A Two-Beam Eight-Element Direct Digital Beamforming RF Modulator in 40-nm CMOS

A digital eight-element beamforming RF modulator allows accurate steering of multiple independent beams. The key to the efficiency is the pairing of area-efficient bandpass ΔΣ modulation with N-path filtering to suppress quantization noise. Beamforming digital signal processing (DSP) is enabled by careful frequency management, which facilitates efficient digital phase shifting, upsampling, and upconversion. A 40-nm CMOS prototype generates two 1.2-GHz beams, with 40-MHz RF bandwidth. The prototype consumes 128 mW and occupies an active area of only 0.19 mm
²
, which is only 16 mW and 0.02 mm
²
per element. This represents an order-of-magnitude improvement in area and power consumption per element compared to the state-of-the-art digital to RF modulators.