Cross-coupled band-pass filter using HTS microstrip resonators

We have fabricated microstrip band-pass filters based on the quadruplet geo metry using high-temperature superconductor. Every half-wavelength resonato r in the filter consists of a loop-like inductor and two patch capacitors a t both ends, The inductive coupling in between the loop-like inductors of n on-adjacent resonators produces transmission zeros in the frequency respons e. The transmission zero can be allocated by changing the polarity and the strength of the cross coupling, We have designed a 9-pole filter for person al communication services (PCS) application using combination of a CAD tool and a full-wave analysis EM simulator. We have fabricated filters using do uble-sided YBa2Cu3O7-delta (YBCO) thin films on LaAlO3 substrates, The filt er has 1.784 GHz center frequency, 11 MHz 3-dB bandwidth, and 0.8 dB insert ion loss at 60 K. Due to the transmission zeros near the passband, the stee p skirt characteristic is exhibited. The attenuation at 1 MHz away from the edge of the passband is - 34 dB.