An improved performance EHF butler matrix

Multiple beams antenna arrays usually require a beamforming network such as the Butler[1] matrix in order to generate a set of orthogonal beams in space. This kind of circuit can be realized using different transmission mediums such as waveguides and microstrip lines. The latter is particularly interesting since its planar nature makes manufacturing possible using the standard photolithographic process which permits an easy integration of components and a volume production. Microstrip realizations at extra-high frequency (EHF) band are extremely sensitive to the errors introduced in the manufacturing process and other sources. Design strategies should be used to minimize their contribution to performance degradation and a sensitivity analysis prior realization of such a circuit in order to investigate the effects of errors such as etching tolerances is highly recommended.