N5161A/62A/81A/82A/83A MXG Signal Generators User's Guide

TroubleshootingRF OutputSignal Loss While Working with a MixerCAUTIONTo avoid damaging or degrading the performance of the MXG, do not exceed 33 dBm(2W) maximum of reverse power levels at the RF input. See also Tips for PreventingSignal Generator Damage on www.agilent.com.To fix signal loss at the signal generator’s RF output during low–amplitude coupled operation with amixer, add attenuation and increase the RF output amplitude.The figure at right shows aconfiguration in which thesignal generator provides alow amplitude signal to amixer.The internally leveled signalgenerator RF output (and ALClevel) is −8 dBm. The mixer isdriven with an LO of +10 dBmand has an LO–to–RFisolation of 15 dB. Theresulting −5 dBm LOfeedthrough enters the signalgenerator’s RF outputconnector and arrives at theinternal detector.RF LevelControlDetectormeasures−8dBmALC levelSignal GeneratorOutput ControlALC Level= −8 dBmEffects of Reverse Power on ALCDetectormeasures−5 dBmreversepowerRF Output= −8 dBmLO Feedthru= −5 dBmDepending on frequency, it ispossible for most of this LOfeedthrough energy to enter the detector. Because the detector responds to its total input powerregardless of frequency, this excess energy causes the ALC to reduce the RF output. In this example,the reverse power across the detector is actually greater than the ALC level, which can result in lossof signal at the RF output.MixerIFLO Level= +10 dBmLO318 Agilent N5161A/62A/81A/82A/83A MXG Signal Generators User’s Guide