Question

!) How to evaluate an IIR filter: when and how it is used

2) how to evaluate an iir filter if filter is an impulse

3) what is meant by Causal and zero-phase filters.when how how it is used

Answer 1

Infinite Impulse Response:

The infinite impulse response (IIR) filter is a recursive filter in that the filter value is determined using current and previous inputs and prior outputs. Because the filter utilizes previous output values, there is input/feedback in the filter configuration regarding the performance.

The impulse result is "infinite" since the filter provides feedback; once you bring in an impulse (a single "1" sample accompanied by several "0" samples), an infinite amount of non-zero values would come out.

When IIR is used?

One of the essential contents of digital signal phase is optical filter. Automatic filter IIR is commonly used in contemporary signal processing systems, with its excellent frequency range feature in lower order relative to FIR. In DSP (digital signal processing), IIR filters are the most powerful type of filter to introduce. They're normally given as filters for "biquad."

EX: Growing peak / notch or shelving filter is a single biquad in the parametric EQ block of a miniDSP plug-in. Within the crossover plates, up to 4 biquads are used on every crossover.That graphic EQ band is a single biquad, so a full 31-band graphic EQ uses 31 biquads per channel.

How IIR is used?

The conventional approach to the design of IIR filters includes converting an analog filter into the digital world, with specified feedback specifications. This is a sensible method, particularly because the art of designing analog filters is highly advanced.

What is FIR?

FIR filters do not use feedback, and the performance still is zero for a FIR filter with N coefficients after the impulse response samples are placed in N.

Pros of IIR over FIR:

Use less memory and measurements, IIR filters may accomplish a specified filtering feature than a related FIR (Finite Impulse Response) filter.

Cons Of IIR:

1.They are more susceptible to finite-length arithmetic issues, such as calculation-generated noise, and limit cycles.

2.Use fixed point calculus they are more complicated (slower) to introduce.

3.They don't deliver the technical benefits of FIR filters for multirate applications (decimation and interpolation).

What is Causal filter?

A causal filter is a linear and time-invariant source mechanism in the transmission of signals. The term causal means that the filter production relies entirely on inputs from past and present. A filter whose output often depends on future inputs is not causal, unlike an anti-causal filter whose output relies exclusively on future inputs.A typical design method for digital filters is to build a viable filter by shortening and/or moving time a non-causal response to impulses

What is Zero-Phase filter?

A filter has a zero-phase reaction when its frequency reaction is measured in real time.A zero-phase filter will be assisted by an odd number of measurements with the center at the middle.If the filter has actual coefficients, the impulse response must be symmetrical with respect to the origin.Unless the filter has imaginary coefficients, the impulse response of the origin must be anti-symmetric.Zero-phase scanning can not be carried out in real time, since the time flow can not be reversed.It cannot be causal filter.Causality is not a prerequisite in certain off-line implementations, such as when extracting the sound file on a computer disk, so zero-phase filters are also favored.