Thanks Firas, It is clear and I will implement it and will come back soon hopefully with successfull results.
Best Regards Firas A. wrote: > > > Hi, > >> On Wed, 4/22/09, kaleem ahmad <kaleem_...@yahoo.com> wrote: >> >> Thanks Firas, >> >> But I can simply tell that it always transmit a fix packet (with >> bitrate=500kbps) of 1220 micro sec including preamble. It means that >> after every T ms (T is repetition cycle time and can be a fixed >> value from range: 1ms...200ms, I selected 10ms for above given data) it >> transmits a 1220 microsec long signal. >> > > If your transmitter works for 1220 microsec (1.22 msec) and it repeat the > transmission (for example) every 10 msec, then your calculations is wrong. > > If you want to sense the time of a signal, you have to run your FFT frames > with a rate at least equal to required minimum signal time. For example in > your case, If the signal to be detected has a 1.22 msec then you have to > collect the data at rate of 500K (USRP decimation =128). The 512 FFT > length will be 1.024 msec. This means (after using appropriate spectrum > threshold value) you need to count number of FFT frames that the desired > signal is exist in it. > > So, back to our example (signal with duty 1.22msec and repetition of > 10msec), if data rate is 500k, and you used 512 FFT points, then you will > see this signal once in every 10 FFT frames. The resolution will be 1.024 > msec. > > However, if you received the signal with data rate of 8MHz (USRP > decimation =8), and you computed 512 FFT points then your resolution will > be 64 usec, which means that the signal will be ON for 19 FFT frames and > OFF for 137 FFT frames. > > Is that clear ? > > > > Best Regards, > > Firas > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- View this message in context: http://www.nabble.com/cycle-period-detection-of-a-cyclic-periodic-transmitter-tp23171564p23175140.html Sent from the GnuRadio mailing list archive at Nabble.com. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
