Fixed-frequency and frequency-agile (Au,HTS) microstrip bandstop filters for L-band applications

In this work, we report on the performance of a highly selective, compact 1.83/spl times/2.08 cm/sup 2/ (/spl sim/0.72/spl times/0.82 in./sup 2/) microstrip line bandstop filter of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) on LaAlO/sub 3/ (LAO) substrate. The filter is designed for a center frequency of 1.623 GHz for a bandwidth at 3 dB from reference baseline of less than 5.15 MHz, and a bandstop rejection of 30 dB or better. The design and optimization of the filter was performed using Zeland's IE3D circuit simulator. The optimized design was used to fabricate gold (Au) and High-Temperature Superconductor (HTS) versions of the filter. We have also studied an electronically tunable version of the same filter. Tunability of the bandstop characteristics is achieved by the integration of a thin film conductor (Au or HTS) and the non-linear dielectric ferroelectric SrTiO/sub 3/ in a conductor/ferroelectric/dielectric modified microstrip configuration. The performance of these filters and comparison with the simulated data will be presented.