Dual-Frequency Folded-Parallel-Plate Antenna With Large Frequency Ratio

This communication investigates a new compact dual-frequency antenna with a large frequency ratio, which consists of a pair of folded parallel plates. It integrates the microwave parallel-plate waveguide resonator antenna (WRA) with the millimeter-wave Fabry-Perot resonator antenna (FPRA), with their resonant frequencies independent of each other. Due to the folded structure, the profile of the proposed antenna is lower than that of the conventional parallel-plate WRA. The WRA part is excited by a hook-shaped strip on its top, whereas the FPRA is excited by an L-probe with a half-ring sleeve. To demonstrate the idea, a dual-frequency antenna that covers the 2.4- and 24-GHz ISM bands was designed. ANSYS HFSS was used to simulate the S-parameters, radiation pattern, and antenna gain and reasonable agreement between the measured and simulated results is obtained.