Small dual-frequency microstrip antennas

The characteristics of a dual-frequency compact antenna, which uses a rectangular microstrip patch with a shorting pin, are studied. Compared with the conventional rectangular patch antenna, this antenna can achieve both a significant reduction of antenna size and a dual-frequency operation with a single feed. A detailed parameter study is performed. The theoretical analysis is based on the finite-difference time-domain (FDTD) method. The FDTD codes are developed and validated by measurement results. One antenna has been designed and fabricated, and the comparisons between the measured results and the calculated results are provided. The effects of several antenna parameters on two resonant frequencies, frequency ratio, and radiation pattern characteristics of the antenna have been analyzed and compared. Results of return loss are also presented. It is shown that various frequency ratios (2.82–4.23) can be obtained by varying the design parameters of this antenna. Several design curves are also presented.