Planar compact, broad-stopband elliptic-function lowpass filters using high-permittivity ceramic substrate

The miniaturization of hairpin lowpass filters by employing two high-permittivity ceramic substrates (with respective dielectric constants of 9.7 and 22.6) are investigated. Microwave dielectric ceramics with high permittivity are commonly applied in several microwave communication components. With the advantages of compact size, high permittivity ceramics can be used as the substrate for low-pass filters. Moreover, the fundamental characteristics of newly developed compact stepped-impedance hairpin resonators with parallel coupled lines have also been described and applied to the design of lowpass filters. In this paper, the designed multiple cascaded stepped-impedance hairpin resonators structures are simulated using an IE3D simulator. The responses of the fabricated filters using Al2O3 (εr = 9.7, Q × f = 350,000 GHz) and 0.2 Ca0.6La 0.26TiO3-0.8Mg0.95Co0.05TiO 3 (εr = 22.6, Q × f = 57,000 GHz) ceramic substrates are designed at a cutoff frequency of 1.8 GHz. This compact, low-loss, sharp cutoff-frequency response, and broad-stopband lowpass filter should be useful in many wireless communication systems.