Structure Design And Simulation Of BST Thin Film Phase Shifter For Phased Array

The wide application and rapid development of phased array radar make phase shifter become the focus of research, which is the key component of phased array radar. Low loss and low cost microwave phase shifters are required to improve performance and reduce the cost of phase array. BaSrTiO3 (BST) thin films have great predominance in microwave phase shifter circuit applications because of their high tunable, relatively low loss, and fast switching speed.After the analysis of some structures commonly used in dielectric phase shifter, a structure named distributed capacitor-loaded phase shifter was carried out. It is comprised of a high-impedance transmission line periodically loaded with BST thin film capacitors, which is called coplanar wave-guide (CPW). After the analysis of CPW BST thin film phase shifter, the fabrication technology and the cost, the interdigital capacitor was used as the loaded capacitor. Based on the model, the parameters was simulated in Agilent ADS 2005A, and then its structure parameter in influencing the reflectance, insert loss and the phase shift of the phase shifter were considered, and an optimized parameter of the structure was chosen. Finally the structure parameters of interdigital capacitors were improved, based on the traditional one, and the layout was designed using ADS. The whole performances of this phase shifter were simulated by computer, and acquired a better result. The reflectance is lower than -9dB, the insert loss is lower than 0.9dB, and the phase shift is nearly 330o.