Tagged Questions

Infinite impulse response (IIR) is a property of signal processing systems.

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Relationship between Difference equation and Impulse response

I'm having some difficulties understanding the relationship between the impulse response and the difference equation for IIR filters
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64 views

Realization of IIR resonator

The measure of a given frequency $\omega$ in a signal $x(t)$ is: $\frac{1}{N}\sum\limits^N_{t=0}x\left(t\right)e^{^{-i \omega t}}$ This is basically an average of the correlation between the signal ...
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Transient cancellation in non causal filtering

I am using the exponential moving average filter (IIR): $$y(n)=\alpha{}\cdot{}x(n)+(1-\alpha{})y(n-1)$$ in a foward-backward filtering scheme, in order to eliminate completely any phase response ...
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48 views

Difference Equation & Impulse Response of IIR filter - deconvolution

What i want to do is to design an IIR-filter that cancels the "echo", such that im only left with the delta[n]. To do so i ofcourse make an IIR-filter, where u take the z-trans of the impulse ...
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FIR / IIR and Wavelets

I am a self-learner of DSP by reading various books. I have accomplished basic understanding of Signals - CT and DT and a few transforms. I recently started to learn FIR / IIR Filters. The part that ...
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1answer
85 views

Filtering out unwanted square wave (Radio: DCS/DPL signal)

I've need to remove a DPL/DCS signal from a recording. Roughly speaking, a DCS signal is a low frequency (67.15Hz) square wave sent at the same time, over the same carrier, as speech. Because it is a ...
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Deriving finite impulse response for polylogarithm

As a part of my research i have to use the following z-transform in matlab 'filter' function so as to derive the convoluted signal from the original one. $$\frac{1}{{\rm Li}_{k}(z^{-1}e^{-b})}$$ ...
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1answer
46 views

How to find the frequency response of a communication channel from input and output symbols' functions in MATLAB?

I want to find the channel frequency response of a digital communications system. I have the functions of the input symbol (a triangle) and the output symbol - a distorted triangle: $$\dfrac{1}{1 + ...
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57 views

Understanding IIR , Low Pass, High Pass, Chebyshev, Elliptic Filter? [closed]

I see these terms everyday in every lecture, I do read stuff from wikipedia, follow lecture notes, study solved exercises. All in all I do have a rough idea about these, I know a little from ...
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21 views

IIR Design with Neural Networks

i'm trying to apply this paper: using C++ Design of Digital Recursive Filter Using Artificial Neural Network In this paper the weights are the coefficients and they start with weight a(0) = 1 and ...
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82 views

linear-phase lowpass filters: frequency responses alignment

These two filters have very similar frequency responses, but those responses are not identical except at a single frequency ωo. I want to find ωo. One way I've seen that done is like this: ...
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138 views

Matlab - Creating a characteristic for Peak and Shelving filter

I have designed few shelving and peak filter. And I have calculated the a, b coeficients for several gains for these filters. Now I would like to create some kind of characteristic in Matlab so I ...
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2answers
236 views

IIR oscillator produces stable output in MATLAB, unstable on chip, how do I tune it?

I'm trying to make an oscillator using IIR filter and I'm having problems tuning it so that it's stable on the platform I'm using (ARM Cortex M4F and CMSIS DSPLib's arm_biquad_cascade_df1_f32). Note ...
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1answer
62 views

L2-optimal IIR Filters

It is widely known that matching a FIR filter of fixed length to a band model is an unconstrained QP-problem. The matlab function "firls" implements a solution to this problem. Basically, one ...
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1answer
152 views

IIR filter that is causal and stable and has more phase lag at lower frequencies

I have a physical system consisting of a microphone, which feeds to a DSP, which drives a speaker. The microphone and speaker system have an amplitude response or gain, as well as a phase response, ...
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1answer
148 views

How can I detect if a filter is FIR or IIR according to impulse response graph?

I have the following two graphs but I don't know how to recognize from the graph if they are IIR or FIR! Can you please guide me through? P.S.: Does MATLAB have a function to detect if an impulse ...
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90 views

IIR biquad coefficients for negative frequencies in IQ data?

Assume I have a (single real float channel) biquad IIR filter implemented in C, and some coefficients for a bandpass filter (right out of RBJ's cookbook). If I convert the input, output, data path, ...
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2answers
119 views

Criteria to distinguish FIR and IIR filters from difference equation?

What criteria should be used to safely decide if it is an IIR filter or FIR filter from a difference equation? FIR filter are always stable, meaning all poles are inside the unit circle AND have ...
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1answer
107 views

How is the MATLAB filter function so fast?

How is the filter function implemented in MATLAB? How is it so fast? What's the fastest implementation of a FIR filter?
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2answers
209 views

Understanding Z-Transforms and Pole Locations

I am trying to gain a better understanding of pole locations in the Z-plane of a given discrete transfer function, $H(z)$. I think I have a pretty good understanding of how to use the Z-transforms ...
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2answers
70 views

Using goertzel confuses me

I am having some troubles understanding the algorithm. My algorithm looks like this. how come am i able to compute the DFT coefficient using this algoritm. As far as i know $$ X[k] = ...
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1answer
158 views

Matlab SOS Filter in C++

I'm struggling to validate that my C++ implementation of a filter I designed in Matlab is correct. My first issue is to make sure I'm implementing the sections in the right order. This is the output ...
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1answer
56 views

Is it possible to implement FIR band pass filter using two FIR band stop filters?

I am trying to filter a signal using a given FIR band stop filter. I have to implement a band pass filter. Assuming I want to get the signal between normalized cutoff frequencies [0.2,0.3] - can I ...
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Is impulse response determined in a different way for systems described with 1st and 2nd order difference equations?

I was studying the book DSP: Principles, Algorithms & Applications, and tried to solve some problems. The book states that the impulse response when one knows the difference equation of the ...
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1answer
52 views

Can I compute my IIR faster given limited possible input values?

I have an IIR routine in C++ I'm trying to speed up. Currently I'm using a DF2 implementation. Since my input signal will always be either 1.0 or -1.0 is it possible for me to optimize the algorithm, ...
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1answer
269 views

Calculate cut-off frequency of lowpass IIR-filter

Given a an IIR lowpass-filter in z-space: $ H(z) = \frac{\sum_{i=0}^P b_{i} z^{-i}}{1+\sum_{j=1}^Q a_{j} z^{-j}} $ How to calculate it's 3dB cut-off frequency? I about evaluating it's fourier ...
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1answer
135 views

Noise Equivalent Bandwith of IIR and FIR Filters?

How do you calculate the noise equivalent bandwidth for an IIR or FIR filter?
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1answer
250 views

Gain of FIR/IIR filters

What are the formulas for signal and noise power gain of digital filters (FIR and IIR)? For a FIR, I've seen in Harris' windowing paper that the DC gain is the sum of the filter weights. $$ G = ...
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1answer
94 views

Very first values of y[n] in an IIR filter

I use a simple biquad IIR filter : ...
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3answers
241 views

How can I prove stability of a biquad filter with non-zero initial conditions

Ok, so the situation is that I have a DFII biquad with some filter coefficients: $w[n] = x[n] - a_1*w[n-1] - a_2*w[n-2]$ $y[n] = b_0*w[n] + b_1*w[n-1] + b_2*w[n-2]$ While the filter is ...
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2answers
139 views

IIR issues when order is high

Thanks to all the people who helped me here, I finally achieved to implement a notch filter (*), with coefficients given by : http://www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html When I do ...
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1answer
388 views

simplest Notch filter in the world

What do you think of this notch / band reject filter for a very very narrow band ? ...
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1answer
108 views

Scaling of a notch filter

Let's say I have an IIR filter that is a notch type with a peak at -20db. How do I modify the coefficients of the filter so that the peak is at -10 db for example? I know I can scale the denominator ...
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1answer
437 views

Design of 10th order high pass filter using 2nd order biquads with Matlab and further substitution on to TI AIC3204

I am involved in designing a 10th order high pass filter with cutoff frequency 300Hz. My hardware AIC3204 has a 5 biquads of direct form I, 24bit coefficient so I have chosen the FDA (filter design ...
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92 views

IIR: get magnitude and phase from coefficients

i'm trying to plot 1)the magnitude and 2)the phase response of an IIR eq with only its coefficients. i've found somewhere that one can find the magnitude response starting with the transfer function ...
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0answers
50 views

interpolation of filter coefficients

i've read that it is possible to interpolate between two sets of filter coefficients (if they are close of course), but how to interpolate between two sets of coefficients which are of different ...
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1answer
72 views

Choosing inverse Z-transform equation, given that $|a|<1$

Given that $|a|<1$, then which of those inverse-Z-transform equations are we to use? I am leaning towards the first because (as I understand it), $z$ is merely a complex number that is ...
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1answer
76 views

Group cascading IIR filters of different orders

Is it possible to make one IIR filter from various cascading IIR filters of different orders? I know it is possible to do it from filters of the same order, but what about filters with different ...
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1answer
40 views

Stability varying with order

I have been doing some research into modelling acoustic spaces, and (with help from this site) I've managed to take the frequency response of fibrous layer model, convert it to a reflection response ...
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1answer
551 views

Designing an allpass IIR filter with arbitrary phase response

could you tell me step by step the algorithm to design an arbitrary phase response IIR allpass filter design ? I know Matlab uses a "brute force" algorithm to find an arbitrary group delay response ...
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1answer
372 views

Complex Least Squares FIR filter design using Levinson' s algorithm

i'm trying to implement an arbitrary IIR filter design. I'm decomposing all the algorithm into smaller pieces that i can test. I currently am on the part where it designs a FIR filter from an ...
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2answers
251 views

Least Square Digital IIR Filter Design (with arbitrary responses)

i'm studying the IIr filter design that is described in the book : Algorithms for the constrained design of digital filters with arbitrary phase and magnitude responses you can get the code at page ...
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3answers
198 views

Berchin's FDLS arbitrary filter design algorithm

i'm trying to use Berchin's FDLS methods (for those that don't know what it is, it's a way to design arbitrary magnitude and phase of an IIR Eq) I tried different things but neither gave me what i ...
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1answer
87 views

Build discrete IIR from a transfer function which is not in terms of $s$

Firstly I should state that my maths knowledge is limited. I'm currently designing an acoustics modelling application which uses a rectilinear FDTD grid for modelling pressure variations - but I've ...
2
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1answer
107 views

What does the stability margin have to do with the quality of a filter?

I designed a 2nd type Chebyshev bandpass filter with passband between 1 and 6 Hz and 30 dB attenuation in the stopband. When I looked at its Bode plot in Mathematica, I noticed "stability margins" ...
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1answer
218 views

What are the effects on filtering upsampled data without interpolation?

I have an application that displays several signals from different sensors at various sample rates. In order to display the data, I "stretch" the signal by repeating samples to match the highest ...
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1answer
145 views

What does the uncertainty principle say about recursive filters?

The uncertainty principle is usually stated as a relationship between a continuous signal and that signal's Fourier transform, and says that $$ \int_{-\infty}^{\infty} \! x^2 f(x) \ \mathrm{dx} ...
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2answers
357 views

Step response overshoot in IIR filters

Is there an analytic expression by which it is possible to calculate overshoot of step-response of second order IIR digital filter? I have tried to search through Mitra's signal processing book and ...
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1answer
291 views

DC blocking IIR filter clipping?

I'm processing audio data for voice input from a mic. The data arrives in 32 bit floats [-1 ~ +1]. My first filter is to remove DC: ...
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1answer
734 views

Hilbert transform filter for audio applications: Using IIR half-band parallel all pass structure

Does anyone have any experience designing wideband IIR Hilbert transform filters with audio applications in mind? I am using the filter for single side band modulation audio effects discussed in this ...