Design and performance of miniaturized quarter-wavelength resonator bandpass filters with attenuation poles

For more size reduction of the high temperature superconducting coplanar waveguide (CPW) bandpass filter (BPF), we introduce the design method of the meanderline quarter-wavelength resonator BPF. The admittance and impedance inverters (J- and K-inverters) are realized by using interdigital gaps and meanderline short stubs. Also, we estimate the slope parameter of the meanderline resonator by using EM-simulator. In order to control the attenuation poles, we adjust the meanderline intervals and shapes of the cross-coupling section, so that we can design the frequency and number of the attenuation poles. The size of the 6-pole CPW quarter-wavelength resonator with two attenuation poles (center frequency = 2 GHz) was 3.5 × 8 mm.