雷达波束横倾角计算

采用坐标变换技术,给出了舰载雷达常用稳定方式下甲板平面及稳定平台平面横倾角的推导过程及计算公式,为舰载雷达伺服控制及相关补偿方法提供理论依据。     

舰载测量雷达船摇稳定回路设计

速率陀螺敏感于天线空间运动角速率,故可将陀螺感受的角速率信息作为反馈信息构成负反馈回路,通过加入船摇扰动前馈补偿环节,实现稳定回路的复合控制。再通过误差校正后将船摇补偿输出到功放,驱动天线方位及俯仰运动,达到隔离船摇扰动对天线指向影响的目的。设计已成功应用于舰载测量雷达的研制中,经对雷达性能测试,船摇隔离度达到50 dB。     

舰载气象雷达伺服系统设计实践

本文主要介绍天线口径为1.83米的舰载气象雷达天线伺服系统的设计,重点叙述如何利用速率陀螺克服舰船运动对天线跟踪性能的影响及天线指向稳定方案的实践。     

舰载雷达侦察系统坐标系转换方法

介绍了舰载雷达侦察系统常用坐标系转换方法,包括舰船地理坐标系到舰船甲板坐标系的变换及逆变换、舰船甲板坐标系到阵面坐标系的变换及逆变换,给出了具体的推导过程及坐标系相互转换的公式,结合坐标系转换的理论方法,阐述了舰载雷达侦察系统坐标系转换的应用实例.     

舰载雷达天线稳定转台系统的结构载荷分析与计算

详细阐述了舰载雷达天线稳定转台系统结构载荷的基本分析计算过程,同时说明了关键设计参数的合理确定对于舰载雷达天线稳定转台结构载荷计算及提高舰载雷达适装性的重要性。     

综合导航系统误差对舰载三坐标相控阵雷达精度的影响分析

对于舰载三坐标相控阵雷达,要保证其在大地坐标系内的空域覆盖及对目标的稳定跟踪,就需要通过动平台补偿来修正波束指向,而波束修正时采用的舰姿态信息会将它的误差引入到雷达的测量误差中,从而影响到雷达的测量精度。只有将这一误差关联效应的机理分析清楚,才能在雷达输出数据出现跳变时有效的隔离出误差来源,正确评估雷达性能。     

天线相对转速对雷达主瓣互扰概率影响的研究

两部舰载雷达天线的主瓣对准时将产生严重的电磁干扰现象,并造成舰载雷达作战效能的下降。针对这一问题,本文分析了雷达在空域上产生互扰的条件及雷达天线转速与主瓣互扰的关系,建立了在不同条件下雷达主瓣互扰概率的数学模型。用Matlab对该模型进行仿真分析,得出雷达间互扰概率随天线相对转速的变化图,最后提出降低主瓣互扰概率的具体措施。     

舰载雷达天线稳定转台系统通用载荷计算软件的设计与开发

通过对舰载雷达天线稳定转台系统典型载荷分析,并分别对各类载荷的计算方法进行了说明,最终形成舰载雷达天线稳定转台系统的通用载荷计算方法。再将该通用载荷计算方法用软件进行实现,为准确快速构建雷达天线稳定转台系统方案提供了有力的支撑。     

舰载雷达的主要关键技术

从未来海战的特点和舰载雷达所面临的“四大威胁”出发，阐述了舰载雷达组网、相控阵雷达、双－我基地雷达、超视距雷达、冲击雷达、数字波束形成、低副瓣和极低副瓣天线、抗海杂波和多路径效应及电磁兼容等方面存在的关键技术及这些关键技术的突破对提高舰载雷达的“四抗”能力和适应未来海战能力的潜在优势及国外在这方面提取得的成果。     

舰载雷达电子战一体化和宽带共孔径天线技术

描述了舰载雷达电子战一体化的产生背景、发展现状及趋势。同时，介绍了几种实现舰载雷达电子战一体化的宽带共孔径天线技术。     

Research on circularly polarized conical-beam antennas

This antenna is intended for communication between a stationary satellite and mobile stations, and is designed to possess circularly polarized conical beams. It generates a beam in the desired direction, by means of changing the inclination angle of the linear-antenna elements, and the spacing between the antenna elements, without phase shifters. The antenna inclination angle (α), the antenna length (e), the distance between antenna elements (d), and the radius of the circular reflector (R), are adopted as parameters, and optimum values for the directivity of the research objective are obtained by calculation. Four elements of the antenna are fed by in-phase signals, the distances between elements are set to appropriate lengths, and by providing spatial phase differences of 90°, circularly polarized waves are obtained. The antenna elements are fundamentally monopole radiators. Ultimately, the antenna parameters were determined as follows: ℒ=0.64λ (120 mm), R=0.43λ (80 mm), α=45°, and d=0.48λ (90 mm). In the calculation, the frequency was set to 1.6 GHz. It was seen that the beam radiation intensity took the maximum value in the angular range of &thetas;=30° to 60°, and that the &thetas; and φ components of the electric field were approximately equal. In other words, the radiated waves were circularly polarized. An experiment for measuring the directivity of the circularly polarized conical-beam antenna was carried out by using four monopole antennas, and the effectiveness of the theoretical analysis was confirmed. Experiments were carried out for the impedance and directivity     

Some new calculations on antenna superdirectivity

The fundamental limitation of superdirective antenna arrays was previously demonstrated through calculation of Chebyshev arrays. Those arrays are not optimum and have an extraneous parameter (sidelobe level). A new calculation is made using maximum directivity arrays and it is shown that log Q varies approximately linearly with directivity. A close fit to this behavior is given by log Q = π(G- G0). The π slope has been inferred from work of Rhodes but cannot be physically justified at this time.     

Reactively Steered Ring Antenna Array for Automotive Application

A novel type of smart antenna, called a reactively steered ring antenna array (RSRAA), is proposed. The antenna features a conformal configuration with three overlapping one-wavelength ring elements. Directivity can be controlled by changing the values of variable reactance circuits that are embedded in the antenna. The antenna can be mounted on the windshield of an automobile without interfering with the view of the driver. An equivalent model of six dipole elements is derived from the original antenna configuration to enable simple calculation of directivity when a set of reactance values is given. The validity of the proposed equivalent model is confirmed by comparing simulation results calculated by the equivalent model and by the method of moments. Another simulation shows that the conventional reactance domain multiple signal classification algorithm can be applied to the proposed antenna while keeping the estimated direction-of-arrival number equal to the number of reactance circuits. In addition, the characteristics of an RSRAA, which is optimized at 2.4 GHz and is mounted on an automobile, are measured in an anechoic chamber, and directivity control is found to be implemented effectively.     

Computer Programs for the Calculation of the Horizontal Far Field Radiation Pattern and Directivity of Full Wave Dipole Panel Antennas

Two computer programs have been developped for the calculation of the horizontal far field radiation pattern and the directivity of full wave dipole panel antenna arrays for the VHF TV Broadcasting. The programs are written in Basic and were run with the aid of a HP-86 personal computer.     

Optimum directivity coverage of fan-beam antennas

Cellular and point-to-multipoint wireless communication systems use fan-beam antennas for sector coverage from the central station. The ratio of the azimuth-to-elevation half-power beamwidth typically ranges from two for sites requiring low-gain antenna values to 25 or greater for sites covering large cells. This article presents an approximate formula for the antenna directivity of the fan-beam antenna using two parameters to describe the azimuth pattern shape, and two parameters for the elevation pattern. The directivity formula presented includes minor lobes. A variation of the fan-beam directivity formula is presented for the omnidirectional antenna. The directivity formula presented in this note is developed from separable-pattern functions, and uses a pattern-shape parameter in addition to the half-power-beamwidth value     

Full-Wavelength Dipole Antenna on a Hybrid GaAs Membrane and Si Lens for a Terahertz Photomixer

A full-wavelength dipole antenna on a GaAs membrane, covered with a silicon lens to improve the output power of a terahertz (THz) photomixer, is proposed. A full-wavelength dipole antenna supported by a GaAs membrane structure has been proven to achieve both high input resistance and high radiation efficiency for improved overall efficiency. However, the antenna has insufficient directivity. An extended hemispherical lens was introduced in front of the antenna in a non-contact configuration and coupled to the antenna radiation to achieve high directivity by beam collimation. This approach greatly enhances the antenna directivity while avoiding an inherent obstacle of the input resistance reduction caused by the high permittivity lens substrate. The resulting antenna after optimization had a 3818-Ω input resistance and a 71.2% radiation efficiency, corresponding to approximately 57% total efficiency at the 1.07-THz resonance frequency. The total efficiency of this structure is approximately 6.8 times that of a full-wavelength dipole antenna with the same hemisphere lens size while exhibiting slightly lower directivity.     

履带车横纵摇对雷达天线指向影响的计算分析

建立了履带车横纵摇对雷达天线指向影响的分析模型，推导了一套计算公式，并实现了程式化，给出了一个算例，对产生的误差进行了分析，用CAD三维系统进行了仿真。     

Nonlinear optimization extends the bandwidth of Yagi antenna

A cost function is given for the optimization of the directivity of an antenna array while simultaneously achieving the flat behavior over the wide range of frequencies. The optimization of a six-element Yagi antenna resulted in a virtually flat directivity over the bandwidth of 33 percent. The allowable tolerances on element lengths of the optimized antenna are 0.25 percent or larger.     

一种基于星载多波束天线的单星干扰源定位方法

针对地球同步轨道通信卫星,提出了一种基于星载多波束天线的单星干扰源定位方法。该方法利用星载多波束天线的方向性,通过求解三个波束的等信号强度曲线交点确定干扰源位置。首先,估计干扰信号在多波束环境下的强度分布;其次结合天线方向图的数学模型,建立关于干扰信号链路计算的方程组;最后求解该方程组实现干扰源定位。采用上述单星定位方法对地面干扰源进行了定位仿真,结果表明了该方法的有效性。     

Short cylindrical antennas with enhanced radiation or high directivity

The feasibility of enhancing the radiated power or improving the directivity of a short cylindrical antenna by double impedance loading is investigated. An approximate solution for the current on a doubly loaded short antenna is developed, and typical current dlstributions, impedances, and radiation patterns of antennas appropriately loaded to implement enhanced radiation or high directivity are presented. Significant improvements in radiated power or directivity can be achieved with optimum impedance loadings. Theoretical predictions are verified by the results of an experimental study.