On Sat, Dec 6, 2008 at 12:09 PM, Bruhtesfa Ebrahim <[EMAIL PROTECTED]> wrote:
> but, does the USB support this much sampling rate of 32 MHZ? No. > Also on simple gnu radio user manual, about gnuradio sounder it says : > "The sounder uses a custom FPGA bitstream that is able to generate and > receive a sounder waveform across a full 32 MHz wide swath of RF > spectrum; the waveform generation and impulse response processing occur > in logic in the USRP FPGA and not in the host PC. This avoids the USB > throughput bottleneck entirely." > > This implies that the processed impulse response that goes to the USB is > of lower sampling rate than 32MHZ. or no? please correct me if i am > wrong. The custom FPGA code performs the correlation in the USRP. The algorithm is a sequential correlator that processes an entire PN code sequence per impulse reponse lag time. So the data rate coming out of the USRP is 64 Msps (ADC rate) divided by 8190 samples per PN sequence (default degree of 12), or about 7.8 ksps. Since each record is 4095 samples long, this outputs a full impulse response record about twice a second. The impulse response record still represents the original 32 Mchip/sec correlation, so in your received data, each sample represents a lag of about 31.25 ns. -Johnathan _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
