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171.
正交投影 (OP)自适应波束形成算法性能优良 ,但需要进行复协方差矩阵特征分解 ,运算量大。提出了一种基于酉变换的OP自适应波束形成算法 ,该算法对取样协方差矩阵Toeptitz化后利用酉变换将其转换为实矩阵 ,然后对实矩阵特征分解进行自适应波束形成。波束形成器的实值运算可节省大量计算时间。理论分析和计算机仿真结果表明此方法是有效的。  相似文献   
172.
《中国航空学报》2020,33(12):3220-3227
The continuous Scanning Laser Doppler Vibrometry (SLDV) developed on the base of the galvanometer scanner system has made it possible to quickly obtain the full field vibration responses within a rectangular area of the structure. In this paper, an arbitrary continuous scanning path generating method for Continuous Scanning Laser Doppler Vibometry (CSLDV) is further put forward in order to allow the CSLDV suitable for testing structures featured by complex shapes not just for regular areas. In the first step, the relationship between position of laser spot and the driving voltages of galvanometer scanner system has been described by a mathematical modeling. Then, a novel arbitrary scanning path generating strategy based on CSLDV is presented by deforming a normalization rectangular scanning path to an arbitrary continuous scanning path. The mapping relation between the normalization rectangular scanning path and arbitrary continuous scanning path is established using the reference points. In the second step, a compressor blade with curved surface was taken as an example for modal test using the proposed method. At the same time, a validated experiment was performed in SLDV. The results show the mode shapes derived from the extended CSLDV are in agreement with those from SLDV and the Modal Assurance Criterion (MAC) between the two are all greater than 0.96. They also demonstrate the feasibility and effectiveness of the proposed method for CSLDV test and show strong potential on further practical engineering applications.  相似文献   
173.
《中国航空学报》2020,33(2):508-519
A Non-Intrusive Reduced-Order Model (NIROM) based on Proper Orthogonal Decomposition (POD) has been proposed for predicting the flow fields of transonic airfoils with geometry parameters. To provide a better reduced-order subspace to approximate the real flow field, a domain decomposition method has been used to separate the hard-to-predict regions from the full field and POD has been adopted in the regions individually. An Artificial Neural Network (ANN) has replaced the Radial Basis Function (RBF) to interpolate the coefficients of the POD modes, aiming at improving the approximation accuracy of the NIROM for non-samples. When predicting the flow fields of transonic airfoils, the proposed NIROM has demonstrated a high performance.  相似文献   
174.
A novel range-Doppler imaging algorithm with OFDM radar   总被引:1,自引:1,他引:0  
《中国航空学报》2016,(2):492-501
Traditional pulse Doppler radar estimates the Doppler frequency by taking advantage of Doppler modulation over different pulses and usually it requires a few pulses to estimate the Doppler frequency. In this paper, a novel range-Doppler imaging algorithm based on single pulse with orthogonal frequency division multiplexing(OFDM) radar is proposed, where the OFDM pulse is composed of phase coded symbols. The Doppler frequency is estimated using one single pulse by utilizing Doppler modulation over different symbols, which remarkably increases the data update rate. Besides, it is shown that the range and Doppler estimations are completely independent and the well-known range-Doppler coupling effect does not exist. The effects of target movement on the performances of the proposed algorithm are also discussed and the results show that the algorithm is not sensitive to velocity. Performances of the proposed algorithm as well as comparisons with other range-Doppler algorithms are demonstrated via simulation experiments.  相似文献   
175.
在传统的无条件安全认证码中,假定发方和收方是相互信任的,他们不会互相欺骗。但有些情况也可能不是这样,发方在发出一个消息后,不承认是他发的,收方捏造了一个消息,声称来自发方,在这种情况下就需要增添仲裁方。带仲裁的认证码能解决通信系统中发方与收方互不信任的问题。利用有限域上二元多项式构造了一个带仲裁的认证码,并计算了所构造码的参数。当编码规则按等概率分布选取时,计算出了敌方与收方成功模仿攻击和成功替换攻击的最大概率.以及发方成功模仿攻击的最大概率。  相似文献   
176.
通过大量的正交试验,研究陶瓷材料在低速下的磨削性能,优化陶瓷磨削参数,对于丰富陶瓷磨削理论,指导实际生产实践具有重要的现实意义.  相似文献   
177.
在正交频分复用(Orthogonal frequency division multiplexing,OFDM)通信系统中提出了一种基于新颖训练序列的同步算法.该训练序列只使用了一个OFDM符号,并且具有中心对称和前后部分一致的双重结构.在进行完粗定时同步和小数倍频率同步后,使用逆快速傅里叶变换(IFFT)运算来进行精...  相似文献   
178.
对宽带信号采用基于多项式聚焦矩阵的方法进行到达角估计,并进行了计算机仿真。计算机仿真表明,多项式聚焦矩阵具有计算量小、抗噪性好、能对相干信号进行到达角估计的优点,但需要满足阵元间距远小于信号半波长的条件。当阵元间距不满足该条件时,会引入较大的估计误差。  相似文献   
179.
通过介绍作者在工作中使用多项式拟合进行接收机频响补偿并取得的良好效果,说明多项式拟合是一种非常有用的工具。  相似文献   
180.
某航天测控系统中Ka下行链路对频率综合器的各项性能指标提出了很高的要求。在设计中,采用对参考频率、L频段本振、S频段频综和Ku频段频综分别设计的方案,综合考虑多种因素,充分利用锁相环、DDS、窄带VCO和正交混频等技术的优势,最终实现了对频率的精确控制、精密步进和良好的相噪特性。  相似文献   
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