Design and implementation of an aperture coupled microstrip power divider for array antennas

Abstract

Power divider circuits are used in radio/microwave frequency applications to split an input signal over two or more output signals with equal or unequal amplitude or phase. Effective design of power dividers is crucial to minimize the dimensions and losses of microwave systems, such as antenna feeders, especially for large phased array antennas. Wilkinson and Gysel are among the popular power dividers and are often implemented using microstrip circuits to achieve minimal insertion loss, high isolation between output ports and exceptional phase and amplitude balance. But to use them in recent multilayer devices such as laminated multi-chip modules, vertical transitions are needed to distribute the input and output ports in different layers. However, the use of these transitions increases the insertion loss of the power divider and limits the operational bandwidth. In this research work, a stacked aperture coupled microstrip power divider is proposed which is compatible with multilayer technology. The basic idea is to use multilayer rectangular resonant patches coupled via rectangular apertures in the common ground planes to excite equal or un-equal in-phase output signals. Design equations are formulated and professional software is to optimize the key characteristics of a power divider, such as: insertion loss, isolation, Internal power dissipation, amplitude and phase balance. Prototypes of the designed equal and unequal 2-way power dividers are fabricated and tested using vector network analyzer. The experimental results from the hybrid power dividers are used to validate the design process of the N-way multilayer power dividers. Prototype of the 4-way power dividers is also designed. Finally, the application of the divider is implemented using 2 x 2 planar arrays on multilayer substrates. The results from both simulation and experiment ascertain the suitability of these power dividers in array antenna application.