Contents I. Introduction
Modern Unmanned Aerial Vehicles (UAV) usually carries a large number of surveillance sensors and communication modules for information gathering and surveillance purposes [1]. It requires extensive communications and data transferring between the sensors, such as GPS receiver and accelerometer, and the Ground Base Station (GBS) [2]. Therefore, antenna systems integrated on the UAV device are critical to establish reliable radio communication links. For this application, patch antenna becomes a good candidate due to its simple geometry, low profile and inexpensive cost. In [3], a directional triple band planar antenna is proposed for WLAN/WiMax access point applications. The triple-band planar antenna consists of a top-loaded dipole for the 2.4 GHz band, two shorter pairs of dipoles are for the 3.5 GHz and 5 GHz bands. In [4], the antenna operates at 1.6 GHz and GHz. Modifying the subtending angle of the arc-shaped slot allows tuning of the frequency bands and the band spacing ratio. In [5], a triple band H-shaped slot antenna fed by microstrip coupling is proposed, exciting a monopole mode, a slot mode, and their higher-order modes, to cover GPS (1.575 GHz) and Wi-Fi GHz and GHz), respectively. In [6]–[8], different antennas have been report to realize tri-band (WLAN/WiMax). They were developed for user terminals, such as mobile handsets or laptop computers with omnidirectional and low radiation gain. However, the antenna for UAV application needs wide bandwidth and high gain. In this paper, a tri-band patch antenna design with a capacitive feeding disk and double-layer stacked substrates is presented. It can be mounted on the side of UAV. With using the capacitive feeding disc and stacked substrate, the impedance bandwidths at both frequencies are much improved. It has wider bandwidth than the antenna in [3] and higher gain than the antenna in [5] to fully support the UAV GPS and Wi-Fi communications. Quadrocopter with three antenna communication systems used in the project
