Antenna and Array Technologies for Future Wireless Ecosystems

7Photonics‐Based Millimeter‐Wave Band Remote Beamforming of Antenna Arrays Integrated with Photodiodes

Shigeyuki Akiba and Jiro Hirokawa

Tokyo Institute of Technology, Department of Electrical and Electronics Engineering, 2‐12‐1 Ookayama, Meguro‐ku, Tokyo, 152‐8550, Japan

7.1 Introduction

In recent wireless communication systems represented by long term evolution (LTE)‐Advanced and 5G, various use cases such as inter‐vehicle communication and the Internet of things (IoT) are expected to expand. It is estimated that the amount of mobile data traffic in the future will become much larger compared with today's data traffic. In order to accommodate such explosive growth of data traffic, it is required to use higher frequencies and to densely install mobile base stations (BSs) covering small areas, which are so‐called “small cells” [1, 2]. In such a situation, however, the radio‐interference among plural BSs degrades signal quality and the new installation of many BSs results in the increase of the total cost and power consumption of radio access networks.

Beamforming by an antenna array is an effective method to ensure high signal quality against the radio‐interference and to realize lower power consumption. There have been many studies of beamforming so far [3–5]. In many cases, however, beamforming techniques need radio frequency (RF) amplifiers to compensate for the RF propagation loss and RF phase shifters to control the relative phases between RF signals to be supplied to ...