Keysight N9923-90001 User’s Guide 137Frequency Offset Using Power Sensor (FOPS) – Option 208OverviewOverviewThis feature allows the FieldFox source frequency to be set independently fromthe power sensor (receiver) frequency. With frequency offset using powersensor (FOPS), the frequency of both the source and receiver are swept, andthe two track each other. The offset frequency can be negative, zero, orpositive.FOPS can be used to characterize the scalar transmission response of devicessuch as mixers and converters. This frequency offset capability is necessary forconversion loss/gain measurements on fr equency-translating devices since, bydefinition, the input and output frequencies of the DUT are different. TheFieldFox source stimulates the DUT and the power sensor is used as themeasurement receiver.Since power sensors are inherently broadband devices (notfrequency-selective), it is your responsibility to ensure that ONLY the signal ofinterest is present at the power sensor input and that all others signals arefiltered appropriately.For some DUTs, the output frequency may sweep in a reverse direction, ascompared to the source frequency. The FieldFox analyzer includes an offsetcalculator that ensures a fast measurement setup.The following shows a typical use case for FOPS:— The DUT is a long section of cable and a frequency converter.— The FieldFox source is tuned to the RF frequency.— The USB power sensor, with an equally long USB/LAN cable, is connectedto the IF Output. USB/LAN extenders ar e NOT provided with the FieldFox orKeysight USB power sensors.— Conversion gain/loss is measured at power sensor.
