $$s_{hp}[n]=(-1)^n s_{lp}[n]$$ But exactly what happened to the unit sample response and difference ...
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### Phase in FIR filters [closed]

Does anyone have any idea what is Clear Phase technology ? How is it implemented ? And which audio channels whether left ,right center , sub woofer should have this technology implemented and why ?
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### Confusions in windows based design of FIR filters?

I am reading the proakis book"DSP USING MATLAB 3rd Edition" In chap 7, article 7.3, i came across example 7.8,where i saw formulas for pass band ripple and stop band attenuation I have ...
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### Help identifying filter

Apologies in advance for asking something so basic, this is not my field at all so I'm a bit lost where else to find this info. I'm trying to understand this piece of code that detects sudden drops in ...
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### Frequency domain filtering: must filter coefficients always be conjugate symetric?

While trying to do frequency domain filtering of audio signals using windowed overlap-add methodology, I came across some pre-calculated frequency domain coefficients. I noticed that the coefficients, ...
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### Calculate moving RMS with exponential averaging

This is moving RMS, now how to add exponential averaging in this df['signal'].rolling(21*24*60).apply(lambda x: np.sqrt(x.mean()))
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### On what it means for a system to be minimum phase

From my undestanding I get that when a system's poles and zeros are all inside the unit circle then it means that it's minimum phase. But I don't get how the location of zeros and poles are related to ...
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### What is phase shift?

I'm reading about when a $H(z)$ system is min phase or max phase, and I get when a system is a min phase or max phase depending on the location of the zeroes. But I don't get at all the phase shift ...
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### Calculation of inverse impulse response in the frequency domain

I want to calculate the inverse impulse response of a LTI system in the frequency domain. I generate a simple impulse response $g$. For this I generate a vector of 100 zeros. I set the value of the ...
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### Finding the wiggles pattern in the original dataset. (Wiggles appear after performing division by another dataset)

I have multiple measurements regarding scientific observations. The problem is that there is a subtle noise pattern caused by the instrument - the wiggles. These wiggles are invisible when looking at ...
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### Comb filter - attenuation

I have a signal and from 'standard information' I know the predominant frequency is at $1\textrm{ Hz}$ and then there should be three harmonics at lower amplitudes. My signal however has a lower ...
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### Speed measurement calibration

I have a sailing yacht where speed is measured using a peddle wheel. It measures speed through water (STW). This measurement contains a measurement error whose magnetude is dependend on both speed (it ...
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### Signal Spectrum Shaping

I am looking for methods/algorithms for signal spectrum shaping. Let's say we have a white Gaussian noise and want to have a desired power-spectral density. The first solution that comes to mind is ...
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### How can I find the transform function, amplitude and frequency response of a digital filter in python?

I have applied a laplace filter mask to an image and now I want to find the amplitude and freqency response of a laplacian filter: [[1,1,1], [1,-8,1], [1,1,1] ]. I know I need to first find the ...
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### Edge detection in spatial or in frequency domain?

I want to ask why everywhere is used to do edge detection in spatial domain and not in frequency domain with FFT of image and apply HP filter. Thank you.
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### How to achieve a smoothed frequency phase response with no outliers

I have two sampled signals, which I then perform wavelet analysis on, by synthesising the Filterbank, perform the dft on each kernel, and the dft on the sampled signals, and multiply together. ...
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### What are the kernels that are used in the Smooted Psuedo Wigner-Ville distribution?

Defined in Matlab's docs for WVD, SPWVD is given by: $\int_{-\infty}^\infty g(t) * H(f) x(t + \frac{\tau}{2}) x^*(t - \frac{\tau}{2}) e^{-j2\pi\tau\,f} \, d\tau$ H(f) and g(t) are the smoothing ...
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### Detect Gradual Increase Before a Decrease in Noisy Data

I have data that'ss 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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### QPSK demodulation

My objective is to demodulate QPSK signal. At this moment, my constellation in the best case looks like in the picture below: and the corresponding eye-pattern: Eyes are completely closed, which ...
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### Why do FIR systems need to be antisymmetric about M/2 to be linear phase?

Why do FIR systems need to be antisymmetric about M/2 to be linear phase? where M=delay.Also im talking about discrete time.And why are hilbert transformers antisymmetric on n=τ?
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### 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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### Relationship between order of filter and amplitude/phase response

I am learning about digital filters, for example a lowpass butterworth filter. In many languages, the implmentation requires specification of the order of the filter, which I believe is the number ...
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### Bio-signal discontinuity after FIR filtering

I'm filtering respiration signal. I have a signal of duration equal to 10 minutes, so I decided to divided it into period of 10 s. I filtered each epoch with FIR filter, but I have discontinuities ...
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### Accelerometer Bias estimation with kalman filter

I have to estimate biases of a 3-axes accelerometer by modyfying an existent kalman filter mounted on a drone. The biases are assumed constant. The filter has 9 states: position (xyz), velocity (xyz) ...
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### Discrete Wavelet Transform (DWT) Filter Bank

I have some stumbling block in my thesis writing. Do we use the same filter pair while implementing DWT filter bank with downsampling of the filter output, or filters do change also from level to ...
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### Is the Bilateral Filter a Solution of Some Variational Method?

I've been watching these video lectures about variational methods in computer vision. In one of such video lectures a it is explained for example that the Gaussian filtering is a solution of the ...
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### FIR Filter design, using different filter length than signal length

Given some neurophysiological application I am filtering in real time data of limited length (e.g. in epochs of 100 ms) using a sampling rate of e.g. 100 Hz. Due to this short time segment I am trying ...
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### 1st and 2nd Gaussian derivatives for edge detection

I have a project about edge detection, I made research on internet about filters and read many articles but there is an article talked about using Sobel and Gaussian derivatives then it mentioned &...
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### Output power of a signal passing through an IIR filter

suppose I have the following discrete time signal $x\left(n\right)=0.7\sin\left(2\pi \times 623\:nT\right)$ where $N=4000$ and $T=\frac{1}{f_s}$, where $f_s=40$ kHz I pass this signal through a simple ...
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### RC high pass filter differential equation

I have the question to derive: $$RC \frac{dy(t)}{dt} + y(t) = RC \frac{dx(t)}{dt}$$ which describes a high pass filter or $CR$ circuit with $x(t)$ the input and $y(t)$ the output. I am really ...
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### Error introduced by smoothing filter at the end of a processing block

I'm running analysis on a multichannel audio signal and due to the size have decided to process it in blocks (my computer doesn't have enough memory to process it in one go). Some of the data produced ...
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### My 3x3 Weighted Median Filter doesn't seem to be improving my image quality

In order to reduce noise in my training dataset,I attempted a WMF whose weights are shown in a 2-D array as follows(values finally get normalized by division by 15: ...
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### Introductory resources to mathematical properties of “dynamically recalculable” filters in audio/musical equalizers?

Introductory resources to mathematical properties of "dynamically recalculable" filters in audio/musical equalizers? Particularly, I want to understand What mathematical features (e.g. monotonicity ...