矩阵空域预滤波目标方位估计

提出了基于矩阵空域预滤波处理的目标方位估计新方法。通过设计一个空域的矩阵滤波器对传感器阵列数据进行矩阵处理,抑制阻带扇面的干扰与噪声,且尽量保证让通带扇面的信号无失真通过。由于该空域滤波器的输出仍为阵元域数据,因此可以很方便地在很多阵列信号处理算法之前通过增加空域预滤波处理来达到抑制空间干扰、提高系统处理能力的目的。文章通过目标方位估计的具体实例来说明矩阵空域预滤波处理对系统性能的改善作用。计算机仿真和实测数据处理结果表明,矩阵空域预滤波处理有效地抑制了空间干扰与噪声,提高了方位估计算法对感兴趣扇面目标的方位分辨与估计性能。此外,仿真结果表明采用分扇面空域预滤波处理方法,使基阵具有了分辨多于阵元数目信号源的能力。     

一种声矢量阵子空间拟合算法及其矩阵预滤波器设计

为了减少矩阵预滤波器通带响应畸变程度,提出了一种基于阻带约束通带最大k个误差范数和(k为约束点的数目)最小化准则的矩阵预滤波器设计方法,通过使通带内最大的k个响应误差范数和最小化,减少了通带响应畸变程度。同时针对声矢量阵方位估计算法计算量过大的问题,提出了一种基于矩阵预滤波的声矢量阵子空间拟合算法,通过对声矢量阵声压、振速信号子空间进行联合处理,将预滤波矩阵和拟合子空间矩阵均减少为M×M维(M为阵元数),从而减少矩阵预滤波器设计和方位搜索所需时间。仿真结果和分析表明该算法性能和预滤波MUSIC算法相当,但在计算量上有较大优势,矩阵预滤波方法能抑制阻带干扰,提高后续算法的分辨和估计性能。      

宽带最优空域矩阵滤波器设计

本文首先针对窄带,分别设计出通带误差或阻带响应满足设定条件,以及通阻带归一化误差之和最小的最优空域矩阵滤波器.利用Lagrange乘子理论,给出了最优解,以及确定最优Lagrange乘子的方程,显著提高了空域矩阵滤波器的设计效率.通过广义奇异值分解,进一步提高了设计效率.其次,从理论上分析了特定频带空域矩阵滤波器对其他...     

零点约束矩阵滤波设计

为解决在空域预滤波阶段抑制强噪声的问题,提出了零点约束矩阵滤波设计方法,并给出了解的表达式。通过设计凸规划问题,在严格约束阻带响应等于零的情况下,使通带误差最小。将凸规划问题转换为线性约束二阶最优化问题,构造Lagrange函数并得到最优解,重排后得出滤波矩阵。仿真可知,本方法可设计出强干扰离散分布或处于某扇面的预滤波器,可用于解决常规波束形成算法受强干扰影响方位估计性能的问题。      

基于分离指标的宽阻带低通滤波器设计

常见的开路短截线和阶跃阻抗结构在微带低通器设计中较为成熟,但是这些结构的低通滤波器受到寄生通带的影响,阻带不够宽。提出了一种基于分离指标的宽阻带低通滤波器设计方法,利用计算机仿真软件ADS,对常见的阶跃阻抗低通滤波器进行结构改进。该方法将低通滤波器设计指标重点分为滚降率和宽阻带抑制两部分,分别利用椭圆滤波器和巴特沃斯滤波器的本身特性实现设计目的,最后进行级联优化。此结构综合设计方法简单严谨,易于实现,改进的低通滤波器性能优越,实现了宽阻带的设计需求,通带0~3GHz,插入损耗<0.5dB,阻带4~12GHz,抑制>45dB。     

新型交叉指型低频宽阻带超导滤波器研究

本文提出了一种用于低频宽阻带滤波器设计的新型交叉指型谐振器(Interdigital Resonator,IDR),该谐振器具有结构紧凑、实现较强耦合、显著推高寄生通带等优异性能.文中设计和制作了中心频率为360MHz、相对带宽为4%的12节高温超导滤波器,实测结果表明,从通带到1.27GHz的阻带抑制超过80dB,第一寄生通带与基频通带频率比超过3.5.测试结果与设计结果符合得很好.     

具有宽阻带特性的6阶自均衡高温超导滤波器

本文提出了一种新颖的L型阶跃阻抗谐振器,该谐振器具有结构紧凑、抑制二次谐波能力强及易于实现电耦合及磁耦合等特点。使用该谐振器设计并制作了一款具有小型化、高选择性及宽阻带特性的6阶自均衡高温超导滤波器。测试结果表明,在70 K温度下滤波器的中心频率为1 601 MHz,3 dB带宽为24 MHz,带内回波损耗<14.87 dB,带内最大插入损耗约为0.22 dB,60%带宽范围内群时延起伏<3.13 ns,通带两侧具有一对深度的传输零点,实现了1 632~5 511 MHz范围内衰减>60 dB的宽平坦阻带。     

基于双SSLR的小型化双通带带通滤波器设计

设计了一种新的具有良好选择性的小型化的双模双通带带通滤波器。该滤波器的谐振结构由两个短路枝节加载谐振器(SSLR)连接到同一个接地金属柱构成。首先通过奇偶模分析方法分析单个SSLR的谐振频率,得到谐振频率的变化规律;然后为了实现滤波器的小型化,将两个SSLR连接到同一个金属柱上并且折叠微带线,通过调节枝节长度分析滤波器通带的变化;设计中使用双枝节分别对谐振器馈电的结构,并且引入了源与负载耦合,可以在上阻带多提供一个传输零点,以提高阻带抑制;最后对滤波器的传输零点进行分析,提高滤波器的选择性。通过上述的分析,对该滤波器进行仿真、加工以及测试,得到最后实物的测试结果与软件的仿真结果较为一致。     

基于矢量水听器阵列空域预滤波处理的多重信号分类算法研究

矢量水听器能同时拾取声压和振速信息,在相同的信噪比、阵元数及阵列孔径下,矢量阵定向性能优于声压阵列。目前,以多重信号分类算法(Multiple signal classification,MUSIC)为代表的高分辨定向算法已经广泛应用于矢量水听器阵列中。但是随着信噪比降低、信号源方位间隔减小,传统MUSIC算法定向精度及分辨概率显著下降。本文采用最小二乘法设计适用于矢量水听器水平阵列的矩阵空域滤波器,用于阵列数据的空间滤波预处理,可以对阻带扇面噪声进行有效抑制。由滤波后的数据协方差矩阵可以得到新的噪声子空间,在传统MUSIC算法基础上修正通带扇面内阵列流型的畸变后即可得到滤波后MUSIC算法的方位谱。仿真结果表明,当信噪比较低时,改进算法有效提高了通带扇面内目标方位分辨性能。最后本文对四基元矢量水平阵列海试数据进行了处理,改进算法对窄带信号定向较常规算法-3 dB束宽减小了13°,旁瓣级降低约8 dB。对有一定带宽的行船辐射噪声定向处理得到了更加精确的航迹图,海试数据处理结果证明了该算法的可行性和有效性。     

声表面波低插入损耗滤波器的研制(Ⅱ)──横向耦合谐振滤波器

目前移动通讯设备对窄带低插损高阻带抑制的滤波器有极大需求，而横向模式耦合谐振滤波器是实现这些性能的最佳方案之一。在理论上，本文应用陈东培和Hartmann等提出的耦合模理论模型对这种滤波器进行了分析设计；在实验上，以ST石英为基底材料，设计制作了152．55MHz频率的器件，器件性能接近目前国外已报道同类器件的水平，最低插损达2．7dB，阻带抑制约60dB，相对带宽0．5%~0．75％。，并能获得平坦的通带。     

Direction-of-arrival estimation using matrix spatial prefiltering approach

An approach to direction-of-arrival （DOA） estimation for multiple narrowband farfield signals is proposed. The technique uses a novel matrix spatial prefiltering approach. Specifically, a matrix filter is designed to spatially filter the incoming data snapshots. The un-wanted components arriving from the stopband angular sectors are attenuated and the desired components from the angular sector of interest pass with minimal distortion. The matrix filter spatially filters the element-space data and the output reserves the element-space data property, which makes it very useful by passing sensor data through a spatial prefilter prior to applying many other array processors to attenuate interferences and improve system performance. Several examples of DOA estimation problem are presented to illustrate the performance of the proposed spatial prefiltering approach. Results of simulation and real data show that the pre-filter can efficiently attenuate the spatial interferences and significantly improve the estimation and resolution capability of DOA estimators at low signal-to-noise ratios for the sources located inside the passband sector. In addition, the use of spatial prefilter makes it possible to estimate DOAs for multiple sources more than the number of the elements of an array.     

Improving excitation and inversion accuracy by optimized RF pulse using genetic algorithm

In this study, a Genetic Algorithm (GA) is introduced to optimize the multidimensional spatial selective RF pulse to reduce the passband and stopband errors of excitation profile while limiting the transition width. This method is also used to diminish the nonlinearity effect of the Bloch equation for large tip angle excitation pulse design. The RF pulse is first designed by the k-space method and then coded into float strings to form an initial population. GA operators are then applied to this population to perform evolution, which is an optimization process. In this process, an evaluation function defined as the sum of the reciprocal of passband and stopband errors is used to assess the fitness value of each individual, so as to find the best individual in current generation. It is possible to optimize the RF pulse after a number of iterations. Simulation results of the Bloch equation show that in a 90 degrees excitation pulse design, compared with the k-space method, a GA-optimized RF pulse can reduce the passband and stopband error by 12% and 3%, respectively, while maintaining the transition width within 2 cm (about 12% of the whole 32 cm FOV). In a 180 degrees inversion pulse design, the passband error can be reduced by 43%, while the transition is also kept at 2 cm in a whole 32 cm FOV.     

Spoof surface plasmon-based bandpass filter with extremely wide upper stopband

We investigate the guiding modes of spoof surface plasmon polaritons(SPPs) on a symmetric ultra-thin plasmonic structure. From the analysis, we deduce the operating frequency region of the single-mode propagation. Based on this property, a spoof SPPs lowpass filter is then constituted in the microwave frequency. By introducing a transmission zero at the lower frequency band using a pair of stepped-impedance stubs, a wide passband filter is further realized. The proposed filter is fed by a transducer composed of a microstrip line with a flaring ground. The simulated results show that the presented filter has an extremely wide upper stopband in addition to excellent passband filtering characteristics such as low loss, wide band, and high square ratio. A prototype passband filter is also fabricated to validate the predicted performances.The proposed spoof-SPPs filter is believed to be very promising for other surface waveguide components in microwave and terahertz bands.     

Design and performance of coplanar waveguide slotline bandpass filter

This paper describes the work involved in designing a coplanar waveguide -slotline bandpass filter. The filter designed to achieve at least -30dB insertion loss (S₂₁)in the stopband (8 to 8.5; 9.3 to 10 GHz) and less than -0.2 dB in the passband (8.75 to 9.05 GHz), with a centre frequency of 8.9 GHz. The filter and transition were fabricated on 1.27 mm thick RT-Duriod 6010.2 substrate and S-parameters were tested using standard SMA connectors with an HP-8510A network analyser.     

Design of sextuple-mode triple-ring HTS UWB filter using two-round interpolation

A single-stage ring resonator capable of introducing six modes within the ultra-wideband (UWB) passband is presented. The sextuple-mode resonator consists of three rings and three sets of stepped-impedance open stubs. Based on this sextuple-mode resonator, a UWB filter fed by the interdigital-coupling line (ICL) is designed. And we propose a two-round interpolation method to obtain the filter's initial dimensions. The designed filter is fabricated on a double-sided YBCO/MgO/YBCO high-temperature superconducting (HTS) thin film for demonstration. The experimental results show that this UWB filter produces eight resonances in the passband eventually, which effectively improves the in-band reflection and the band-edge steepness. Moreover, the upper stopband performance is enhanced due to the transmission zeros (TZs) generated by the stepped-impedance open stubs and the ICL structure. The measured good performance verifies the practicability of the two-round interpolation approach, which can also be extended to other odd-even-mode filter designs.     

Designing PMF with negative tap coefficient

DIRECT global optimization algorithm is innovatively used in design of PMF. Tap coefficient is attained by achieving DIRECT algorithm with C language and Matlab language is employed to simulate the amplitude response of filters. We have designed PMF (photonic microwave filter) with negative tap coefficient and then optimize the design. The minimum shape factor is as low as 1.3180. The results show that the algorithm is highly efficient in designing filter and can produce necessary passband and stopband response characteristics. In the meantime, transition band becomes steeper in the process of further optimization and the shape factor is closer to 1.     

矢量声纳高速运动目标稳健高分辨方位估计

针对水声矢量信号处理框架中的高速运动目标低信噪 比小快拍条件下的稳健高分辨方位估计问题, 将压缩感知技术应用于水声矢量信号空间谱估计模型中. 结合声矢量传感器结构特性, 探讨了基于声压振速联合处理的广义时域滤波方法; 结合矩阵空域预滤波理论, 设计了基于阻带约束通带均方误差最大值最小的空域滤波器, 研究了矢量声纳空域预滤波方法; 结合以上分析, 提出了基于压缩感知技术的时空联合滤波高分辨方位估计方法, 给出了方法的数学模型、物理解释及具体实施步骤.理论分析和计算机仿真试验表明, 新方法对于小快拍数 条件下的矢量声纳高速运动目标高分辨方位估计问题, 具有较低的双目标分辨门限和较高的估计精度, 有着良好的应用前景.湖上试验验证了方法的有效性. 关键词： 声矢量传感器 空间谱估计 时空滤波 压缩感知     

拖曳线列阵声呐平台噪声的空域矩阵滤波抑制技术

针对拖曳线列阵声呐平台噪声构成近场强干扰影响声呐弱目标探测的问题,利用近场平台噪声的多途传播特性,将匹配场定位技术和平面波目标方位估计技术结合,使用平台噪声到达接收阵的拷贝向量以及平面波方向向量共同设计平台噪声零响应约束空域矩阵滤波器,实现了平台噪声抑制.推导得出滤波器设计最优化问题的最优解,利用广义奇异值分解简化最优解表达式,并给出滤波器对平面波方向向量整体响应误差以及对平台噪声拷贝向量响应。利用平台噪声拷贝向量与远场平面波方向向量相关性,解释了平台噪声构成强干扰的原因,以及滤波后存在探测盲区的原因。由仿真可知,空域矩阵滤波处理可获得更小的探测盲区,同时获得盲区外更高的探测能力.      

Box-like spectral response of 2-D microring resonator arrays

In terms of the coupled mode theory and the transfer matrix technique, novel formulas of the transfer functions are presented for a 2-D microring resonator array. By using these formulas, transmission characteristics are analyzed for this kind of Si based polymer device. Simulation shows that by means of parallel-cascading multiple microrings in every filter element, the passband can be flattened, and the box-like spectral response can be formed; in terms of series-cascading such several filter elements, the passband becomes precipitous, and the non-resonant light and the crosstalk become weak.     

双折射滤波器光谱透射率函数的平坦化优化计算

对于双折射偏振光干涉滤波器，提出了一种产生平坦化光谱透射率函数的傅里叶级数对比的搜索方法，可在较大的通带和阻带范围内寻找到抖动很小时的所有可能的晶体偏转角度的数值解。给出了三块双折射晶体结构的抖动不大于0．1％时的晶体偏转角度的数值解，讨论了晶体偏角和厚度的变化对透射率函数波形的影响。