LTCC Antenna Array with Integrated Liquid Crystal Phase Shifter for Satellite Communication

Abstract

Low Temperature Cofired Ceramic (LTCC) is used as a substrate material for microelectronic devices in satellite communication. Its dielectric properties and excellent variability allows a good compactness and a high level of integration. An LTCC antenna array for microwave signals operating at 30 GHz is presented. All components such as radio frequency distribution network, four waveguide phase shifters and horn antennas are integrated in one ceramic module. The phase shifters are implemented as high volume cavities in the LTCC. A tailored mixture of liquid crystal can be stored inside the cavities. By applying an electric field, the anisotropic LC-molecules are aligned. The field is provided through a biasing network with four electrodes and screen printed resistive layers with resistance values in the MΩ/□ range. The alignment and with it the phase shifting is nearly seamless. The antenna module is manufactured in multilayer technology and consists of more than 40 layers. Lamination is carried out by thermocompression in two steps. A water based adhesive is used in the second. The cofiring is done in a sintering press. Temperature and pressure profile are chosen carefully, considering the high volume of the laminate and the buried cavities inside the module. After sintering, the horn antennas are milled into the front side of the ceramic body, which is about 5 mm in height.