Low-power millimeter-wave (mm-wave) transceivers are of interest for achieving energy-efficient high data rate short-reach wireless and guided-wave links.
Spatial modulation or space-shift keying (SSK) can provide energy efficiency improvements by using antenna-switching or transmission direction switching for data modulation. Such links are particularly attractive at millimeter-wave frequencies due to small physical antenna size and large available bandwidths at mm-wave. SSK links are particularly suitable for slowly-varying channels and have potential applications on mm-wave wireless links within server chassis. A low-power pulsed two-element mm-wave transmitter (TX) is demonstrated that maintains energy-efficiency while enabling spatial modulation. A pulsed mm-wave digitally-controlled oscillator (DCO) provides low-power pulsed frequency-shift keying (FSK) capability, while variable DCO trigger pulse delay achieves controlled relative phase shift between TX elements for low-power space-shift keying (SSK). A two-element FSK/SSK 65nm CMOS TX prototype is packaged with PCB antennas to demonstrate a 2-FSK/4-SSK 3Gb/s TX with 21.4mW power consumption, achieving ~7.1pJ/bit. Two different implementations of two-element mm-wave FSK-SSK receiver (RX) are presented using 65nm CMOS that concurrently demodulate FSK and SSK, with series-FSK-SSK and parallel-FSK-SSK configurations. SSK demodulation is achieved using relative outputs of a two-element quadrature hybrid to detect angle of incidence. The 65nm CMOS 68GHz 2-element RX prototype is packaged with aperture-coupled PCB antennas to demonstrate >2Gb/s data rates while consuming <30mW across both elements. The first end-to-end CMOS FSK-SSK link using CMOS TX and RX is demonstrated with 2Gb/s data transfer across ~6cm in a reflective channel.
Guided mm-wave links over metal wire waveguides have been proposed and promise another direction for achieving energy-efficient high data rate links. The low loss and wide dispersion-flat bandwidth of Sommerfeld-wave propagation on a single conductor wire (SCW) and TEM-wave propagation on a two-metal-wire (TMW) make such guided mm-wave electrical links promising. The first fully-integrated end-to-end low-power wireline transceiver system on a SCW using Sommerfeld-wave propagation mode is demonstrated using a 60GHz carrier frequency. Implemented in 65nm CMOS, the proposed system includes on-chip radial-mode antennas as well as integrated serializer, 60GHz OOK modulator, demodulator, deserializer and clocking. The link achieves 7Gb/s data rate across 20cm of 26AWG bare copper wire (diameter = 0.4mm), while consuming 70.9mW of power. Operating at 6Gb/s and 7Gb/s, this demonstration achieves BER < 1e-12 and 1e-5 respectively. The two-metal-wire waveguide also has the low loss that are measured to be ~0.2dB/cm at 60GHz and relative flat group delays. A 60GHz continuous-phase frequency shift keying (CPFSK) transceiver is implemented in 65nm CMOS as a prototype to potentially enable energy efficient high data rates guided mm-wave links over two-metal-wire and multi-lane two-metal-wire waveguides.