Microstrip antenna with a height discontinuity (MAHD)

Mobile communication has become an increasingly important part of living due to consumer demand. Antenna technology for mobile systems is continuously evolving with today's mobile antennas necessarily have to be small and efficient; however, antenna size reduction and efficiency improvement tend to not go hand-in-hand. In order to reduce antenna size, there is an increasing focus on electrically small antennas (antennas whose size is much smaller than the wavelength at the operating frequency) as a research topic. Because of the fundamental limitations of electrically small antennas, careful choice of geometry and material properties is required in order to utilize a small available volume efficiently. Microstrip antennas are commonly used for antenna miniaturization because they are lightweight, and can be easily integrated into mobile systems as a part of the circuit board containing other sub-systems.;In this research, an electrically small microstrip antenna with a height discontinuity (MAHD) is proposed for size reduction. A MAHD is formed when the radiating patch spans two substrate heights. This MAHD can alleviate the decreasing radiation efficiency problem of the electrically small antennas. For theoretical analysis of the proposed antenna, a cavity model using mode-matching technique is applied. Variations of the type, location, and ratio of height discontinuity are investigated. A set of MAHDs are designed, manufactured, and tested to validate the theoretical results. Compared to quarter-wavelength microstrip antennas, the size of MAHDs is shown to be reduced for the same operating frequencies. For the proposed MAHD, radiation, conduction, and dielectric quality factors are theoretically computed and the radiation efficiency is evaluated for a set of height discontinuity ratios. The results are compared with simulation from HFSS, a commercially available software based on numerical full-wave techniques. The degradation of radiation efficiency with size reduction is shown to be mitigated.