# Questions tagged [infinite-impulse-response]

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

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### simple iir filter implementation in C++

I am programming the simplest way of implementing and IIR filter. However, I am struggling with the use of buffers. Do any of you have any simple implementation of an IIR filter implementing manually ...
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### When is the sum of two (parallel) minimum-phase filters also minimum-phase?

Say I have two minimum-phase filters: $$\frac{A(z)}{B(z)} \: \text{ and } \: \frac{C(z)}{D(z)}$$ That is, the roots of $A(z)$, $B(z)$, $C(z)$ and $D(z)$ are all in the stable region. If add them ...
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### What does poles in unit circles center mean?

Suppose i have all my poles in unit circle center. What kind of information this gives me? Can i determine if this filter is IIR or FIR?
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### Approximation and IIR Filters

Consider the discrete-time time-invariant system with input $x[n]$ and output $y[n]$ satisfying $$y[n] = \sum_{k=1}^5{x[n-k]}$$ Consider approximating the desired system with a second-order IIR system ...
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### How to practically correct for group delay imposed by a digital filter (Python)

I'm using Python to filter a signal using a Butterworth filter (scipy.signal.butter) and subsequently passing this through a forward-backward filter with cascaded second order sections (scipy.signal....
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### Frequency response of a digital state variable (Chamberlin) filter

I recently implemented a digital state filter based on the recommendation here. I've tested this filter's performance as a very low cutoff low-pass filter with limited coefficient quantization ...
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### Mitigate floating-point numerical errors for very-low corner frequency low-pass filter with DSP

I'm designing a low-pass filter for a digital signal processing application that ideally just passes a very small bandwidth above DC. I'm using an IIR biquad filter for this, where the coefficients ...
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### What is the purpose of the recurrence relation in low and high pass (audio) filters?

Newbie here. I'm familiar with time and frequency domains from math. I think I understand what low and high pass filters do, sonically. But digging into an implementation of ...
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### Why does Pre-warping work with a notch filter but not a low pass filter?

Hey guys a little bit of a continuation from a previous post I made here, I found the solution as why the pre-warping was not working at the time, However I was just playing around and found out pre ...
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### IIR filter relationship between number of poles, order and second order sections

I have ported Iowa Hills Code Kit to a mcu to calculate IIR filter coefficients. They are used to initialize the CMSIS Biquad Cascade IIR Filters Using a Direct Form II Transposed Structure. Trying to ...
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### Are IIR filters (and specifically Butterworth filter) causal?

I am new to signal processing. I am learning now about filtering and I am trying to implement high pass filter (HPF),and later band-pass filter (BPF). I implement the filters in ...
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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). ...
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### IIR bandpass filter with very low corner frequencies

I'm trying to get in the MATLAB Signal Processing Toolbox a bandpass IIR filter having the following specifications: pass-band [0.1-0.5] Hz and stop-band attenuation 30 dB. I'm using the following ...
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### Polynomial division to separate FIR and IIR in cascade

I have a FIR filter $L(z)$ and an IIR filter $H(z) = \frac{B(z)}{A(z)}$ which are cascaded together as $L(z)H(z) = L(z)\frac{B(z)}{A(z)}$. For specific reasons I want to calculate a parallel topology ...
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### Why can't realisable IIR filters have linear phase?

I am studying IIR Filter Design and came across this arbitrary statement in my textbook which says that 'physically realisable and stable IIR filters can not have linear phase'. Would really ...
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### Is this the correct solution for finding the samples of phase delay at a given frequency of an IIR BiQuad filter?

I want to calculate the number of samples of phase delay at a given frequency of an IIR BiQuad Filter. I believe I have solved this, but I would like to confirm I have done it correctly. My work is as ...
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### Invertibility of an ideal differentiator

Is the system $y(t)= dx(t)/dt$ invertible or not? If yes, please determine the inverse system for it.