Optical communication technologies: Photonic antennas and its application to radio-over-fiber wireless communication systems

Abstract

In this paper, presented were the recent works on development of photonic feeding coplanar patch antennas for microwave and millimeter-wave wireless communication system. An experiment setup for optical modulation of sub-carrier, photodetection of the sub-carrier-modulated optical wave and integration of the photodetector with a coplanar patch antenna have been described. Experimental results of optical modulation using a traveling-wave LiNbO3 optical modulator, RF output from a photodetector: UTC-PD, and the RF output dependence on modulation index have been presented and discussed. The experiment showed that the photodetector can generate relatively large RF power at microwave and millimeter-wave frequencies, for example, more than 10 mW at both 10 GHz and 20 GHz and around 10 mW at 38 GHz and 7 mW at 60 GHz. Based on this experimental fact, introduced was a concept of direct integration of an antenna with the photodetector to realize a simple photonic feeding RF radiation unit to avoid serious transmission loss and simplify the RF system especially in high frequency wireless system. A planar antenna: coplanar patch antenna was newly proposed and designed for the direct integration with the photodetector which is of a coplanar waveguide output structure. Simulation, design, fabrication and measurement have been done for the antennas. Experiment on a hybrid integration of the photodetector and the coplanar patch antenna demonstrated a good performance of photonic microwave generating, direct feeding, transmitting and receiving. The results clearly showed the effectiveness and the potential application of the present integration configuration to the future microwave and millimeter-wave wireless communication system based on the optical fiber network.