减少定向井方位漂移的途径新探

方位漂移是影响定向井准确中靶的主要因素之一。根据定向井施工中“井斜角较大时，方位漂移量相对较小”的规律，提出了“通过缩短较小井斜角斜井段长来减少施工过程中的方位漂移量”的方法，并介绍了实现该方法的2种途径。     

An algorithm for the computation of the solar position

A new algorithm for the determination of the solar position is proposed. The importance of tracking accurately the position of the sun is evident when considering high concentration thermal systems. In the literature are found many fast algorithms for the determination of the sun position within 0.01°, and complex astronomical algorithms that allow a precision of 0.0003° but at the price of a large amount of calculation. The algorithm proposed in this work has a precision that is half-way between the two cases (maximal error 0.0027°), that should be sufficient for all the applications in solar engineering, with a computational cost comparable to the cost of the fast algorithms.     

基于TMS320LF2407芯片的天线跟踪控制设计

为解决机载天线自动对星的问题,基于TI公司TMS320LF2407芯片,设计了一种通过正交编码脉冲计数进行天线跟踪控制的具体设计方法。该设计方法采用位置环、速度环双闭环控制,以获取良好的动态响应和跟踪精度,并给出了控制系统中相应的软件设计流程图。另外也详细给出了机载天线对星角度的具体算法。     

相控阵雷达反演口径分布中的运动补偿

目标的径向运动对时序Ｗａｌｓｈ－Ｈａｄａｍａｒｄ相位权重反演相控阵雷达的口径幅相分布会产生影响,这一影响可以通过运动补偿的方法消除。运动补偿方法需要先测出目标的多普勒频率,由于目标运动对相控阵天线输出信号的影响是使该输出信号的相位产生偏移。这个偏移可以由多普勒频率计算得到,从而可以求解出经过运动补偿后的口径分布。多普勒频率的测频精度愈高,反演口径分布的误差愈小。数值仿真表明,１Ｈｚ的测频精度已足以     

某型雷达天线座方位壳体的优化设计

为提高某型雷达天线座的适装性,对其进行了整机结构优化设计,其中占整机质量比重较大的方位壳体是改进设计的重点之一。在对原设计进行分析的基础上,对其壁厚及部分外形尺寸进行了优化设计,对改进后的方位壳体进行了静态及模态分析。改进后的方位壳体质量大幅降低,并通过了试验验证。     

方位捷联平台速率陀螺动态误差模型试验方法研究

建立方位捷联平台速率陀螺的误差模型,提出了在 H_2范数意义下采用正交多项式逼近算法,估计方位捷联平台速率陀螺的动态误差模型。并研究了平台偏离水平面时的处理方法。试验结果表明该方法具有较好的准确性,采用方位捷联平台惯导系统的某导弹靶试结果,证明其工程实用价值是显著的。     

Performance analysis of azimuth electronic beam steering mode spaceborne SAR

Pointing angle and pattern of the antenna can be changed swiftly to actualize the azimuth beam scanning by using electronic beam steering, which makes the Synthetic Aperture Radar (SAR) system more flexible and achieve a high resolution or cover a long strip within short time span. When the pointing angle is steered away from boresight, some aberrations may appear on the antenna pattern, e.g., the grating lobe appears, the main lobe gain decrease, and antenna pattern broadens, e.g., the aberrations result in the worsening of system performance, and complicate the corresponding performance analysis method. Conventional computation methods of performance parameters do not account for the rapid change of the antenna pattern. It introduces remarkable errors when the scanning angle is large. In this paper, a method of calculating performance parameters is proposed for the beam steering mode, which achieves the parameters by the energy accumulation in time domain. Actually, the proposed method simulates the working process of SAR and obtains accurate performance parameters. Furthermore, we analyze the effects of the grating lobe on the Azimuth Ambiguity to Signal Ratio (AASR), and present the generic Pulse Repetition Frequency (PRF) choosing principle which can also prevent the ambiguous area from weighting by the grating lobe. Finally, the effect of the antenna configuration on the performance parameters is analyzed by a system example.     

Prediction of the optimum slope and surface azimuth angles using the Genetic Algorithm

In this paper, the Genetic Algorithm is applied to calculate the optimum slope and surface azimuth angles for solar collectors to receive maximum solar radiation. An area of Iran is selected to verify the results of this algorithm. The optimum angles and the collector input solar energies for these angles are calculated in hourly, daily, monthly, seasonally and yearly bases respectively. Then, the influence of different combinations of solar radiation components on the optimum slope angle and the energy gain is investigated. The results show that the Genetic Algorithm is a useful technique to find the optimum angles specifically when the number of independent parameters is large. The results show that the daily, monthly and yearly optimum surface azimuth angles for receiving the maximum solar energy are zero. Adjusting the collector at the daily optimum slope angle slightly increases the collector input energy compared with the case of monthly optimum slope angle so that the gain of solar energy is almost the same. The results also show that the hourly optimum surface azimuth angle is not zero and mounting the solar collector at the hourly optimum slope and azimuth angles increases the input energy significantly compared with the case of daily optimum angles. It is shown that the optimum slope angles are mostly dependent on the beam solar radiation. Furthermore, the results indicate that the optimum slope angles of solar collector and Photovoltaic panels are almost the same.     

一种应用于斜视聚束模式的改进极坐标格式成像算法

极坐标格式算法(Polar Format Algorithm, PFA)通常应用于正侧视聚束SAR成像,当PFA应用斜视聚束时,传统沿视线插值(Line Of Sight Interpolation, LOSI)PFA方法会导致方位频谱非等间隔采样。该文针对上述问题提出一种新的方位频谱插值方法,根据斜视聚束的几何模型可以得到方位频谱精确的插值形式,从而实现对方位频谱等间隔重采样。在获得了均匀的频谱后进行2维逆傅里叶变换,便可以得到大范围的斜视聚束场景。为了验证该文算法的有效性,进行了实验仿真及实测数据验证,该方法与传统插值的方法进行比较,能够增大斜视聚束场景范围。     

基于Chirp_z变换与方位变标地球同步轨道SAR成像算法

针对地球同步轨道合成孔径雷达(GEO SAR)成像距离向处理复杂,方位向空变性强问题,该文提出一种基于Chirp_z变换与方位变标的成像算法。首先在回波模型中考虑停-走-停假设带来的相位误差,然后给出目标点的斜距表达式,并利用泰勒级数对斜距进行了高阶展开,通过级数反演法得到信号频谱表达式,利用高效的Chirp_z变换校正距离走动,简化距离向处理,利用改进的变标因子校正方位向信号一次,二次,三次展开项系数线性时变性,并在方位频域内补偿变标操作引入的相位误差。仿真结果表明该算法能够实现地球同步轨道SAR聚集成像。