This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

This review of array antennas highlights those elements of theory and hardware that are a part of the present rapid technological growth. The growth and change in array antennas include increased emphasis on "special-purpose" array techniques such as conformal and printed circuit arrays, wide angle scanning arrays, techniques for limited sector coverage, and antennas with dramatically increased pattern control features such as low sidelobe, adaptively controlled patterns. These new topics have substantially replaced large radar arrays in the literature and constitute a major change in the technology. The paper presents a tutorial review of theoretical developments emphasizing techniques appropriate to finite arrays, but indicating parallel developments in infinite array theory, which has become the useful tool for analysis of large arrays. A brief review of the theory of ideal arrays is followed by a generalized formulation of array theory including mutual coupling effects, and is appropriate to finite or infinite arrays of arbitrary wire elements or apertures in the presence of a conducting ground screen. Some results of array tolerance theory are summarized from the literature and retained as reference throughout discussions of array component requirements and device tolerance for low sidelobe arrays. Examples from present technology include conformal and hemispherical coverage arrays, lightweight printed circuit arrays, systems for use with reflectors and lenses in limited sector coverage applications, and wide-band array techniques.

Phased array theory and technology

Wearable antennas have gained much attention in recent years due to their attractive features and possibilities in enabling lightweight, flexible, low cost, and portable wireless communication and sensing. Such antennas need to be conformal when used on different parts of the human body, thus need to be implemented using flexible materials and designed in a low profile structure. Ultimately, these antennas need to be capable of operating with minimum degradation in proximity to the human body. Such requirements render the design of wearable antennas challenging, especially when considering aspects such as their size compactness, effects of structural deformation and coupling to the body, and fabrication complexity and accuracy. Despite slight variations in severity according to applications, most of these issues exist in the context of body-worn implementation. This review aims to present different challenges and issues in designing wearable antennas, their material selection, and fabrication techniques. More importantly, recent innovative methods in back radiations reduction techniques, circular polarization (CP) generation methods, dual polarization techniques, and providing additional robustness against environmental effects are first presented. This is followed by a discussion of innovative features and their respective methods in alleviating these issues recently proposed by the scientific community researching in this field.

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Wearable Antennas: A Review of Materials, Structures, and Innovative Features for Autonomous Communication and Sensing

The simultaneous improvement in radiation and scattering performance of an antenna is normally considered as contradictory. In this paper, wideband gain enhancement and radar cross section (RCS) reduction of Fabry–Perot (FP) resonator antenna are both achieved by using chessboard arranged metamaterial superstrate (CAMS). The CAMS is formed by two kinds of frequency-selective surfaces. The upper surface of CAMS is designed to reduce RCS based on the phase cancellation principle, and the bottom surface is used to enhance antenna gain on the basis of FP resonator cavity theory. Both simulation and measured results indicate that compared with primary antenna, the gain of the proposed FP resonator antenna is enhanced by 4.9 dB at 10.8 GHz and the 3 dB gain bandwidth is from 9.4 to 11.1 GHz (16.58%). Meanwhile, the RCS of the proposed FP resonator antenna is reduced from 8 to 18 GHz, with peak reduction of 39.4 dB. The 10 dB RCS reduction is obtained almost from 9.6 to 16.9 GHz (55.09%) for arbitrary polarizations. Moreover, the in-band RCS is greatly reduced, owing to the combined effect of CAMS and FP resonator cavity.

Wideband Gain Enhancement and RCS Reduction of Fabry–Perot Resonator Antenna With Chessboard Arranged Metamaterial Superstrate

Fabry-Perot cavity antennas, while offering design simplicity and high directivity, are promising candidates for microwave and millimeter wave communication links. Recommendations for effectively truncating the 1-D/2-D periodic structures, designed to act as superstructures in such antennas, are presented. It is shown that the aperture size in such antennas contributes, in part, towards the directivity-bandwidth product. A simple Fabry-Perot cavity antenna which uses a two layered 1-D Electromagnetic Band Gap (EBG) structure as its superstructure is studied to quantify the effects of aperture size on peak directivity and half-power directivity-bandwidth. Conventional aperture size for such antennas ranges from 5-6λ02, which results in over-dimensioning as well as narrowband behavior. It is shown that comparable performance with existing designs can be achieved by using much smaller aperture sizes and thus reducing the antenna footprint. This work serves as a guide to effectively choose and fine-tune aperture sizes for Fabry-Perot cavity antennas, thus reducing the redundant computational load in the full-scale design process.

Effect of truncating the superstructures in broadband Fabry-Pèrot cavity antennas

A low profile, wideband resonant cavity antenna (RCA) is presented. It uses a simple and planar wideband feed antenna. The use of this planar, printed feed antenna reduces the overall height of the RCA. The RCA has a single-layer superstrate, which has radially non-uniform permittivity in the transverse plane. Excellent wideband matching was obtained for the RCA with a −10dB return loss bandwidth ranging from 20.81 to 25.32 GHz. Numerical results predict a peak boresight gain of 16.97 dBi. This RCA is well-suited for scalable RCA configurations such as sparse arrays or switched-polarization arrays with printed feed networks.

A planar feeding technique for wideband, low-profile resonant cavity antennas

In this paper the suitability and effectiveness of transparent conductive fabric for design and realization of transparent wearable antennas is studied. In contrast to the other expensive and non-flexible transparent conducting materials, transparent conductive fabric is an effective alternative for the realization of flexible transparent antennas. When embedded in polydimethylsiloxane (PDMS) this fabric becomes mechanically robust against repeated bending which is a requirement for many wearable devices. The performance of the transparent conductive fabric embedded in PDMS is evaluated for the wearable antenna application by fabricating a simple patch antenna operating at 2.45 GHz and testing its performance. The antenna prototype has been fabricated by using transparent conductive fabric VeilShield to form the conducting parts including the radiating element and PDMS as the substrate and encapsulation. Experimental investigations of the antenna demonstrate the applicability of the proposed material for the realization of transparent wearable antenna through a simple and inexpensive fabrication process.

Feasibility Study of PDMS Embedded Transparent Conductive Fabric for the Realization of Transparent Flexible Antennas

Resonant cavity antennas (RCA) are superstrate based antennas which are capable of enhancing the directivity of simple sources such as dipoles and patches These antennas have recently received significant research interest from antenna community owing to their simple design, planar nature and highly directive characteristics but narrowband nature One of the main research goals associated with RCAs is to enhance their half power directivity bandwidth In this paper, a very simple RCA design is proposed which improves the half power directivity bandwidth almost 74% more than that exhibited by the conventional RCAs The proposed antenna has a peak directivity of 20dBi with less than ±05dB variation over most of the operating bandwidth The improved bandwidth of the antenna along with stable directivity, consistent beam quality and sufficiently suppressed sidelobe levels make it highly suitable for wireless point-to-point communication links

A simple resonant cavity antenna with improved directivity-bandwidth performance for high-capacity wireless data links

A resonant cavity antenna (100) includes a ground plane (110), a superstrate (e.g., 120, 125), and a feed antenna (140). The superstrate (120, 125) is spaced above the ground plane (110) to form a resonant cavity (135) therebetween. The superstrate (120) may have a permittivity gradient such that the pennittivity decreases from the innermost portion to the outermost portion of the superstrate (120). The superstrate (125) may have a constant permittivity value and a thickness gradient such that the thickness decreases from the innermost portion to the outermost portion of the superstrate (125). The feed antenna (140) is configured to excite the resonant cavity (135).

Raheel M. Hashmi

Papers

Effect of truncating the superstructures in broadband Fabry-Pèrot cavity antennas

A planar feeding technique for wideband, low-profile resonant cavity antennas

Feasibility Study of PDMS Embedded Transparent Conductive Fabric for the Realization of Transparent Flexible Antennas

A simple resonant cavity antenna with improved directivity-bandwidth performance for high-capacity wireless data links

Wideband high-gain resonant cavity antenna