Radial Multiway Isolated Branch Line Quadrature Couplers: Design and Applications

This article presents a useful concept of multiway fully isolated quadrature branch line couplers. Basic branch line couplers are wellknown, and they find use in many applications, prominent among them is power division/combination. Expanding this classic network to have more than four ports enables the designer to realize multiway fully isolated quadrature couplers. These new networks can be easily used in applications such as power combiners and power sampling with improved performance. This article presents design examples for single-section and multisection couplers with equal and unequal power split, providing design tables and utilization schemes for many useful cases. A novel radial multiway topology is proposed in coaxial technology to demonstrate the potential of the proposed concept. Design examples of coaxial five-way ten-port networks are provided as proofs-of-concept. A radial prototype was fabricated and tested demonstrating measured results that agree well with theoretical predictions.