Hi, all:
I used AWR1642 for product developing. Recently, I found several problems related to DSP_fft16x16 function when running mmwave 16xx demo (p.s. - the FFT input and output data are both captured for offline analysis compared with matlab floating FFT results)
1. With strong reflector (1 object) in test environment, FFT distortion and ghost peak(s) will appear in the output.
As shown below, the blue one is AWR1642 FFT output (distortion and ghost peak occur), the red one is the output of matlab fft processing for the same captured adc signal.
2. Same test environment (1 strong object), after scaling the adc signal by 2^4, I got following result:
As shown, after scaling, no ghost target and FFT distortion.
I've viewed the DSPLIB reference manual, no scaling operation in 16 bit FFT interface (DSP_fft16x16) , while scaling do for 16×32 and 32×32 interfaces. It's known that for large signal, the FFT output will overflow, thus when large and small object coexist in test environment, it's hard to detect the small one.
So maybe this is an issue with the dsplib fft interface? But I didn't find any known similar issues with it. (from here)
Thx so much!
--
Regards
Lin
