Modified Microstrip Lines with Low Impedance and Enhanced Coupling for Applications in Passive Circuits

• Main Authors: Liang, Cheng-Hsien, 梁正憲
• Other Authors: Chang, Chi-Yang
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/51215576290804090644

博士 === 國立交通大學 === 電信工程研究所 === 99 === This dissertation first proposes a novel low-impedance microstrip line structure. By inserting ground strips inside the conventional microstrip line, the characteristic impedance of the microstrip line can be controlled by the signal and ground strips in a coplanar manner. Compared to the conventional microstrip line with the same transverse width, the effective capacitance of the microstrip line increases so that the characteristic impedance decreases. The decreasing amount is particularly large for the thick substrate. In addition, we also insert signal strips in the microstrip ground plane to further decrease the characteristic impedance. The low-impedance microstrip line is applied in the quarter-wavelength stepped-impedance resonator. The designed filter can be insensitive to fabrication tolerances and have a smaller size and a wider upper stopband. Then, we propose several coupled microstrip line structures which can provide strong coupling. These tight-coupling structures are used to design miniaturized wideband bandpass filters and single- and multi-section 3-dB directional couplers. Although the proposed circuits need more via-holes, they can be easily fabricated on a single-layer substrate by the conventional printed circuit board (PCB) process with low cost.