Novel Phase Detector Measurement Procedure Using Quasi-Synchronized RF Generator

Abstract

This article presents a new procedure for phase detector measurements that allows the use of generators that share a 10-MHz reference oscillator but do not synchronize in phase, in other words, quasi-synchronized RF generators. The objectives are taking advantage of the benefits of using two generators but recovering lower cost generators that have worse synchronization performance and opening the door to the possibility of using a very simple control element based on Arduino Uno and cheaper instruments. The new procedure is characterized by continuously alternating calibration and measurement sequences to make up for the phase drift of quasi-synchronized generators and guarantee a maximum phase error specification (±1° in this article). Data acquisition has been divided into two stages: measurement of detector curves without phase reference (in-phase and phase-shifted) and measurement of reference data. All the data are later combined to obtain correctly referenced in-phase detector curves. The technique can be reproduced with other equivalent instrumentation. The novel procedure that allows compensation for errors (amplitude, phase shift, mismatching, etc.) is detailed, and its relationship to the required measurement accuracy is amply discussed. The proposed technique is applied to characterize a phase detector based on in-phase and phase-shifted multiplication from 3 to 8 GHz with 1-GHz step. Measurements have a final maximum error of ±2° for both frequency and calibrated input power, according to the accuracy specifications of the vector network analyzer (VNA) used to calibrate the signal distribution network, added to ±1° specified in this new procedure.