Polyphase decimators

1. What is polyphase in DSP?
2. Why polyphase filter is used?
3. What is a polyphase structure?
4. How does a polyphase filter work?

What is polyphase in DSP?

Polyphase is a way of doing sampling-rate conversion that leads to very efficient implementations. But more than that, it leads to very general viewpoints that are useful in building filter banks.

Why polyphase filter is used?

The polyphase FIR filter realization can provide advantages in computational efficiency when used for decimation or interpolation of discrete time signals.

What is a polyphase structure?

A polyphase quadrature filter, or PQF, is a filter bank which splits an input signal into a given number N (mostly a power of 2) of equidistant sub-bands. These sub-bands are subsampled by a factor of N, so they are critically sampled.

How does a polyphase filter work?

A polyphase filterbank uses the DFT (discrete fourier transform) to modulate (move in frequency) a prototype filter and perform summation, effectively returning multiple bands of decimated and filtered time-domain data from the DFT stage. The DFT operation is typically performed using the FFT (fast fourier transform).