Hi Everyone!I am using SDK 2.4.1 with CW 4 on a DSP56F826 platform without external memory. I have written a program that sucks in a 128 sample vector at a sample rate of 8000 sps, submits this to dfr16RFFT then takes the resulting dfr16_tInplace vector and submits it to dfr16RIFTT to recover the time domain signal. I would have expected this to result in a nice clean signal but I see what looks like dropped samples at the boundaries of the sample vectors (ie. every 16 ms). This is apparent when I am sending a tone which is not commensuate with the size of the sample vector. That is if I submit a 1000 Hz signal (1000/62.5 = BIN 16) then the output of the IFFT is clean. However if I submit 1100 Hz (say) which will not "fit" into the sample vector then I see the boundary problem. Does anyone know if this is a limitation of the process? I would have thought that all the time domain information would be recoverable from an FFT frequency domain representation. And there ought not to be discontinuities at the boundaries because I am sucking out the 128 sample vectors one after another so the edges should align. What am I missing here?? Any help would be appreciated... 73, Larry |

# Using SDK'd RFFT and RIFFT for Filtering

Started by ●March 22, 2003