Problem setting USRP transmitting signal power

GNU Radio
1

Hi~

I found some strange problem setting USRP transmitting signal power. The
method I change the transmit power is to use a constant to multiply the
signals. the problem is that I use bigger constant like 2.0, the SNR
value i
calculate is lower than using constant like 1.0. the transmit signal
values
are 0.005,-0.005. my experiment platform is USRP N210 plus motherboard
RFX2400. Is there anything wrong or there are better method to setting
USRP
transmiting power?

thanks!!!

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2

On Sun, Feb 24, 2013 at 10:36 PM, warren4300137
[email protected] wrote:

thanks!!!
The USRPs take in normalized signals, so you want to scale your
signals to +/-1 at most. If you want increased power, adjust the gain
of the USRP itself.

The reason you’re seeing a bad signal as you increase the amplitude is
that you are causing nonlinearities in the hardware from a signal
that’s too large. So even though the USRP will take in a +1 signal,
you’ll want to back off some to keep the signal in the linear range of
the transmitter.

Tom

3

Hi,

that’s too large. So even though the USRP will take in a +1 signal,
you’ll want to back off some to keep the signal in the linear range of
the transmitter.

Tom

So how much should one want to back off? Can u please quantize the
complex sample amplitudes that would map to the linear region of the
transmitter? I am using USRPN210 with XCVR2450. Thanks.