Two-port measurements with the tracking generator
R&S FSH
1145.5973.12 4.102
E-14
The reflection calibration remains valid until the center frequency or the span is changed on the
R&S FSH to such an extent that the new span falls outside the calibrated frequency range. Uncal is
displayed in the upper right-hand corner of the screen when calibration is no longer valid.
If the reference is changed after calibration, a larger measurement uncertainty must be anticipated. The
R&S FSH retains the calibration data but places a red dot before the reflection display in the upper
right-hand corner of the screen
•
FSH-Z2: Refl. to indicate a possible increase in measurement
uncertainty.
Changing other parameters like bandwidth, detector, sweep time or measurement range has no effect
on measurement accuracy. This means they can be changed after calibration without any reduction in
accuracy.
When a data set for scalar reflection measurement is stored with calibration performed, the calibration
data can be stored along with the other settings (see Chapter 2, section "Saving Calibration Data").
Thus, once the setting has been retrieved, measurement can be performed without first performing a
calibration.
If the temperature of the R&S FSH deviates by more than 5 °C from the temperature during the
calibration, the R&S FSH outputs a red dot in front of
•
FSH-Z2: Refl. to indicate increased
measurement uncertainty. In this case, recalibration is advised.
Vector measurement of reflection
(only available with option R&S FSH-K2)
Unlike with scalar measurement, the R&S FSH corrects the waveform reflected by the DUT according
to magnitude and phase by means of the correction values obtained from calibration. In addition to
calibration with open circuit and short circuit, calibration with a 50 termination is necessary. Thus, the
characteristics of the VSWR bridge (directivity and impedances) no longer affect the measurement
result. Rather, the decisive factor is the quality of the calibration parameters open circuit, short circuit
and 50 termination. Vector measurement therefore yields higher dynamic range and thus accuracy.
Due to the higher dynamic range, the display ranges for the VSWR and VSWR 1 –1.5 and VSWR 1 –
1.1 have been expanded. As a result, extremely well matched DUTs can be measured more accurately
and at a higher display resolution. However, a major advantage of the vector measurement is the
capability to display the complex test results in a Smith chart. This allows for a much more detailed look
at the DUT characteristics than with the reflection magnitude display as return loss, reflection coefficient
or VSWR. Moreover, the vector reflection measurement allows you to determine the phase, the group
delay and the electrical length of a DUT. The specified measurements become available only after
calibration has been performed. With vector measurements, the R&S FSH sets the bandwidths (Res
BW and Video BW) to a fixed, unchangeable value. It invariably uses the sample detector as a detector.
All other measurement parameters can be set as with scalar measurement.
Switching on vector measurement:
Press the MEAS key.
Press the MEAS MODE softkey.
Select VECTOR from the menu using the cursor
keys or the rotary knob.
Confirm your choice with the ENTER key or the
MEAS MODE softkey.
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