One or the critical design aspects in ferroelectric tunable microstrip Filt
ers is choosing the: right bias configuration, for large tunability as well
as to maintain the filter's passband characterisitics . This work based on
strontium titanate (STO) ferroelectric thin-film based tunable microstrip
filters for cryogenic temperature applications. Large tunability factors ha
ve been demonstrated in YBCO/STO/LAO two-layered microstrip filters when op
erated at or below 77 K. The effect of the do electric field (primarily res
ponsible For tuning) and critical design parameters such as the insertion l
oss, frequency tunability, return loss, and bandwidth of superconductor/fer
oelectric/dielectric microstrip tunable K-band microwave filters is discuss
ed in this work.