Beam upwarping suppression for the horizontal omnidirectional monopole antenna in broad bandwidth by using a composite structure

Abstract

Due to the ground plane effect, the horizontal omnidirectional pattern of the monopole antenna will tilt upwards, thereby affecting the communication quality in the horizontal direction. In this paper, one composite structure (CS) composed of mushroom structures (MSs) and parasitic metal pillar elements (PMPEs) is introduced, loading uniformly around the source antenna (SA) to suppress the beam upwarping. The individual MSs can enhance the current on the ground plane, coupling more electromagnetic energy to the horizontal plane in the band outside the bandgap. Meanwhile, the PMPEs act as directors, guiding the space wave energy along the horizontal plane in a wide band. By using the two structures as one CS together, beam upwarping suppression is realized for the monopole antenna in broad bandwidth. This structure can achieve 4–25° of suppression at 410–522 MHz and 0.97–2.3 dB improvement on the horizontal plane gain, which is much better than the condition when the two structures are loaded alone. The experimental results prove the theoretical analysis. This structure can provide more stable communication for the design of high-performance devices.