Efficient floating-point decoder for BPSK/QPSK manchester code

[Moses Browne Mwakyanjala]

Hi everyone,
I've been struggling to decode manchester signals. I have tried to use some ad-hoc methods for BPSK that work well. However, there were some if-else branches that tax the CPU greatly, especially at high symbol rates. The input is 2 SPS, output 1 SPS. And they didn't seem to work for QPSK.

I have tried to use the matched-filter approach (treating the manchester pulse as 1,1,-1,-1), with 4 SPS input, and 1 SPS output. The PFB taps are thus the convolution of manchester taps (1,1,-1,-1) and SRRC. This approach didn't work well. Upon further examination, I discovered that the symbol synchronizer failed to lock.

I was wondering if there were alternative algorithms that could work for both BPSK and QPSK.


Thanks in advance,

Moses.