Semi-circular array antennas for DOA-estimation and beamforming

In this contribution, the application of two semi-circular array antennas, consisting of monopoles and microstrip patches backed by a metallic reflector are investigated for smart antenna systems with a wide angular-operating range. The pattern of the monopoles or patches depends upon the respective position in the array. Therefore, and due to the nonlinear arrangement of the elements, a transformation to an alternative manifold is needed prior to the usual signal processing techniques. The investigated transformations are based on the least-mean squares solution of an over-determined set of equations and they already include the calibration, in the case of measured data. The transformation is successfully applied to theoretical and measured array steering vectors within a predefined angular-operation range of 78°.