Questions tagged [filter-design]

Fiter design is the process of designing a filter.

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26 views

Why ignores constant when applying integral into differential-equation.?

I studied how to draw 'Direct-form I' and 'Direct-form II' from differential equation. The book taught me like this: $$\mbox{Give equation: }{a_0}{y(t)}+{a_1}{y'(t)}+{a_2}{y''(t)} = {b_0}{x(t)}+{b_1}...
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3answers
4k views

What does 'canonical' mean?

What does 'canonical' mean? e.g. 'write IIR or FIR in canonical form' I get the gist of it but maybe someone here has a precise definition. In a non-DSP context it would mean something like '...
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2answers
425 views

Multiple cheap IMUs vs one expensive IMUs

In my project, there is a possibility of either buying one expensive IMU or 5 cheaper IMUs. They have to be cheaper due to budget limitations, and the idea is to use them in order to be able to do "...
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1answer
541 views

Practical vs ideal lowpass interpolator

Consider a signal with a sample rate $f_s = 44.1$ kHz. Let us upsample the signal by a factor of $L = 2$ and interpolate the zeros. An ideal lowpass interpolator would have a gain of $L$ and a cutoff ...
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4answers
2k views

Design Hilbert filter at matlab (pure 90 phase and magnitude 0db)

I need to design a filter able to take a measurement of alternate current and shift the phase of the input by 90°. The filter should work between 40 and 60Hz and at this range should have unity ...
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3answers
928 views

Designing a 2x interpolation filter for audio

I want to perform 2x interpolation on an audio signal sampled at 44.1KHz by upsampling the signal by adding a zero after each original sample and then using a lowpass filter to interpolate the results....
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5answers
907 views

Fields of math needed for digital filter design

I want learn digital filter design. My knowledge of math is at high school level. I can learn math through the Internet. Then, what fields of math do I have to learn?
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1answer
232 views

Precise Centre frequency of an All-pole digital filter

I'm not an engineer and have essentially taught myself all I know - this present problem is giving me some problems. I have an all-pole filter (a gammatone filter - impulse response is essentially a ...
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2answers
7k views

Zero-lag butterworth filtering

Recently, I've read several papers where zero-lag Butterworth filters are used (both low-pass and high-pass). I have a fair understanding of (Butterworth) filters, but how can we design one with zero ...
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0answers
393 views

Alternatives to pole-zero cancellation

I read that pole zero cancellation is a method to get rid of poles outside the unit circle. But I believe exact cancellation could be much harder because of finite precision effects. Are there any ...
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1answer
817 views

Relation between poles and cut off frequency of a filter

I noticed that for a low pass Butterworth filter, as the cut off frequency reduces, the poles get closer to the unit circle. Is it applicable to all filters and why is this so? As the normalized cut ...
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1answer
181 views

Is it possible to design a digital filter that rejects 60Hz noise while keeping step response in the time domain below one mili-second [closed]

Have been trying to design IIR and FIR 60Hz notch filters but all have step response way above 10ms.
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1answer
697 views

How to stabilize a filter

Suppose we have an unstable all-pole filter with transfer function $H(z) = A(z)^{-1}$. What is the best way to design a stable filter with frequency response as close to that of $H$ as possible. (I ...
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3answers
708 views

Splitting the Unit Delay

Please refer to the paper Splitting the Unit Delay - Tools for fractional delay filter design by Laakso, Valimaki et.al. I am not able to visualize how the fractional delay is obtained by resampling ...
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2answers
809 views

A basic question in FIR filter design using MATLAB

I was reading from Internet about FIR filter design using MATLAB, and I saw parameters like passband frequency, stopband frequency, passband attuenation, stopband attuenation, etc. What made me ...
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1answer
660 views

Hamming window for filtering unwanted terms

I am trying to filter off two unwanted terms in this frequency spectrum (the spectrum on top). First, I used a convolution between a rectangular window to make the unwanted terms equal to zero. the ...
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1k views

Design IIR Butterworth filter using bilinear transform

Write listing in MATLAB which design a low-pass IIR filter basis on Butterworth (Rp=2dB, Rr=40dB, fp=1000 Hz, fr=1300 Hz, fs=5000 Hz) as a prototype and using bilinear transform without built-in ...
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1answer
2k views

How to transform lowpass fir filter to bandpass fir filter without using a built in function in matlab

The FIR low-pass filter was designed in MATLAB which characteristics are listed below. Coefficient of this filter was written in variable h. Basis on this filter design a band-pass filter with central ...
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1answer
2k views

What is a 'notch' in image processing?

I cannot find out what does "notch" means in image processing? We have selective filters that one of the best of them is Notch filters. but what does the concept of "Notch"? why they are called "...
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1answer
1k views

Minimum phase FIR method

I am trying to make a minimum phase filter (in wxMaxima) according to these steps: first create a "normal" FIR (a simple sinc, wc=0.4, random example, but in the pictures a remez with Octave) ...
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1answer
187 views

FIR filter design for response inside unit circle

I would like to design an FIR filter such that its Z-transform has a certain profile in certain regions. For example, if I'd like to have an FIR filter that nulls the decaying exponential $\left(\...
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1answer
157 views

What is the name of the following 1st order high-pass IIR filter?

What is the name/family behind the following high-pass IIR filter: $ T = 1/f_s \\ f_c = 5 \\ c_1 = \displaystyle \frac{1}{1 + \tan(\pi f_cT)}\\ c_2 = \displaystyle \frac{1 - \tan(\pi f_cT)}{1 + \tan(\...
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2answers
6k views

Complex low pass filters

I am searching for documentation on the behaviour of complex low pass filters, and their application in telecommunications. Thank you
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1answer
1k views

Are noncausal filters ever used in practice?

Basically what it says in the title; I have just started reading about these things and find noncausal filters pretty interesting in concept, but also they do not seem like they would have any ...
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0answers
82 views

Get the distinctive deltas of quite noisy and very variable / dynamic measurement values

for my thesis I need to point out the distinctive deltas of my measurements for further use. The jumps can occur with different heights over different time slots. And the absolute base values can ...
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1answer
214 views

Additional peak after resampling

I prepared a Matlab script, which re-samples spectrum from 24kHz to 20kHz. When I used up-sampling, a fir filter, and then up-sampling again at the end, I get an additional peak at 4kHz which is not ...
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3answers
494 views

What are the differences between notch filter & Goertzel?

I would like to integrate in my application a tone detector but I'm confused between 2 kinds of filters: Goertzel or Notch? I saw that Goertzel is a recommended for tone detection. But - what if I ...
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2answers
7k views

Any good C# library for signal processing?

Does anyone can link me to a good C# DSP library? I saw some good C++ libraries but I don't have much with C++. Is there any way to wrap them ? My main porpuse is to apply some filters(Lowpass, ...
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0answers
475 views

What is Single pole filter?

Can anybody tell me why do we use single pole filter? And may be an example of Single pole filter in matlab. Good literature recommendations are also welcomed.Moreover, that would be good if anyone ...
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1answer
3k views

How to test digital filters?

First the question(s): How should I write unit tests for a digital filter (band-pass/band-stop) in software? What should I be testing? Is there any sort of canonical test suite for filtering? How to ...
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0answers
142 views

How to determine cut off frequency for high pass filter using spectral density?

I have filtered out the low frequency noise from the signal. For further analysis, I want to compare it with FIR filters (for which I require cut off frequency). Hence, I took the power density ...
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1answer
149 views

Fir filter not working according to frequency response

I have designed a FIR filter with following parameters fs=30, f_pass1 = 1, stop1 = 0.5, f_pass2 = 3, f_stop2 = 4, A_pass = 1,A_stop = 40 Here is code : ...
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1answer
3k views

How to normalize predesigned IIR filter coefficients to have unity gain?

There is a low pass filter with difference equation already provided. $$ y_n = (x_n - 2x_{n-6} + x_{n-12}) - (-2y_{n-1} + y_{n-2}) $$ $$ a_0 = 1, a_1 = -2, a_2 = 1 $$ $$ b_0 = 1, b_6 = -2, b_{12} = ...
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2answers
4k views

How to design an inverse for a Butterworth low-pass filter?

I have a signal that has a spectral shape very similar to the transfer function of a second-order lowpass filter (butterworth design). I would like to whiten the spectrum of this spectrum in the time ...
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1answer
87 views

Filter implementation and alternatives

I'm learning of digital filters and found a question asking why a filter with a impulse response $$h[n]= \begin{cases} \frac{1}{n^2+3n+2} & n\geq 0 \\ 0 & n<0 \\ \end{cases}...
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1answer
290 views

Possible to implement simple IIR filter with greater than 6 db/octave slope?

I am using the following IIR code as a low-pass filter in a software project, and it works great. However, I would like the slope of the filter to be much steeper as the one here seems to be very ...
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1answer
762 views

What is the Reference tap of an equalizer (FIR Filter)

Currently I'm using the built-in Equalizer (EQ) object from Matlab to equalize my signal. For the EQ there is a parameter called the Reference tap. With different value of the reference tap i got also ...
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1answer
461 views

Necessity of Cyclic Prefix in OFDM

I have a question on CP-OFDM. In recent years people are talking about filter bank approach where they are trying to filter out the out of band side lobes using filters. Besides they are presuming ...
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1answer
1k views

Any simple Digital All-Pass Filter Design Tools?

I would like to be able to implement an All-Pass filter with a frequency-dependent group delay. I need a maximum group delay at low frequency of about 20 samples (for Fs = 44.1kHz), and it needs to ...
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2answers
3k views

Which filter for an audio equalizer

I’m new to DSP and I have to do an audio equalizer in c++. I did a lot of research about it and tried some stuff in the last month, but I’m a little overwhelmed with all those informations and it’s ...
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0answers
1k views

ECG noise filtering using FIR Bandpass Filter

I am new to signal processing and examine ECG data corrupted with noise. The clean data has a frequency spectrum like this. And the corrupted one looks like this (sorry for the different scale) I ...
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1answer
100 views

Help with Hankel transform filters

I found a filter for Hankel Transform . As far as i understand this is effectively used as an approximation for $J_0(x)$ and $J_1(x)$. But how will the change in input affect these filter terms (e.g....
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1answer
58 views

Equiripple Filter-Design

I have a requirement to design minimax filter with linear programing (linprog in MATLAB). To build the filter I must choose vector $\omega$ (frequency sample), how ...
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1answer
2k views

Sampling frequency and oversampling factor

A quite naïve question. I need some clarification regarding choosing the sampling frequency and oversampling factor. The scenario is as follows: I have an OQPSK modulated sequence with symbol rate 2 ...
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2answers
3k views

Find Stopband Edge Frequency

I tried to find the stopband edge frequency.I know that the signal amplitude falls to -3 dB below the passband edge frequency.I examine a lot of DSP books so i don't any information about how to ...
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1answer
308 views

What windowed Sinc might be closest to a Parks–McClellan low-pass filter?

In another question on dsp.stackexchange, a statement was made that the output of MATLAB firpm() or firls() for an anti-alias low-pass filter was "close" to the coefficients of a windowed-Sinc low-...
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1answer
47 views

Calculating the network function of a filter

Given a system, that behaves as a 1st order filter with network function $H(s)$. We input: $$v_1 (t)=1+3\cos(10^4 t)$$ And we obtain as output: $$v_2(t)=1+1.5\cos \left(10^4 t -\dfrac{\pi}{3}\right)$$...
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2answers
929 views

FIR Filter Design - input parameters conversion

I am new to DSP and filter design. I have developed a code in C++ to calculate FIR coefficients using Parks-McClellan algorithm. The inputs to calculations are: Filter type (Low-Pass, High-Pass) ...
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1answer
729 views

Convert low pass continuous time filter design to bandpass, discrete time

I am trying to convert the continuous time transfer function of a second order lowpass Butterworth filter is given by: To a bandpass fourth order bandpass digital filter, I first apply the mapping to ...
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1answer
395 views

Parks-McClellan - compiling C++ code from Iowa Hills page [closed]

I am trying to compile C++ code for FIR filter design using Parks-McClellan algorithm from http://www.iowahills.com/Example%20Code/NewParksMcClellan.txt . However, I cannot find the following header ...

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