Dear, Sylvain Munaut, Thanks.I got a hint from your answer.
What about using moving average instead LPF? I think moving average (MA) is much simpler than LPF if computational cost is considered. But, another issue is, precision on estimation A and A/2. In that case, LPF would be better. Anyway, I will do applying either LPF and MA on my flow graph. Thanks. Regards, Jeon. 2015-05-05 16:27 GMT+09:00 Sylvain Munaut <[email protected]>: > Hi, > > > (Bipolar: a signal swings between +A volts (or amperes) and -A volts; > > Ethernet, USB, Wi-Fi, ... are using bipolar signals, > > Unipolar: a signal swings between +A volts and 0 volts) > > There is no difference ... "0 volt" is just an arbitrary reference point. > > 0 <-> +A swing is the same as > -A/2 <-> A/2 swing if you shift your reference ... > > Ethernet and USB are _differential_ but that's just to improve signal > integrity / noise immunity and such. At the receiver end, the > differential input buffer essentially compares both and see which one > is higher. (a bit simplified, but that's the gist of it). > > > Is there anyone already implemented unipolar preamble detection > > succesffully, or could anyone give me some hints on mathematical > approach or > > something? > > If 'A' is known, just remove -A/2 from your input signal. > If it is unknown,you can use a very long time constant low pass to > find it. (assuming your signal doesn't have long runs of 0 or 1). > > Cheers, > > Sylvain > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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