Design and Analysis of CPW Filters with Slow-Wave and PBG Structures

• Main Authors: Chin-Min Chang, 張志明
• Other Authors: Man-Long Her
• Format: Others
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/g8mg6j

碩士 === 逢甲大學 === 電子工程所 === 90 === In this thesis, the slot-loaded end-coupled resonator CPW bandpass filters have been studied. Results show that by cutting proper number of transverse slots on different positions of the resonators can effectively shift the resonance frequency. It was also found that the interdigitated slot-loaded filter structure has more pronounced effect on resonance frequency due to its longer mode current path. The insertion loss, however, is seen to be less sensitive to the transverse slot. Next, a technique which implements the tapered PBG structures in both the ground plane and the signal strip of a CPW bandstop filter is proposed. The doubly tapered PBG structure can effectively improve the degrading of the stopband rejection of the case when tapered PBG structure exists only in the ground plane. With the additional tapered PBG structure implemented in the signal strip, the stopband rejection and bandwidth can both be increased, while the upper passband loss can still be maintained to an acceptable lower level. For a PBG structure, it usually needs more PBG cells to achieve better passband and stopband characteristics. This results in a relatively larger circuit area. In this work, a novel CPW PBG unit cell is proposed which can provide the bandgap characteristic in some frequency bands, but it needs only one cell or series connection of some cells. The equivalent circuit for the proposed periodic structure is extracted by mean of 3-D field analysis method. The equivalent circuit parameters are extracted by using a simple circuit analysis method. Finally, a CPW bandpass filter combines with the novel CPW PBG cells that can furnish attenuation poles in upper and lower stopband is proposed.