Design method of miniaturized HTS coplanar waveguide bandpass filters using cross coupling

A new design method of miniaturizing HTS coplanar waveguide bandpass filters using cross coupling is presented. When the size of the filter decreases, the cross coupling between the resonators tends to appear, which causes attenuation poles. In order to control the cross-coupling section, we redesigned the meanderline interval and shape, so that we can design the frequency and number of the attenuation poles. The half-wave length resonator bandpss filter (BPF) is designed by using the 2.5-dimensional electromagnetic field simulator. 7-pole cross-coupled CPW BPF (center frequency of 2 GHz, bandwidth of 15 MHz, ripple of 0.1 dB and two attenuation poles on both sides of pass band) is packed within 6 mm × 10 mm substrate. Simulated performance is in good agreement with the designed one. This BPF has the skirt steepness of 20 dB/MHz (40 dB attenuation), which is the same skirt characteristic of 11-pole Chebyshev BPF. Moreover, we tested YBCO BPF by using our present design theory at cryogenic temperature.