Tx amplifier non-linearity


#1

Hi,

I use USRP 1 and RFX2400…I try to find if the amplifier of the
transmitter has
a non-linear region. Do you know anything about this topic? Is there a
non-linear region that i could find? I try to find a relation of P_in
versus
P_out at the amplifier of the transmitter.

If there is only linear region, please tell me…

Thanks in advance,
Kardaras Giannis


#2

On Thu, May 14, 2009 at 6:01 AM, removed_email_address@domain.invalid wrote:

I use USRP 1 and RFX2400…I try to find if the amplifier of the transmitter has
a non-linear region. Do you know anything about this topic? Is there a
non-linear region that i could find? I try to find a relation of P_in versus
P_out at the amplifier of the transmitter.

If there is only linear region, please tell me…

The RFX2400 (and other RFX boards) begin to go into nonlinearity at
about 20 dB below its maximum output power, though this is a rough
approximation and varies board-to-board. In practice, you can stay in
the linear region by ensuring the amplitude of your TX signal stays
below 0.1 or so (when using USRP2), or below 3000 (when using USRP1).

If making this precise is important to you, you can perform a two-tone
test using usrp_siggen.py and a spectrum analyzer to measure the IMD
products directly and adjust the transmit power until they meet your
specification.

Johnathan