R&S FSH3 Setting and Using the Measurement Functions
Taking additional attenuation into account
When the Directional Power Sensor R&S FSH-Z44 is connected to a test point not directly but via a
cable, the influence of cable attenuation can be taken into account. For this purpose, the cable
attenuation for the measurement frequency in question is to be entered, i.e. as a positive dB value if the
power and matching are to be measured at the source and the cable is connected between the source
and the power sensor, and as a negative dB value if the power and matching are to be measured at the
load and the cable is connected between the load and the power sensor. The R&S FSH-44 then
corrects the power and matching values to produce the results that would have been obtained if the
R&S FSH-Z44 had been directly connected to the test point.
¾ Press the AMPT key.
¾ Press the REF OFFSET softkey.
The value entry box for the reference offset opens.
¾ Enter the desired offset using the rotary knob, the
cursor keys or the number keys and confirm the
entry with the ENTER key.
The selected offset is displayed in the middle at the top
of the screen and is taken into account in the power
(level) and matching results.
If high powers are applied that exceed the maximum input level of the R&S FSH-Z44, a directional
coupler or an attenuator has to be connected ahead of the power sensor. In such cases, the coupling
attenuation of the directional coupler or the attenuation value of the attenuator are to be entered as
positive dB values (see above) into the R&S FSH3 to ensure true measured power readout. In both
cases, a termination or an attenuator of sufficient power-handling capacity has to be connected to the
power sensor at the load end. The matching readout is irrelevant in such case since it is likewise
corrected by taking into account the attenuation value of the termination or attenuator (see
measurement via cable).
Two-port measurements with the tracking generator
(Only for R&S FSH3 with tracking generator: Order No. 1145.5850.13 and 1145.5850.23)
The R&S FSH3 can be supplied with an optional tracking generator to measure the transfer functions of
two-ports or the reflection coefficients of one-ports and two-ports. The tracking generator outputs a sig-
nal at the current R&S FSH3 frequency. The nominal output level of the tracking generator is –20 dBm.
In model 1145.5850.23, the nominal output level can be switched to 0 dBm.
Two-port transfer functions can be determined directly by connecting the input of the DUT to the output
of the tracking generator and the DUT’s output to the R&S FSH3’s RF input. A bridge is required to
measure the reflection coefficient, e.g. the VSWR Bridge R&S FSH-Z2.
Thanks to the calibration technique used, the R&S FSH3’s measurement accuracy is high for both
transmission measurements and reflection measurements. The R&S FSH3 offers scalar calibration
methods as standard; i.e. with transfer function and reflection measurements, the magnitudes are
corrected. Vector calibration methods and measurements (option R&S FSH-K2) are possible for
increasing the dynamic range and the measurement accuracy. The operation of vector measurements
primarily differs in the expanded calibration routines.
1145.5973.12 4.53 E-6
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