Miniaturized Flat Archimedean Spiral Antenna

This paper presents the design and tests of a miniaturized flat Archimedean spiral antenna. The antenna has two gold Archimedean spiral arms on the surface of a thick alumina cylinder. This cylindrical substrate has an outer diameter of 1.1 mm and a thickness of 0.52 mm. These reduced dimensions make the presented antenna at least an order of magnitude smaller than any previous planar Archimedean spiral antenna reported in the literature. This small antenna can be used for communication in small devices, wireless power transmission for implantable sensors, microrobots and other micro applications. Despite its reduced size, the antenna has a relatively low resonant frequency, which was measured at 4.9 GHz. The characteristic length of the antenna can be reported as only 0.018λ. The design and simulations of the fundamental parameters of the antenna are presented, showing a uniform radiation pattern. Also, the manufacturing process is described. Seven prototypes of the antenna have been manufactured and their reflection coefficient was measured. The tests showed good agreement with simulations. The repeatability of the measurements and the reliability of the fabrication process are demonstrated.