Miniaturized Dual-band Bandpass Filters Using Stepped Impedance Resonators

摘要

Based on the synthesis of dual-passband filter (DPBF) with frequency transformation technique, λg/4 type SIR coaxial harmonic unit is introduced in the design of DPBFs by using the basic principle of stepped impedance resonators, whereafter two miniaturized coaxial DPBFs respectively have inline and cross-coupling topology are designed. As compared to the traditional coaxial filters with λg/4, the proposed dimension is reduced almost 50%. The simulation results show that both in-band return losses of two pass-bands were higher than 18 dB, while insertion loss was lower than 0.1 dB with its good attenuation characteristic between two passbands, in addition, the DPBF with cross-coupling can generate two transmission zeros in the insertion loss response, which fully satisfies the requirements of miniaturization, low insertion loss, high selectivity in communication systems. So it can be widely used in dual-frequency communication systems.