Measurement Parameters


This topic contains the following information:

Learn about Balanced Measurements

See other 'Setup Measurements' topics

S-Parameters

S-parameters (scattering parameters) are used to describe the way a device modifies a signal. For a 2-port device, there are four S-Parameters.  The syntax for each parameter is described by the following:

S out - in

out =

analyzer port number where the device signal output is measured (receiver)

in =

analyzer port number where the signal is applied (incident) to the device (source)

Move the mouse over each S-parameter to see the signal flow:

For two-port devices:

The analyzer automatically switches the source and receiver to make a forward or reverse measurement. Therefore, the analyzer can measure all four S-parameters for a two-port device with a single connection.

See the block diagram (including receivers) of your VNA.

Common Measurements with S-Parameters

Reflection Measurements
(S11 and S22)

Transmission Measurements
(S21 and S12)

  • Return loss

  • Standing wave ratio (SWR)

  • Reflection coefficient

  • Impedance

  • S 11 , S 22

  • Insertion loss

  • Transmission coefficient

  • Gain/Loss

  • Group delay

  • Deviation from linear phase

  • Electrical delay

  • S 21 , S 12

Receiver Measurements

All analyzer models have test port receivers and reference receivers. See the block diagram of your VNA.

For 4-port models...

Models with more than 4 ports must specify receivers using Logical Receiver Notation. Learn more.

Ratioed Measurements

Ratioed measurements allow you to choose your own ratio of any two receivers that are available in your analyzer. S-parameters are actually predefined ratio measurements. For example S11 is A/R1.

The following are common uses of ratioed measurements:

Your VNA MAY have front-panel jumper cables that go directly to measurement receivers. Learn about the front-panel jumpers on your VNA.

Unratioed (Absolute Power) Measurements

The unratioed power parameter measures the absolute power going into any of the receivers that are available on your analyzer.

The reference receivers are internally configured to measure the source power for a specific analyzer port. Performing an absolute power measurement of a reference receiver using a different source port will measure very little power unless the front panel jumpers are removed and signal is applied directly to the receiver. An example of this would be an R1 measurement using port 2 as the source.

New / Change Measurement dialog box help

Note: The only measurements that are available are those in the measurement class currently assigned to the active channel. Other measurements are NOT compatible.

To create a measurement other than these, first assign the appropriate measurement class to a new or existing channel. Learn how.

Click a tab to create or change measurements.

  • When creating NEW measurements, you can choose more than one.

  • When changing an EXISTING measurement, you can choose ONLY one.

Tabs

S-Parameter  Select a predefined ratioed measurements. Learn more about S-parameters.

For Setup:<= 4-Port

For Setup: Multiport (>4 ports)

Note: Greater than 4 ports is not supported on the P937xA.

Balanced  Select a balanced measurement type.

Topology  Click to invoke the Balanced DUT Topology / Logical Port mappings dialog box. Learn more about Balanced Measurements.

For Setup:<= 4-Port

For Setup: Multiport (>4 ports)

Note: Greater than 4 ports is not supported on the P937xA.

The table only show parameters for up to the first four VNA ports being used. Balanced Parameter Selector at the bottom allow you to select other parameters.

Multiport setup is shown in Custom under Topology. The setting in Custom only can change with SCPI command.

Select All  Will only select the parameters shown and will not select the check box of the Receiver selector at the bottom.  

Receivers  Select receivers to make Ratioed and Unratioed (absolute power) measurements. Learn more about receiver measurements.

Ratioed  Click on the check box to select the parameters and create measurement. Receiver selector at the bottom allow you to define ratios. Select a receiver for the Numerator, select another receiver for the Denominator, then select a source port for the measurement.

The Source port is ALWAYS interpreted as a logical port number.

For convenience, the table is populated with common choices.

Select All  Will only select the parameters shown and will not select the check box of the Receiver selector at the bottom.  

Unratioed  Same as Ratioed, but select 1 as the Denominator.

Waves  Select receiver notation to make ratioed and unratioed measurements.

Click on the check box to select the parameters and create measurement. Wave selector at the bottom allow you to define ratio.

Select All  Will only select the parameters shown and will not select the check box of the Wave selector at the bottom.

Receiver Notation

Receivers can be also selected using logical receiver notation. This "8510-style" notation makes it easy to refer to multi-port receivers.

  • aN - Reference receiver for logical port N

  • bN - Test port receiver for logical port N

For example:

  • For Ratioed measurements: "b12/a1" refers to the logical test port 12 receiver / the logical port 1 reference receiver.

  • For Unratioed measurements: "b10" refers to the logical test port 10 receiver.

The VNA-style notation (A, B, R1 and so forth) can still be used to refer to physical receivers in less than 4 ports. Learn more.

However, ratioed measurements MUST use the same notation to refer to both receivers; either the physical receiver notation (A, R1) or the logical receiver notation (aN, bN). For example, the following mixed notation is NOT allowed: A/b3 and a5/R2.

Programming

When entering receiver letters using programming commands, neither logical or physical receiver notation are case sensitive.

AUX  Select input of Auxiliary on the rear panel to make DC measurement.

Note: Aux Tab is shown when the M9341B is installed or Active - Show in UI for the external device is checked.

Click on the check box to select the input of auxiliary and create measurement. Auxiliary selector at the bottom allow you to define auxiliary and other parameters such as PMAR and DVMs.

Select All  Will only select the parameters shown and will not select the check box of the Auxiliary selector at the bottom.

Channel / Window Selections

These selections are NOT AVAILABLE when changing an EXISTING measurement. Learn how to change a measurement.

Channel Number  Select the channel for the new traces.

Create in New Window

  • Check to create new traces in a new window.

  • Clear to create new traces in the active window. When the traces per window limitation has been reached, no more traces are added.

About Measurement Parameters (top of page)

Balanced Source / Topology dialog box help

Topology Tab

See the dialog for Integrated True Mode Stimulus Application (iTMSA).

Create or edit DUT Topology and Logical Port Mapping.

A Logical Port is a term used to describe a physical analyzer test port that has been remapped to a new port number. You can assign logical single-ended ports to logical balanced ports.

Note: These selections apply to ALL measurements in the channel. If the device topology is changed, any existing measurements in the channel that are incompatible with the new topology will be automatically changed to one that is compatible.

Topology:  Describes your DUT as you would like it tested. The following device topologies can be measured by a multiport analyzer.

  • BAL  DUT has a single balanced port.
  • BAL-BAL  DUT has two balanced ports.
  • BAL-SE   DUT has one balanced port and one single-ended port.
  • BAL-SE-SE - DUT has one balanced port and two single-ended ports.
  • SE-BAL   DUT has one single-ended port and one balanced port.
  • SE-SE-BAL - DUT has two single-ended ports and one balanced port.
  • All SE
    (Changes all entries to Single-ended)

  • All BAL
    (Changes all entries to Balanced)

  • All Unused
    (Changes all entries to Unused) This is a convenience feature to help set up custom topologies, but it is not possible to have only Unused ports. If the OK button is clicked and all ports are listed as Unused, the topology will be set up to have 1 SE Port.

  • Custom
    (Maps the physical VNA ports to a device of balanced and single-ended logical ports for multi-port systems with greater than 4 ports.)

These topologies can be used in the reverse (<==) direction to measure:

  • Balanced / Single-ended topology

  • Balanced / Single-ended - Single-ended topology

For example, to measure a Balanced / Single-ended topology, measure the S12 (reverse direction) of a Single-ended / Balanced topology.

A balanced port can be any one of four physical port combinations:

1 - 3

1 - 4

2 - 3

2 - 4

Balanced Port  Number of rows equals number of VNA ports. User may select each port as SE or BAL or Unused. Unused ports are always forced to the bottom of the list and some Unused port selectors may be grayed-out when all the VNA ports are used.

VNA Port  Displays physical port numbers. But will display logical port numbers if logical ports are used. Balanced port requires (+) and (-) VNA port definitions; SE port only requires a single VNA port definition.

True Mode  Define true mode independently for each BAL port. SE ports cannot be defined as true mode. See this dialog for Integrated True Mode Stimulus Application (iTMSA). This function is not supported in model M980xA and P50xxA. So the checkbox is grayed out.

Port Z Tab

Provide an enable for both Common and Differential Conversion and SE Port Z Conversion.

Balanced Port  Shows all ports defined on the balanced topology page.

Default Z  Shows the default impedances that will be applied if the port Z conversions are not enabled. The SE Default Z always equals the System Zo defined for the VNA. The Differential and Common Default Z will display values calculated from the single-ended port impedances.

Converted Z  User may enter the real or imaginary component of the impedance.

Power Waves  (default) This was legacy method used.  If a load is the complex conjugate of the system impedance, then it will be displayed as a perfect match.

Traveling Waves  This is newly added. If a load equals the complex system impedance, then it will be displayed as a perfect match.

Warning Dialog  The dialog is displayed if "Conversion" is enabled and "Apply Fixtures" is currently disabled.

See Also