Millimeter wave antennas and applications

Future wireless communication systems will inevitably require data rates of the order of several Gigabits per second (Gbit/s) to meet the exponential increase in the quantities of data (particularly for high-definition (HD) video) to be transmitted, whether for fixed or mobile networks. Similarly, the growth in the market for automotive radars for road safety or imaging systems for civil security (airports or tracking of persons deemed to be a threat) is generating strong research and engineering activities to improve the resolution of these systems in order to distinguish and classify targets at medium to long range (up to a few hundred meters). These requirements call for millimeter-wave [30-300GHz] technology, to ensure that the frequency bandwidth (several Gigahertz) available to meet these new system specifications is sufficient. Applications such as future 5th generation (5G) high-speed networks, indoor data transfer systems at 60GHz, or automotive radar [76-81GHz], require not only the implementation of low-cost, high-performance transmission-reception systems, but also the design of dedicated antennas, i.e. with good gain and radiation performance. In most cases, these antennas need to be reconfigurable in order to effectively combat obstruction phenomena due to the propagation channel (indoor in particular). The use of the millimeter spectrum, however, imposes major technological constraints, such as the use and mastery of low-loss dielectric materials, the interconnection of antennas and active modules, and high-gain antennas (20-30dBi or more) with the possibility of reconfiguring the radiation pattern (mechanical or electronic beam scanning, variable beamwidth, etc.).

The aim of this article is to present the main industrial applications and the specific features of the millimeter frequency spectrum, including high attenuation in free space, atmospheric absorption of waves by certain molecules (oxygen at 60GHz), and antenna efficiency problems due to losses induced by the materials used. Several industrial applications, such as high-speed indoor communication systems at 60GHz, automotive radars in W-band (79GHz) or imaging systems for civil security, are then presented, along with the problems associated with each of them.

Concrete examples of reconfigurable antennas illustrate the issues and solutions presented.

A glossary and table of acronyms and symbols are provided at the end of the article.