An electronically scanning array with closely-spaced antenna elements

The mode-based beamforming concept is applied to develop an electronic scanning array with closely-spaced antenna elements. The major advantage of this approach is that the antenna element spacing of the array can be as small as 0.1lambda without suffering significant performance degradation due to mutual coupling effects. Thus, comparing with traditional array modules, mode-based array modules can be much smaller in size and be more readily integrated into nowadays miniaturized handheld wireless devices. While providing a brief discussion of the background concept, experimental results have been provided to demonstrate and proof the feasibility of this mode-based approach. A compact four-monopole array module including matching networks and the MDN has been fabricated. The orthogonal radiation modes for this particular module have been clearly seen in the measurements. In addition, the beamforming and full 360-degree scanning capability has been demonstrated by using a software-based signal combining technique. The experimental results have provided a strong support to the proposed concept, showing its promising potential for many classical as well as new applications.