[USRP-users] Extended multipath (10 ms) at an indoor environment.

Matt Ettus matt at ettus.com
Mon Apr 29 12:12:35 EDT 2013


Ian,

I think you may be seeing IQ imbalance which will cause fake responses.
 Have you run the IQ Balance calibration utility?

Matt


On Thu, Apr 25, 2013 at 8:39 AM, Ian Song <ajsongs at gmail.com> wrote:

> I used USRPB100+WBX daughter board to transmit linear modulated frequency
> (LFM) signals at the center frequency fc (fc=80 or fc=83 MHz). The LFM
> signal sweeps from fc-16 kHz to fc+16 kHz in 0.05 or 0.5 s. The other
> USRPB100 +WBX daughter board did the reception. The two devices were placed
> in a large room, separated by variable distances (20 cm to a couple of
> meters). I also changed the gain in both the source and the receiver
> (varying gain from -5 to 20 dB for both).
>
> Then I examined the received LFM signals through matched-filtering
> operations. The part that I do not understand that the calculated impulse
> responses also had extended multipath. I can see four or five strong
> multipaths, always with one dominating path. The channel time span was 10
> ms. To me, it seems impossible to have such a long mutlipath. Can everyone
> explain the long delayed multipath? Is it real or due to the device
> distortion? Any suggestions?
>
>
> Many thanks,
>
>
> Ian
>
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