A silicon-based, all-passive, 60 GHz, 4-element, phased-array beamformer featuring a differential, reflection-type phase shifter

摘要

This paper presents an all-passive, 4-element, phased-array beamformer based on a differential, reflection-type phase shifter (RTPS) operating in the 60GHz band. The RTPS consists of a differential, vertically-coupled, coupled-line hybrid and variable, parallel-LC, resonant, reflective loads, both of which enable low-loss millimeter-wave operation. The design considerations for a silicon-based implementation of all the beamformer elements are discussed in detail. In particular, the influence of the different RTPS components on its insertion loss is analyzed. The beamformer IC and a breakout of the RTPS are implemented using CMOS-only features of IBM''s 8HP 0.13¡jm SiGe BiCMOS process, and employ areas of 2.1mm² and 0.33mm², respectively, without probe pads. Differential s-parameter measurements at 60GHz show a phase-shift range greater than 150°, insertion losses of 4–6.2dB in the RTPS and 14–16dB in the beamformer, and an isolation better than 35dB between adjacent beamformer channels. Measurements across temperature and process variations are also presented.