Adib- > > Important Note: > > Beside tunning time depends on the hardware (RF syenthesizer speed), > > one should remameber that the time needed to collect 1024 samples > > with decimation rate=8 (minimum USRP decimation) is 128 usec > > > > while : > > > > Time needed to collect 1024 samples with decimation rate=256 (maximum > > USRP decimation) is 4.096 msec > > > > This means that the tune delay in the case of decimation rate =256 > > should be larger than that used for deimation = 8. > > > > > > i have a question regarding the above quote, if we are taking 1024 bin FFT, > do we need to have 1024 of signal samples?
It's not necessary, you can "zero-fill" remaining samples until 1024. In some analyses, the time domain collection frame size is held constant (it may be dependent on the nature of the data) and the FFT size increased, giving more "bins per Hz" and an improved view of what's going on. But if you do this, then you may want to apply a Hamming or other window prior to the FFT to avoid a potentially abrupt amplitude cutoff at the zero-fill point. -Jeff _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
