The FFT4T core implements a 128 point complex FFT and IFFT over 12 data streams in hardware. It runs at the clock frequency four times higher than the insput sampling frequency.
FFT4T core is a specialized FFT/IFFT processor intended for a situation where an RF signal is recieved over multiple channels in parallel and its filtering is to be performed in the frequency domain. The core fits nicely into, for example, a multichannel GPS system.
Pin Description
| Name | Type | Description |
| CLK | Input | Core clock signal(4x sample clock) |
| Cen | Input | Synchronous enable signal. When LOW the core ignores all its inputs and all its outputs must be ignored. |
| enable[5:0] | Input | RF band enable signals. Each bit controls two streams (path A and path B).
|
| fftD[] | Input |
Input of FFT, Multiple samples in parallel, one for each stream. The samples shall be clocked in on the sample clock. |
| fftDstart | Input | HIGH pulse clocked on the sample clock indicates the initial 0 sample of the 128-sample frame of fftD |
| fftQ[ ] | Output |
Output of the FFT, multiple samples in parallel. Each stream is output contiguously on sequential sample clocks |
| fftQstart | Output | HIGH pulse on sample clock marks the first word of fftQ output (n = 0, samples 0..15) for the stream |
| fftQstream[3:0] | Output | The value between 0 and 11 indicates the stream number |
| ifftD [ ] | Input |
Input of the IFFT, Multiple samples in parallel. Each stream is clocked in put contiguously on sequential sample clocks. |
| fftDstart | Input | HIGH pulse clocked on the sample clock indicates the start of the 128 sample frame (n = 0, samples 0..15) for the stream |
| fftDstream[3:0] | Input | The value between 0 and 11 indicates the stream number |
| fftQstart | Output | HIGH pulse on the sample clock indicates the initial 0 sample of the 128 sample frame of fftD path A streams |
| fftQ[ ] | Output |
Output of IFFT, 12 samples in parallel, one for each stream. The samples shall be clocked on sample clock. |
