Research On Microwave Photonic Beamforming Network Chip Based On Switchable Delay Lines

Traditional electronic beamforming network is limited by the aperture effect,and can not meet the large bandwidth requirements of the modern phased array radar.Besides,the scanning range is small and the scanning speed is slow.In recent years,microwave photonic technology has been introduced into beamforming networks,which has effectively improved the operation bandwidth and the anti-interference capabilities.However,most of the systems use discrete optical devices,there is big room for improvement in size,weight,and power consumption.Integrated beamforming networks are only demonstrated with limited integrated components,which can not effectively solve the above problems,like large size and high power consumption.Therefore,we propose and realize a silicon integrated microwave photonic beamforming network chip based on optical switchable delay lines.The chip contains a silicon Mach-Zehnder modulator,a silicon eight-channel optical beamforming network,and 8 germanium photodetectors.The total footprint is only 11.03×3.88 mm~2.The silicon eight-channel optical beamforming network consists of a 2×8 optical power splitter and eight 5-bit digitally switchable optical delay lines.The minimum delay step of each delay line linearly increases from 2 ps to 16ps.Therefore,by adjusting the switching states of all the switch elements in each delay channel synchronously,we can change the difference of time delay between each two adjacent emitter elements.As a result,the beam is steered.In this thesis,the beam scanning principle of phased array radar is firstly explained theoretically,and the reason for the aperture effect of traditional beamforming networks and the advantages of using reconfigurable optical delay lines are explained from mathematical derivation.Secondly,we introduce the working principle and function of each component in this beamforming network,present the theoretical analysis and simulation of these components.Finally,we present the experimental setups for characterizing the detailed performance of each module,and give the assessment of the beamforming performance of the chip with the measured results.Through testing,it was found that the microwave photonic beamforming network chip based on the switchable delay lines can support a signal bandwidth from 8 to 18 GHz,covering the X and Ku bands.It has a large scanning range from-65.02°to 64.63°,with 31 distinguishable steering angles.The scanning speed of the beam is 56?s.The power consumption of the entire chip is 960 m W.To the best of our knowledge,this is the first study to evaluate the performance of a silicon monolithic microwave photonic beamforming network chip.The chip has the advantages of compact volume,low power consumption,fast scanning speed and simple control algorithm.The experimental results show the chip a promising candidate for the next generation microwave photonic phased array radar.