KEYSIGHT's N9951A-208 option 208 for the N9951A enables a power measurement versus frequency. The power is measured using a USB power sensor. FieldFox's source frequency can be set independently from the power sensor (receiver) frequency. The frequency of both the source and receiver are swept and the two track each other. The offset frequency can be negative, zero, or positive.
Option 208 can be used to characterize the scalar transmission response of devices such as mixers and converters. This frequency offset capability is necessary for conversion loss/gain measurements on frequency-translating devices, since by definition, the input and output frequencies of the DUT are different. The FieldFox source stimulates the DUT and the power sensor is used as the measurement receiver.
Source power, gain/loss, and receiver or output power can be displayed on the FieldFox display.