K-band tunable phase shifter with microstrip line structure using BST technology

A design framework of a K-band tunable phase shifter with microstrip line structure using Barium Strontium Titanate (BST) technology is presented in this paper. A conventional microstrip line structure is improved as a phase shifter and a layer of BST is deposited between substrate and strip line. In order to put on direct-current (DC) voltage, DC bias poles have been designed on the strip line and beneath BST layer. The permittivity of the BST material changes as the electrostatic field across BST layer changes. Therefore, effective permittivity of changes and the reflection phase can be continuously available by controlling outside voltage. S parameter simulation results indicate that the designed phase shifter has satisfying transmission characters. Simulation results also exhibit around 51.7° phase swing at 21 GHz, 231° phase swing at 23 GHz and 84.1° phase swing at 25 GHz. As phase swing range is proportional to length of this phase shifter, it could be designed flexible depend on actual requirement.