This paper describes the design and realization of an extra high frequency band 8 × 8 microstrip Butler matrix. Operation at 36 GHz is achieved with a frequency bandwidth exceeding 400 MHz. The circuit is implemented on a bi-layer microstrip structure using conventional manufacturing processes. This planar implementation of a Butler matrix is a key component of a switched beam smart antenna with printed antenna elements integrated on-board. Conception details, simulation results, and

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... s are also given for the components (hybrid couplers, cross-couplers, and vertical inter-connections) used to implement the matrix.