Dual-Substrate Capacitive Loading for Size Reduction in Shorted Annular Ring Antennas

This communication presents a capacitive loading technique capable of providing significant size reduction in shorted annular ring antennas. Capacitive loading techniques are utilized in many antenna geometries to reduce the size of the radiator. Many such structures generate capacitance between parallel conducting planes. The new loading structure utilizes two separate microwave substrates. One substrate is contained beneath the radiator, and a high dielectric substrate is present between the parallel conductors to increase the capacitive effect. The new loading technique is verified with simulations and measurements with excellent agreement between the two.