Diode power detector X‐parameters™ model extraction using LSNA‐based measurement system

Abstract

A study is presented on the problems that may arise when characterising low frequency device behaviour with a large signal network analyser (LSNA)-based measurement system. A diode power detector has been measured and, for the first time, an X-parameters based detector model was extracted from measurements. Difficulties measuring the detector output voltage dependence with baseband impedances, especially when those impedances showed resonant effects, were observed and a method to overcome the problems encountered is presented. The measurement-based detector X-parameters model demonstrated its usefulness to predict power detector behaviour under twotone excitations and complex loads.Introduction: Diode power probes have been used successfully for many years for high-speed power measurements, when the measured signal is a single sinusoid [1,2]. In recent works [3,4] it has been demonstrated that calibrating a diode-based power probe with a singletone signal does not guarantee accurate detector calibration for complex signals. It was identified that this is related to long-term memory effects caused by the detector baseband impedances. Thus, the detector output DC voltage may vary depending on the RF input signal bandwidth.In [4], an X-parameters model for diode power probes was proposed, which will be extended in the future for calibration purposes with modulated signals. In [4], this model was extracted from simulated data. DC measurements were used to validate the detector behaviour.In this Letter, a method to perform the required measurements to extract and validate an X-parameters model for power probes using an large signal network analyser (LSNA)-based measurement system, is proposed. Difficulties encountered and possible solutions are discussed.