Design of 180-Degree Hybrids with Arbitrary Filtering Response and Power Division Using Coupled Resonators

• Main Authors: Wan-Rou Liu, 劉婉柔
• Other Authors: Ruey-Beei Wu
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/95545734968090543905

碩士 === 國立臺灣大學 === 電信工程學研究所 === 101 === This thesis focuses on integrating a 180° hybrid and bandpass filters into a single device, and establishing a general method to achieve an arbitrary filtering response and power division. To begin with, based on the groundwork for the coupled-resonator filter design, it provides an easier way to synthesize the required coupling coefficients, and the external quality factors. Next, in order to verify that this method is flexible and can be extended for different orders, responses and power division ratios, three examples of 180° hybrids using microstrip resonators are presented. In-phase or out-of-phase response of the 180° hybrid is realized by electric coupling, magnetic coupling, or mixed coupling between adjacent resonators. Its physical dimensions should satisfy the calculated coupling coefficients, and external quality factors. Simulated and measured results agree well with the design specification. In comparison to the conventional rat-race coupler, a size reduction of 65% ~ 80% can be achieved. In addition, the circuit size will be further miniaturized if smaller resonators are adopted. As a result, this method has the advantages of not only reducing the circuit size but also ensuring frequency selectivity. By using the proposed method, SIW filtering 180° hybrids can also be implemented in the LTCC technology. The idea is to arrange all cavities in the same plane, so that no additional transition is required for measurement. According to the field pattern of TE101 mode, two types of planar coupling mechanisms are investigated to fulfill the required phase response of the 180° hybrid. Two Ka-band Chebyshev filtering 180° hybrids with different power division ratios are designed to verify the approach.