Fractional Delay using Polyphase Filter

1. What is fractional delay filter?
2. Why polyphase filter is used?
3. How does a polyphase filter work?
4. What is polyphase interpolation filter?

What is fractional delay filter?

A fractional delay filter is a filter of digital type having as main function to delay the processed input signal a fractional of the sampling period time.

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.

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).

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.