Keysight N9923A, User Manual, Page: 137 / 276

Keysight N9923-90001 User’s Guide 137
Frequency Offset Using Power Sensor (FOPS) – Option 208
Overview
Overview
This feature allows the FieldFox source frequency to be set independently from
the power sensor (receiver) frequency. With frequency offset using power
sensor (FOPS), 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.
FOPS 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.
Since power sensors are inherently broadband devices (not
frequency-selective), it is your responsibility to ensure that ONLY the signal of
interest is present at the power sensor input and that all others signals are
filtered appropriately.
For some DUTs, the output frequency may sweep in a reverse direction, as
compared to the source frequency. The FieldFox analyzer includes an offset
calculator 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 connected
to the IF Output. USB/LAN extenders are NOT provided with the FieldFox or
Keysight USB power sensors.
— Conversion gain/loss is measured at power sensor.