A new type of metallic electromagnetic structure has been developed that is characterized by having high surface impedance. Although it is made of continuous metal, and conducts dc currents, it does not conduct ac currents within a forbidden frequency band. Unlike normal conductors, this new surface does not support propagating surface waves, and its image currents are not phase reversed. The geometry is analogous to a corrugated metal surface in which the corrugations have been folded up into lumped-circuit elements, and distributed in a two-dimensional lattice. The surface can be described using solid-state band theory concepts, even though the periodicity is much less than the free-space wavelength. This unique material is applicable to a variety of electromagnetic problems, including new kinds of low-profile antennas.

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High-impedance electromagnetic surfaces with a forbidden frequency band

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

Dual-printed inverted-F antenna diversity systems for terminal devices operating at 5.2 GHz under both switched and combining schemes are presented. Diversity performance is evaluated by means of the calculated envelope correlation coefficient, the mean effective gain and the effective diversity gain of the two antennas. An investigation into the effect of the antennas' placement and of the corrugated ground plane on the performance of the system has also been conducted. It is shown that many configurations can provide uncorrelated signals of the same power level, but with significantly different radiation pattern complementarity, antenna efficiency, and effective diversity gain.

Compact dual-printed inverted-F antenna diversity systems for portable wireless devices

A novel dual polarized ultrawide-band (UWB) feed with a decade bandwidth is presented for use in both single and dual reflector antennas. The feed has nearly constant beam width and 11 dBi directivity over at least a decade bandwidth. The feed gives an aperture efficiency of the reflector of 66% or better over a decade bandwidth when the subtended angle toward the sub or main reflector is about 53/spl deg/, and an overall efficiency better than 47% including mismatch. The return loss is better than 5 dB over a decade bandwidth. The calculated results have been verified with measurements on a linearly polarized lab model. The feed has no balun as it is intended to be integrated with an active 180/spl deg/ balun and receiver. The feed is referred to as the Eleven antenna because its basic configuration is two parallel dipoles 0.5 wavelengths apart and because it can be used over more than a decade bandwidth with 11 dBi directivity. We also believe that 11 dB return loss is achievable in the near future.

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The eleven antenna: a compact low-profile decade bandwidth dual polarized feed for reflector antennas

A 4 $\,\times\,$ 4 L-probe patch antenna array using multilayer low temperature co-fired ceramic (LTCC) technology is presented for 60-GHz band applications. The proposed antenna array is designed with a high gain in the impedance bandwidth by introducing a novel soft-surface structure. The soft-surface structure comprised of metal strips and via fences reduces the losses caused by severe surface waves and mutual coupling between adjacent elements to improve the radiation performance. The proposed antenna array is convenient for integrated applications. The fabricated antenna array excluding the measurement transition has dimension of 14.4 $\,\times\,$ 14.4 $\,\times\,$ 1 mm $^{3}$ . The simulated and measured impedance and radiation performance are studied and compared. Good agreement is achieved between simulation and measurement. The proposed antenna array shows a wide simulated impedance of 29% from 53 GHz to 71 GHz for $\vert {S}_{11}\vert dB, measured broadband 3-dB gain bandwidth of 18.3% from 54.5 GHz to 65.5 GHz and the gain up to 17.5 dBi at 60 GHz, respectively.

Wideband High-Gain 60-GHz LTCC L-Probe Patch Antenna Array With a Soft Surface

The paper presents a study of some elementary antennas, such as a dipole, a waveguide aperture, a microstrip patch, a spiral and a helix, when they are mounted on a ground plane with circular corrugations acting as a soft surface. The results of both experiments and calculations are described. The latter have been done either by the uniform geometrical theory of diffraction (UTD) or by the moment method (MM), and are in good agreement with the measurements. It is found that the corrugated soft ground plane makes the radiation patterns of all the antennas more rotationally symmetric with lower sidelobe levels and lower crosspolarisation when compared to using a smooth conducting ground plane.

Improvements of dipole, helix, spiral, microstrip patch and aperture antennas with ground planes by using corrugated soft surfaces

A compact flare angle controlled corrugated horn antenna with a 60° half beamwidth is optimised by using a moment method for bodies of revolution. The horn has corrugations with simple rectangular cross-sections and is excited by a smooth wall circular waveguide. The resulting 15 dB beamwidth varies by <18% and the crosspolar sidelobe levels are more than 26 dB below the mainlobe, both over a 1.8:1 bandwidth. All results are confirmed by measurements. The horn is suited for broadband feeding of e.g. prime-focus reflectors in radio astronomy applications.

Broadband compact horn feed for prime-focus reflectors

We study a vertical monopole on a circular metallic disk which is loaded in different ways to provide a soft boundary condition, e.g., by transverse corrugations or by dielectric or lossy material coatings. The different realizations are calculated by the uniform geometrical theory of diffraction (UTD), the incremental theory of diffraction, the moment method (MM) with an impedance boundary model, and MM using equivalent currents on all material interfaces. The calculated results are compared with measured results for specific geometries. Some general characteristics of the different realizations of the soft surfaces are extracted from the results. It is verified that the artificially soft boundary condition can be realized by different surface loadings. In particular, a nearly soft boundary condition can be realized over a large bandwidth by coating a conductor with a thin layer of lossy magnetic material. It is found that the surface impedance model works very well for modeling corrugations. It may also work for material coated surfaces provided the surface wave is prohibited from radiating. The bandwidth of the different soft surfaces are given, including corrugations with different cross-sectional shapes.

Study of different realizations and calculation models for soft surfaces by using a vertical monopole on a soft disk as a test bed

The authors investigate the use of soft surface, ie, a corrugated ground plane, to replace the smooth conducting disk of the Kraus helical antenna It is shown that the sidelobe level and the cross-polarization can be improved compared to using a smooth disk The same improvements are obtained by only corrugating the outer part of the disk The return loss is almost identical to that obtained by a smooth conducting disk The improved helical antenna with a soft corrugated disk is an attractive cheap feed for a primary-fed reflector or dual-reflector antenna This improved model can also be used as an element in an array The reduced sidelobe in the ground plane surface direction will also reduce the mutual coupling >

Reduced sidelobes and cross-polarization of axial mode helix using a soft corrugated ground plane

It has been demonstrated that polarization-independent soft surfaces in electromagnetism can be realized artificially in several ways, e.g., by using corrugations, strip loaded dielectric slab, or lossy or anisotropic material coating. The frequency response of various artificially soft surfaces is investigated by both moment method computations and experiments. It is shown that the bandwidth of a corrugated surface can be increased significantly by cavity loading or strip loading. The tilted corrugations have a smaller bandwidth than the conventional corrugations. The dual depth corrugated surfaces must be designed with widely separated bands, and soft surfaces realized by dielectric loading has a smaller bandwidth than when realized by corrugations.

Zhinong Ying

Papers

Improvements of dipole, helix, spiral, microstrip patch and aperture antennas with ground planes by using corrugated soft surfaces

Broadband compact horn feed for prime-focus reflectors

Study of different realizations and calculation models for soft surfaces by using a vertical monopole on a soft disk as a test bed

Reduced sidelobes and cross-polarization of axial mode helix using a soft corrugated ground plane

Bandwidth of some artificially soft surfaces