【作者】 李勇；

【导师】 郑会利；

【作者基本信息】 西安电子科技大学 ， 电磁场与微波技术， 2019， 硕士

【摘要】 反射面天线由于结构简易、造价低廉、增益高、副瓣低等特性,因此在分米波频段到毫米波频段都有广泛的应用。随着雷达为了达到对目标进行识别和区域覆盖的目的,于是人们对天线的波束形状也有了不同的要求,比如余割平方赋形波束、某区域赋形波束等。因此,一套完整的赋形反射面天线系统的设计方法非常重要,鉴于此,本文系统性的阐述了采用双弯曲赋形反射面实现方位面窄波束,俯仰面余割平方赋形波束的设计方法,实测结果显示赋形角度、副瓣电平等指标参数均较好。最后通过实际反馈,提出了几种改进馈源的方法,并且与原赋形反射面的赋形指标做了对比,简化了馈源结构的同时使天线的次级赋形方向图的方位面整体副瓣电平下降1.5dB以上,特别是针对在水平面60°至140°范围内副瓣电平较高且高于第一副瓣电平问题有明显改进作用,相比之前该角度范围内副瓣电平均下降2dB以上,同时均低于第一副瓣电平值。最后,文中也介绍了赋形阵列的设计方法,通过阵列方法来得到赋形方向图。本文主要工作内容包括如下所示:首先介绍了余割平方波束赋形理论,然后根据反射面天线在方位面实现窄波束而在俯仰面实现余割平方波束赋形的特征,依次理论分析了实现该波束特点的反射面天线的中截线、条带方程,对各种条带的优缺点也做了详细的阐述,并且对反射面与初级场的匹配进行了理论分析。其次理论分析了馈源喇叭双波束的形成原因,给出了作为赋形反射面馈源的波瓣宽度、指向等指标要求,并且加工实测了馈源喇叭相关指标参数。接下来针对馈源在I波段第一副瓣较高的原因,介绍了在馈源喇叭的辐射口径下方加一块特殊反射挡板的改进方法,解决了馈源喇叭I波段方向图右侧第一副瓣电平较高的难题。最后依次建模仿真分析了馈源辐射口径处无栅片、辐射口径处加厚、辐射口径处无栅片同时加厚这三种改进情况对H、I波段的波瓣宽度、副瓣电平和波束指向的影响,为后面仿真得到次级赋形方向图奠定了馈源基础。然后介绍了赋形反射面的计算部分,首先估计了反射面的系统参数、选取了合适的焦距和条带方程、以及计算得到中截线方程和反射面的张角,接下来建模得到赋形反射面,得到两个频段的方位面和俯仰面方向图的仿真和实测结果。最后依次仿真了馈源喇叭辐射口径处无栅片、辐射口径处加反射挡板、辐射口径处加厚以及辐射口径处无栅片同时加厚这四种馈源改进情况对次级反射面的次级方向图影响,分别与原来的次级方向图做了对比,得出了改进的结论。最后介绍了阵列天线的基本知识,理论分析和仿真了通过阵列单元来实现俯仰面余割平方波束赋形,给出了阵列单元的激励幅相分布。最后,根据天线技术的发展也介绍了关于相控阵的部分知识。更多还原

【Abstract】 Reflector antenna is widely used in the decimeter band to the millimeter band because of its simple structure,low cost,high gain and low sidelobe level.With the radar to achieve target recognition and regional coverage,there are different requirements for the shape of antenna beams,such as cosecant square shaped beams,regional shaped beams and so on.Therefore,a complete design method of shaped reflector antenna system is very important.In view of this,this paper systematically expounds the design method of narrow beams in horizontal plane and cosecant square shaped beam in vertical plane with double-curved shaped reflector,The measured results show that the shape angle and sidelobe electrical equality index parameters are good.Finally,through actual feedback,several improved feeder methods are proposed and compared with the shaping index of the original shaping reflector.The problem that the sidelobe level of the shaped pattern of the antenna is higher than that of the first sidelobe level in the range of 60 to 140 level has been solved for a long time.The sidelobe level of the improved antenna decreases about 1.5 d B in the range of the angle compared with the previous one,and is also lower than that of the first sidelobe level,The overall sidelobe level of azimuth plane also decreased by more than 1.5d B.Finally,the design method of shaped array is introduced,and the shaped pattern can be obtained by array method.The main contributions of this dissertation are as follows:Firstly,the cause of horn double beam formation is analyzed theoretically and the lobe width and direction as the feed of shaped reflector are given and the parameters of the feed horn are measured in practice.Secondly,aiming at the high side lobe of the feed in I-band,the improved method of adding a reflective baffle under the radiation aperture of the feed horn is introduced and the problem of high right first sidelobe level in I band of feed horn is solved.Finally,the effects of the presence of absence of gratings at the radiation aperture,thickening the radiation aperture’s thickness and the absence of gratings at the radiation aperture and thickening the radiation aperture’s thickness on the H-band with lobe width,sidelobe level and direction are modeled and simulated.It lays the foundation of the feed for the simulation to get the secondary shaped radiation pattern.Secondly,the theory of cosecant square shaped beam is introduced.Then,according to the antenna’s characteristics of narrow beam in horizontal plane and cosecant square beam invertical plane,the central-section curve and strip equation of reflector antenna for realizing the beam characteristics are theoretically analyzed.The advantages and disadvantages of various strips are described in detail,and the far field of reflector is theoretically analyzed by physical optics method.Then the calculation part of shaped reflector is introduced.Firstly,the system parameters of the reflector are estimated,the focal length and the angle of the reflector are selected,and the central-section curve’s equation and strip equation are calculated.Then,the shape reflector is modeled and the simulation results and measurement results of secondary shaped radiation pattern in horizontal plane and vertical plane in two frequency bands are obtained.Finally,the effects of the presence of absence of gratings at the radiation aperture,thickening the radiation aperture’s thickness and the absence of gratings at the radiation aperture and thickening the radiation aperture’s thickness on the H-band with Secondary radiation pattern are simulated.The author compares new radiation pattern with the original radiation pattern,and gets the conclusion.Finally,the basic knowledge of the array antenna is introduced,theoretical analysis and Simulation of the cosecant square shaped beam in vertical plane and the knowledge of phased array are presented.更多还原