Power Sensor Measurements vs. Frequency
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), the user should ensure that only the signal
of interest is present at the power sensor input and that all others signals are filtered appropriately.
Setup parameter
Source frequency
Receiver frequency
Frequency offset
Frequency step size
Number of points
Center/span or start/stop. Range determined by FieldFox
Range determined by power sensor range
0, > 0, < 0
30 kHz minimum
2 to 1601
Combination of number of points and frequency step size limited by span.
Dwell time/point: 0 to 1.0 sec
Source frequency span must be equal to receiver frequency span.
Receiver sweep direction: forward (default setting) or reverse.
For some DUTs, the output frequency may sweep in a reverse direction, as compared to the source frequency. The basic
relationships between the source, receiver and offset frequencies are shown in the table below. The FieldFox analyzer
includes an offset calculator that ensures a fast measurement setup.
Src sweep direction
Forward f2rc > f1src
Rx sweep direction
Forward f2rx > f1rx
Frequency calculations
Receiver frequency = Source frequency ± Offset
Forward f2src > f1src
Reverse f2rx < f1rx
Receiver frequency = Offset – Source frequency Offset > Source
frequency
Description
Measurements
Source power, gain/loss and receiver (Rx) power
Gain = Rx power / source power (memory). Source power (memory) is measured during
setup.
Output power
Dynamic range
Refer to the test port output power typical data on page 5
The dynamic range with FOPS is dependent on FieldFox’s output power and the power
sensor’s dynamic range. Supported USB power sensors:
www.keysight.com/find/fieldfoxsupport
25
KEYSIGHT [ Keysight Technologies ]
