On Mon, Dec 15, 2008 at 8:28 AM, Emanuel Birge <manneor...@gmail.com> wrote:
> I'm interested in calculating an estimate of the impulse response of a > speaker cable, using pseudo-white noise and bypassing all forms of > interpolation/decimation/modulation/demodulation-blocks, for as wide a > bandwidth as possible. However, and please correct me if I'm wrong, the > USB-interface on the USRP is too slow (8 MHz) to, so to speak, do this > "online". Say I want to use 10,000 pseudo-white samples with at least 8bit > resolution. Is this possible without rewriting very much of the > Verilog-code? The BasicRX and TX do not pass DC; they are transformer coupled and have a ~100 KHz highpass response at the low end. The alternative is the LFRX and LFTX cards, which do pass DC, but have lowpass filtering at ~30 MHz. So you will only be able to calculate the impulse response convolved with that of one of these filters. There is a GNU Radio component called gr-sounder, which implements a custom FPGA build for the USRP. The transmitter will generate an m-sequence PN code of a configurable length and chipping rate for channel sounding purposes; this is likely suitable for what you need. The receiver will correlate the received signal at all possible PN code phases and produce a complex vector of the correlation results. Also, your results will be affected by the coupling of the USRP daughterboards to the speaker cable. They are designed for a broadband match of 50 ohms across their frequency range. Speaker cable is not typically designed with this in mind and the mismatch will like cause a frequency-dependent amplitude response. Maybe that is what you trying to measure, however. -Johnathan _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
