The demand for wireless mobile communications services is growing at an explosive rate, with the anticipation that communication to a mobile device anywhere on the globe at all times will be available in the near future. An array of antennas mounted on vehicles, ships, aircraft, satellites, and base stations is expected to play an important role in fulfilling the increased demand of channel requirement for these services, as well as for the realization of the dream that a portable communications device the size of a wristwatch be available at an affordable cost for such services. This paper is the first of a two-part study. It provides a comprehensive treatment, at a level appropriate to nonspecialists, of the use of an antenna array to enhance the efficiency of mobile communications systems. It presents an overview of mobile communications as well as details of how an array may be used in various mobile communications systems, including land-mobile, indoor-radio, and satellite-based systems. It discusses advantages of an array of antennas in a mobile communications system, highlights improvements that are possible by using multiple antennas compared to a single antenna in a system, and provides details on the feasibility of antenna arrays for mobile communications applications.

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Applications of antenna arrays to mobile communications. I. Performance improvement, feasibility, and system considerations

The authors propose a novel feed structure to excite a plane TEM wave in a parallel-plate waveguide. The feed waveguide is composed of densely arrayed posts on the same layer as the parallel plate. The posts can be easily fabricated at low cost by making metalized via holes in a grounded dielectric substrate. Such a procedure results in a quite simple fabrication of the antenna. The feed waveguide is designed to obtain a uniform division, which is confirmed by measurements on a 40-GHz band model.

Single-layer feed waveguide consisting of posts for plane TEM wave excitation in parallel plates

Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

A near object detection (NOD) system includes a plurality of sensors, each of the sensors for providing detection coverage in a predetermined coverage zone and each of the sensors including a transmit antenna for transmitting a first RF signal, a receive antenna for receiving a second RF signal and means for sharing information between each of the plurality of sensors in the NOD system.

Near object detection system

A method is presented, for the efficient derivation of the dispersion equation associated with electromagnetic bandgap (EBG) structures composed by lossless frequency selective surfaces (FSS) printed on stratified dielectric media The method, valid for the range of frequency where a single propagating Floquet mode occurs, is based on Foster's reactance theorem applied to an equivalent transmission line network This theorem implies that the admittance functions of frequency which represent the FSS satisfy the pole-zero analytical properties of the driving point LC admittance functions By these basic properties and by the full-wave identification of the FSS resonances, an analytical form of the dispersion equation is obtained This equation is next solved for both surface wave and leaky wave modes by a conventional numerical technique The results are successfully compared with those from a full-wave analysis

A pole-zero matching method for EBG surfaces composed of a dipole FSS printed on a grounded dielectric slab

We propose a slot array antenna for dual-polarization operation in the 60 GHz band. To realize the dual-polarization, cross-shaped radiating slots and a multilayer feeding structure are employed. A 16 $\,\times\,$ 16-element array is fabricated by diffusion bonding of laminated thin copper plates, which has the advantages of high precision and low loss characteristics. To suppress the grating lobes, we employ several design techniques, such as a thick cavity structure and dense element spacing. The high antenna gain higher than 32.0 dBi and the antenna efficiency near 80.0% are obtained over 60.0–64.0 GHz for two different polarizations. The 1-dB-down gain bandwidths reach 10.4% and 10.9%. High isolation above 50 dB is achieved between the two input ports.

Design and Fabrication of a Dual-Polarization Waveguide Slot Array Antenna With High Isolation and High Antenna Efficiency for the 60 GHz Band

This communication proposes high gain antennas having broad bandwidth characteristic for the 120 GHz band. The proposed antennas are fabricated by diffusion bonding of laminated thin copper plates which have the advantages of high precision and low loss characteristic even in a high frequency region such as the 120 GHz band. For stable fabrication using diffusion bonding, we propose a feeding structure which has a double layer. A 32 × 32-element array antenna shows more than a 38 dBi antenna gain with over 60% antenna efficiency and 15 GHz bandwidth (119.0-134.0 GHz) and a 64 × 64-element array shows a higher than 43 dBi antenna gain with over 50% antenna efficiency and 14.5 GHz bandwidth (118.5-133.0 GHz), respectively.

64 $\,\times\,$ 64-Element and 32 $\,\times\,$ 32-Element Slot Array Antennas Using Double-Layer Hollow-Waveguide Corporate-Feed in the 120 GHz Band

A 45° linearly polarized hollow-waveguide slot array antenna has been proposed to achieve low sidelobes in the E- and H-planes by a diamond-shaped array arrangement. A layer for radiating slots was added into the conventional plate-laminated antenna. The 2 × 2-element sub-array was designed to suppress grating lobes and low cross-polarization. The 16 × 16-element array in the 60-GHz band was fabricated by diffusion bonding of the laminated thin metal plates. The first sidelobe levels in the E- and H-planes were -25.5 and -26.1 dB, respectively, and the cross-polarization was - 31.5 dB in the boresight. High antenna efficiency of 70% with greater than 32 dBi gain over 5 GHz was maintained by the corporate-feed hollow waveguide structure. Quantitative amount of fabrication error due to etching and alignment was revealed by simulations.

A 45 $^\circ$ Linearly Polarized Hollow-Waveguide Corporate-Feed Slot Array Antenna in the 60-GHz Band

A two-beam slotted leaky waveguide array for mobile reception of dual-polarization direct broadcast from satellite (DBS) is realized in a single-layer structure. Two feed waveguides attached at both ends of cross-slotted radiating waveguides excite the leaky waves propagating in opposite directions. Each of them radiates either of two circularly polarized waves in symmetrical beam directions. Balanced design of two beams for each polarization imposes symmetry in the array design of slots. The slot coupling distribution is optimized for the maximum gain under this symmetry condition. A model antenna in about a 300-mm square is fabricated for experiments in the 12-GHz band. Antenna efficiency of 71% and 64% is obtained for each beam in different polarizations.

A two-beam slotted leaky waveguide array for mobile reception of dual-polarization DBS

A wideband and continuous beam steering flat antenna is proposed in the 60-GHz band. The antenna consists of two layers and is made of two parts: 1) a feeding network and 2) a slotted plate. The relative rotation movement between the two antenna parts generates a phase gradient across the radiating part, and a continuous beam is generated in the upper hemisphere. The mechanical movement between the two antenna parts is facilitated by the use of gap waveguides; therefore, no electrical contact is needed between the two metallic parts. To validate the antenna concept, an antenna has been designed and fabricated in the 60-GHz band. Good agreement has been obtained between the simulations and the measurements. The antenna field of view is up to ±60°. The antenna bandwidth is up to 13% for VSWR <2. The loss within the antenna structure is estimated to be around 0.86 dB.

Makoto Ando

Papers

Design and Fabrication of a Dual-Polarization Waveguide Slot Array Antenna With High Isolation and High Antenna Efficiency for the 60 GHz Band

64 $\,\times\,$ 64-Element and 32 $\,\times\,$ 32-Element Slot Array Antennas Using Double-Layer Hollow-Waveguide Corporate-Feed in the 120 GHz Band

A 45 $^\circ$ Linearly Polarized Hollow-Waveguide Corporate-Feed Slot Array Antenna in the 60-GHz Band

A two-beam slotted leaky waveguide array for mobile reception of dual-polarization DBS

Wideband and Large Coverage Continuous Beam Steering Antenna in the 60-GHz Band