Several microstrip-based conductor/thin film ferroelectric phase shifter designs using (YBa2Cu3O7-δ,Au)/SrTiO3/LaAlO3 structures

We have designed, fabricated, and tested several novel microstrip-based YBa2Cu3O7-δ/SrTiO3/LaAlO3 (YBCO/STO/LAO) and Au/SrTiO3/LaAlO3 (Au/STO/LAO) phase shifters. The first design consists of eight coupled microstrip phase shifters (CMPS) in series. This design using YBCO achieved a relative insertion phase shift (Δφ) of 484° with a figure of merit of 80°/dB at Vdc=375 V, 16 GHz, and 40 K. A Δφ of 290° was observed while maintaining the insertion loss below 4.5 dB. At 77 K, a Δφ of 420° was obtained for this phase shifter at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. A second compact design, consisting of an Au meander line and a CMPS section was also tested. Of the two samples tested, the best showed a figure of merit of 43°/dB with Δφ = 290° and 6.8 dB loss, at 40 K, 10 GHz and 400 V. Experimental and modeling results on these circuits will be discussed in the context of potential applications.