[Discuss-gnuradio] Re: Single-tone test using USRP2 with RFX2400 and XCVR2450

[Changkyu Seol]

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.
> 
> Matt

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
XCVR2450.

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.
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