We report a new type of microstrip bandpass spiral filter structure, which
exhibits much smaller size than other existing miniaturized bandpass filter
structures, and is particularly useful in developing high-temperature supe
rconducting (HTS) compact filters for cellular communication systems. A pro
totype three-stage HTS bandpass spiral filter with center frequency of 633
MHz was designed and fabricated on a 20 mm x 8 mm x 0.5 mm LaAlO3 substrate
. The measurement results of the spiral filter have good agreements with it
s electromagnetic full-wave simulation results.