Dear all,

Please help me understand this output from usrp_rx_cfile.py. I have

attached the plot as the jpeg at the end:

- I send a file with 1500 bytes of spaces (Space = 0x20 = 0010 0000 in

binary) - I use usrp_rx_cfile.py to capture the samples, and focus in on

roughly

24600 samples (because 1500 bdpsk modulated bytes = 1500*8*2 + preamble

CRC…)

3. multiplied by 2 because its 2 samples per symbol (one bit per

symbol).

Therefore, I ignore every other sample. So down to 12300 samples

roughly.

4. I turned off whitening and dewhitening. Hence, I should now see dbpsk

samples that represent 0010 0000 0010 0000…

5. I do see the pattern when I look at the angle formed by those complex

symbols in MATLAB [using plot(angle(read_complex_binary(‘s.dat’)))]

6. But I also see some kind of unexplainable shifting once I take the

absolute value of the angles of the complex symbols [shown in the jpg].

Can somebody please tell me if there is some kind of shifting

implemented in

the dbpsk modulation which causes the plot of the angle of these complex

samples

captured by usrp_rx_cfile.py to look like this. Please note that I turn

off

whitening/dewhitening so the pattern do resemble 0010 0000 0010 0000

somewhat.

-Thank you for your time,

-B.