Johnathan Corgan wrote:
>
> 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
Thank you for the replies Johnathan!!!
But, i still get some problems when i experiment with it.
My objective is to measure impulse response of a room and extract
information on the movement of people inside the room.
1. I tried to monitor the impulse response of the room for 5 sec. So,
according to the discussion above(i.e since the FPGA computes impulse
response of length 4095,32MHZ in 0.5sec), I will have 10 impulse
response vectors in 5sec. But when i set { samples = 10 *
self._length**2 in usrp_sounder_rx.py } and run the code, it takes about
160 seconds to complete. So, I am confused. Does the recorded impulse
response correspond to 5sec or 160sec?
2. As, expected there is frequency offset on the received impulse
response. what can i do to synchronize transmitter and receiver
daughter boards? Thanks!
Bruhtesfa
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