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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1answer
66 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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46 views

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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45 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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32 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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1answer
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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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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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42 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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42 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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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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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
58 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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108 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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47 views

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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72 views

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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1answer
49 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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1answer
18 views

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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86 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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41 views

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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1answer
162 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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2answers
42 views

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
44 views

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
63 views

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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1answer
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
187 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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1answer
42 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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75 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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1answer
43 views

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
71 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
39 views

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
191 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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1answer
49 views

Strange Response of a fir1 Filter in Matlab

i have been tinkering with some fir filters to bandpass-filter a signal. Even though the filter looks pretty descent in frequency domain, i receive a quite strange "filtered" signal in time-domain. I ...
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1answer
125 views

Separation of signals without loss of information about the signals themselves

There is a signal that contains: Rectangular pulses on frequency of 1 kHz Rectangular pulses on frequency of 1.4 kHz Other noises. Required: Separate 1kHz pulses from everything else and measure ...
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4answers
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Remove brighter regions in an image on frequency domain

I'm newbie and maybe this is not the right place to ask this question, or this question has no sense. I'm very interested in working on filtering images on frequency domain. I have found a few ...
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1answer
21 views

Constraints for Type 3 Linear Phase Filter

This might be a strange question - but most of the Type 3 LPF I'm seeing are having this in common for $h[n]$, assuming $h[n]$ is real: We cannot have outermost element of h[n] lower than middle ...
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1answer
177 views

Relationship between wavelet shape and wavelet filters

MATLAB has a library of wavelet functions, showing their "continuous forms" as well as the the decomposition and reconstruction filters. In decimated wavelet transform the filter size remains the ...
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1answer
31 views

Wavelets: Reconstruction Filters for 2 Level Decomposition

I am trying to understand the reconstruction part after discrete wavelet decomposition and how do we get approximations and details at various levels. Most textbooks show the complete reconstruction ...
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1answer
53 views

When is a discrete time transfer function unrealizable?

I don't understand why the following makes sense: Given a second-order mass damper system in continuous time: $H(s) = \frac{1}{ms^{2}+cs}$ Its inverse $H^{-1}(s)$ is unrealizable as a transfer ...
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112 views

is y[n] = x[n] + n time invariant?

My steps were as follows: $\ x_2[n] = x[n-k] $ $\ y[n-k] = x[n-k] + (n-k) $ and $\ y_2[n] = x_2[n] + n = x[n-k]+(n-k)$ Does this mean that it is indeed time invariant?
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87 views

Is there a relation between the dead zone of sigma delta modulator and filter order?

This question refers to the link https://pure.tue.nl/ws/portalfiles/portal/1546321/521243.pdf. In chapter 4 it discusses the topic of dead zone, which appears in the delta sigma modulator. Dead zone ...
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1answer
51 views

Transfer function given as z-Domain fraction: gain calculation

I am stuck on a question regarding transfer functions. I have the answer and have attempted the question but am having trouble solving it. Q: Given the transfer function of a digital filter is (5z-5)/...
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FFT response for noisy signal, averaging the response and

I try to analyze a system's state with acceleration sensors by measuring the frequencies and amplitudes. Since a cheap sensor is used, I have a noisy signal in the beginning (up to 40Hz - see below). ...
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2answers
348 views

Help with my first (simple) Z-transform

I need to transform this Laplace function to the z-domain: From the answer I received: $s=(1-z^{−1})/T$ Then substitution into my Laplace function would give: $t(z) = 2R/(m*(1-z^{−1})/T + 2R)$ Is ...
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Meaningful output of FIR filter output

I have implemented FIR filter using tapped delay line method. I start getting output as soon as first input sample is passed to it, I am wondering from which sample I will get the proper output(...

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