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

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Digital Filter for FRDMKL25Z

I was wondering if I can get some comments for my filter design. Signal to Filter: F(x)=sin(2*pi*80*t)+sin(2*pi*125*t) Since I'm implementing this in C for an embedded system I have chosen and IIR ...
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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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63 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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78 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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63 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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87 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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78 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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174 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
59 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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115 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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40 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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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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228 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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103 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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157 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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82 views

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

I use a simple biquad IIR filter : ...
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142 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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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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257 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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99 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
250 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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131 views

Polyphase IIR halfband decimator using biquad stages

I am trying to use matlab to generate coefficients for polyphase IIR halfband decimator. Which can be achieved using : ...
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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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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
65 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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61 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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37 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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454 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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257 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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176 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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157 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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82 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 ...
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91 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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159 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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129 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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306 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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245 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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533 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 ...
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181 views

IIR Filter structure implementation dynamic range

I want to implement an IIR filter. The filter is going to implement by cascading second order sections. Below there are 3 pictures that implement this filter using: Denominator - Numerator using ...
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357 views

Pole-Zero Plots Diagram Explanation

I experiment with the coefficient quantization in an IIR filter. I change some values like the passband ripple and also how many bits i want for the quantization method. In the first picture i have ...
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408 views

How to find the group delay of IIR filters in Python/SciPy

I sent a square wave signal (red) through a IIR filter (butterworth in this case), to make it more "realistic". Then there's a slight group delay in my output signal (blue). Is there a way to find out ...
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271 views

IIR filter for smoothing

I am using IIR filter for smoothing $$y[n] = ax[n]+(1-a)y[n-1]$$ My question is, if I add another IIR filter, will it be the second order of IIR filter? If not, what it can be called? My second ...
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220 views

IIR filter design in digital domain using Magnitude Squared

Does anyone have any good references for deriving parameters of an IIR Low pass/High Pass filter directly in the digital domain using the magnitude squared at the corner frequency? I have been able ...
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2k views

What is the exact meaning of unstable system in DSP?

In physical systems I understand what is the meaning of stability or unstability. An operational amplifier for example, if working in positive feedback will either saturate or start osscilating (i.e ...
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861 views

IIR filter design in matlab

I have to design 2 IIR bandpass filter with the following specifications: Sampling frequency 1000 Hz Pass-band 50 Hz to 200 Hz Order 6 using bilinear transform and impulse invariance with Butterworth ...
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3answers
582 views

Why is the gain of my IIR filter positive?

Sorry, two questions in one day! I'm struggling to understand what I'm doing wrong in this very simple filter design. I want to design a simple, single pole low pass filter and implement it as an IIR ...
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1k views

Pre-emphasis / De-emphasis filter design

I've designed a simple FM communication system and found that high-frequency noise is a real problem. It appears that this is a well known issue, which has been solved through pre-emphasis of high ...
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complementary IIR filters

I would like a pair of complementary IIR filters (lowpass/highpass). By complementary, I mean, when the output from the two filters is summed, the original signal is recovered. I thought I could build ...
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626 views

Do FFT-based filtering methods add intrinsic latency to a real time algorithm?

In a current audio processing application, I am working entirely in the time domain using IIR filters. This is so I can use an audio buffer of just 3 or 4 samples and can guarantee that there will be ...