Continuously tunable phase shifters for phased arrays based on liquid crystal technology

This paper presents a novel liquid crystal technology for tunable microwave devices, primarily developed by the TU Darmstadt and Merck consortium over the last 10 years. This paper focuses on quasi powerless continuous (analog) tuning of phase shifters implemented in different transmission line topologies, which are used for electronically-controlled phased arrays aimed for various applications and frequency ranges. It consists of phase shifters and antenna arrays in planar topologies, in LTCC microstrip line and substrate integrated waveguide and rectangular waveguide topologies using liquid crystal filled cavities to tune the velocity of the traveling waves along the various line phase shifters. The measured figure of merit of the various phase shifter values range from 45° dB^-1 to 72° dB^-1 @ 30 GHz for LTCC integrated phase shifters and 62.5°dB^-1 @ 17.5 GHz for planar phase shifters as well as 120° dB^-1 to 200° dB^-1 for waveguide phase shifters. Besides the phase shifter performances, far field measurements are presented as well to demonstrate the scanning capabilities of a 2 × 2 and 4 × 1 array antenna built with different topologies.