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Re: [Discuss-gnuradio] Re: Single-tone test using USRP2 with RFX2400 and

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] Re: Single-tone test using USRP2 with RFX2400 and XCVR2450
Date: Mon, 27 Apr 2009 12:50:52 -0700
User-agent: Thunderbird (X11/20090320)

Changkyu Seol wrote:
Matt Ettus wrote:
Yongsang Kim wrote:

What you are seeing are normal transmitter non-idealities, including DC
offset (aka carrier feedthrough), and IQ imbalance (aka sideband
suppression.  These can be improved through tuning, but they are not bad
as is.  Also, on the XCVR you are seeing the phase noise skirts as well.


With the XCVR2450 and USRP2, we also observed that the 2MHz (at baseband) is appearing at (f_c-2MHz) not (f_c+2MHz) where f_c is the center frequency. It seems that the complex conjugate of original baseband signal is transmitted at

We verified this with OFDM signal which is demodulated
successfully when we flip the left and right of the FFT ouput before
processing (integer frequency offset compensation, channel estimation, etc)
at the receiver.

Please update your firmware and try again. I believe I have fixed this problem now.


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