Polyphase filter structure

1. What is polyphase filter structure?
2. Why use polyphase filter?
3. What is polyphase interpolation filter?
4. How does polyphase filtering save computation in decimation filter?

What is polyphase filter 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.

Why use polyphase filter?

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

What is polyphase interpolation filter?

With the modified implementation, the input samples to the filter is clocked at the original sampling rate of . However, we need to have additional circuitry to dynamically load the coefficients and latch the output at the upsampled frequency . These filtersets are called polyphase filters.

How does polyphase filtering save computation in decimation filter?

The concept behind a decimating polyphase filter is to avoid wasted computation due to the discarding of samples. Decimation is the process of low-pass filtering (LPF) followed by downsampling, shown in Figure 1. The LPF minimizes aliasing coming from the discarding of samples from downsampling.