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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Path delay influence in BER performance using Rayleigh channel

I am simulating a DSSS modulation in a Rayleigh channel to get the BER performance. For these purpose I am using the comm.RayleighChannel object. My problem comes when I change the Paths delays of the ...
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40 views

Reducing one frequency in song

How would I take a song input and output the same song without certain frequency ranges? Based on my research so far, the song should be broken down into chucks, FFT it, reduce the target frequency ...
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Trouble with understanding moving average filter as an oversampling filter

I am struggling with understanding how an moving average filter can increase ENOB in a given sample. I wrote a test for a simple MA (moving average) filter in matlab. The algorithm to create new MA ...
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120 views

Cascaded One-Zero Filter IR

given the one-zero digital filter, $$y[n] = x[n]\cdot \frac{1}{2} + x[n-1] \cdot \frac{1}{2}$$ Which has the transfer function: $$H(z) = (1+z^{-1})\cdot \frac{1}{2}$$ and taking $M$ of these ...
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Can a Kalman Filter Be Applied Using Measurement-Space Dependent Sensors?

I'm currently attempting to apply a Kalman filter to track the angular position, velocity, and acceleration of a bike wheel, and I'm having a lot of trouble, so I want to check if I'm even applying ...
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65 views

Calculating phase shift between two sines of equal, unknown, amplitude and frequency

I've got a source signal $s_1(t)$ and a system affecting that, yielding a phase-shifted version $s_2(t)$; \begin{align} \color{blue}{s_1(t)} &= A\sin(t+\phi_1)\\ \color{red}{s_2(t)} &= A\sin(...
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Weiner filter vs Analytical Linear optimal estimator

I've been learning recently about estimation of stochastic processes in general, and linear estimation in particular. On one hand I've seen the following estimation of $X[n]$ from $Y[n]$ - $X_{opt} ...
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Rotation matrix covariance to quaternion covariance in attitude estimation

Given a $3 \times 3$ rotation matrix $\mathbf{R}$ with an associated $3 \times 3$ covariance matrix $\mathbf{P}$ how do I compute the associated $4 \times 4$ covariance matrix $\mathbf{Q}$ of the ...
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Why do we need a delay in unity STF for sigma delta modulation (SDM)?

In the design of sigma delta modulators it is often seen that a noise transfer function (NTF) is designed first and quite often Signal transfer function (STF) is assumed to be unity. In addition it is ...
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Butterworth filter transfer function in time domain

Preliminaries I need to know the response of Butterworth filter in time domain of the following input (at least numerically): $$ x(t) = \theta(t)(1-\exp\{-at\})\exp\{-bt\}, \quad a,b>0,\quad a\gg ...
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Whitening Filter for Noise Estimation

The signal I'm working on includes some noise which is I assume Gaussian white noise with zero mean and an arbitrary variance. So, it is like; ...
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32 views

A Delay Between Two Filtered Chaotic Signals

it is a common practice to use a shift of cross-correlation peak to evaluate a group time delay of two signals (chaotic signals are included). Can one synchronously and equally filter these chaotic ...
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Who first understood the importance of poles?

Who first understood (or at least published papers on) the importance of poles in understanding transfer functions in the frequency domain? If I had to guess, I'd suggest Nyquist or Bode but I know ...
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65 views

y(t) a of an integrator circuit

I have a signal $$ x(t)= \frac{1}{T} e^{-\frac{t}{T}} u(t) - \frac{1}{T} e^{\frac{t}{T}} u(-t) $$ and I know that it transits in a integrator circuit and I have to find y(t) in time and frequency ...
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Why we measure bandwith at -3dB?

To characterize a signal it's a common use to determine bandwidth at -3dB from the peak (half power). Also, filter's cutoff frequency is pointed at -3dB. Why we use this rule?
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Pandas resample.mean()

I have a question to all you filter experts out there. I have some engine data sampling irregularly at about 50Hz. Recently I've been downsampling via the Pandas resample().mean() method. Basically ...
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How is the formula of the cutoff frequency of a 2nd order Butterworth low-pass filter derived?

According to articles and notes, the cutoff frequency of a 2nd order Butterworth lowpass filter: is expressed by the formula: $\omega _c = {1\over\sqrt{R_1R_2C_1C_2}}$ and since $\omega _c = 2 \pi ...
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42 views

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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24 views

Time response of complex frequency response function

In the frequency domain I have the following function: $$ H(f)=A(f)\cdot e^{i\beta(f)} $$ Where both $A(f)$ and $\beta(f)$ are known functions. The thing I would like to do is to model the response ...
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Low pass filter with different non linear phases [closed]

I want to design low pass filters with different non linear phases. Means the magnitude response of all low pass filters will be same but having different non linear phases.
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Understanding liftering as the final step in MFCCs features extraction

In the book here, they apply liftering, as a final step of MFCCs features extraction, to isolate the system component by multiplying the whole cepstrum by a rectangular window centred on lower ...
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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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46 views

filterbank: understand the different responses at the center frequency of each filter

I'm computing filterbank by applying 26 triangular filters on a Mel-scale to the power spectrum of an audio frame to extract frequency bands, and I found that some references use filterbank with equal ...
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Choosing Right Type of Filter for time series data

I am working on a temperature time-series data which is very noisy. I am trying to measure true low and ...
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33 views

Step-by-Step calculation of stationary wavelet transform gives shifted results?

Good morning, I am doing an SWT by hand to understand it better, and have a couple of questions. Maybe someone here has experience with this? I am using the book "Conceptual Wavelets" by Fugal, ...
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How should I model my low-pass filter to get best SNR of a peak?

So, I'm trying to understand how to use a low-pass filter and optimize the cut-off frequency while getting the "best" amplitude of a peak I am interested in. I have attached picture 1 which shows the ...
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36 views

Choosing right cut-off frequency for a LP filter in upsampler

I'm implementing a upsample function in Matlab but it's not perfect right now,for reasons I'm not sure. Here is my code: ...
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15 views

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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Finding defects in wall paint (finding difference in textures)

I have been experimenting with computer vision techniques to find defects in paintings, more specifically defective brush strokes. I have tried a handful of techniques such as different filters, One ...
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1answer
55 views

What is the slope of a transfer function?

Lets say I have a Transfer function (H) plot as below. I need to find the SLOPE of the transfer function in dB/MHz. That is... i need a plot (db/MHz) vs frequency. How can i go about it ? ...
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88 views

Draw a structure for IIR Filter given H(z)

This is the transfer function for the Direct Form 1 of the IIR Filter: I'm trying to understand the rules to convert $H(z)$ into its corrispondent structure I've just understood how to draw $H_1(z)$,...
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FIR Filter Magnitude Response

This is the shape of the bipolar amplitude function for a FIR filter with odd m: I have 2 questions : If i want to use this FIR as a low pass filter between 0 and $\frac{F_{c}}{2}$ , how can i set ...
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Spectral filtering

I am working with a STFT spectral processing toolkit I wrote in C, now focusing on a module for spectral filtering. In its first implementation, the module simply multiplied an user drawn spectral ...
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46 views

FIR Linear Phase Condition

This is the linear phase condition for FIR filters as expressed by my prof: I don't understand why $G(f)$ can be negative. Isn't the Fourier transform expressed in polar form ? So the magnitude is ...
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Understand diagram of a process

I've found this diagram in a slide, but i have no backround to properly understand it. Could you explain to me, in simple terms, how this process behaves and what's the purpose of the blocks $z^{-1}$ ?...
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46 views

Formula for calculating IIR filter coefficients for a high order low pass?

I'm trying to make a filter for use in real-time audio processing and I'm trying to figure out how to produce coefficients for a low pass with a steep attenuation curve. I've found a few examples of ...
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High Order Buttersworth Filter

Let's suppose i want to implement a Buttersworth filter of order 12 (N=12). First of all ,I can decompose the Buttersworth polynomial in elemental polynomials: Now, if i know how to physically ...
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Correct notation for Frequency Response [duplicate]

I noticed that some textbooks denote frequency response as $H(\omega )$ and other ones as $H(j\omega )$. What is the correct one and why ? Thanks
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112 views

How determine the delay in my signal practically

I am trying to practically determine filter group delay so that I can try to reduce or adjust for it. I have tried all kinds of methods but still can't get the right result. I know that theoretically ...
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Transfer Function vs Frequency Response

Talking about Butterworth filters my prof said that a filter is described by its frequency response $H(\omega )$. What I think is that filter is really described by its transfer function, since there ...
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2answers
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Does a raised-cosine filter have infinite support?

I recently asked a question here regarding limiting the bandwidth of a digital baseband signal and was introduced to pulse-shaping using a "raised-cosine filter". At the time, I mistakenly assumed ...
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1answer
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What did I do wrong with this simple filter build?

I tried to put everything I have learned from people here together to code my first filter from scratch. Unfortunately, it didn't go well and I'm not getting the expected output. The math/code became ...
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75 views

Question about zeroes of simple 2nd order FIR filter

I have a question about the zeroes in a simple second order FIR filter. I'll list out the major beat points of calculating where the zeroes are before asking the question (I'm following "Designing ...
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1answer
167 views

Does mixing brown noise and white noise create pink noise?

What happens if you take a white noise generator, run it through a one-pole LPF set to a low cutoff frequency, and then mix the two together? Do you get pink noise? Say you have this code: ...
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36 views

How to perform dechirping of SAR image in MATLAB?

I have the transmitted pulse and the raw SAR image before range compression (dechirping). I understand the pulse compression its a convolution along the columns but I am not able to make it work. I've ...
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2answers
73 views

Does such filter exist?

Assume the following operation on input $x$ with filter $w$ of size $2L+1$: $y[i] = \frac{\sum_{k=-L}^{L} x[i+k] w[k]}{\sum_{k=-L}^{L} x[i+k]}$ In other words, my desired filter does a convolution ...
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Normalizing white noise to match pink noise's amplitude at a given frequency?

I have a pinking filter which I am running white noise through to get pink noise. I would like to then mix the white noise with this pink noise, where the amplitude of the white noise will match the ...
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1answer
59 views

Synthetic Aperture Radar (SAR). How to do Range Compression?

I am trying to perform range compression to a raw SAR image [fast times, sensor position], Dr in code. I have the transmitted signal (chirp), g in code, and literature says range compression is ...
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1answer
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Kalman Filter for position : introducing acceleration estimates

I want to estimate the position on a 3D environment by introducing only acceleration estimates. Is that possible? If I use the extended Kalman Filter and introduce these estimates will I have the ...
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1answer
189 views

The selection of the amplitude of the signal, consisting of rectangular pulses, at different frequencies

I already asked a similar question, but did not receive an answer and did not find a solution, I want to make another attempt to get to the bottom of the truth. There is a signal consisting of ...

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