RF harmonic distortion measurement | RF harmonic testing procedure

This page describes RF harmonic distortion measurement and harmonics test setup. It describes RF harmonic distortion testing procedure used for harmonic measurement with the help of harmonic distortion analyzer.

When any input frequency signal is applied to the nonlinear device, it will generate unwanted frequencies other than the input signal. This unwanted frequencies if present at integer multiple of input frequency then they are referred as harmonics. Figure depicts harmonics(i.e. 2fc), which is at twice of input frequency (fc). Refer harmonics definition.

Test Equipments for harmonic distortion measurement

Following test equipments are needed for the harmonic distortion measurement setup.
• RF Spectrum analyzer used as harmonic distortion analyzer
• RF Power Meter
• Device Under Test (DUT)
• RF signal generator or CW source
• RF Attenuator (Fixed or variable)
• RF Directional Coupler

RF harmonic testing procedure for harmonic measurement

Following RF harmonic testing procedure is used for RF harmonic distortion measurement.
➨Do the setup as shown in the figure-1.
➨Feed the CW frequency (say 'Fc') to the nonlinear DUT (either RF Transceiver or RF Power Amplifier).
➨Connect the RF attenuator at the output of DUT and feed the signal output to the directional coupler.
➨Connect one port output of directional coupler to the RF power meter and the other port to the RF spectrum analyzer which can be used as harmonic distortion analyzer.
➨Place the markers at point 'P', point 'P1' and point 'P2'. P is the reference center frequency(Fc), P1 is the first harmonics at 2*Fc and P2 is the second harmonics at 4*Fc.
➨Difference between power levels at P and P1 will provide first harmonic distortion measurement. Difference between power levels at P and P2 will provide second harmonic distortion measurement.
➨It is measured in dBc. Greater the difference between the points better is the system.
Refer envelope tracking procedure used in power amplifier.

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