60 GHz 0-360˚ Passive Analog Delay Line in Liquid Crystal Technology based on a Novel Conductor-backed Fully-enclosed Coplanar Waveguide

Abstract

A new 0-360° continuously-variable true-time-delay phase shifter (delay line) based on liquid crystal (LC) is prototyped targeting 60 GHz inter-satellite cross-links. The device is developed on a stray-modes-free conductor-backed fully-enclosed coplanar waveguide (CB-ECPW). The novelty is underpinned by an electric field homogenisation concept, as well as insertion losses balancing at various phase-delay states by smart impedance-matching to remove beam-steering distortions without using amplitude compensation networks. The manufacturing features nickel-free gold-plating and vias plated shut. Measured worst-case insertion loss being -7.04 dB (0-360° phase-shifting) and phase-tuning rise time being 0.6 seconds at 60 GHz, the device demonstrates an improvement of up to 1 dB for the forward transmission coefficient, as well as a reduction of 3.4 seconds for the response time compared against our previously optimised LC-based ECPW phase shifter. These enable the new device to compete with existing waveguide-based LC analog delay lines in terms of various figure-of-merits and agility.