相关干涉测向天线关键技术和实现

以五单元天线阵为例,探讨了相关干涉测向体系中测向天线设计过程中通过合理设置孔径和基线组合来消除相位模糊和测量误差,以及天线原始相位样本采集等关键技术和实现方法。     

2.4GHz无线电波的相位干涉测向研究

讨论了利用相位差测量2.4 GHz入射电磁波方位角和仰角的方法.在理想情况下分别对接收天线为三元阵和五元阵时对测向系统进行仿真,针对其测向精度比较二者的优劣性.对于五元阵接收到的信号所具有的“相位模糊”问题,采用“虚拟基线法”解相位模糊,提高测向精度.     

一种多接收通道的增益与相移失配均衡方法

针对多个接收通道增益、相移特性的不一致给测向带来很大误差,提出一种通过标准测试信号,建立通道频率传输特性补偿数据库的方法,对实际接收信号进行精确的通道均衡补偿,有效解决了接收通道增益失配与相移失配问题及减少了测向误差.仿真证明:在比幅法测向系统中.间距d越小,幅度补偿带来的好处越明显;在比相幅法测向系统中,间距d在较大的变化范围内.相位补偿对测向误差都有明显改善.这种算法具有简洁、运算速度快的特点,适合天线数目、信道数目不多的中、小型可移动测向设备.     

一种战术车载式短波测向的新算法

本文针对现有的战术车载式短波三信道测向体制,提出了一种新的测向算法.该算法采用三信道模型,从采集到的三个信道的数字信号相关函数入手,导出了快速估计到达波方向的新算法.考虑到实际测向系统三个信道的振幅、相位的不一致性,提出了一种有效的校准算法.另外,本文也提出了一个实用的信号检测方法,以进一步提高新算法的抗噪声性能.理论分析表明,该算法可以很好地解决调制方式兼容、低信噪比下的测向精度以及信道间的幅度、相位失配等问题.针对AM、SSB信号进行了外场实测实验,结果显示了该算法的良好性能.     

相移干涉三维形貌纳米检测及算法研究

基于相移干涉理论设计并实现了微平面三维形貌测试系统，针对三维形貌检测解包裹过程中出现的问题，改进了现有的残差点判断法，能够更加准确、快速地确定残差点的存在．对相位解包裹算法进行了系统研究．分析了干涉图中残差对相位解包裹的影响，提出了一种基于二阶导数的区域增长解包裹算法．在实际测量中，最终结果得到了明显的改善，证明了该方法的有效性，提高了系统精度、采用此算法，系统的纵向测量误差小于2nm．     

被动定向浮标数字解复用技术

介绍了被动定向浮标信号传输系统中复合信号解复用的工作原理,推导了解复用的过程,解释了罗盘补偿矢量传感器自转对浮标测向的影响。提出了一种解复用的数字信号处理算法．在信号处理板上软件实现解复用。设计了一种软件导频锁相环,解决了偶极子信号解调过程中频率相位精确跟踪的问题。该技术降低了浮标接收机的复杂性,保证了通道一致性,提高了可靠性和定向精度,同时降低了浮标的成本。通过仿真对导频锁相环的性能作了评价,并通过湖上试验对其进行了验证。     

合成孔径声纳干涉相位图噪声抑制方法分析

讨论了合成孔径声纳的干涉相位图降噪问题。利用加性噪声模型,分析了四种降噪算法:像素平均法、非线性条件邻域均值法、模糊中值法和向量滤波法。通过仿真数据生成的干涉相位图进行降噪分析得到结论:通过像素平均法和条件邻域均值法降噪后不能准确地生成高度图,不推荐在实际中使用。而模糊中值法和向量滤波法通过降噪可以准确地生成高度图。通过相位图残留点数和高度图方差对比发现,向量滤波法性能最优,是一种快速有效的噪声抑制方法。     

基于蛙跳思想的量子编码遗传算法

量子门旋转相位、变异概率大小的确定,是目前制约量子遗传算法效率的两个主要问题。本文提出一种基于蛙跳思想的量子编码遗传算法(QRGA),该算法采用自适应的方式对量子旋转门旋转角进行调整,并基于模糊逻辑将蛙跳的步长进行量化以指导变异概率调整,保证进化的方向性和提高算法效率,对比实验结果表明算法可以避免陷入局部最优解,并能快速收敛到全局最优解,在运行时间和解的性能上都取得了较好的效果。     

一种改进的WSF算法在单矢量水听器多目标方位估计中的应用

文章针对单个矢量水听器的多目标方位估计,提出了一种基于加权子空间拟合(WSF)的算法,该算法首先对单个矢量水听器接收数据作一任意的时间延迟,而后仿照ESPRIT算法的思路求解阵列响应矩阵,从中抽取各目标的波达方位。该算法在保留WSF算法分辨力高、估计方差小的优点的同时,通过结合ESPRIT算法的思想,克服了WSF算法计算量大,需迭代求解的缺点。由于该算法和声源频率无关,因而可直接应用于宽带声源的测向,并避免了传统ESPRIT算法中因估计延时相位而导致的频率-方位模糊问题。文中通过数值仿真和推导Cramer-Rao下界,给出了该算法的性能评价,数值仿真和湖试实验结果也充分验证了该算法的有效性。     

GPS双星航姿测量研究

提出用两部测量型GPS接收机，实时观测两颗以上GPS卫星在站心坐标系下的高度角，方位角和载波相位，来推算基线（船线）的航向和姿态，初步解决了整周模糊度的解算问题，文中对影响航向和姿态准确解算的因素进行了分析，并提出了改进的办法。     

A Genetic Algorithm Applied for Optimization of Antenna Arrays Used in Mobile Radio Channel Characterization Devices

This paper presents a proposed method for synthesizing scenario-dependent channel characterization system arrays that are adapted to the mobile radio environment where measurements take place. The criterion for synthesizing the array is the minimization of the angular CramÉr–Rao lower bound, which is the lower bound of the mean square estimation error (MSEE) for an unbiased estimator. The core of the process is a genetic algorithm (GA) that seeks for the most advantageous array topology for each scenario. Simulation results show that the method succeeds in synthesizing feasible antenna arrays that have increased direction of arrival (DoA) estimation accuracy and are superior to the arrays typically used during actual measurement campaigns.      

Ambiguity Resolution in Direction of Arrival Estimation with Linear Antenna Arrays Using Differential Geometry

Linear antenna arrays (LAs) can be used to accurately predict the direction of arrival (DOAs) of various targets of interest in a given area. However, under certain conditions, LA suffers from the problem of ambiguities among the angles of targets, which may result in misinterpretation of such targets. In order to cope up with such ambiguities, various techniques have been proposed. Unfortunately, none of them fully resolved such a problem because of rank deficiency and high computational cost. We aimed to resolve such a problem by proposing an algorithm using differential geometry. The proposed algorithm uses a specially designed doublet antenna array, which is made up of two individual linear arrays. Two angle observation models, ambiguous observation model (AOM) and estimated observation model (EOM), are derived for each individual array. The ambiguous set of angles is contained in the AOM, which is obtained from the corresponding array elements using differential geometry. The EOM for each array, on the other hand, contains estimated angles of all sources impinging signals on each array, as calculated by a direction-finding algorithm such as the genetic algorithm. The algorithm then contrasts the EOM of each array with its AOM, selecting the output of that array whose EOM has the minimum correlation with its corresponding AOM. In comparison to existing techniques, the proposed algorithm improves estimation accuracy and has greater precision in antenna aperture selection, resulting in improved resolution capabilities and the potential to be used more widely in practical scenarios. The simulation results using MATLAB authenticates the effectiveness of the proposed algorithm.     

基于反卷积的双线阵聚焦波束形成被动定位方法

为了提高双线阵聚焦波束形成在阵元数少或频率低时的定位精度,文章研究了一种基于反卷积的双线阵聚焦波束形成被动定位方法。首先在测量区内对双线阵接收信号进行球面波补偿,给出噪声源分布的声图信息。然后根据阵型的参数,计算双线阵的指向性函数。最后利用一种适用于移变阵列的二维扩展R-L反卷积算法,对声图波束输出和双线阵的指向性函数做反卷积,求解基于反卷积波束形成的源的分布。该方法旁瓣更低,分辨力更高,有效提高双线阵聚焦波束形成的定位精度和左右舷分辨能力,为后续的减振降噪、噪声检测等工作提供了参考。     

Wi-Fi/WiMAX双极化阵列天线研究

提出一种应用于Wi-Fi/WiMAX的宽带高增益双极化阵列天线.它由+45°和-45°正交极化的两个天线组成。当频率为2.38~2.72 GHz时,天线的回波损耗大于-10 dB;端口1与端口2之间隔离度大于20 dB;端口1在2.45 GHz时获得最大增益为17.14 dBi,端口2在2.483 GHz时获得最大增益为17.15 dBi.仿真和测试很好相吻合,该双极化天线能满足Wi-Fi/WiMAX通信网络要求.     

Edge‐adaptive color interpolation for complementary color filter array

Complementary color filter array (CCFA) is widely used in consumer‐level digital video cameras, since it not only has high sensitivity and good signal‐to‐noise ratio in low‐light condition but also is compatible with the interlaced scanning used in broadcast systems. However, the full‐color images obtained from CCFA suffer from the color artifacts such as false color and zipper effects. These artifacts can be removed with edge‐adaptive color interpolation (ECI) approaches which are generally used in primary color filter array (PCFA). Unfortunately, the unique array pattern of CCFA makes it difficult that CCFA adopts ECI approaches. Therefore, to apply ECI approaches suitable for CCFA to color interpolation is one of the major issues to reconstruct the full‐color images. In this paper, we propose a new ECI algorithm for CCFA. To estimate an edge direction precisely and enhance the quality of the reconstructed image, a function of spatial variances is used as a weight, and new color conversion matrices are presented for considering various edge directions. Experimental results indicate that the proposed algorithm outperforms the conventional method with respect to both objective and subjective criteria. © 2006 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 16, 92–102, 2006     

一种相控阵雷达天线极化特征的外场测试方法

为了解决相控阵雷达天线极化特征的外场测量问题,研究了极化的幅相测量法和斜天线测试场的布局方法,设计了基于双通道接收技术的相控阵雷达天线极化特征的一种外场测试方法。给出了应用该种方法的测量装置、测量布局、测量内容、测量步骤,分析了测量误差。该种测试方法在相控阵雷达天线极化特征测试任务中得到成功应用,为某武器系统的研制提供了准确的测量数据和宝贵的研究资料。     

The cross algorithm for phase-aberration correction in medical ultrasound images formed with two-dimensional arrays

Common-midpoint signals in the near-field signal-redundancy (NFSR) algorithm for one-dimensional arrays are acquired using three consecutive transducer elements. An all-row-plus-two-column algorithm has been proposed to implement the one-dimensional NFSR algorithm on two dimensional arrays. The disadvantage of this method is that its ambiguity profile is not linear and a timeconsuming iterative method has to be used to linearize the ambiguity profile. An all-row-plus-two-column-and-a-diagonal algorithm has also been proposed. Its ambiguity profile is linear, but it is very sensitive to noise and cannot be used. In this paper, a novel cross algorithm is proposed to implement the NFSR algorithm on two-dimensional arrays. In this algorithm, common-midpoint signals are acquired using four adjacent transducer elements, which is not available in one-dimensional arrays. Its advantage includes a linear ambiguity profile and a higher measurement signal-to-noise ratio. The performance of the cross algorithm is evaluated theoretically. The region of redundancy is analyzed. The procedure for deriving the phaseaberration profile from peak positions of cross-correlation functions between common-midpoint signals is discussed. This algorithm is tested with a simulated data set acquired with a two-dimensional array, and the result shows that the cross algorithm performs better than the all-row plus-twocolumn NFSR algorithm.     

Implementation of the near-field signal redundancy phase-aberration correction algorithm on two-dimensional arrays

Near-field signal-redundancy (NFSR) algorithms for phase-aberration correction have been proposed and experimentally tested for linear and phased one-dimensional arrays. In this paper the performance of an all-row-plus-two-column, two-dimensional algorithm has been analyzed and tested with simulated data sets. This algorithm applies the NFSR algorithm for one-dimensional arrays to all the rows as well as the first and last columns of the array. The results from the two column measurements are used to derive a linear term for each row measurement result. These linear terms then are incorporated into the row results to obtain a two-dimensional phase aberration profile. The ambiguity phase aberration profile, which is the difference between the true and the derived phase aberration profiles, of this algorithm is not linear. Two methods, a trial-and-error method and a diagonal-measurement method, are proposed to linearize the ambiguity profile. The performance of these algorithms is analyzed and tested with simulated data sets.     

矢量水听器阵列自适应子空间跟踪算法

矢量水听器能同时共点获得声场中声压和振速,与其他水听器相比,能获得更多的信息量,具有很好的应用前景。矢量水听器阵列的MUSIC算法能实现360°无模糊方位估计,然而对于方位时变的目标源,该算法很难完成对上述目标源方位进行实时跟踪估计。鉴于此,将MALASE算法和MUSIC算法相结合,提出了一种矢量水听器阵列的自适应子空间跟踪算法。仿真结果表明,该算法既保留了MUSIC算法的性能,又实现了对目标源进行实时跟踪估计,且方位估计误差仅为0．4°左右。