A Miniature Non-Uniform Conformal Antenna Array Using Fast Synthesis for Wide-Scan UAV Application

Abstract

To overcome the limited payload of lightweight vehicles such as unmanned aerial vehicle (UAV) and the aerodynamic constraints on the onboard radar, a compact nonuniform conformal array is proposed in order to achieve a wide beamscanning range and to reduce the sidelobes of the planar array. The non-uniform array consists of 7x4 elements where the inner two rows follow a geometric sequence while the outer two rows follow an arithmetic sequence along the x axis. The element spacing along the y axis is gradient from the center as well. This geometry not only provides more degrees of freedom to optimize the array radiation, but also reduces the computation cost when synthesizing the excitation and the configuration of the array for a specific beam pattern. As field cancellation may happen due to the convex and concave features of the non-canonical UAV surface, a fast and low-cost in-house code to calculate the radiation pattern of a large scale conformal array for an arbitrary surface and element pattern is employed to optimize the array structure. As a proof of concept, the proposed array with a total volume of 142x93x40 mm3 is implemented at ISM band (5.8 GHz) using a miniature widebeam single-layer patch antenna with a dimension of 0.12lambdax0.12lambdax0.025lambda. By using the beamforming technique, an active onboard system is measured, which achieves the maximum gain of 21.8 dBi and a scanning range of >50deg and -28deg~28deg with a small scan loss of 2.2 and 0.5 dB in elevation and azimuth, respectively. Therefore, our design has high potential for wireless communication and sensing on UAV.