A Novel Technique in Simplifying the Fabrication Process and Improving the Reflection Coefficient of the Linear Polarized Radial Line Slot Array (LP-RLSA) Antennas

Abstract

A novel technique in simplifying the fabrication process of LP-RLSA antenna as well as improving the reflection coefficient of LP-RLSA antenna is proposed in this paper. This technique utilizes a FR4 board added on the top of the normal LP-RLSA antenna. Theoretically, FR4 dielectric material is able to reduce antenna reflection coefficient since it produces the signal that has a different phase with the propagating signal within the antenna cavity. Moreover, by utilizing the copper part of the FR4 board as the radiating element, the fabrication process can be simplified since the antenna slots can be cut utilizing the simple low cost etching process. In this paper, the theory about how the utilization of the FR4 board can improve the reflection coefficient response is explained. The parameters that influence the capability of FR4 board in improving the reflection coefficient response are also discussed. A LP-RLSA antenna with FR4 board and a LP-RLSA antenna without FR4 board are designed and simulated at frequency of 5.8 GHz. The simulation result shows that the thickness and permittivity values of FR4 board influence the reflection coefficient response and the antenna gain. The best values of the permittivity and thickness of the FR4 board are 4.3 and 1.6, respectively. The simulation result shows that these values can improve antenna gain up to 2.45 dB. They can also improve reflection coefficient response significantly from –3 dB to –25 dB. It is discovered that the LP-RLSA with FR4 board also produces the beamsquint effect from –10° up to 10° from the boresight direction. The prototype of the designed antennas is fabricated and measured. The measurement and simulation results show that the LP-RLSA with FR4 board has a better gain and better reflection coefficient than the LP-RLSA without FR4 board, thus prove the concept of the novel technique.