Groups of filters

• IIR - Infinite impulse response
  filter that is designed using feedback or storage elements
  its impulse response will, in principle, last forever

• FIR - finite impulse response
  filter with no feedback elements
  its impulse response is finite
  FIR filters can be implemented by using analogue or digital method

• The primary advantage of IIR filters over FIR filters

o Typically meet a given set of specifications with a much lower filter order than a corresponding FIR filter

o Delay of these filters is often much shorter than for an equal performance FIR filter

• FIR filters have the following primary advantages:

o Upper passband frequency for low-pass filters

o Can have exactly linear phase

o Always stable

o Design methods are generally linear

o Can be realized efficiently in hardware

o Filter startup transients have finite duration