Electromechanical Coupling Analysis And Performance Compensation Of Active Phased Array Antennas In Operating Environment

Active phased array antennas(APAA)have many advantages such as fast scanning speed,flexible beam agility,strong anti-interference ability and good stealth performance.It has been widely used in many fields such as ground defense,airborne fire control,missile guidance,and spaceborne imaging,etc.The electrical performance of the antenna,including the radiation and scattering performance will be affected significantly when it serves under different platforms.With the development of APAAs toward high frequency band,high performance,and high integration,the impact of service environmental loads will be more prominent.Due to the complex mechanism of the influence of service environment on antenna electrical performance,it is difficult to provide effective compensation methods to ensure reliable antenna performance in service.Therefore,the structure-electromagnetic coupling relationship and electrical performance compensation method of APAA in service environment are studied.The main work are as follows:1.The structural deformation of large-caliber ground-based active phased array antenna caused by solar radiation,wind load and other factors will lead to the degradation of the radiation performance.Based on the structure-electromagnetic coupling model of active phased array antenna,the quantitative influence of structural deformation on the radiation performance of the antenna is obtained.Based on this,the radiation performance of the deformed antenna is compensated by adjusting the excitation phase and amplitude phase of the antenna array element respectively.For the method of amplitude and phase compensation,the least squares method and the FFT method based on the structure-electromagnetic coupling model are proposed.Compared with the traditional phase compensation,which is usually used to guarantee the performance in the main lobe area,whereas the method proposed can compensate the radiation performance in the entire observation area of the antenna.Finally,an X-band active phased array antenna experimental platform was built to test and compensate the electrical performance under various typical deformation conditions in the service environment,and the effectiveness of the compensation method was verified.It provides a theoretical basis for the reliable service of APAA under structural deformation.2.The limited space of the platform,high installation density of electronic components and high thermal power consumption of array surface are the problems that the airborne active phased array antenna face nowadays.The T/R component will have performance drift because of the influence of high temperature.The power supply ripple,the AC component superimposed on the output DC voltage,will also cause amplitude and phase errors on the output current of the T/R component through amplitude modulation and phase modulation.Therefore,the influence of temperature on the performance of the surface power supply and T/R components are deeply analyzed.The calculation model of the ripple coefficient which characterizes the power supply ripple and the temperature drift curve of the T/R component are given.Based on this,a coupling model of power supply ripple,T/R component amplitude and phase error and antenna radiation performance under high thermal power consumption is established.The change law of antenna radiation performance under the influence of feed error is quantitatively analyzed,and the influence of high thermal power consumption on the radiation performance of the antenna is reduced by adjusting excitation amplitude.The above work can also provide a theoretical reference for the heat dissipation design from the perspective of antenna electrical performance.3.The vibration load will cause structural deformation of the airborne APAA,then the positional offset of the array element will lead to the degradation of the antenna.At the same time,the phase distribution in space of the scattered wave reflected by the array element will also change,and the scattering performance of the antenna will be improved.The search and tracking capabilities and stealth capability of the airborne antennas are very crucial considering the mobility requirements.Therefore,considering the radiation performance and scattering performance of the airborne active phased array antenna,the influence of structural error on the scattering performance of the antenna is analyzed,and the calculation model of the scattering performance including the statistical characteristics of the random structure error is established.The model solved the problem that the influence of structural error on antenna scattering performance is difficult to quantitatively evaluate.At the same time,combined with the existing statistical models of antenna radiation performance,the effects of random structural errors in different directions on antenna radiation and scattering performance are analyzed,and the adjustment direction of antenna sub-array structure is determined when the antenna sub-array structure is used for compensation.Finally,combined with genetic algorithm,the comprehensive compensation of antenna radiation performance and scattering performance is realized.The above work lays a theoretical foundation for ensuring the high radiation performance and high stealth performance of the active phased array antennas.4.For the missile-loaded active phased array antennas flying at supersonic and hypersonic speeds,the radiation performance of the antenna will be affected seriously because of high temperature ablation.So the influence of high temperature ablation on the radome of the missile antenna is studied,and the unsteady high temperature ablation model of the radome is given,which can be used to analyze the temperature field variation and ablation thickness of the radome under high temperature ablation.Also the sharp increase of the temperature of the radome will also heat the antenna inside the radome through heat conduction and heat radiation,resulting in feeding error.For this reason,the electromechanical coupling models between the structure and physical property parameters of the radome,the feeding error of the antenna element and the radiation performance of the missile antenna under high temperature ablation is established,which can quantitatively predict the influence of high temperature ablation on the radiation performance of the missile antenna.The effect of high temperature ablation on the performance of the antenna inside the radome is compensated by adjusting the excitation current of the antenna.Two calculation methods of excitation amplitude and phase adjustments are given to compensate the influence of high-temperature ablation at multi-frequency points and multi-scan angles.At last,a software for analyzing and compensating the electrical performance of the missile antenna under high temperature ablation was developed.The above work can ensure the high-precision guidance performance of the missile antenna during high-speed flight without changing the design of the radome structure.5.The space thermal environment can cause the thermal deformation of the spaceborne active phased array antenna.Due to the space and load requirements of the spaceborne platform,it is difficult to directly measure the deformation displacement of the antenna.The strain sensor can overcome the limitation of the carrier platform,and it is easy to install,and reliable,also it can collect the strain information of the antenna in real time.Therefore,the influence mechanism of structural strain and antenna radiation performance is analyzed.A strain-electromagnetic coupling model of active phased array antenna is established.Furthermore,phase compensation and amplitude and phase compensation based on the strain-electromagnetic coupling model are proposed to reduce the influence of space thermal environment on antenna radiation performance.The radiation performance can be quickly predicted according to the collected strain information,and the required excitation current compensation amount can be given.On the active phased array antenna experimental platform,the deformation analysis information system of the array surface based on the strain information is constructed.The effectiveness of the strain-electromagnetic coupling model and the compensation method is verified by the experiments.The above work can provide theoretical basis for real-time compensation for the spaceborne active phased array antennas in space thermal environment.