A Broadband Impedance Matching Method for Proximity-Coupled Microstrip Antenna

In a proximity-coupled microstrip antenna, when a laminate used is too thick for the antenna layer, the coupling will be decreased. And it is hard to achieve broadband impedance matching. The authors present a method to optimize impedance matching through narrow cavity backed configuration. A prototype antenna is designed with this method and fabricated. Simulation and measurement results indicate that the bandwidth of the antenna exceeds 40% (VSWR < 2.0). The antenna has a larger effective coupling as compared with the conventional proximity-coupled antenna without the narrow cavity backed configuration. It is easier to enhance the bandwidth with a thicker laminate. Meanwhile, this antenna is benefit for manufacturing and assembling to an array due to its simple configuration.