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TRF370417 CW output

Izik
Expert 1545 points

Hello 

My customer wants that the transmitter will be used both for modulated signal and also for high spectral purity CW signal for calibration.  

My LO to the modulator is very clean, so I would like to use it, Is there an option to bypass the IQ mixer inside the modulator, or to set value of 0Hz (DC?) at the IQ BB inputs to just pass the LO to output? What would be the conversion loss then? the spectral image? 

Thanks

  • 0
    TI__Mastermind 18065 points

    There will be some LO bleed-through to the output during normal operation.  Nominal carrier feed-through is around -40 dBm.  This value is predicated on the DC offset balance within the BB I/Q lines (1.7V in your case).  If you want to purposively get higher LO feed-through, you can purposively distort the DC offset balance on the I/Q line.  You can do this by setting DC offset on I like normal and Q to 0V.  This should degrade LO feed-through to something like -10 dBm (given a 0 dBm input LO).  You can jack up the LO power higher if you need more CW on the output.  You can jack up to 18 dBm without issue.  IIf you do not send any AC signal on the I/Q lines during this operation, then there will be no modulated signal on the output.

    --RJH

  • 0 in reply to RJ Hopper
    Expert 1545 points

    Hi

    Thank you for your answer. So basically if there are no IF signals than there will be no MxN mixer products at modulator output besides LO harmonics?

  • 0 in reply to Izik
    TI__Mastermind 18065 points
    Correct. --RJH
  • 0 in reply to RJ Hopper
    Expert 1545 points
    Thanks!