Single-feed dual-frequency microstrip antenna with two patches

A variety of dual-frequency microstrip antennas have been previously reported. However, it is noted that these dual-frequency designs usually support limited tunable frequency ratios for the two operating frequencies. To provide a very flexible frequency ratio for a single-feed dual-frequency microstrip antenna, the design with two circular patches has also been shown. Such a design, however, uses a relatively complicated matching network between the two patches. We present a new structure of using an inset-microstrip line to simplify the matching network, which makes the present proposed design simpler and easier to be constructed. The proposed design method applied to two rectangular patches has been successfully implemented. The obtained frequency ratio of the two operating frequencies can be flexible, and good dual-frequency performances are also observed. Details of the antenna design and experimental results are presented and discussed.