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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How to get rid of ripples from a gradient image of a smoothed image?

I have a gray scale uint8 image. When I smooth it with a Gaussian filter and then compute the gradient image with a Sobel filter in OpenCV, ripples would appear. The first image is what happens when ...
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2answers
38 views

Kalman Filter with single input?

Is a Kalman Filter still a Kalman filter if there are no inputs that explicitly predict the next state of the system? For instance, if I have a signal where I know it has characteristics of a first ...
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20 views

What is the best technique for implementing high sample rate FIR filters on FPGAs? [closed]

What is the best technique for implementing FIR filters in SERDES implementations for GSPS applications? Are poly-phase filters (non-decimated) the best technique?
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166 views

Prewarping both resonant frequency $f_0$ and bandwidth (or $Q$) when using bilinear transform

RBJ's Audio EQ cookbook takes into account only frequency prewarping when case Q is used for bandwidth. Why not $Q$ prewarping as well with some of those filter ...
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3answers
62 views

How to design a digital filter with a frequency dependent phase delay?

I want to design a filter with a custom phase delay related to frequency. As frequency increases, phase delay should increase. The time delay as a function of frequency can be expressed as: $t_d = \...
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37 views

Polyphase Analysis Channelizer in MATLAB

I am attempting to reproduce results for both polyphase analysis and synthesis channelizers found in "Non-Maximally Decimated Filter Bank and Its Applications in Wideband Signal Processing". Detailed ...
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1answer
32 views

Summation of audio tone

Suppose you transmit at a single tone $\omega\textrm{ rad/sec}$ and you have two receiving microphones $i=1,2$ which sample at $r$ samples per second. Assume you have a direct path with coefficients $...
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58 views

Merge 7 audio buffers

I've implemented an 7 band EQ using EQ10Q filters. Doing some measurements with the smaart software I realized that my bands were overlapping each other giving an extra undesired gain. I think this ...
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20 views

FIltering data from Accelerometer in soil (Shaking table test)

I performed a test in a shaking table in San Diego. In this test, there were several accelerometers embedded at different depths in the soil. I am using these accelerometers to determine the ...
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43 views

Do filters work on a “per sample basis”?

I'm confused because of filter length, whether (such) filters can be used to filter audio on a "per sample basis"? By per sample basis I mean that I would like to filter audio one sample at a time, ...
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1answer
120 views

Biquad coefficients using Magnitude (or Phase) Invariance Mapping Method

I'm trying MIM (Magnitude Invariance Method) and PIM (Phase Inveriance Method) for to improve biquad LPF response at low sampling rates. I'm not sure if these methods can be used for this purpose so I'...
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55 views

Sampling the impulse response

Given two IIR filters (one Low-Pass and one High-Pass) designed using Butterworth, how can I know if they can be obtained using sampling the impulse response?
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96 views

Making a low pass filter for irregular samples

We are interested in reconstructing the red channel of a scene. The red channel is slowly varying. Unfortunately the camera does not have a Bayer sensor, and the red samples are irregularly spaced ...
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13 views

Frequency subtraction of noise by sampling small region of background (in matlab)

I have a very noisy image that I want to filter. The problem is that the noise is not pepper and salt but has features of its own; it looks like the ridges of a mountain (when you look from the sky). ...
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33 views

Non-causal FIR. Is that possible?

I know that a FIR (Finite Impulse Response) filter has the same quantity of poles than zeros. And I believe all the poles are at $z=0$. And a FIR filter is always stable, so it's ROC has to include ...
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20 views

All-pass filter

I know that I can write an all-pass system as: $$H_{ap}(z) = \frac{z^{-1}-a^*}{1-az^{-1}}$$ because it has magnitude $1$ (or magnitude = constant) And I can also write it like: $$H_{ap}(z) = \frac{1-...
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52 views

Transform linear-phase FIR to minimum-phase FIR

Given a FIR filter (non-causal) with phase zero and real coefficients given by $$H(z) = \sum_{n=-M}^{M}h[n]z^{-n}$$ with ripple $\delta_2$. How can I obtain a filter $H_{{\rm min}}(z)$ of minimum ...
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2answers
51 views

Can you get flat response with Linkwitz-Riley cross-over?

Many pictures display that the Linkwitz-Riley has $-6\textrm{ dB}$ dips at the cross-over frequencies. Are these fixed or can these made flat?
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46 views

Generalized linear-phase filter

I know I can write the frequency response of a Generalized linear-phase system as: $$H(e^{j\omega}) = A(\omega) e^{-j\left(\alpha \omega - \beta\right)}$$ where $A(\omega)$ is real. I need to prove ...
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84 views

Changing voice characteristics so it sounds like someone else voice

I have a recording of speech, and I want to manipulate the voice, so a listener will perceive the manipulated voice and the original one as belonging to two different people. The manipulated voice ...
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1answer
38 views

Parametric EQ vs multiple bandpass filters

Will filtering a signal through multiple bandpass filters, where each filter is passed the complete signal, and then combining the output have the same result as a parametric EQ? What if the signal ...
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0answers
20 views

How to find frequences domains in a 2D FFT (or DFT)?

I try to understand the FFT (and 2D FFT) with some basic R functions. x=1:10 plot(Re(fft(x))/length(x)) For the signal x, we ...
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1answer
57 views

Output of lowpass filter with damped sine wave input

The random process $$Y(t)=\cos(\omega_0t)\cos(\omega_0t+\pi N(t))$$where $N(t)$ is a Poisson process of parameter $\lambda$ enters a lowpass filter with transfer function $$H(j\omega) = \left\{ \...
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2answers
68 views

Is convolution the only way to apply filters?

So I've read about the discrete convolution and how it applies to filters. But Is convolution the only way to apply filters (to input signals)?
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26 views

Deriving an FIR filter that interpolates the missing color components on a Bayer array

Hirakawa and Parks' paper on adaptive homogeneity-directed demosaicing of Bayer-filtered images has a section on designing a FIR filter that, when input one line of sensor data, will interpolate all ...
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30 views

Low-pass elliptic filter design: equation for calculating required minimum order

In this paper on page 4 (or in slide page, 23), it describes the equation for calculating the minimum required order for elliptic filter for design specification. However, it says it is only the ...
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42 views

Designing bandpass FIR filter MATLAB

I am trying to design a FIR bandpass filter for a STM32F407 microcontroller with a passband of 1kHz between 59500 Hz and 60500 Hz or something similar (since I don't really know how tight I can ...
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22 views

Does the S-transform have phase linearity?

S-transform is said to be a time-frequency distribution and also it is linear with frequency. Is it linear with phase also? If not, how can I find the phase relation between two signals?
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42 views

Derivation of Bessel filters

I was reading Winder's Analog and Digital Filter Design and the section on Bessel filter. I was hoping to see a complete derivation of the Bessel filter theory, but Winder's book gives only \begin{...
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4answers
122 views

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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1answer
31 views

How to construct a preemptive digital filter to neutralize an unwanted filter

I'm trying to think of how to construct a filter based on the following scenario. I have some time trace with a certain known power spectral density (I can verify this with a periodogram of the time ...
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1answer
59 views

Bandpass general equation to difference equation

I know this is a very basic question and I am coming out from a quarter of DSP. I want to create a function in Java which can taken in two parameters, either ...
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2answers
78 views

Remove noise from linear signal

This signal represents the distance in an experimental device. As the speed is constant, the signal should be linear (untill it drops). However, for some reason the device showed interferences as ...
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68 views

Decomposition of $H(z)$ as maximum-phase, minimum-phase

The frequency response is: $$H(z) = 2-7z^{-1}+7z^{-2}-2z^{-3}$$ I see that it has $3$ zeros: $z_{01} = \frac 12$, $z_{02} = 2$, and $z_{03} = 1$; and $3$ poles in: $$z_x = 0$$ Now, I have to write ...
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1answer
46 views

Confusion about adjoint of convolution

I have the following problem with convolution operators. I know that if I have a filter $g$, then the adjoint filter would be given by $h(x,y)=g(-x,-y)$, so that $\langle g * u,v \rangle = \langle u,...
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1answer
42 views

Maximum phase with the same magnitude response

I'm trying to solve an exercise in a general way and I can't find if my answer is correct. Given this frequency response: $$H(z) = 4 + 2\sqrt2 z^{-1} + z^{-2}$$ I need to find a frequency response ...
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18 views

Difference between Envelope filters and a unit with variable envelope response

Would a unit with variable envelope response shape a square sound wave into a sine wave? I know that an envelope filter kind of does that through subtractive synthesis. I'm trying to find a way to ...
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2answers
100 views

Inter-filter bit width

I'm designing a $2$-stage filter and was simulating the effect of quantization to a certain number of bits at the filter output. The result I got was far from expected - and would appreciate any ...
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865 views

Can you turn a square wave into a sine wave using a low pass filter?

And if it could, would it make the sound of the square wave thinner than before because of losing its harmonics?
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1answer
29 views

Smoothing complex data by convolution

I need to smooth noisy complex data with a Gaussian filter. Right now, I apply the filter to real and imaginary part of the data separately, which needs two convolutions. The intended results are the ...
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29 views

4-band FIR filter equivalency with 2-band filter compositions?

On pg. 18 of this paper: On the Dual-Tree Complex Wavelet Packet and M-Band Transforms there is a discussion about creating a single 4-band filter bank from a 2-level, 2-band set. There are two ...
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66 views

What is the difference between convolution filter, low-pass filter, and median filter?

Isn't blur filters, like median filter, a type of convolution filter? How does a low-pass filter relate to them? Why does this guy differentiate convolution filters here from blur filters here?
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Image processing - Is mean filter shift-invariant?

Update: So, according to this article. For a 2D mean filter, $$ H[f(x,y)]=\frac{1}{NM}\sum_{k=0}^{N-1}\sum_{p=0}^{M-1}f(x-k,y-p)=g(x,y)\tag{1} $$ $$ g(x+x_0,y+y_0)=\frac{1}{NM}\sum_{k=0}^{N-1}\sum_{p=...
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1answer
42 views

System identification/ Filter estimation to mimic frequency equalizer of audio with Scipy

At the current problem I'm working on, I have two signals: One "original" signal that contains audio (voice). The second signal is the same audio file but edited with a frequency equalizer, for ...
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1answer
77 views

Sampling signal after root raised cosine

I am generating series of 1 and 0. then pulse shaped them with root raised cosine and after than deciding to do match filtering and recovering the bits however it turns out that I am not getting the ...
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1answer
42 views

Multiple biquads vs higher order filtering

I've heard that you can stack biquads on top of each other to get the same (or similar) effect as higher order filters. For instance a biquads is order 2, so putting something through 3 biquads is ...
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48 views

Synthetic sounds to describe motion in 3d or 100d

Watch a butterfly flitting about, or an optimizer chugging along in 3d or 100d -- a sequence of points $X_1 \ X_2 \ X_3\ \ldots$ How could one generate synthetic sounds that convey moving fast or ...
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What does a Sobel Norm of an image represent?

Why would we want to find the Sobel Norm of an image?
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58 views

LMS filter weight update

I have a general question regarding Least mean squares adaptive filters. Using the example of noise cancellation, I understand that if you have a set of reference signals (S) and corrupted signals (S+...
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80 views

detect what is noise in audio signal

I'm trying to filter noise from an audio signal. The signal was and is going to be recorded in a city environment which always contains some white/pink noise. At this moment I'm using two options to ...