One-chip endless phase shifter IC's for space diversity combiner

This paper describes a one-chip endless phase shifter IC for a space diversity (SD) combiner in multi-carrier digital microwave radio systems; the combiner has an in-phase control circuit in each carrier. The endless phase shifter, which is the key device for this combiner, was miniaturized by using bipolar IC technology, and embedded on a single chip. First, the design methods of this monolithic endless phase shifter which focus on obtaining highly accurate characteristics in the UHF frequency bands are described. Thereafter, the characteristics of the endless phase shifter in the UHF band are examined in detail. This one chip endless phase shifter IC is found to be applicable to multilevel QAM (16-QAM) systems. Then, a new 90/spl deg/ combiner that achieves higher frequency response in the microwave frequency band is proposed and its effects are examined. Based on the design methods for the individual elemental circuits (90/spl deg/ combiner and balanced modulator), it is expected that the endless phase shifter can also be achieved in the microwave frequency band.