A Novel Dual Band Bandpass Filter Using Vertically Coupled Strips and Split Ring Structure

• Main Authors: YuChuan Huang, 黃禹銓
• Other Authors: Wanchu Hong
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/85939696232285661956

碩士 === 國立彰化師範大學 === 電信工程研究所 === 96 === Abstract In this thesis, we propose the new structure of dual-band bandpass filter, design the transmission zero between two passband using coupled resonators, the structure of resonator to composed by two concentric split-ring-resonators (SRRs) has negative permeability. When SRRs placed in concentric form, these have a capacitance between the coupled resonators control the transmission zero. This property has to produce the transmission zero between the two passband which controlled by the gap between two SRRs. By using the vertically coupled structure strips (VCS), the transmit path go through VCS not the substrate, and the VCS has high quality because of low loss tangent of air. In the input part of filter we replace the gap coupling with enhance coupling for the better insertion loss, but the insertion loss still lower then -5dB. And hence using the vertically coupled strip (VCS) line lower the insertion loss to -3dB. In order to make the insertion loss lower than -1dB, we add the ladder structure into the vertically coupled strip line to transmit the signal into the z-direction, the insertion loss is lower than -1dB efficiently. Finally, we design the passband in the 2.4GHz/5.2GHz respectively for the WLAN. Because of the transmission zero between the passband and the characteristic of ring, we have very narrow bandwidth which is what we desired. The fractional bandwidth of passband is 2.8% and 4.8% respectively. The fractional bandwidth of traditional dual-band bandpass filter is about 10%, using the vertically coupled strip structure reduce the bandwidth more than 50%.