Re: [Discuss-gnuradio] Could transmitter and receiver alternately work in time on the same USRP1 with LFTX/RX?

[Nick Foster]

On Tue, 2011-02-08 at 13:29 -0500, Yan Nie wrote:
> Dear all,
> 
> I'm developing a radar transmitter and receiver on USRP1 and LFTX/RX. The 
> transmitter and receiver are working fine separately on two USRP1 with TX and 
> RX daughter board plugged in. I'm trying to make the transmitter and receiver 
> alternately work in time on the same USRP1. For instance, transmitting signal 
> for 0.52ms then disabling TX and enabling RX simultaneously for signal 
> reception for 1ms. Then this process will repeat over and over again. 
> 
> Is it possible to get the TX and RX wok on the same USRP1 motherboard with 
> both RX and TX? The reason why I'm asking this question is that it seems 
> impossible to call usrp_source or usrp_sink block every millisecond to enable 
> TX or RX, since usrp_source loads FPGA image only with TX path enabled and 
> usrp_sink does only with RX path enabled, if my reading of the source code 
> usrp_standard.cc services me right. In addition, loading the whole FPGA image 
> takes longer time than 1ms, which will cause USRP overrun problem if shifting 
> TX to RX or RX to TX every millisecond as my experiments showed me. 
> Therefore, I'm wondering if there is an approach to allow the TX and RX to 
> alternately work in time on the same USRP1 board rather than calling 
> usrp_source or usrp_sink to make this TX/RX altering. Simply, is there any 
> mean to shift TX and RX back and forth every two milliseconds and repeat over 
> and over again by loading FPGA image only once for the whole process. 
> 

You might consider just running TX and RX simultaneously instead of only
enabling RX after the TX pulse. This has the ancillary benefit of giving
you a precise time reference for the outgoing pulse, removing any
uncertainty in the delay time between turning off TX and turning on RX.

--n

> I will really appreciate if any suggestion on how to solve this problem.
> 
> Wish you a great day!
> 
> Thanks,
> Yan
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