Polyphase Real FIR Filter¶
Block: Polyphase Real FIR Filter (
Block Author: Henry Chen
Document Author: Ben Blackman
This block, combined with an FFT, implements a real Polyphase Filter Bank which uses longer windows of data to improve the shape of channels within a spectrum.
|Size of PFB (2? pnts)
|The number of channels in the PFB (this should also be the size of the FFT which follows).
|Total Number of Taps
|The number of taps in the PFB FIR filter. Each tap uses 2 real multiplier cores and requires buffering the real and imaginary streams for 2*PFBSize* samples.
|Which windowing function to use (this allows trading passband ripple for steepness of rolloff, etc).
|Number of Simultaneous Inputs (2?)
|The number of parallel time samples which are presented to the FFT core each clock. The number of output ports are set to this same value.
|Double up the inputs to match with a biplex FFT.
|The number of bits in each real and imaginary sample input to the PFB.
|The number of bits in each real and imaginary sample output from the PFB. This should match the bit width in the FFT that follows.
|The number of bits in each coefficient. This is usually chosen to match the input bit width.
|Use Distributed Memory for Coeffs
|Store the FIR coefficients in distributed memory (if = 1). Otherwise, BRAMs are used to hold the coefficients.
|Latency through adders in the FFT.
|Latency through multipliers in the FFT.
|Latency through BRAM in the FFT.
|Specifies the rounding behavior used at the end of each butterfly computation to return to the number of bits specified above.
|Bin Width Scaling (normal=1)
|PFBs give enhanced control over the width of frequency channels. By adjusting this parameter, you can scale bins to be wider (for values > 1) or narrower (for values < 1).
|Indicates the next clock cycle contains valid data
|The (real) time-domain stream(s).
|Indicates that data out will be valid next clock cycle.
|The (real) PFB FIR output, which is still a time-domain signal.