Measurement Parameters

This topic contains the following information:

S-Parameters (pre-selected ratios)
Ratioed (choose your own ratio)
Unratioed Power (absolute power)
How to Select a Measurement Parameter

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:

When the source goes into port 1, the measurement is said to be in the forward direction.
When the source goes into port 2, the measurement is said to be in the reverse direction.

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 PNA.

Common Measurements with S-Parameters

Reflection Measurements (S11 and S22)	Transmission Measurements (S21 and S12)
Return loss Standing wave ratio (SWR) Reflection coefficient Impedance S11, S22	Insertion loss Transmission coefficient Gain/Loss Group delay Deviation from linear phase Electrical delay S21, S12

Receiver Measurements

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

For 4-port models...

R1, R2, R3, and R4 are reference receivers. They measure the signal as it leaves the analyzer source.
- R1 measures the signal out of Port 1
- ...
- R4 measures the signal out of Port 4
A, B, C, and D are test port receivers. They measure the signal out (or reflecting off ) of the DUT.
- A measures the signal into PNA Port 1
- B measures the signal into PNA Port 2
- C measures the signal into PNA Port 3
- D measures the signal into PNA Port 4

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

Note: Beginning with PNA Rev. 7.22, you can use the internal ADC (Analog-Digital Converters) as measurement receivers. 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:

Comparing the phase between two paths of a device. An example could be something simple like a power splitter or more complicated like a dual-channel receiver.
Measurements that require a higher dynamic range than the analyzer provides with S-parameters.

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

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.

Measuring phase using a single receiver yields meaningless data. Phase measurements must be a comparison of two signals.
Averaging for Unratioed parameters is computed differently from ratioed parameters. Learn more.
To calibrate ratioed or unratioed receiver (power) parameters, the recommended method is the Guided Power Calibration. The Unguided Response Calibration can also be used to calibrate a single unratioed or ratioed parameter at a time.

How to create a NEW trace The only measurements that can be created are those in the same measurement class as is currently assigned to the active channel. To create a measurement other than these, first assign the appropriate measurement class to a new or existing channel. Learn how.
Using front-panel hardkey [softkey] buttons	Using Menus

Press trace 1, 2, 3, or 4	Click Trace/Chan then New Trace

How to CHANGE the active trace The only measurements that can be selected are those in the same measurement class as is currently assigned to the channel. To select a measurement other than these, first select the appropriate measurement class to a new or existing channel. Learn how.
Press Meas then select a new parameter	Click Response then Measure then select a new parameter

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.

Balanced Select a balanced measurement type.

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

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

Ratioed Check Activate to create or change a measurement. 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.

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

Learn More about Unratioed Measurements.
See the block diagram of receivers in YOUR PNA.
The internal ADCs (Analog-Digital Converters) can be used as measurement receivers. Learn more.

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.

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.

Auto-Create Windows Check to create new traces in as many windows as necessary. See number of windows limitation.

About Measurement Parameters (top of page)

Balanced DUT Topology / Logical Port mappings dialog box help

See this 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.

Balanced
(1 logical port - <2 actual ports>)
Balanced / Balanced
(2 logical ports - <4 actual ports>)
Single-ended / Balanced
(2 logical ports - <3 actual ports>)
Single-ended - Single-ended / Balanced
(3 logical ports - <4 actual ports>)
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.