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In this paper we introduce a novel technique to overcome the drawbacks of passive tuners and active loops when characterizing very high power transistors and amplifiers. The methodology combines a passive tuner and an active loop, the former used to tune the fundamental output impedance of a device under test, the latter exploited to change its harmonic termination. Since the passive tuner changes also the harmonic load in an unpredictable way, we present for the first time a method to quickly find the correct settings for the active loop to achieve the desired harmonic load. This methodology, is easy to implement, relatively quick, and does not imply long system pre-calibration time when changing the characterization frequency.