Ultra-Compact Reflective Loaded Lines for Low-Loss Sub-Degree Resolution Passive mm-Wave Phase Shifters

In this paper, we introduce a new mechanism to passively generate broadband phase shift with 10-bit resolution for highly-directive mm-wave beamforming applications. By using the phase shift that occurs after cutoff in a resonant filter in combination with a reflective-type phase shifter (RTPS), very high-resolution phase tuning can be achieved without high insertion loss. We present two bidirectional, broadband phase shifters operating in the 20-35 GHz 5G MIMO frequency bands. The phase resolution of under 0.3° is the sharpest among reported digitally controlled low-loss passive phase-shifters in these bands and with superior linearity. The ultra-compact footprint of 0.065 mm2 is achieved through the combination of coiled, capacitor-bank loaded lines and a miniature quadrature hybrid coupler integrated in 28 nm FDSOI CMOS.