A 17 mW 8-Element 2-Beam Hybrid Slepian Beamforming Receiver with SAR-ADC-Based Charge-Domain Multiply and Accumulation

True-time-delay (TTD) beamformers are very desirable for wideband wireless communication but existing approaches suffer from high hardware costs especially for large-scale arrays. In this work, a hybrid Slepian beamforming receive architecture reduces the power and area costs for TTD implementations. The proposed architecture employs charge-domain complex multiply and accumulate (MAC) inside SAR ADCs. A multi-phase tunable clock generator is optimized for MAC and ADC control. The beamformer supports 8 IF inputs and 2 simultaneous baseband outputs. Fabricated in 28 nm CMOS, the prototype consumes only 17 mW and occupies 0.035 mm2. The measured error vector magnitudes (EVMs) are better than -30 dB for quadrature amplitude modulation (QAM)-16 and QAM-256.