多端口T/R组件的单通道噪声系数测试方法

多端口T/R组件输出端口的噪声由各个通道共同决定,要测试单独通道的噪声系数非常困难。提出了一种基于衰减器改变的多端口TR组件单通道噪声系数测试方法,消除了其他通道的噪声影响,实现了对单独通道噪声系数的测试。通过测试一个8通道T/R组件的各个通道噪声系数,与单独通道测试结果进行了对比,两种方法测试结果最大差异为0.08 dB,验证了该方法可以很准确地测量多端口网络的单通道噪声系数。     

一种考虑场景静止的非均匀性校正方法

针对用神经网络法进行非均匀性校正时,当场景长时间静止会使校正图像像质变差和产生重影的问题,提出了一种考虑场景静止的非均匀性校正方法.算法中提出一种新的判断场景运动与否的方法,如果判断为场景静止则对其增益和偏置进行相应的处理,以达到更好的校正效果.仿真结果表明该方法有效地解决了像质变差和重影的问题.     

基于微波多层板的小型化多通道接收前端设计

基于微波多层板技术,通过对单片微波集成电路(MMIC)、微机电系统(MEMS)和低温共烧陶瓷(LTCC)滤波器等微组装工艺的优化和分析,使多通道接收前端进一步实现小型化设计和应用。同时,对电路和结构进行改进,使前端组件具有更好的幅相一致性和高隔离度。最终实现的C频段四通道接收前端尺寸为120 mm×50 mm×12 mm,幅相一致性分别小于±0.8 d B和±5°,通道间隔离度高于60 d Bc。该设计方法的实现为小型化多通道接收前端的工程化应用提供了一种有效的解决方案。     

Power output fluctuations in large scale pv plants: One year observations with one second resolution and a derived analytic model

The variable nature of the irradiance can produce significant fluctuations in the power generated by large grid‐connected photovoltaic (PV) plants. Experimental 1 s data were collected throughout a year from six PV plants, 18 MWp in total. Then, the dependence of short (below 10 min) power fluctuation on PV plant size has been investigated. The analysis focuses on the study of fluctuation frequency as well as the maximum fluctuation value registered. An analytic model able to describe the frequency of a given fluctuation for a certain day is proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

Uncertainty of the spectral mismatch correction factor in STC measurements on photovoltaic devices

Valuation of photovoltaic devices depends strongly on the measured power output of the device. This quantity is usually determined under artificial sunlight in production line measurement systems or industrial or research test labs. A practical calibration chain is realized essentially with measurements at solar simulators. The measurement conditions are defined in the IEC 60904 series of standards. An important part of the standard testing conditions is the definition of a specific spectral distribution of the sunlight (AM1.5 global). The inevitable deviations of the spectrum of artificial light sources from the standard spectrum have to be taken into account by a spectral mismatch factor. The uncertainty of this crucial correction is spectrally dependent, in most cases unknown and complex and inconvenient to evaluate. In this article a randomizing method is proposed which allows one to calculate the uncertainty of the mismatch factor from the uncertainties of the input parameters determined with high spectral resolution. Based on a range of different spectral responses of solar cells on the one hand and variations of the solar simulator spectral distribution on the other, we are able to generalize the results to a broad set of measurement configurations. A sensitivity analysis reveals the crucial wavelength regions and thus allows the systematic optimization of simulator spectra and selection of reference cells. Copyright © 2010 John Wiley & Sons, Ltd.     

基于改进型巴特勒矩阵的短波8元圆环阵列多波束技术研究

传统短波接收天线为单一的波束指向天线或全向天线。为提高接收天线增益,同时产生多个波束指向不同方向,提出利用巴特勒矩阵作为短波接收天线阵的无源波束形成网络。在传统8×8巴特勒矩阵结构的基础上,设计改进型8×8巴特勒矩阵。以均匀8元圆环阵列为天线模型,利用FEKO仿真分析了其天线特性。在3~11 MHz频段内,P2、P3、P6、P7四个端口分别在202.5°、292.5°、112.5°、22.5°方向上得到了方向性较强的单一波束,7 MHz时波束增益达到最大11.9 dBi,波瓣3 dB宽度平均为60°;在P1、P4、P5、P8端口产生相同的2个波瓣,7 MHz时其波束增益达到最大9.8 dBi,波瓣3 dB宽度平均为89°。由以上仿真分析得出,该改进型8×8巴特勒矩阵能够同时产生6个波束,波束覆盖8个方向,提高了波束的方向性,提高了天线增益。     

Multiple Emitters Localization by UAV with Nested Linear Array: System Scheme and 2D-DOA Estimation Algorithm

Unmanned Aerial Vehicle(UAV)equipped with uniform linear array has been applied to multiple emitters localization.Meanwhile,nested linear array enables to enhance localization resolution and achieve under-determined Direction of Arrival(DOA)estimation.In this paper,we propose a new system structure for emitters localization that combines the UAV with nested linear array,which is capable of significantly increasing the positioning accuracy of interested targets.Specifically,a localization scheme is designed to obtain the paired two-dimensional DOA(2D-DOA,i.e.azimuth and elevation angles)estimates of emitters by nested linear array with UAV.Furthermore,we propose an improved DOA estimation algorithm for emitters localization that utilizes Discrete Fourier Transform(DFT)method to obtain coarse DOA estimates,subsequently,achieve the fine DOA estimates by sparse representation.The proposed algorithm has lower computational complexity because the coarse DOA estimates enable to shrink the range of over-complete dictionary of sparse representation.In addition,compared to traditional uniform linear array,improved 2D-DOA estimation performance of emitters can be obtained with a nested linear array.Extensive simulation results testify the effectiveness of the proposed method.     

光伏系统DC/DC变换器设计与仿真

本次研修主要针对整个光伏发电系统前端的DC/DC转换器部分进行研究、设计和仿真。此部分不仅要根据设计要求设计选择合理的占空比和元件参数,完成DC/DC变换,还需要考虑最大能量跟踪控制,以保证最大可能的利用能源,提高系统效率。     

混合同余法产生随机噪声的FPGA实现

在电子对抗领域,利用FPGA产生伪随机序列模拟噪声源的方法,可为实现各种噪声干扰带来便利。文中设计了基于混合同余法和中心极限定理产生随机噪声的FPGA实现方法。算法上对传统混合同余法进行了简化,避免了FPGA实现时大量的乘除运算。测试结果表明,该方法不仅有效可行,且简捷高效,生成的伪随机数具有周期、均值、方差等关键参数灵活可控,概率分布类型可变的特点,可为各种噪声干扰提供不同的噪声样本。     

一种改进的水下运动目标远航程导航定位方法

当前水下运动目标定位主要采用船载水听器基阵-声信标跟踪定位方法和船拖水听器基阵-声信标跟踪定位方法,但这两种方法存在跟踪定位精度较低、实施难度大以及设备维护修理困难等问题。基于此,提出了采用水下目标加装光纤陀螺仪-差分全球定位系统(DGPS)组合制导技术,以实时测量、记录水下目标的航行姿态、航行速度和位置坐标,通过编码把目标的位置坐标数据实时转换为同步水声多频多脉冲时延编码信号发射,利用船拖水听器测量水声多频多脉冲时延编码信号,通过船载基站实时解算,从而实现指引测控船完成远航程水下目标的实时跟踪、定位、监测任务。试验结果表明,该方法可有效实现对远航程水下目标的跟踪定位和实时监测。