Evolutionary Generation of Subwavelength Planar Element Loaded Monopole Antenna

A very compact monopole antenna with an evolutionarily generated subwavelength planar element is proposed for the antenna miniaturization without using any lumped capacitors and inductors. The monopole antenna is composed of a coaxial-fed short line etched on one side of dielectric substrate and a subwavelength element on the other side, enabling an easy fabrication using a printed circuit technology. To design the arbitrarily shaped subwavelength element, an efficient genetic algorithm (GA) design technique is employed. As a design example, a monopole antenna with 1/23-wavelength height and 1/17-wavelength width at 430 MHz is demonstrated. The predicted results of the radiation pattern and the reflection characteristic are compared to measured data, and good agreement between the two results is achieved.