Preface 1. Introduction 2. FDTD Method for periodic structure analysis 3. EBG Characterizations and classifications 4. Design and optimizations of EBG structures 5. Patch antennas with EBG structures 6. Low profile wire antennas on EBG surfaces 7. Surface wave antennas Appendix: EBG literature review.

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Electromagnetic Band Gap Structures in Antenna Engineering

The concept of surface wave antennas (SWA) was initiated in the 1950s [1–2] and numerous theoretical and experimental investigations have been reported in the literature [3–10]. To support the propagation of surface waves, a commonly used structure in SWA designs is a corrugated metal surface. However, the corrugated structure is thick, heavy, and costly, which may limit the applications of surface wave antennas in wireless communication systems. In this chapter, novel surface wave antennas are presented. Compared to traditional SWA designs, surface waves are now guided along a thin grounded slab loaded with periodic patches, resulting in a low profile conformal geometry. In contrast to the previous wire-EBG antennas or patch antennas that radiate to the broadside direction, the proposed SWA achieve a monopole-like radiation pattern with a null in the broadside direction. The low profile SWA is more attractive than a traditional monopole antenna that is a quarter-wavelength high. A grounded slab loaded with periodic patches Comparison of two artificial ground planes We start with analyzing a complex artificial ground plane, which will be subsequently used in surface wave antenna designs. Figure 7.1 shows two artificial surfaces: a mushroom-like EBG surface and a grounded dielectric slab loaded with periodic patches. In the latter structure vertical vias are removed, which results in different surface wave properties in the two ground planes. To compare the electromagnetic properties of these two structures, the finite difference time domain (FDTD) method is used to simulate their performance [11–12].

Electromagnetic Band Gap Structures in Antenna Engineering: Surface wave antennas

This paper presents a novel surface-wave antenna that realizes a low-profile configuration using a thin patch-loaded grounded slab, which has an in-phase reflection coefficient for plane waves, but no band gap for surface waves. When a dipole antenna is horizontally positioned near this artificial ground plane, it works like a transducer that converts the energy from the feeding probe into surface waves in the ground plane. The propagation and diffraction of the surface waves generate a monopole-type radiation pattern. The attractive antenna height, which is less than 10% of a typical monopole antenna, is desirable for wireless-communication systems. The performance of the surface-wave antenna is demonstrated through both the FDTD simulations and the measured results. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 240–245, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21136

A novel surface-wave antenna design using a thin periodically loaded ground plane

This paper presents a low-profile log-periodic monopole array antenna with end-fire radiation and vertical polarization. It consists of 15 monopole elements and a conductor-backed coplanar strip line as the feeding line. The monopoles are of the same height but loaded with top hats of different sizes to achieve the required resonant frequencies. A wideband transition from coaxial line to conductor-backed coplanar strip line is designed for the antenna feed. A prototype is fabricated and tested. Measured results show that an impedance bandwidth from 1.5 to 6.8 GHz (4.53:1) for $\text{VSWR { and a gain better than 4.5 dBi over the same operating frequency band are obtained while the antenna has a very low profile of only $0.047\;\lambda_L$ ( ${{{\lambda}}_L}$ is the free-space wavelength at the lowest operating frequency).

Low-Profile Log-Periodic Monopole Array

A novel patch-fed surface wave antenna (PFSWA) that realises a monopole-like radiation pattern with an attractive low-profile configuration is presented. The surface wave antenna consists of a thin grounded dielectric slab loaded with periodic square patches, which is designed to support the propagation of surface waves, and a centre-fed circular patch, which is used to excite the surface waves. The diffraction of surface waves at the edge of the ground plane generates a monopole-like radiation pattern (both in pattern shape and polarisation state). The radiation mechanism and performance of the PFSWA are described, and parametric studies are performed to understand the radiation characteristics of the PFSWA. An antenna prototype with only 3 mm thickness (<0.05lambda) is fabricated and tested, which resonates at 4.74 GHz with a 5.6% impedance bandwidth and a 5.6 dBi gain. The low-profile PFSWA has a great potential for modern wireless communications such as vehicle radio system

Low-profile patch-fed surface wave antenna with a monopole-like radiation pattern

The existence of a surface wave which propagates across a corrugated metallic surface at an oblique angle with the teeth is investigated both experimentally and theoretically in this paper. Expressions are derived which give the variation of the wave velocity and amplitude with the change of wave direction. Experimentally measured values of the surface velocity compare favorably with the theory. The radiation pattern of an experimental antenna is given which demonstrates that a low sidelobe, narrow azimuth beam scannable to \pm30 degrees with a cosecant-squared elevation pattern is attainable. A method of feeding this antenna to give a low silhouette, making the corrugated scanner antenna suitable for flush mounted applications is illustrated.

R. Hougardy

Papers

Scanning surface wave antennas--Oblique surface waves over a corrugated conductor