R&S FSH
Two-port measurements with the tracking generator
1145.5973.12 4.109
E-14
Defining the reference impedance
By default, the Smith chart is standardized to an impedance of 50 . In other words, the matching point
in the center of the Smith chart corresponds exactly to 50 . However, reflection measurements using
suitable matching networks and calibration standards can also be carried out in systems with different
impedance values. In this case, the reference impedance for the Smith chart can be modified as
needed.
Press the MARKER key.
Using the rotary knob or the cursor keys, select
IMPEDANCE from the menu and confirm by
pressing either the MARKER MODE softkey or the
ENTER key.
The R&S FSH will open a list for selecting the
reference impedance. The selected reference
impedance with be highlighted in green. The values
are predefined for 50 and 75 systems. If a system
has a different impedance value, any value from 1 m
to 10 k can be entered.
Selecting a predefined reference impedance:
Using the rotary knob or the cursor keys, select the
50
or 75 predefined values for the reference
impedance from the IMPEDANCE menu and
confirm by pressing either the MARKER MODE
softkey or the ENTER key.
Entering the reference impedance:
Using the rotary knob or the cursor keys, select
SET Z0 from the menu. Using the numeric keypad,
enter the reference impedance you want and
confirm by pressing either the MARKER MODE
softkey or the ENTER key.
Limit lines in the Smith chart:
To allow visual monitoring of VSWR limits, the R&S FSH offers VSWR limit values in the Smith chart. In
a Smith chart, a VSWR limit value is shown by a circle whose center point is the reference resistance
and whose radius is determined by the VSWR value. All values within the circle have a VSWR value
that is smaller than the VSWR value defined by the circle.
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