On Mon, Apr 12, 2010 at 22:11, Ian Holland <ian.holl...@rlmgroup.com.au> wrote:
> I have been studying up on the Costas loop, and have a couple of queries as > to the benchmark_tx.py and benchmark_rx.py as a result. > > Firstly, for BPSK, there should in theory be a 180 deg. phase ambiguity when > using a Costas loop. Why does this not seem to occur with the > benchmark_rx.py example? Is this related somehow to the PN code introduced > by the scrambler. The digital-bert example uses a self-synchronizing scrambler to generate a bit sequence that occupies the full baseband bandwidth of the channel. The scrambler/descrambler pair is insensitive to the phase ambiguity; however, this comes at the price of generating extra bit errors on the descrambled sequence for every bit error in the channel. > Secondly, I came across another post in which it was mentioned the Costas > loop should only operate on a single sample per symbol. However, as I read > the source code, it seems as though it is actually passed sps samples per > symbol, where sps > 1. Have I misread something here? Not sure what post you are referring to. While a Costas loop can indeed operate on a single sample per symbol, it can also operate on more than that. Different strategies in a receiver chain places the frequency/phase synchronization at different places. Johnathan _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
