Research On The Key Technology Of Optically Controlled Phased Array Antenna

Phased array radar antenna is more and more important in modern communication system,because of the advantages of high speed,low visibility and difficult to be detected.In order to improve the anti-jamming ability of the radar,reduce the threat of the anti radiation missile,enhance the target resolution and discrimination and solve the problem of multi-target imaging,phased array antenna should have the large instantaneous bandwidth as same as other antennas.However,the aperture effect and the aperture transit time of the phased array antenna make the direction of the beam change with the frequency,that is,there is a certain delay in the signal transmission and reception.The optical technique can compensate the beam deflection and improve the true time delay beam control with wide instantaneous bandwidth of radar system.Optical phased array has a huge advantage in the realization of the instantaneous bandwidth in large scanning angle.Optical fiber can realize the function of signal delay,signal distributor,and it also can be a transmission channel.The accuracy of the signal delay regulator depends on the cutting accuracy of the optical fiber,so high precision fiber can be used to obtain high precision and accuracy.In recent years,it becomes a hot topic how to use optical fiber to eliminate the aperture effect and aperture transition time of phased array antenna.The antenna elements of this paper are based on the traditional microstrip Yagi antenna.The gain and bandwidth of the antenna elements are improved by adding directions.The antenna elements are smaller than the traditional microstrip Yagi antenna by reducing the size of the antenna.The results of simulation and test show that the antenna elements have the performance of wide bandwidth and high gain.By using the antenna elements,all the antenna arrays of two elements,four elements,six elements and eight elements linear array are designed in this paper.The simulation and test results show that the gain of the antenna array increases and the antenna performance becomes better with the increase of the elements number.In the design of the optically controlled phased array antenna,the input RF signal is directly modulated by laser.The modulation signal was shunt by the optical coupler.Then signals were delayed by the fiber of different lengths.The delayed signals were demodulated into the RF signal and the optical signal by the photoelectric detector.At last the RF signal was output to free space through the antenna array.It can achieve a large instantaneous bandwidth in large scanning angle,improve the resolution and recognition ability of radar,solving multi-target imaging by using the optoelectronic technology in phased array antenna.Besides,it has a huge advantage in term of anti-radiation missile,simplify structure,reducing volume,weight,resistance to harsh electromagnetic environment,easy maintenance and so on.The optical phased array antenna system presented in this paper has high theoretical and practical significance.