Composite measurement is a technique that allows multiple measurements to be performed in parallel on the same acquired data. This technique leads to faster measurement times because all the measurements in a composite set are based on the same acquired data, and they are processed in parallel threads on the CPU. Although the same data set is used for each measurement in a composite set, NI-RFmx allows different configuration settings for each measurement, enabling multifaceted signal analysis.
The following figures show the difference between serial measurements and composite measurements.
When the composite measurements are performed, only a single acquisition is made and each measurement in the composite set is performed on the same acquired data. Internally, NI-RFmx merges the acquisition settings from all the measurements in a composite set to provide the acquisition settings that satisfy the needs of all the measurements being performed. However, not all measurements can be performed as composite measurements. For example, a harmonics measurement cannot be performed in composite with an ACP measurement, because a harmonics measurement requires multi-segment acquisitions for different harmonics.
To perform multiple measurements as composite measurements, use the Multiple personality of the Select Measurement node, and wire in an array containing the measurement types you want to perform together.
Besides faster test execution times, composite measurements also allow you to see different measurements on the same DUT signal, enabling you to debug difficult issues. For example, you can see if a bad ACP result is correlated to a bad EVM result.