UCLA

While the 5G standard has mainly focused on enhanced data connectivity, the next generation, 6G, will attempt to converge many technologies (AI, ML, communication, computing). The use of the D-band for its wide bandwidth is attractive for such systems. But the high path loss requires a large beam-forming array and hence high power consumption. Thus, compact, low-power D-band radios are of high interest. We describe a receiver with a minimum NF of 4.7 dB that draws 40 mW, a factor of 2.5 less than state of the art, and, requires only a 250-MHz reference frequency while providing a phase shift range of more than 180°in each beamforming element. This performance is achieved by several new techniques: (1) an RF path with low-impedance interfaces to ease the noise-stability trade-off, (2) a 94-GHz subsampling PLL, (3) a new quadrature LC QVCO, and (4) a new phase shift technique that resides at low frequencies. The new QVCO reduces the phase noise by 6 dB and resolves the mode ambiguity observed in conventional QVCOs. Our proposed phase shift technique offers several benefits. First, it avoids the loss-phaseshift trade-offs encountered in the RF or LO paths. Second, it has no effect on the signalpath’s gain. Third, it operates at low frequencies, consuming 0.5 mW and producing an rms jitter of 15 fsrms. Moreover, the RX and its dedicated PLLs occupy a total area of 1.1 mm x 0.9 mm in 28-nm CMOS technology, offering a low-cost compact solution. In addition to the architecture and circuit concepts proposed below, this work reduces the power by avoiding three types of circuits, namely, buffers, passive power splitters, and passive frequency multipliers.