A balanced reflection type HMIC vector modulator over 34–36GHz based on cold state pHEMTs

Abstract

A vector modulatorat Ka band consisting of two balanced I/Q bi-phase attenuatorsis presented in this paper. The bi-phase attenuators are of reflection type, in which cold state pHEMTs are employed as tunable impedance loads. Due to the balanced structure, parasitic effects of the pHEMTs are effectively cancelled. A prototype of the vector modulator is fabricated by HMIC technique. The measured dynamic range of amplitude is about 28dB with 360 degree tunable phase. The maximum transmission coefficient is about -8dB while the return loss is better than 15dB at the whole operation band of 34-36GHz.