With the demanding system requirements for the fifth-generation (5G) wireless communications and the severe spectrum shortage at conventional cellular frequencies, multibeam antenna systems operating in the millimeter-wave frequency bands have attracted a lot of research interest and have been actively investigated. They represent the key antenna technology for supporting a high data transmission rate, an improved signal-to-interference-plus-noise ratio, an increased spectral and energy efficiency, and versatile beam shaping, thereby holding a great promise in serving as the critical infrastructure for enabling beamforming and massive multiple-input multiple-output (MIMO) that boost the 5G. This paper provides an overview of the existing multibeam antenna technologies which include the passive multibeam antennas (MBAs) based on quasi-optical components and beamforming circuits, multibeam phased-array antennas enabled by various phase-shifting methods, and digital MBAs with different system architectures. Specifically, their principles of operation, design, and implementation, as well as a number of illustrative application examples are reviewed. Finally, the suitability of these MBAs for the future 5G massive MIMO wireless systems as well as the associated challenges is discussed.

Multibeam Antenna Technologies for 5G Wireless Communications

Preface. Microelectromechanical Systems (MEMS) and Radio Frequency MEMS. MEMS Materials and Fabrication Techniques. RF MEMS Switches and Micro Relays. MEMS Inductors and Capacitors. Micromachined RF Filters. Micromachined Phase Shifters. Micromachined Transmission Lines and Components. Micromachined Antennae. Integration and Packaging for RF MEMS Devices. Index.

RF MEMS and their applications

Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.

Method and apparatus for coupling an antenna to a device

A distributed antenna and backhaul system provide network connectivity for a small cell deployment. Rather than building new structures, and installing additional fiber and cable, embodiments described herein disclose using high-bandwidth, millimeter-wave communications and existing power line infrastructure. Above ground backhaul connections via power lines and line-of-sight millimeter-wave band signals as well as underground backhaul connections via buried electrical conduits can provide connectivity to the distributed base stations. An overhead millimeter-wave system can also be used to provide backhaul connectivity. Modules can be placed onto existing infrastructure, such as streetlights and utility poles, and the modules can contain base stations and antennas to transmit the millimeter-waves to and from other modules.

Backhaul link for distributed antenna system

A distributed antenna system is provided that frequency shifts the output of one or more microcells to a 60 GHz or higher frequency range for transmission to a set of distributed antennas. The cellular band outputs of these microcell base station devices are used to modulate a 60 GHz (or higher) carrier wave, yielding a group of subcarriers on the 60 GHz carrier wave. This group will then be transmitted in the air via analog microwave RF unit, after which it can be repeated or radiated to the surrounding area. The repeaters amplify the signal and resend it on the air again toward the next repeater. In places where a microcell is required, the 60 GHz signal is shifted in frequency back to its original frequency (e.g., the 1.9 GHz cellular band) and radiated locally to nearby mobile devices.

Remote distributed antenna system

The radiation characteristics of conical horns loaded with dielectric cones are investigated. The horn radiates low crosspolarisation over a wide band of frequencies with cones made of foam or solid dielectrics. They make high performance feeds for reflector antennas. A modal-matching technique is used to investigate the behaviour of the higher order modes excited along the horn that influence the radiated cross-polarisation. A parametric study is described to assess the influence of the aperture and cone diameters, the flare angle, and the permittivity of the dielectric.

Dielectric cone loaded horn antennas

The results of a computational method for determining the propagation characteristics of a radially inhomogeneous dielectric cylinder are presented. A continuous variation in permittivity is represented by means of a staircase function, and the corresponding propagation problem for a cylindrically stratified dielectric is solved using a digital computer. For refractive-index profiles commonly used in optical waveguides, the propagation coefficient differs negligibly from the asymptotic value when the number of layers is equal to five.

Electromagnetic-wave propagation along radially inhomogeneous dielectric cylinders

The attenuation characteristics are predicted for the dominant hybrid mode in corrugated circular waveguide. Over a substantial frequency band, which includes the optimum frequency for antenna-feed applications, the attenuation is lower than that of the dominant mode in a circular wave-guide without corrugations.

Attenuation in corrugated circular wave-guide

A modal-matching method is used to evaluate the transmission and reflection coefficients at a junction between two planar surface waveguides. Results are obtained for parameters which represent the junction between a solid-state laser and a planar optical waveguide. Favourable comparison is made with results obtained from an integral-equation method.

Modal matching applied to a discontinuity in a planar surface waveguide

The paper describes the synthesis of shaped-beam dual-reflector antenna patterns using two methods. In the first, for a prescribed far field the antenna aperture field is obtained initially and then a Geometric Optics synthesis method used to define the reflector coordinates. In the second method an optimisation procedure is employed to shape the reflectors directly, so as to generate, through Physical Optics, the desired far field. The two methods are compared for the pattern corresponding to the EUTELSAT 2 spacecraft. Close agreement is found and differences ascribed to initial constraints.

P.J.B. Clarricoats

Papers

Dielectric cone loaded horn antennas

Electromagnetic-wave propagation along radially inhomogeneous dielectric cylinders

Attenuation in corrugated circular wave-guide

Modal matching applied to a discontinuity in a planar surface waveguide

Synthesis of shaped-beam reflector antenna patterns