Pfb_fir_real - david-macmahon/wiki_convert_test GitHub Wiki
Block: Polyphase Real FIR Filter (pfb_fir_real)
Block Author: Henry Chen
Document Author: Ben Blackman
Summary
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.
Mask Parameters
| Parameter | Variable | Description |
|---|---|---|
| Size of PFB ((2^?) pnts) | PFBSize | The number of channels in the PFB (this should also be the size of the FFT which follows). |
| Total Number of Taps | TotalTaps | 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. |
| Windowing Function | WindowType | Which windowing function to use (this allows trading passband ripple for steepness of rolloff, etc). |
| Number of Simultaneous Inputs ((2^?)) | n_inputs | 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. |
| Make Biplex | MakeBiplex | Double up the inputs to match with a biplex FFT. |
| Input Bitwidth | BitWidthIn | The number of bits in each real and imaginary sample input to the PFB. |
| Output Bitwidth | BitWidthOut | 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. |
| Coefficient Bitwidth | CoeffBitWidth | The number of bits in each coefficient. This is usually chosen to match the input bit width. |
| Use Distributed Memory for Coeffs | CoeffDistMem | Store the FIR coefficients in distributed memory (if = 1). Otherwise, BRAMs are used to hold the coefficients. |
| Add Latency | add_latency | Latency through adders in the FFT. |
| Mult Latency | mult_latency | Latency through multipliers in the FFT. |
| BRAM Latency | bram_latency | Latency through BRAM in the FFT. |
| Quantization Behavior | quantization | 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) | fwidth | 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)). |
Ports
| Port | Dir | Data Type | Description |
|---|---|---|---|
| sync | IN | Boolean | Indicates the next clock cycle contains valid data |
| pol_in | IN | Inherited | The (real) time-domain stream(s). |
| sync_out | OUT | Boolean | Indicates that data out will be valid next clock cycle. |
| pol_out | OUT | Inherited | The (real) PFB FIR output, which is still a time-domain signal. |
Description
Usage
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.