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From: | Daniel Labarowski |
Subject: | Re: [Discuss-gnuradio] Optimising performance of N210 + XCVR2450 |
Date: | Wed, 25 Jul 2012 12:03:23 -0400 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120410 Thunderbird/11.0.1 |
Michael, 1) For 8 bit you change the wire format parameter of the UHD Source and Sink from "automatic" to "sc8". This is one of the options you get when double clicking the Source/Sink in GRC. Changing the output type of the block in GRC has no effect on the wire format. No modification to hardware or firmware necessary. Also, decimation would lower the bandwidth but, once again, all you have to do is change the option. 2) First off, the XCVR2450 is half duplex, so it can only transmit or receive at a time, not both. Maybe check out the SBX daughterboard if you want to do both (depends on your application, there are a few full duplex daughterboards in the ism band.) Also, remember that Ethernet has discrete TX and RX lines and each line is limited to roughly 50MSPS at 8bit, so you cant only transmit or only receive at 100MSPS. 3) It's always a good idea to terminate a transmitter as high power reflections could damage your amplifier. It's been a while since I used the XCVR and I can't remember exactly how it divided its ports. Not sure whether (since its half duplex) if it used the same port for both tx and rx by default or if they default to separate ports. You can definitely select the port when only transmitting or receiving. There is an antenna option in the usrp sink.source blocks. I've never used that option myself though so I'm not sure what type of input it expect. An integer would be my best guess so maybe start at 0 and see what you observe. If you wanted to transmit and receive on the same port you would have to stream tag the tx stream and set both blocks (sink and source) for the same port. The device defaults to receive and when it receives a tx_sob alongside the transmit signal it will switch to tx. When it receives a tx_eob, it will switch back to rx. Switching time for the xcvr is in the microsecond range. If the signals you are observing on J1 are very low power compared to those on J2, this could be poor isolation. The rf switch on the two output ports should provide 30dB of isolation. It's possible isolation on the board itself might cause some leakage too. Good luck and I hope this helps! -Dan On 07/25/2012 05:30 AM, Michael Hill wrote: I have a few queries regarding some of the options for improving the performance of the XCVR2450 + N210. |
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