Short‐Wave Broadband Antenna Based on Composite Loading Technique

In this letter, a broadband antenna is investigated for direction‐finding application. The presented antenna consists of 12 pairs of orthogonal dipoles that can achieve full azimuth coverage. By increasing the distance of the dipoles, the elevation angle of the maximum radiation direction is reduced and the directivity is increased. The directivity increased by up to 2.33 dBi. Instead of the traditional resistive coupling device, a composite coupling device incorporating both an inductor and a capacitor is introduced. This device effectively broadens the operating band of antenna, achieving a VSWR of less than or equal to 1.6 across the 3 ~ 30 MHz range. Additionally, it enhances the lightning protection performance of antenna. The dipoles are vertically arranged and orthogonally placed. The sizes of the antenna are 0.14 λ 0 *0.14 λ 0 ( λ 0 ‐the wavelength corresponding to the lowest frequency). Moreover, a non‐uniform l ‐shaped array is presented, which is composed of five unevenly arranged antenna elements. Non‐uniform array effectively addresses the phase ambiguity issue in direction‐finding application while enhancing the angular resolution of the direction‐finding system. Additionally, the array possesses the capability of sensing signals throughout the entire space and achieves high directivity. A prototype of the antenna was fabricated and measured to verify the simulation results.