14. Compact Topologies of Microstrip Ring Coupler

Today, due to the rash development and increasing complexity of radio engineering devices operating in the microwave range, they are subject to increasingly stringent requirements to reduce the dimensions of which limit their use in complex radio engineering systems. Moreover, miniaturized devices must have characteristics at least as those of full-sized devices. There are matching circuits including a microstrip ring coupler, among them. Therefore, the task of optimizing their design in terms of minimizing the geometric dimensions is important. The purpose of this work is to develop a miniaturized microstrip ring coupler by using a simple and effective way, not burdened with the necessity of additional mathematical calculations. In this connection, the research problem is to choose a suitable method and its applicability justification, and the comparison of developed designs with conventional topology. The paper proposes a technique based on bending the microstrip lines it is composed of. Comparative characteristics of electric lengths of straight microstrip lines and those of the bent microstrip line are provided. Designs of several developed topologies are given. The procedure of reasoning and the process of obtaining the final topologies are described in detail. A computer simulation is carried out. S-parameter dependencies obtained by computer simulation are presented. It was possible to reduce the initial construction area by 81.8% with reduction of operating frequency band by 7%.