RFX900 full duplex limitations

GNU Radio
1

On the pdf from ettus.com (for the RFX900 daughterboard and the like) it
says that:

• Full-duplex capable (with some limitations)

Does anyone know what those limitations are or is there more specific
information somewhere?
We were specifically looking at the RFX900 board.

Thanks.

–
Newell

http://www.gempillar.com
Before enlightenment: chop wood, carry water
After enlightenment: code, build circuits

2

I guess the transmitter leaks into the receiver. This may be worse when
the
frequencies are close - multiples of 64MHz should probably be avoided.
I
have also sometimes noticed that the gain of the receiver changes
slightly
when the transmitter is activitated. This may be no issue in many
applications. My guess is that this is due to that the gain of the
AD8437
slightly changes when the voltage on the board drops due to an increased
power consumption.

BR/
Per

From: discuss-gnuradio-bounces+per.zetterberg=removed_email_address@domain.invalid
[mailto:discuss-gnuradio-bounces+per.zetterberg=removed_email_address@domain.invalid] On
Behalf
Of Newell J.
Sent: den 16 december 2008 08:54
To: gnuradio mailing list
Subject: [Discuss-gnuradio] RFX900 full duplex limitations

On the pdf from ettus.com (for the RFX900 daughterboard and the like) it
says that:

. Full-duplex capable (with some limitations)

Does anyone know what those limitations are or is there more specific
information somewhere?
We were specifically looking at the RFX900 board.

Thanks.

–
Newell

http://www.gempillar.com
Before enlightenment: chop wood, carry water
After enlightenment: code, build circuits

3

On Mon, Dec 15, 2008 at 11:53 PM, Newell J. [email protected]
wrote:

• Full-duplex capable (with some limitations)

Does anyone know what those limitations are or is there more specific
information somewhere?

The isolation between the transmitter and receiver is only about 30db
(primarily the leakage through the antenna switching network).

Depending on what you are transmitting, this can impact the first
receiver amplifier, causing IMD and raising the noise floor
unacceptably.

-Johnathan

4

On Tue, Dec 16, 2008 at 1:24 PM, Johnathan C. <
[email protected]> wrote:

On Mon, Dec 15, 2008 at 11:53 PM, Newell J. [email protected]
wrote:

• Full-duplex capable (with some limitations)

Does anyone know what those limitations are or is there more specific
information somewhere?

The isolation between the transmitter and receiver is only about 30db
(primarily the leakage through the antenna switching network).

Is this for the TX/RX port or are you also refering to the TX and RX2
ports? If I use the RX2 port to receive with its own antenna and the
TX/RX
port with its own antenna is the isolation still about 30 dB?

Thanks for the replies.

–
Newell

http://www.gempillar.com
Before enlightenment: chop wood, carry water
After enlightenment: code, build circuits

5

On Tue, Dec 16, 2008 at 1:28 PM, Newell J. [email protected]
wrote:

Is this for the TX/RX port or are you also refering to the TX and RX2
ports? If I use the RX2 port to receive with its own antenna and the TX/RX
port with its own antenna is the isolation still about 30 dB?

I may have misspoken. In the full duplex configuration, there are two
switches worth of isolation between them, each of them at least 25dB
isolation, but there may be other leakage paths, including coupling
through the common power line. It’s probably worth measuring.

-Johnathan

6

If you actually measure this please share you results.

– David

Sent with SnapperMail
www.snappermail.com

… Original Message …
On Tue, 16 Dec 2008 13:38:16 -0800 “Johnathan C.”
[email protected] wrote:

On Tue, Dec 16, 2008 at 1:28 PM, Newell J. [email protected]
wrote:

Is this for the TX/RX port or are you also refering to the TX and RX2
ports? If I use the RX2 port to receive with its own antenna and the
TX/RX