Photonics-Based Millimeter-Wave Band Remote Beamforming of Array-Antenna Integrated With Photodiode Using Variable Optical Delay Line and Attenuator

For simplification of mobile base station architecture, we present remote beamforming of an array antenna integrated with photodiode based on photonics. Variable optical delay lines (VDLs) and variable optical attenuators (VOAs) are utilized for tailoring the RF phases and amplitudes and radio-over-fiber (RoF) technique is adopted for RF signal transmission. First, we show a simple demonstration of 60-GHz antenna beamforming using VDLs and VOAs with the aim of simplification of RoF signal generation at a control site. Next, we present experimental results on 60-GHz band digital signal transmission at 7 and 14 Gbit/s with beamforming function, in which eight compact antenna modules are arrayed in a row. Finally, we investigate RoF signal generation at 40 GHz utilizing the 1.3-μ m band electroabsorption modulator-integrated laser diode, where an optical filter and an optical amplifier are used to boost the modulation component and the successful formation of various beam patterns by tuning VDL and VOA is shown.