#### Impedance

The Impedance submenu contains the functions to convert S-parameters into matched-circuit impedances.

Matched-circuit impedances and open-circuit Z-parameters

The analyzer provides two different types of impedance parameters that are essentially based on different n-port circuit models:

- The matched-circuit impedances describe the impedances of a DUT that is terminated at its outputs with the reference impedance Z0.

- The open-circuit Z-parameters describe the impedances of a DUT with open output ports (I = 0). Open-circuit parameters can be selected in the More Z-Parametersdialog.

Mixed mode measurements are available for both types of impedance parameters.

- Z <– S11, Z <– S12, Z <– S21, Z<– S22
  select the forward and reverse matched-circuit impedances of a 2-port DUT.

- More Impedances...
  opens a dialog to define and select matched-circuit impedances for more ports or mixed mode measurements.

##### Z <– S11, Z <– S12, Z <– S21, Z <– S22

Select the 2-port matched-circuit, converted impedances. The parameters describe the impedances of a 2-port DUT, obtained in forward and reverse transmission and reflection measurements:

- Z11 is the input impedance of a 2-port DUT that is terminated at its output with the reference impedance Z0 (matched-circuit impedance measured in a forward reflection measurement).

- Z22 is the output impedance of a 2-port DUT that is terminated at its input with the reference impedance Z0 (matched-circuit impedance measured in a reverse reflection measurement).

- Z12 and Z21 denote the forward and reverse transfer impedances, respectively.

The analyzer can also provide matched-circuit impedances for more drive ports or balanced port configurations; see More Impedances
.

Relation with S-parameters

Use the More Z-Parameters
dialog to measure open-circuit Z-parameters. Use the Smith chart
to obtain an alternative, graphical representation of the converted impedances in a reflection measurement.

Remote control: | CALCulate<Ch>:PARameter:MEASure "<Trace_Name>", "Z-S11" | "Z-S12" | "Z-S21" | "Z-S22" [SENSe<Chn>:]FUNCtion[:ON] "...:POWer:Z<11 | 12 | 21 | 22 >" Create new trace and select name and measurement parameter: CALCulate<Ch>:PARameter:SDEFine "<Trace_Name>", "Z-S11" | "Z-S12" | "Z-S21" | "Z-S22"

##### More Impedances

Opens a dialog to select converted, matched-circuit impedance parameters for more ports or balanced port measurements.

The notation for converted impedance parameters and the functionality of the More Impedances dialog is analogous to the definition of S-parameters
.

- Z<— selects the type (left pull-down list) and the port number assignment (right pull-down list) of the impedance parameter. Mixed mode parameters are only available if a balanced port configuration is active. They are expressed as Y<mout><min>, where <mout> and <min> denote the output and input port modes. The port numbers are assigned in the order Y<out>< in>, where <out> and <in> denote the output (response) and input (stimulus) port numbers of the DUT.

- Balanced and Measured Ports
  opens the dialog of the same name to define the properties of the test ports. Single-ended (unbalanced) impedance parameters are assigned to the physical test ports of the analyzer. Balanced impedance parameters are assigned to logical test ports. Selecting a balanced port configuration with logical test ports means that the unbalance-balance conversion
  is switched on and that the analyzer provides mixed mode parameters
  .

- The graphics above the Balanced and Measured Ports button illustrates the current port configuration.

The port configuration is valid for all traces in the channel

The settings made in the Balanced and Measured Ports dialog are channel settings and therefore apply to all traces assigned to the channel (Balanced and Measured Ports is also accessible through Channel –Mode–Port Config...). Within a channel the analyzer measures either single-ended or mixed mode parameters. If a balanced test port configuration is selected the single-ended parameters assigned to the channel are converted into mixed mode parameters.

Single-ended and mixed mode parameters

Relation between impedances and S-parameters

The relation between the generalized (multiport and mixed mode) impedance parameters and the S-parameters is analogous to the 2-port case. For reflection measurements:

and for transmission measurements:

where Z 0i denotes the reference impedance of the analyzer port no. i.

Remote control: | CALCulate<Ch>:PARameter:MEASure "<Trace_Name>", "Z-S11" | "Z-S12" ... Create new trace and select name and measurement parameter: CALCulate<Ch>:PARameter:SDEFine "<Trace_Name>", "Z-S11" | "Z-S22" | ...