A Coupled-RTWO-Based Subharmonic Receiver Front End for 5G $E$ -Band Backhaul Links in 28-nm Bulk CMOS

An E-band direct-conversion subharmonic receiver (SHRX) is designed exploring a coupled-rotary-travelingwave-oscillator-based (coupled-RTWO-based) architecture. Distributed oscillators are leveraged to generate N = 8 differential phases at f
_LO
= f
_RF
/4. Current-mode passive mixers (MXs) are adopted to enable <;1-V supply operation and greatly simplify the layout. An inductively degenerated neutralized common source (DCS) low-noise amplifier (LNA) is embedded in a fourthorder transformer-based matching network to allow broadband impedance scaling and high reverse isolation. Implemented in a 28-nm bulk CMOS technology without ultra-thick top metal option, the realized prototype outperforms prior reported CMOS designs in terms of phase noise, figure of merit (FOM), and tuning range. The SHRX front end achieves 8.3-dB noise figure (NF), 12.5 GHz -3-dB RF bandwidth (BW), and -25-dBm ICP
_{1 dB}
, while consuming <;100 mW.