A novel tunable true-time delay line/phase shifter based on distributed Schottky structure

Abstract

True time delay lines and phase shifters are widely used in RF timed/phased array systems. Conventional delay lines and phase shifters often associate with reflection type circuits or distributed (periodically loaded) transmission lines. In this paper, we propose a new type of distributed circuit which composed of uniform transmission lines built on integrated Schottky active layer. A bi-functional chip is designed based on the new distributed structure. An Archimedean spiral topology is adopted to reduce the chip area. Theoretical analysis of the design method and circuit parameters is performed and a miniaturized prototype is implemented with p-HEMT technology to validate the design theory. Measurement results shows that this chip could work as either an areaefficient true-time delay line or a low-voltage phase shifter over the bandwidth 11-15 GHz. As an area-efficient true-time delay line, this chip provides 82.1 ps delay time per square millimeter when the biasing voltage fixed at −1.4 V. As a low-voltage phase shifter, this chip provides 26.43°p hase shift per volt when the biasing voltage sweeps form 0 V to −1.4 V.