This topic contains the following information:
S-Parameters (pre-selected ratios)
Ratioed (choose your own ratio)
Unratioed Power (absolute power)
Learn about Balanced Measurements
See other 'Setup Measurements' topics
S-parameters (Scattering Parameters) are used to describe the way of a device modifies a signal. An S-parameter is defined by the ratio of two complex numbers and contains information on the magnitude and phase of the signal.
For a 2-port device, there are four S-Parameters. The syntax for each parameter is described by the following:
S out - in
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out = |
VNA port number where the device signal output is measured (receiver) |
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in = |
VNA 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.
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Reflection Measurements |
Transmission Measurements |
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All VNA models have test port receivers and reference receivers.
For 4-port models
R1, R2, R3 and R4 are reference receivers. They measure the signal as it leaves the VNA source.
R1 measures the signal out of Port 1
R2 measures the signal out of Port 2
R3 measures the signal out of Port 3
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 VNA Port 1
B measures the signal into VNA Port 2
C measures the signal into VNA Port 3
D measures the signal into VNA Port 4
Receivers can also be specified using Logical Receiver Notation. Learn more.
Ratioed measurements allow you to choose your own ratio of any two receivers that are available in VNA. S-parameters are actually pre-defined 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.
The unratioed power parameter measures the absolute power going into any of the receivers that are available on VNA.
The reference receivers are internally configured to measure the source power for a specific VNA 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.
Choose Response Cal if ONLY unratioed parameters are being measured. If S-parameters are also being measured, then SmartCal will calibrate the test port receivers in use.
Click a tab to create or change measurements.
Tabs S-Parameter - Select a predefined ratioed measurements. Learn more about S-parameters.
When the number of ports is more than 4, the following dialog box is displayed. You can set the S parameter with the selection at bottom. When your configuration is 2 chassis, the chassis has the M9310A and M9309A is assigned as the first chassis (Chassis A). The most left module in it is assigned as port 1.
By entering "x.x" also can set the S parameter.
Balanced - Select a balanced measurement type. (Multiport VNAs ONLY) 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.
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
About Measurement Parameters (top of page) |
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Balanced DUT Topology / Logical Port mappings Dialog Box Help |
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Create or edit DUT Topology and Logical Port Mapping. A Logical Port is a term used to describe a physical VNA test port that has been remapped to a new port number.
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 VNA. When the unit is 2-port model, only balanced can be selected.
These topologies can be used in the reverse (<==) direction to measure:
For example, to measure a Balanced/Single-ended topology, measure the S12 (reverse direction) of a Single-ended/Balanced topology.
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Last modified:
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18-May-2016 |
First Release |
