A 6 GHz 160 MHz Bandwidth MU-MIMO Eight-Element Direct Digital Beamforming TX Utilizing FIR H-bridge DAC

This work extends the bandwidth and frequency range of digital-phase-shifting direct-digital-to-RF TX, paving the way for use in MU-MIMO wireless networking applications. A sigma-delta modulation chain enables an inherently linear 1b RF DAC. Low-loss FIR filtering suppresses sigma-delta DAC noise. An H-bridge combines current-DAC, FIR-filtering and RF up-conversion for efficiency. A 28 nm CMOS 8-element 6 GHz beamforming TX has a per-element area of 0.01 mm
²
and a perelement power of 47.5 mW.