Measurement of magnitude and phase of harmonics generated in nonlinear microwave two-ports

A method for simultaneously measuring the magnitude and phase of the harmonics generated by a microwave two-port is reported. The two-port under test is driven with a sinusoidal microwave signal strong enough to force it into nonlinear operation. Its output harmonics are measured in the frequency domain with a setup that includes a vector network analyzer. For phase calibration at the harmonic frequencies, a millimeter-wave Schottky diode is used as a reference device. The system allows the measurement of harmonics with a phase accuracy of about ±10° at 20 GHz (referred to f₁=5 GHz). It can be built for any frequency (<40 GHz) at which a vector network analyzer and a suitable signal generator with multiplier are available. For low-amplitude harmonics, higher sensitivity compared to time-domain measurements with a sampling scope results in better measurement accuracy. The accuracy should improve further if the nonideality of the diode reference circuit is characterized more precisely