Specifications

10
Figure 7. Input SWR measurement
Figure 8. Complex output impedance measurement
Return loss, SWR, and reflection coefficient
Return loss (RL), standing wave ratio (SWR) or
reflection coefficient (rho) are commonly specified
to quantify the reflection mismatch at the input
and output ports of an AUT. Because reflection
measurements involve loss instead of gain, power
levels are lower at the receiver inputs. Therefore, it
may be necessary to increase power levels for
reflection measurements. Alternatively, the noise
levels can be reduced by increasing the averaging.
1. Set up the 8510C for an S
11
measurement.
[S11]
2. Display the return loss, SWR, and reflection
coefficient of the input port of the AUT.
[LOG MAG]
FORMAT [MENU] {SWR}
{LINEAR MAGNITUDE}
3. Similarly, the output match of the AUT can be
measured by repeating the procedure for S
22
.
Complex impedance
When the phase and magnitude characteristics of
an AUT are desired, the complex impedance can be
easily determined.
1. Set up the analyzer for an S
11
measurement.
[S11]
2. Display the input impedance of the AUT.
[SMITH CHART]
Markers used with this format display R + jX. The
reactance is displayed as an equivalent capacitance
or inductance at the marker frequency. Marker val-
ues are normally based on a system Z
O
of 50 Ω. If
the measurement environment is not 50 Ω, the net-
work analyzer characteristic impedance must be
modified under [CAL] {MORE} {SET Z0} before
calibrating. In addition, a minimum loss pad or
matching transformer must be inserted between
the AUT and the measurement port.
3. Display the complex reflection coefficient (G).
The linear magnitude and phase will be displayed
at the marker frequency.
FORMAT [MENU] {Re/Im mkr on POLAR}
4. Similarly, the output impedance of the AUT can
be measured by repeating the process for S
22
.