Design of Miniaturized Substrate Integrated Coaxial Line Bandpass Filters with Quarter-Wavelength Spiral Resonator

摘要

In this article, several miniaturized bandpass filters (BPFs) with substraternintegrated coaxial line quarter-wavelength spiral resonators were proposed. The couplingrncoefficients and external quality factors of proposed structures were examined by using therncommercial simulation software. With different combinations of the proposed resonators,rnthree two-order and two high-order miniaturized BPFs operating at 1.2 GHz with 3-dBrnfractional bandwidth of 8% were designed, fabricated, and measured. The measured resultsrnshowed that all the return losses were better than 10 dB over the entirely passbands, andrnthe overall circuit sizes of two-order and high-order BPFs were only 0.044λ_0 ×0.028λ_0 andrn0.047λ_0 × 0.047λ_0, where λ0 is the wavelength in free space at the center frequency of thernpassband. Good agreements were observed between the simulated and measured results.