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 approach reduces the number of ADCs and delays for TTD but retains the digital-delay advantage of digital beamforming. The proposed architecture employs charge-domain complex multiply and accumulate (MAC) inside SAR ADCs. The beamformer supports eight IF inputs and two simultaneous baseband outputs. Fabricated in 28 nm CMOS, the prototype consumes only 17 mW and occupies $0.035 \mathrm{~mm}^{2}$. The measured error vector magnitudes (EVMs) are better than -30 dB for quadrature amplitude modulation (QAM)-16 and QAM-256.