Single-Ended Oscillation-Based Test Technique for Passive RF Phase Shifters

Phased array systems have become paramount to the development of next generation wireless communication networks, with errors on phase shifters contributing to beam pointing error. Oscillation-based built-in self-testing (OBIST) of phase shifters may improve on this accuracy. We propose a single-ended oscillation-based test technique for passive RF phase shifters. The method uses a negative resistance oscillator topology, where the phase shifter is used to capacitively load the active negative resistance circuit resulting in a dependency between relative phase shift and output oscillation frequency. Simulation results indicate an average sensitivity of 0.14 MHz/° of phase shift around a nominal 617 MHz output oscillation when testing an X-band reflection-type phase shifter, while the addition of OBT circuitry increases the phase shifter’s mid-band insertion loss by 0.93 dB.