Injection locking circuit techniques for high-efficiency millimeter-wave transmitter arrays in SiGe and CMOS SOI processes

Millimeter-wave systems require circuit innovations that enable high efficiency with complex waveforms. Injection locking circuit techniques are presented that enable low-power outphasing modulation and phase shifting for millimeter-wave radio transmitters integrated in highly-scaled Silicon CMOS and BiCMOS technologies. This paper reviews the efficiency penalties for operating arrays under back-off conditions to compare the advantages of transmit architectures at mm-wave bands. A microwave injection locking outphasing modulator is described to realize wideband, high-efficiency operation confronting these array architectures. An injection-locked outphasing modulator circuit is implemented in 45-nm SOI CMOS and exhibits 22.7% overall system efficiency with 64-QAM at 2.1% EVM. Injection locking techniques for phase shifters are demonstrated to offer high phase and low amplitude variation in a 90-nm SiGe BiCMOS 2 × 2 transmit/receiver phased array at 71-86 GHz.