Design of a closed cylindrical beam forming network fed circular array for space diversity applications

A new family of 3D multiple beam forming networks is introduced. They are particularly well adapted for azimuth multiple beam circular array applications as they naturally direct the power related to each beam towards a specific sector of the circular array while providing sufficient overlap between adjacent beams to cover a full 360° azimuth angular range. The general concept is described. Proposed network is characterized by a Gaussian amplitude and coherent distribution. First characteristic is particularly attractive to reduce side love level while the second provides beam pointing stability over a wide frequency range. Performances of this new beam forming network topology are investigated through a specific design used to feed a 20-element circular array antenna generating 10 evenly distributed highly similar beams. Simulation results at 6GHz confirm the potential of this solution at feeding network level with a simple micro-strip technology implementation. Theoretical estimation of expected radiation performances are also described and compared to an equivalent circular array antenna with uniform amplitude distribution.