A cavity-backed antenna loaded with complimentary split ring resonators

This paper presents a high gain antenna with a nearly unidirectional radiation pattern. The antenna is composed of concentric complementary split ring resonators (CSRRs) that radiate at different frequencies as determined by the circumference of each ring slot as well as the mutual coupling between them. The antenna is optimized for operation at 2.45 GHz, which is one of the frequencies commonly used for body-worn communication devices. It is found that the concentric CSRRs behave like a filter in the radial direction and prevent surface currents from reaching the edges of the ground plane resulting in broadside radiation. The antenna shows a return loss of higher than 25 dB in both measurement and simulation. The front-to-back ratio (FTBR) is improved by backing the ring slots with a metallic rectangular cavity yielding FTBR of 21.2 dB and gain of 7.87 dB in measurements. The achieved radiation characteristics prove that the designed antenna is a good potential candidate for body-worn communication devices, where human body exposure to radiation must be minimal.