Thin-Film Ferroelectric-Coupled Microstripline Phase Shifters With Reduced Device Hysteresis

This work deals with the performance of coupled microstripline phase shifters (CMPS) fabricated using BaxSr1-xTiO3 (BST) ferroelectric thin films. The CMPS were fabricated using commercially available pulsed laser deposition BST films with Ba:Sr ratios of 30:70 and 20:80. Microwave characterization of these CMPS was performed at upper Ku-band frequencies, particularly at frequencies near 16 and 18 GHz. X-ray diffraction studies indicate that the 30:70 films exhibit almost a 1:1 ratio between the in-plane and out-of-plane lattice parameters, suggesting that their cubics create strain-free films suitable for producing CMPS devices with reduced hysteresis in the paraelectric state.