An inherently linear phase-oversampling vector modulator in 90-nm CMOS

Abstract

A four-antenna vector modulator (VM) beamforming receiver in 90-nm CMOS operating between 2.4 and 4.9 GHz is presented. The VM is based on a phase-oversampling technique that allows the synthesis of inherently linear, high-resolution complex gains without complex variable gain amplifiers. It achieves 360° phase shift programmability with 8-bit digital control, a measured < 4.2° phase error at a back-off of 4 dB from the maximum gain setting, and a complex gain constellation with a mean error vector magnitude of < 2%. The monolithic beamformer also demonstrates an interference cancellation of > 24 dB for interferers impinging from different directions.