# Questions tagged [infinite-impulse-response]

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

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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, ...
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### Calculating pre-history of recursive filter from state space representation when optimising for initial z

For a recursive filter, suppose a set of $b$ and $a$ coefficients have been calculated. Assume a state-space representation for which an initial set of $z$-values have also been calculated as in ...
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### Practical implementation of IIR/biquad filters following non-textbook transfer function of real-wold analog filter

I am trying to program a DSP filter to study prototypes of loudspeaker filters, which will be implemented as passive analog circuits in the final speaker system. This process involves simulation of ...
296 views

### How to compare many bandpass filters (for their signal propogation delay)?

Let's say we have an audio signal sampled at 96 kHz, and we want to compare several bandpass filters to find the one with the lowest rectangular-envelope-propagation-delay (see graph below). The band ...
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### How to transform a Fractional Order Laplace Transfer Function into a digital filter?

I'm working with loudspeaker impedance analysis. Electrical behavior of loudspeakers can be modeled with RLC networks. But real loudspeakers have components, that exhibit some non-linear and frequency ...
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### Stable digital filter with leading zeroes

I'm looking construct a stable pole-only filter where the feedback coefficients start with a block of zeroes, i.e. \begin{align} a_0 &= 1\\ a_i &= 0, \textrm{ for}\ 1 \le i \lt k\\ a_i &\...
158 views

### How to design all-pass filter by specifying phase requirements?

I want to delay the part of signal above (or below) specified frequency, but I don't find any books or tutorials to tell how to design is. The commonly used biquad APFs (such as the one introduced in ...
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### Is there a tool for automatically converting filter implementation forms?

I am looking for alternate tools that will automatically convert filter implementation forms (or signal flow network diagrams in general) to simplest or alternate forms; for example for going between ...
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### How would one design a (quasi) linear phase adaptive notch filter for a single complex tone?

While IIR notch filters are attractive, I need to retain phase linearity at the filter output. I imagine that it's possible to use a standard IIR notch filter: https://www.researchgate.net/...
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### Vary poles/zeros of digital IIR filter

Many applications that produce sound, such as software synthesizers, are able to apply a filter that varies with time, such as applying a low pass filter that varies with an LFO. I currently have a ...
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### bibliography about implementation of IIR filters

I need to implement a 6th order IIR filter. The filter I need to implement is the A-weighting. I've simply used the bilinear function of Matlab with an fs of 20Khz. I need to implement this over the ...
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### Phase noise modeling using gnuradio IIR filter

I need some advice regarding phase noise modeling using gnuradio IIR filter. I'm trying to synthesize phase noise (multiplicative) with a given noise mask. In one paper, the authors were able to ...
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### Which IIR form has lowest round-off noise?

We are making some audio effects using IIR, and seeking ways to optimize its round-off noise. After searched some materials, most of them tells transposed form II has lowest round-off noise, and many ...
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### Fixed point Error Spectrum Shaping (noise shaping) for biquads

Based on that article and all the resources on the internet that advise the use of noise shaping for fixed-point filter implementations, I tried to make a few simulations on Matlab for the biquad I'm ...
366 views

### Converting floating point IIR to fixed point arithmetic, given its difference equation

Is there some general way to perform the task given in the question? I have a filter given as follows: ...
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### Appropriate model for IIR filter to compare with spectral ratios

A quick, basic question. I have measured spectral ratios - comparing a measured signal to an 'ideal' signal. I am fitting a specific, simple IIR filter to that data for transfer functions. So, if I'...
278 views

### Problems implementing IIR filter in VHDL

I am having some difficulty making an IIR filter in VHDL work as expected. I have implemented it by shifting the coefficients by a certain number of bits (in this case 27 bits). The outputs are then ...
107 views

### Can picking an inappropriate roll-off frequency for a digital filter just alias the roll-off value?

I believe a related question is asked here, but my question deals more with what filter is realized if one fails to consider design parameters relative to sampling rate. In designing an IIR filter we ...
471 views

### How to compute DFT of IIR

This question pertains to frequency domain filtering. I'd like to multiply an IIR filter's frequency response by a buffer of samples that have been FFT'd. I get how I'd evaluate an FIR, I'd FFT and ...
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### 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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### 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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### 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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### 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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### Can I get some help plotting an IIR filter frequency response in Python?

The problem I'm trying to solve is described here. In my script, I used Euler's identity to calculate z^-n, such that z^-n = cos(omegan) - jsin(omegan). I find the magnitude of these values from a ...
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### pressure decay filtering

So, I've been dealing with a series of pressure decay curves from a pressure transducer. Each one has a waterhammer effect as a consequence of shutting down pumps. Here are examples of 3 curves: I'm ...
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### Impulse response of an infinite-length system

I have a system which is expressed as following: y[n] + $\alpha$ y[n-N] = x[n] where y is the output and x is the input. When I take the z-transform of both sides, I've found the transfer function ...
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### Factoring digital IIR filter as a causal and anticausal pass?

Background: I'm new to signal processing and I'm reading some papers on B-spline interpolation of digital signals and trying to understand how a computation is derived. If I'm given samples from some ...
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### IIR Direct FormII Filter second order in VHDL, false output

I am trying to implement an IIR second order in Direct FormII in VHDL. To make it easier to understand for me and to avoid former timing issues, I implemented the operations sequentially. In my ...
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### Filter design for decimation of 1.1 kHz sensor sample rate to 100 Hz processing rate

Suppose, you have a signal source which is sampled by 1100 Hz and is "somehow" band limited to either 235 or 440 Hz. In my application, that's the ST IIS3DHHC accelerometer. There is an appnote for ...
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