Signal Processing Stack Exchange
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Questions tagged [infinite-impulse-response]

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

Systems with this property are known as IIR systems or, when dealing with filter systems, as IIR filters. IIR systems have an impulse response function that is non-zero over an infinite length of time. This is in contrast to finite impulse response (FIR) filters, which have fixed-duration impulse responses. The simplest analog IIR filter is an RC filter made up of a single resistor (R) feeding into a node shared with a single capacitor (C). This filter has an exponential impulse response characterized by an RC time constant.

IIR filters may be implemented as either analog or digital filters.

Source: Wikipedia.

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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 will not have any stable state). thats clear to…
gpuguy
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Designing an IIR to generate a specific data sequence

I know that it's possible to design an IIR with specific poles and zeroes to create specific frequency responses. Is it also possible to design an IIR such that when you give it an impulse, it generates values of a desired sequence? Or at least a…
Alan Wolfe
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Is there a common name for the first order IIR averaging filter?

Is there a term to describe this IIR averaging/smoothing filter? $ y[n] = \alpha x[n] + (1 - \alpha) y[n - 1] $
MaxRunFast
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IIR filters with variable roll-off

I have a filter design problem in which lowpass filters have to be designed with varying roll-off. E.g: 2.7 db/ocatve or 1.4 db/ocave. See picture below. This is easy to achieve with a FIR filter, yet its computational cost is too large. Therefore,…
user7488
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IIR Filter: check for limit-cycle oscilations

So I am studying IIR filters and I came to read about limit-cycle oscillations in IIR filters. From what I understand that are two type of oscillations granularity limit-cycle: when signal levels become very low or constant for a period of time,…
Granger Obliviate
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what space of functions can be represented by the impulse response of an IIR?

I'm trying to understand the expressiveness of the impulse response of an IIR. For example, I know that second order causal IIRs are capable of having impulse responses that are growing or decaying sinusoids. What else can they represent? For a…
Karima Ma
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What is the best way(In terms of speed) to implement a direct form type 2 IIR Filter in VHDL?

I am trying to implement a 4th order direct form type II IIR filter in VHDL(Specifically, in xilinx FPGA) and when i implement it i get correct output yet very low maximum clock rate(Around 80 Mhz). So i wanted to know what is the best way to…
Krsh
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IIR - How the gain is calculated?

I try to extend my understanding of digital filter design, so I play around with some YouTube videos and the MicroModeler DSP with the following IIR design (based on a video): I use the following parameters: Zeros: 0.57 ± 0.78i Poles: 0.51 ±…
Kampi
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Polyphase decomposition of IIR filter

Is there a way to decompose IIR filter into set of poly phase components, that are All pass. E.g. a an IIR filter of order M, can be decomposed into a cascade of All zero filter of order 2*M( which can be implemented as polyphase) and all pole of…
user915783
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Design the digital IIR filter with the following specifications

Lower stopband edge = 25 Hz Lower passband edge = 100 Hz Upper stopband edge = 225 Hz Upper passband edge = 150 Hz Stopband attenuation = 18 dB Passband ripple = 3 dB Sampling frequency = 500 Hz.
sakthidhar koneru
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What could cause ripples in the output of an IIR filter fed with a pure sine wave?

I am using an IIR bandpass filter designed using the elliptic filter in matlab to filter out unwanted frequencies. The filter is fed with a test input that has a dc offset and sine wave of frequency within the passband. The output has some ripples…
Simactricals
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What would be the right interpretation of this IIR block diagram?

Will this block diagram always produce on the top-right arrow the following difference equation? $y[n]=x[n]+y[n-1]*(-2r)+y[n-2]*(-r^{2})$ Or by the contrary, it can produce also the following? $y[n]=(x[n]+y[n-1]*(-2r)+y[n-2]*(-r^{2})) +…
rober_dinero
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Chebyshev Filter design using bilinear transformation-2 methods-2 transfer functions-which is right and which is wrong?

I got myself a book after looking the advice from stackexchange, it has been so far helpful for me. But I got confused in this numerical given in the book. The other method is this-: https://www.youtube.com/watch?v=VhoVH2wB9dc&t=1248s But the…
achhainsan
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Implementing an IIR filter in Pytorch using RNN with no nonlinearity

Is it possible to implement an RNN layer with no nonlinearity in Pytorch like in Keras where one can set the activation to linear? By removing the nonlinearlity, I want to implement a first-order infinite-impulse-response (IIR) filter with a…
Reza
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How to take multiple IIR filters efficiently

I have a collection of IIR filters (exponential decay at various decay rates). I'd like to compute all of them on a discrete time series efficiently. Is there a way to do this that is faster than $$O(\mbox{num_filters} \times \mbox{num_points})$$?
James Pinkerton
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