Re: Is RFX900 simultaneous transmit and receive funtion possible?

Hi to all,

I need to implement a RFID reader using GNURadio RFX900.
I wanted to know urgently that is it possible to use a single
RFX900 for simultaneously transmitting and receiving.
I am in a hurry to purchase the stuff so I can receive it before holidays.
Prompt responses are highly appreciated.
Thanks in advance.

Regards,
Subodh

I have developed a GNU Radio based Gen 2 RFID reader that can
communicate
with standard tags from a few feet away. The code has been uploaded to
George N.’ Comprehensive GNU Radio Archive (
https://www.cgran.org/wiki/Gen2). As RFID needs to transmit and receive
on
the same frequency, my setup uses two RFX900 boards, one for transmit
and
one for receive. As long as the antennas are a few inches apart the
transmit
signal doesn’t entirely swamp the receive chain and you can pick up the
backscattered tag responses. The main difficulty in getting the system
to
work was reducing system latency to < 500 us. The modifications
involved
some tweaks to the way GNU Radio interfaces with the USB driver. This
means
that it should also help other applications that want low latency.

If the code I have developed is useful to you, it would be great if you
wanted to spend your energy improving the system instead of starting
from
scratch. There have been posts before on this list by other people
interested in RFID with the USRP, and this way everyone else could
benefit
from your work. The reader code could definitely use some more work.

-michael

Hi all,

I used the usrp1 for implementing a UHF gen2 reader(not the entire
functionality though). I have used a single board at the same frequency
without any problem. RFX900 has 2 antenna ports TX/RX and rx2 so tx and
rx antennas can be connected simultaneously.
However I found a major problem with latency. transmitting was not a
problem but recd signal was delayed quite a bit.

@Michael - did you use usrp1 or usrp2? since usrp2 has ethernet
interface, it should give lower latency than mine.

Regards
-Rush

From: Michael Buettner
Sent: Friday, November 20, 2009 1:04 PM
To: [email protected]
Subject: Re: [Discuss-gnuradio] Is RFX900 simultaneous transmit and
receive funtion possible?

Hi to all,

I need to implement a RFID reader using GNURadio RFX900.
I wanted to know urgently that is it possible to use a single
RFX900 for simultaneously transmitting and receiving.
I am in a hurry to purchase the stuff so I can receive it before holidays.
Prompt responses are highly appreciated.
Thanks in advance.

Regards,
Subodh

I have developed a GNU Radio based Gen 2 RFID reader that can
communicate with standard tags from a few feet away. The code has been
uploaded to George N.’ Comprehensive GNU Radio Archive
(https://www.cgran.org/wiki/Gen2). As RFID needs to transmit and
receive on the same frequency, my setup uses two RFX900 boards, one for
transmit and one for receive. As long as the antennas are a few inches
apart the transmit signal doesn’t entirely swamp the receive chain and
you can pick up the backscattered tag responses. The main difficulty in
getting the system to work was reducing system latency to < 500 us. The
modifications involved some tweaks to the way GNU Radio interfaces with
the USB driver. This means that it should also help other applications
that want low latency.

If the code I have developed is useful to you, it would be great if you
wanted to spend your energy improving the system instead of starting
from scratch. There have been posts before on this list by other people
interested in RFID with the USRP, and this way everyone else could
benefit from your work. The reader code could definitely use some more
work.

-michael