Measurement and analysis of miniature multilayer patch antenna

Although the microstrip patch antenna has a number of advantages such as low-cost and light weight, its physical size is quite large at low microwave frequencies. In this paper, the designs of multilayer miniature patch antennas with coaxial feed are presented. The first design is a rectangular two-layer patch antenna. Both measured results and results of a preliminary analysis are presented. The projection area of the two-layer patch antenna is kept the same as the single-layer rectangular patch antenna. The resonant frequency of the two-layer antenna is reduced by 50% and has bandwidth of 5%, which is wider than the single-layer rectangular patch antenna. In the second design, the upper patch is cut into a bow-tie shape. This results in a 60% reduction in resonant frequency and a 12% bandwidth. Both the two-layer rectangular and the two-layer bow-tie antennas have good radiation patterns, with cross-polarization level lower than the copolarization level by more than 20 dB.