A dual-frequency small microstrip antenna

A novel dual-frequency compact antenna, which uses an H-shaped microstrip patch loaded with shorting pins, is proposed and studied. This antenna can achieve both a significant reduction of antenna size and a dual-frequency operation with a single feed. More freedom for tuning the resonant frequencies, the ratio of two resonant frequencies, and the input impedance is available due to more design parameters. A detailed parameter study is performed and the theoretical analysis is based on the finite-difference time-domain (FDTD) method. The effects of several antenna parameters on two resonant frequencies, frequency ratio, and radiation pattern characteristics of the antenna are analyzed and compared. It is shown that various frequency ratios (1.91-4.23) can be obtained by varying the design parameters of this antenna. Several design curves are presented.