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TRF3704-17 performance on DAC348x EVM

This question is answered
Kang Hsia
Posted by
on Oct 31 2011 22:09 PM
Genius15695 points
TRF3704-17.zip

RF team,

A customer is observing some distortions on the RF spectrum. The distortions looks like higher order RF distortion. The DAC3482's spectrum is functional and all the settings appears to be correct. Could you take a look and provide feedback to this forum post? Thanks.  

From the customer:

"Two of the captures appear to be OK.  The DAC_I_OUT was taken directly from the transformer coupled output of the DAC.  The board was then modified to output RF and MOD_OUT was taken from the modulator output.  Then I enabled QMC and we got more spurs.  Also of concern is the noise floor raising which is more dramatic as the LO frequency is increased.  See MOD_OUT_DISTORTION where the LO is 5.8 GHz.

In all of the captures, we used the multitone generator to generate a 20 MHz offset tone sampled at 250 MHz, the DAC was set to 4x interpolation, FPGA clock divide by 16."
-KH

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  • Xiaobing Wu
    Posted by
    on Jan 31 2012 17:48 PM
    Verified Answer
    Verified by
    Prodigy530 points

    The atatched document revealed:

    • The noise floor rising-up was caused by the noisy LO source, not by TRF3704.
    • A signal generator like E4438C could have a noisy far-out noise floor, which leads to the elevated noise floor at TRF3704 outpu
    • HP 8673E has a much cleaner far-out noise floor than E4438C.
    • A BPF filter could be used to clean the dirty LO noise floor before sent to TRF3704 as LO source.
    Report Abuse

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