What is the difference between Pcomp, Pharm, and PT measurements, and how can I match them?

Pharm is used to measure the power spectrum, whereas Pcomp is used to measure the power at a specific harmonic component; for instance, a harmonic index of 1 would be the power at the fundamental. The power is returned as a complex magnitude of the RMS power. PT, however, is used to measure the total power delivered to the load, including the power at DC and all other harmonics, and automatically returns only the Real part of the power.

When preforming Pcomp and Pharm measurements on schematics with complex port terminations, select Real instead of Mag in the Modify Measurement dialog. This will produce the same results as the PT measurement. This assumes that any other harmonic is much lower than the main tone that is being measured. If this is not the case, then Pcomp, Pharm, and PT measurements should not match.

Schematic

The circuit schematic shows a simple NL_AMP model terminated in a complex impedance.

Graph

Power Measurements graph shows PT, Pcomp, and Pharm measurements all in agreement with each other. Notice that Pcomp and Pharm are set to return only the Real part of the complex RMS power. If Pcomp and Pharm are changed back to Mag, you will start to see the measurements diverge in answer.

Team SimTech

Cadence Design Systems