Microstrip Magnetic Monopole Endfire Array Antenna With Vertical Polarization

A new microstrip endfire array antenna with vertical polarization is proposed in this paper. The novel array element consists of two symmetrical rectangular patches on both sides of a substrate with two edges shorted and other edges opened. We use a cavity model to analyze the mechanism of the array element, which we find can work as a “magnetic monopole antenna.” The magnetic current on the open sides, which features quarter cycle sinusoidal variation, generates a tilted monopole-like radiation pattern. The tilted angle can be easily determined by the length-to-width ratios of the magnetic monopole antenna. A two-element endfire array and a four-element endfire array are proposed here to achieve endfire vertical polarization with a very low profile (3 mm). The two-element endfire array has a bandwidth from 2.42 to 2.48 GHz and a peak endfire gain of 5.3 dBi. With four array elements, the peak endfire gain can be enhanced to 7.7 dBi in a bandwidth from 2.40 to 2.48 GHz.