Wideband, Electrically Small, Planar, Coupled Subwavelength Resonator Antenna With an Embedded Matching Network

A wideband, electrically small, planar, coupled D-ring subwavelength resonator antenna is presented. Two planar coupled D-ring resonators operating at even mode have been demonstrated experimentally to have a strong coupling to radiation. In this paper, we investigate a novel feeding method of driving the planar coupled D-rings to achieve a wide bandwidth. Dual-mode radiation is observed in the antenna. In one mode, the coupled D-ring driven by the inter-digital monopole acts as a major radiator resonating at a frequency of 1.7 GHz. In another mode, the driving monopole becomes a major radiator capable of resonating at a lower frequency of 1.2 GHz due to an embedded matching network comprised of the D-ring and a meandering line. As a result, the antenna can achieve an impedance bandwidth of 1 GHz-1.7 GHz. The antenna has a size, in terms of ka, of 0.49 to 0.75 over the bandwidth. The efficiency of the antenna is predicted to be very close to the upper bound given by the Chu limit.