[USRP-users] Full Duplex w/ X310 & UBX-160

mleech at ripnet.com mleech at ripnet.com
Wed Mar 30 13:07:04 EDT 2016


 

If you're transmitting at a frequency other than you're receiving at,
why would you expect to be able to receive it? I don't understand. 

On 2016-03-30 13:02, Dave NotTelling wrote: 

> Oh, sorry, I meant that I no longer see the GFSK transmission. I also should have added that I don't get a correct spectrum from the RX side *at all*. If I disable one of the two chains (disable all TX or RX) then everything works fine. 
> 
> On Wed, Mar 30, 2016 at 1:00 PM, <mleech at ripnet.com> wrote:
> 
> What do you mean by "it all breaks down"? Error messages? 
> 
> On 2016-03-30 12:55, Dave NotTelling wrote: 
> Marcus, 
> 
> This is odd then. Please see the attached for my example flow graph in GNU Radio. The basics are that I am transmitting a GFSK (just for giggles) on 1.001 GHz and receiving on 900 MHz. When the graph starts up, the TX side is working properly. I can tell this by looking at the output of my B200 which is tuned to 1.001 GHz. The moment I change a parameter (RX/TX gain/freq) it all breaks down. Is this possibly an issue with the X300/X310 UHD driver and/or GNU Radio gr-uhd? Or am I just doing something stupid? 
> 
> Thank you! 
> 
> -Dave 
> 
> On Wed, Mar 30, 2016 at 12:22 PM, <mleech at ripnet.com> wrote:
> 
> The RX and TX synthesizers are totally separate on the UBX, so you can frequency-split however you want. 
> 
> The larger the split, the easier it will be to prevent de-sense between TX and RX, since it would be easy to, for example, insert a notch filter for your TX band into the RX path, etc. 
> 
> On 2016-03-30 11:18, Dave NotTelling via USRP-users wrote: 
> 
> Can I transmit at say 100 MHz while simultaneously receiving at say 1 GHz? If so, can I also use different sampling rates between the TX and RX paths? Are there any existing examples of how to do simultaneous TX and RX in GNU Radio? 
> 
> If this is not possible, then what is the max frequency difference? I was assuming that if I were transmitting at 1 GHz, then I could tune the RX side up and down by half the master clock rate. 
> 
> Thank you! 
> 
> -Dave 
> 
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