Research On Key Technologies For Reconfigurable Microwave Photonics Beamforming

Thanks to the advantages of microwave photonics beamforming technology,such as large bandwidth,low loss,and true-time delay,optically controlled phased array antennas effectively eliminate the “beam squint effect” in the phased array antennas based on electronic phased shifter and have become research hotspots in the field of radar,wireless communication,space detection,and electronic countermeasures.With the development of multi-task radar,advanced wireless communication,and microwave satellite communication,the next-generation electronic information system proposes new application requirements,such as intelligentization,reconfigurability,high efficiency,low power consumption,and low cost.However,the beamforming network in current optically controlled phased array antennas cannot fully satisfy the technology requirement of reconfigurable.Therefore,the study of reconfigurable microwave photonics beamforming technology is of great significance in solving the above technical problems,and it is expected to promote the new generation of dynamic adaptive optically controlled phased array antennas.This dissertation is focused on the key technologies of reconfigurable microwave photonics technology,including theoretical analysis,beam-reconfigurable,antennareconfigurable,subarray-reconfigurable,etc.The main contents and innovation are as follows.1.The structure and characteristics of microwave photonics beamforming are studied.Based on the optical beamforming network(OBFN),which consists of optical true-time delay,and optical signal distributing and combining network,by adding the optical routing networks,the mapping relationships between the signal transceiver and the optical true-time delay to the antenna elements are established,and the mathematical model of reconfigurable beamforming is obtained.Furthermore,the beamforming principle of beam-reconfigurable,antenna elements-reconfigurable,fully reconfigurable,and their beam pattern expressions are derived,providing the reference and theoretical guideline for the structure design of reconfigurable microwave photonics beamforming in various application scenarios.2.The multi-beam OBFN structures are studied based on variable and fixed truetime delay.Based on the optical switching array and fixed true-time delay array,the reconfigurable multi-beam OBFN transmitter is proposed.The optical multibeamforming experimental system with 16 signals,16 antenna elements,and a fiber-fixed true-time delay array is constructed.Experimental results demonstrate the system forming16 fixed pointing beams and covering the angle range ±23.6°,with delay accuracy better than 0.38 ps,amplitude consistency better than 2.1 d B,and beam direction accuracy better than 1.1°.The reconfigurable simulation experimental system with four signals and four fixed beams based on the Benes switching network is constituted,and the 4×4 multibeam reconfigurable is realized.The benefits of the proposed structure include using fewer optical switches,easy-controlling,and equaling beam directions.Based on the optical switch array and splitter array,an optical splitter with variable output numbers is designed and optimized,and the reconfigurable multi-beam OBFN receiver is proposed.The simulation experimental system with 16 antenna elements and four beams is constructed.The system achieves on-demand reconfiguration between 1,2,and 4 beams,obtaining beamforming gains of 24.08,18.06,and 12.04 d Bi,respectively.The results indicate that the proposed approach reduces optical power loss and enhances efficiency.3.The impact of reconfiguring the antenna elements on the beam performance is studied.The antenna-reconfigurable OBFN transmitter structure is proposed.Based on the “Optimized Selecting-Splitting” OBFN structure by designing and optimizing,the antenna elements enabled by one single signal arbitrarily are achieved.The reconfigurable OBFN transmitter simulational system with four signals and 64 antenna elements is constituted.The performance in various application scenarios is simulated,including one signal enabling 8×8,6×6,and 4×4 antenna elements to form one beam and achieving the beamforming gain of 18.26,15.59,and 11.89 d Bi,respectively.4 signals enabling four 4×4 antenna elements to form 4 beams with different directions,simultaneously,and covering the azimuth range from-180° to 180° and elevation range from 0 to 45°.The proposed method enhances the optical power efficiency and spatial coverage capability of optically controlled phased array antennas.4.The principles of subarray partitioning and reconfiguring in phased array antennas are studied.The subarray-reconfigurable OBFN is proposed by dynamically partitioning the subarray scale according to the demand of the input signals.In this scheme,a cascaded optical signal distribution network is designed based on the number of signals in order,and optical switch arrays are used to select input signals in different stages,which achieves dynamic subarray partition and beam reconfiguration.Leveraging SOI(SiliconOn-Insulator)integrated optical technology,a subarray-reconfigurable chip with four signals and 16 antenna elements is designed to provide reconfigurable connections between 4 inputs and 16 outputs.The simulation results indicate that the chip achieves the beamforming gain of 19.26,12.24,and 7.18 d Bi in single-beam,dual-beam,and quadruple-beam modes,respectively.The proposed approach is verified as feasible while maintaining high optical power efficiency,minimal resource utilization,and lowering control complexity.