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

These are useful for electronically steerable ferroelectric reflectarray antennas.

This work deals with the performance of coupled microstripline phase shifters (CMPS) fabricated using Ba_xSr_1-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.