Highly accurate harmonic tuners for load pull testing

Abstract

Highly reflective harmonic tuners with high resolution tuning accuracy between 0.2/spl deg/ and 0.7/spl deg/ over the whole 0-360/spl deg/ interpolated tuning range are presented. This can be obtained through precise alignment supported by calibration and nonlinear interpolation algorithms that allow reproduction of arbitrary impedances with accuracy typically exceeding -50dB, at the very edge of the Smith Chart. These tuners are used in a compact and accurate harmonic load pull system. This allows characterization of complex and strongly nonlinear behavior of microwave transistors, including: hot IV curves, saturation plots and load pull contours all under controlled conditions of the 2nd and 3rd harmonic impedances.