Re: [Discuss-gnuradio] USRP1 + RFX900) + ATR

[Eric Blossom]

On Mon, Aug 31, 2009 at 01:22:09PM +0100, David Evans wrote:
> Hi,
>
> I am using 2 x (USRP1 + RFX900) for simple transceiver test (USRP1 to  
> USRP2 back to USRP1), and can successfully transmit OOK packet (preamble  
> + payload) and receive response.
>
> However, if I enable ATR on the sender, the received response by the  
> sender is corrupted (I successfully correlate preamble, but following  
> payload is corrupted). It's as if the received signal level becomes  
> reduced after the ATR switches, or the sampling becomes off cut.

I suspect that not all of your transmitted burst is getting out.
You need to append enough zeros to the data to ensure that it's
flushed out of the FPGA DSP pipeline before the transmitter switches over.

Eric

> Basically, the simple transceiver works, until Automatic Transmit  
> Receive switch is enabled. I would like the transmitter to switch on  
> only when transmitting, thus removing the LO breakthrough when in a  
> quiescent state.
>
> Is there timing constraints I should adhere to, is there any further  
> info on use of ATR I could be pointed to,
>
> Thank you,
> David.