A design of bi-directional and low-profile antenna using microstrip element

Abstract

A low profile antenna using microstrip element that has vertical polarization and bi-directional beam pattern is designed and measured. Vertically polarized antennas have been used in various applications such as mobile stations. However, the dimension tends to be high as like monopole antennas. Capacitive-disk loading is a well-known technique, however, such antennas have still omnidirectional radiation pattern. In some applications, omnidirectional radiation pattern is not necessary but relatively high gain is required. Furthermore, using low-profile antennas are required, for especially car, from a view point of design. In this paper, the authors would like to propose a low-profile monopole antenna with bi-directional radiation patterns having a simple structure. The proposed antenna consists of a microstrip element and capacitive patch-loaded monopole antenna. Furthermore, the design process of the antenna is also presented in this paper. The proposed antenna resonating at 10 GHz were fabricated and measured. As a result, the proposed model has the desired frequency besed on the design process discussed and bi-directional beam patterns. The proposed antenna has only about 3.2mm thickness and an antenna gain of 4.3 dBi at 10 GHz. However, some side-lobes still exist in the radiation pattern. We would like to present some additional idea for solving this problem. Probably the design and the mechanism is unique and interesting even though the structure is simple.