Design of electrically small planar antennas using inductively coupled feed

A class of electrically small planar antennas with an inductively coupled feed structure is proposed. The antennas are optimised using the Pareto genetic algorithm. These antennas are self-resonant and capable of good efficiency and bandwidth performance without any additional matching networks. Several prototypes are fabricated and measured and the results agree well with simulation. A lumped element circuit model is presented to explain the operating principle of these antennas.