Millimeter-wave mobile access system with smart antenna and radio on fiber

Abstract

For any wireless network based on mm-wave radio systems to be viable, the cost of the infrastructure must be much lower than is currently the case. One approach that promises this cost reduction is the radio over fiber, where radio signals at the carrier frequency are delivered over an optical network to the radio access point. Benefits of this centralized approach are that expensive and delicate pieces of equipment can be located in a begining environment and costs can be shared between a number of radio access point. However, the integration of such systems is conditioned by the development of low cost radio components, antennas, the packaging as well as the optic/radio transductors. However, due to large propagation losses in this MMW/radio-on-fiber system, large transmission power is required to cover the wide area of cell zones. In addition, the effect of the multipath becomes serious when the signal bandwidth is wide. To cope with these problems, intelligent antennas are expected to solve the problems of large propagation losses and multipath fading in MMW. Therefore, an intelligent antenna that enables beam control is one of the key components in this millimeter wave fiber wireless systems with the options such as range extension, improved immunity to flat fading, interference suppression, and Spatial Division Multiple Access. The paper explores therefore the areas of strategic importance in integration of new antenna array topologies which are appropriated for use as a building block for the millimeter wave fiber wireless system which employs an intelligent multibeam antenna where the direction of each sharp beam can be adaptively controlled. Thereby, the objective of truly monolithic array with integrated planar antennas and phase shifters was the driving force behind the development of the aperture coupled patch element which is especially relevant for these systems. Challenges arising from the development of this EHF-band antenna array include the minimization of the array's feed network loss, coupling between antennas and between feedlines and antennas, and the overall architecture that the system requires. The effectiveness of this antenna array has been theoretically confirmed. Finally, it worthy noting that the small wavelengths allow miniaturize of the size of components such as antennas which are very important for portable sets as well as base station (BS) facilities, which need to be readily installed.