Wideband Stripline Directional Coupler design

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Kertész József
Department of Broadband Infocommunications and Electromagnetic Theory

The oldest microwave systems used waveguides, symmetrical lines and coaxial cables to transfer information and electromagnetic waves. In practice these structures had many disadvantages such as the robust waveguides, the unshielded copper wires, and they needed serious design considerations to produce these. Because of the robust and large elements they were hard to connect with integrated circuitry.

The first planar waveguides were developed during World War II, sterner development begun around the 1950's. First stripline structures were used, which can be described as a near flat coaxial cable.

I made my thesis at Bonn Hungary Electronics Ltd. The company is specialized at making microwave instruments, and they needed a 10 dB coupler in the mobile-communication band with a given structure. My project laboratory work played a big role in selecting this topic. I designed a VSWR-meter and the directional coupler attached before my circuitry got my attention.

In the first chapter of my thesis, I describe what a directional coupler really is, describe the analysis of such device.

In the second chapter, I lead you through the simulation part of my work, describing the usage of the Microwave Office software. I explain the basic difference between the two main simulation modes (linear and electromagnetic) and the usage of the optimization methods.

The third chapter of this paper will be of the results of the manufactured directional coupler. I explain why some errors (if any) occurred, and also expose the reasons why these could have happened.


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