Infinite impulse response (IIR) is a property of signal processing systems.
2
votes
1answer
60 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 ...
4
votes
1answer
103 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:
...
3
votes
1answer
94 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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votes
2answers
76 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 ...
1
vote
2answers
128 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 ...
2
votes
0answers
34 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 ...
4
votes
2answers
76 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 ...
2
votes
1answer
111 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 ...
5
votes
3answers
175 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 ...
2
votes
1answer
113 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 ...
1
vote
2answers
89 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 ...
1
vote
1answer
420 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 ...
7
votes
2answers
175 views
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 ...
6
votes
1answer
297 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 ...
8
votes
2answers
276 views
What bandpass filter design will yield the shortest impulse response?
Designing a simple 2nd order IIR bandpass Buterworth filter with a centre frequency of 500 Hz and a 1 octave bandwidth gives me the following frequency response ...
Now, if I take the impulse ...
2
votes
1answer
241 views
Sliding DFT: I think my results are accurate, but I can't buy a swap-swap IDFT
I've got a sliding DFT implementation that appears to be working (judging from an output plot). I would like to be able to invert this implementation using the standard tricks of swapping the real and ...
3
votes
1answer
975 views
Realtime fixed point IIR filter implementation in C
I would like to implement a fourth order fixed point low-pass IIR filter in C (with Q15 arithmetic), and I will prepare this filter by using two stages cascaded direct form-II bi-quad filters.
I have ...
5
votes
5answers
305 views
How can I vectorize the computations for a first-order recursive filter?
I have a simple single pole low pass filter (for parameter smoothing) that can be explained by the following formula:
$$
y[n] = (1-a) y[n-1] + a x[n]
$$
The architecture that I'm using has access ...
4
votes
2answers
2k views
How does MATLAB handle IIR filters?
MATLAB has a butter, which constructs a Butterworth filter given an order and relative cutoff frequency. The filter created can be used to ...
6
votes
2answers
1k views
Downsampling lowpass filter for audio: FIR or IIR?
I'm working on a real-time audio processing project in which I have to downsample a 44.1 kHz to a yet-to-be-determined lower sampling rate essentially for reducing computational complexity. I'm ...
12
votes
3answers
834 views
What is the best first-order IIR approximation to a moving average filter?
Assume the first order IIR Filter:
$ y[n] = \alpha x[n] + (1 - \alpha) y[n - 1] $
How can I choose the parameter $ \alpha $ s.t. the IIR approximates as good as possible the FIR which is the ...
12
votes
3answers
855 views
How does cascading biquad sections for higher order filters work?
I'm trying to implement an 8th order IIR filter and every application note and textbook I've read says that it is best to implement any filter of order more than 2 as second order sections. I used ...
11
votes
3answers
365 views
How can I design a very narrow filter?
Suppose I've got an audio signal sampled at $48000$ Hz, and I'd like to design a low-pass filter that isolates everything below ~$60$Hz. In the digital world, this is a low-pass filter with the ...
14
votes
2answers
683 views
Are there any standard implementation forms for tunable Butterworth filters?
One of the standard ways to implement a Butterworth filter is with a cascade of second-order sections, each corresponding to a pair of complex-conjugate poles. For a fourth-order filter, for example, ...
13
votes
4answers
305 views
What factors should I consider when choosing an IIR filter realization?
IIR filters may be implemented as direct form 1 or 2. But how do you decide which form to use? What are the pros and cons of each?
