Tuneable hollow waveguide devices for space applications based on liquid crystal

This paper presents an overview in the field of passive, continuously tuneable liquid crystal (LC) devices in hollow waveguide topology. In particular, the designs and measurements of a Ka-band phase shifter as well as a K-band band-pass filter based on an LC filled waveguide resonator are shown. Both demonstrators are designated to be space qualified as their field of application is in satellite communications. While the high performance phase shifter will be integrated in a phased array antenna for beam scanning purposes, the high quality (Q) factor band-pass filter will be used to change the operating frequency and band allocation of a satellite.The key feature of the LC based hollow waveguide phase shifter is its high efhciency, dehned by the maximum differential phase shift divided by the maximum insertion loss in all tuning states, which is measured in the design frequency range of 23 GHz to 27 GHz to more than 130°/dB by means of electric biasing. The key feature of the band-pass hlter is its high Q-factor of up to 484, resulting in a comparatively small bandwidth compared to common hlters based on planar topologies. For the presented hlter, a relative bandwidth of 1% is measured at 20 GHz.