Two-Dimensional Planar Array for Digital Beamforming and Direction-of-Arrival Estimations

A compact uniplanar design of 2-D antenna arrays is presented for digital beamforming (DBF) and direction-of-arrival (DOA) estimations. The array is based on switchable microstrip slot antennas that are series fed in one dimension and parallel fed in the other dimension. In conjunction with spatial multiplexing of local elements (SMILE) techniques, the array is able to use both the series- and parallel-fed antennas for 2-D beamforming and DOA estimations. The combination of series and parallel feeding provides a simple way of constructing 2-D DBF arrays with a simple and uniplanar feed network. Other advantages are its low cost and compatibility with a microwave integrated circuit process for the receiver system. A 4 $times$ 4 receiving array test bed at a 5.5-GHz operating frequency is fabricated, and DBF and DOA tests on this test bed are successfully demonstrated.