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calibration after reversing couplers

Question asked by matth on Jan 31, 2008
Latest reply on Feb 1, 2008 by dgun
In order to increase the dynamic range in my application, I have reversed both couplers on a E8362B ("rotation" of the jumpers of option 014). After a full two port SOLT calibration, I obtain error terms which look OK except both source match and load match at low frequency (-10dB at 10 MHz decreases below -20 dB only above 500 MHz). I find the same behavior on the uncorrected  return loss measured when a thru is connected between both ports (see attachment).

Is this behaviour normal ? (maybe are the receiver not so well impedance-matched at low frequency, which would explain why one measures so much reflected power when the receivers are directly connected to the main path of the couplers) or should I worry about that ?

Thank you in advance for your help