New techniques to design performance improved power dividers and directional couplers using the new scattering parameter relations

Abstract

Wide bandwidth provides with several benefits in RF applications such as enabling high data rates for communication applications, enhancing the multi tread avoiding capabilities of the jamming systems, improving the effectiveness of spread spectrum techniques. Operation in a wide bandwidth requires either broadband components or multiple narrow band components together with sophisticated multiplexing methods. There are several trivial methods to increase the bandwidth of the RF components. For instance the bandwidth of a power divider can be increased by increasing the number of sections which directly increases the insertion loss and circuit size, burdening a big trade off for the designer. The methods avoiding such a trade off are life savers in most of the applications. Such methods require new design approaches. This work aims to develop such methods with a special focus on improving the bandwidth and performance of the power dividers and directional couplers. We derive new scattering parameter relations and show that the relations require tricky design guidelines. S-parameter relations for a number of power divider types and directional coupler schemes are investigated. The derived equations have significant usages. One of the equations is used to design the optimal isolation network for the Wilkinson power divider. A number of equations imply a reduction in the number of the optimization parameters in the design of n-section or n-way dividers. Another equation is used to increase the directivity of microstrip directional couplers in a wide bandwidth. Experimental results are presented verifying the theoretical work.