Thin film multilayer conductor ferroelectric tunable microwave components for communication applications

A study of Au/SrTiO3/YBa2Cu3O7-delta/LaAlO3 and (Au,YBa2Cu3O7-delta)/BaxSr1-xTiO3/LaAlO3 (x = 0, 0.50, and 0.40) multilayered structures is presented. At 1.0 MHz, the largest tuning of Au/SrTiO3/YBa(2)Cu(3)0(7-delta) parallel plate capacitors corresponded to single-phased, epitaxial 300-500 nm thick SrTiO3 thin films deposited at 800 degrees C. For SrTiO3/LaAlO3 structures having SrTiO3 films of similar quality, we observed that at 1.0 MHz and 77 K, interdigital capacitors exhibit higher tunabilities and lower losses than parallel plate configurations, but required higher dc voltage. For a 300 nm thick SrTiO3 film, a 25 Omega YBa2Cu3O7-delta/SrTiO3/LaAlO3 phase shifter exhibited a phase shift similar to 2.6 times larger than its Au/SrTiO3/LaAlO3 counterpart. At 19 GHz and 32V, a 360 degrees phase shift could in principle be achieved with coupled microstripline sections only 7.0 mm long. At 14 GHz, 77 K and 260 V, for 1.0 mu m and 300 nm thick SrTiO3 films, 25 Omega 360 degrees Au/SrTiO3/LaAlO3 phase shifters would be nominally 4.0 mm and 12 mm long, respectively. For a 2 lambda YBa2Cu3 O7-deltaSrTiO3/LaAlO3 ring resonator a tuning rate of 0.7 MHz/Volt was achieved at 10 GHz and 77 K. The relevance of these structures for phased array antennas and as tunable elements in discriminator-stabilized oscillators is discussed.