A High-Gain Antenna Based on Ultrathin Planar-Feed Air-Filled Resonant Cavity

This paper presents the antenna characteristics of the high gain and low-profile planar configuration at 10 GHz. The antenna structure is based on a 3-D air-filled cavity between parallel surfaces consisting of a square patch array and perfect ground conductor. The patch array behaves as a partially reflective surface to interact with a perfect conductor plane in order to control a reflection-phase response. Its property enables a resonant transmission associated with a metamaterial by applying the electromagnetic image theory. The narrow aperture source was embedded into a perfect ground conductor fed by a short-end coplanar waveguide (CPW) as a driven radiator. The patch array and planar CPW-fed aperture are patterned on an μm-thin liquid crystal polymer (LCP) film to form a resonant cavity antenna. The overall thickness of the proposed antenna is ~1.0 mm with respect to ~λ/30. The radiation aperture of ~55×55 mm² corresponds to ~1.83×1.83λ² for the effective antenna structure. The investigation shows that the effect of a finite-size lateral structure of 4×4 unit cell was observed for enhanced gain and radiation response. That of the proposed cavity antenna results the directive characteristics of 13.7 dBi which is useful for telemetry applications.

I. Introduction

The sub-wavelength resonant cavity antenna (RCA) has played an essential role in an antenna research community in order to enhance the directive radiation and gain performance. Its advantage is a low-profile antenna configuration that is applied instead of using an antenna array with the complicated feeding network to their antenna elements. The RCA configuration is usually formed by one cavity structure and single source radiator such as an aperture and patch resonant element. The existing cavity antennas can be shaped by paralleling two specific surfaces (planar structure) of a partially reflective surface (PRS) and perfect electric conductor (PEC) or artificial magnetic conductor (AMC) [1][2]. The optic ray approach is used to analyze the interaction with a reflection phase in a resonance distance. The analysis of the cavity distance is also associated with the Fabry-Perot (FP) resonator to figure out the two-surface separation. The two novel types of the PRS superstrates (act as a radiation aperture) consisting of the dielectric slab [3] and metallo-dielectric inclusion or frequency selective surface (FSS) [1][2]. The half-wavelength (λ/2) cavity creation can be formed by tailoring a quarter-thickness dielectric layer or particular FSS placing above a PEC surface. Moreover, the existing quarter-wavelength (λ/4) cavity configuration can replace the PEC surface with an AMC structure. In order to overcome the thin-profile cavity structure, the physical patterns both the PRS and AMC surfaces are able to modify for an arbitrary phase response of that the reflection property can deal with a phase difference in a small cavity distance [4]-[11]. The ultrathin RCA designs have been presented utilizing a multi-layer structure as an AMC-PRS inclusion of the complementary patterned array (patch- and mesh-type metallic surfaces) on a dielectric material slab. The formation of the AMC structure with a primary antenna was proposed by applying a high impedance profile. However, the overall height of their antenna designs increases due to the PRS and AMC thickness assembled consisting of multi-layer patterned arrays. In addition, it has a lot of the physical design parameters of metallic array patterns in a design process.