Study And Design Of Dual-Band Directional Coupler Based On Broadside-Coupled

In recent years, with the rapid development of mobile communication and wirelesscommunication system, the study and design of multi-band and miniaturized microwavecomponents have become the mainstream trend. So design of multi-band and miniaturizedmicrowave directional coupler, one of the most important elements in the communicationsystem, is a popular topic for researchers. Based on this background, dual-band directionalcouplers using broadside-coupled method have been studied in this thesis in the form ofwaveguide and microstrip, respectively. They have the advantage of compact size, highspace utilization, easy for integration, etc.The main work and innovation can be summarized as:1. Design and implement a multilayer dual-band coupler based on CompositeRight/Left-Handed (CRLH) Folded Substrate Integrated Waveguide (FSIW). The mainwork in this section has three parts:First of all, CRLH structure has been introduced into FSIW and it can generatedual-band characteristic in the waveguide.Secondly, in the common ground wall, rectangular slots have been used forbroadside-coupled, and it can been analyzed by the Bethe small hole theory to obtainarbitrary coupling ratio.Finally, further miniaturization has been achieved when the FSIW structure andbroadside-coupled method are adopted simultaneously.2. Designed and implemented a compact dual-band coupler using broadside-coupledmicrostrip. The novelty includes the following points:First, the coupler has a wide frequency ratio range and arbitrary power dividing ratiowith three-section microstrip used for broadside-coupled.Second, admittance matrix analysis method has been used, which is very simple. Theclosed-form expressions for the even-and odd-mode characteristic admittances areintuitive.Finally, according to the empirical formulas, the analytical expressions for the initial geometry of the coupler can be determined, which is very meaningful for guiding thedesign.