An orthogonal beam-forming network (BFN) is proposed for 4G pattern-diversity applications. Different from the traditional Butler beam-forming networks with 2N orthogonal beams, the orthogonal BFN, composed of three 180° hybrids and a 90° phase shifter, provides three orthogonal beams. Design procedure of the orthogonal BFN based on the factorization of its transmission matrix is derived. Moreover, in order to implement the proposed orthogonal BFN with low insertion loss, a rat-race has been used to realize unequal power distribution between its two output ports. The measured scattering parameters of the orthogonal BFN are compared with the analytical and the simulated scattering parameters, validating the expected behavior. In addition, by varying the output power ratio of the non-equi-amplitude 180° hybrid, the performance of the orthogonal BFN is improved when the proposed orthogonal BFN is used in an antenna array.
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