星载微波辐射热定标源辐射性能研究与应用

基于周期性阵列角锥结构星载微波辐射热定标源,运用时域有限差分算法(Finite Difference Time Domain,FDTD),建立有限大辐射体电磁波散射模型,探索该结构下热定标源在6.3～230 GHz 内辐射特性变化趋势,分析热定标源辐射性能(包括反射率r和发射率e)随涂层厚度t、角锥高宽比以及角锥宽度p 的变化规律。研究结果表明:热定标源反射率在低频段主要依赖涂层吸波性能,高频段则主要取决于涂层界面反射率;在低频段内,随涂层厚度的增加,热定标源反射率逐渐减小,发射率有所增大,但在高频处,呈现出较快的震荡趋势;在特定涂层厚度下,随着角锥高宽比增加,热定标源在全工作频段内反射率减小,发射率增大,且随着角锥宽度的增加,反射率增大,发射率减小。综合热定标源辐射性能研究结果,结合型号产品具体应用需求,设计开发出热定标源产品,并进行发射率测量,实测发射率均为0.998。     

手机液晶显示屏色温矫正

为了改善手机液晶显示屏白画面主观偏色的问题,本文运用了色度分析仪测量系统,对手机液晶显示屏白画面偏色矫正方法进行了研究。首先,分析了影响手机液晶显示屏白画面偏色的主要的原因,基于成本的考量,只进行后期模组段的色温矫正,借助设备厂商的色度分析仪测量手机液晶显示屏出厂时的白点坐标的分布范围,对比分析了色坐标优先(方案一)和亮度优先(方案二)两种色温矫正的方法。实验结果表明:方案一可以做到色坐标公差在±0.01以内,甚至更小(看算法的需要和设备的精度),但是无法应用于工程生产领域。方案二虽然牺牲了色温的一致性(±0.015),工厂的生产效率相比方案一提高了两倍多。综合考量成本和工厂生产效率的因素,方案二更好地满足了实际工程应用的需求。     

一种高效稳健的均匀圆阵互耦校正方法

紧凑均匀圆阵（UCA）的强电磁互耦效应严重影响波束赋形（BF）和波达方向（DoA）估计的性能,本文利用UCA的特殊圆对称性,提出了一种稳健高效的互耦参数校正方法.该方法只需要单个信源和单次校正实验,并且信源方向并不需要事先精确校准.首先互耦矩阵在离散傅里叶空间被转化为具有中心对称的一个参矢量,随后在一个有限的先验二维空间角域内进行搜索,从而根据基于对称性的目标函数将互耦参数估计出来.仿真对比实验验证了新校正算法的有效性和鲁棒性,同时揭示了秩损（RARE）校正方法不够稳健,为基于UCA的雷达、移动通信等应用提供了简单且高效的互耦误差校正方法.     

结合高位深相位光栅图的LC-SLM标定

为了提高对液晶空间光调制器（LC-SLM）的校准精度,采用高位深相位光栅图对LC-SLM进行了标定。在LC-SLM上加载16位深度相位光栅图,并使光束经LC-SLM调制后生成衍射光斑;测量衍射光斑中心光强,经过计算分析得出计算机灰度信号与相位调制量之间的映射关系,最终得出针对488nm激光的LC-SLM标定LUT文件（LUT16）。结果表明,在LC-SLM上加载0~2π涡旋相位,并结合LUT16文件调制光束可以得到光斑质量很好的中空光斑,这与结合LUT8文件调制的中空光斑相比,光斑质量从0.53提高到0.76,提高了1.43倍。针对特定波长,利用高位深相位光栅图标定LC-SLM得到的LUT文件可以使LC-SLM根据加载相位对光束进行有效调制,且调制效果优于结合LUT8对光束进行调制的结果,对LC-SLM的校准精度得到提高。     

Amplitude and phase errors calibration method in satellite-borne dynamic power allocation network

For the mobile communication satellite each beam communication traffic distribution was not balanced,leading to differences in transmission power of downlink beam.The implementation architectures of dynamic power allocation network was given,which could allocate the transmitting beam power automatically according to the traffic demand,at the same time ensured the high efficiency of power amplifier.Because the performance of dynamic power allocation network was severely impaired by the mutual coupling among signals when amplitude/phase mismatch was existed,which led to a sharp drop in beam performance.A calibration method for the amplitude and phase errors was proposed.The decoupling of calibration signal was realized by using the cross-correlation orthogonal characteristic of the orthogonal zero-correlation zone (ZCZ) sequences in the zero correlation interval,and communication was free from calibration by reducing the transmit power for the excellent self-correlation characteristic of the ZCZ sequences.Performance simulation and far field test show that under the condition that the calibration signal power is less than the normal signal 10 dB,the amplitude error is less than 0.1 dB,the phase error is less than 0.3°,and the gain loss within the main lobe is less than 0.2 dB after calibration.     

数字多用表自动校准系统的分析与设计

由于数字多用表型号众多、量程宽、每一个量程及校准点的技术指标各不相同,造成校准过程耗时长,数据处理繁琐等问题.为了减少数字多用表校准过程中出现的失误几率,有效提高校准数字多用表的工作效率及质量.本文分别从数字多用表自动校准系统的主体结构、硬件架构和软件设计等多方面进行论述,设计开发出性能稳定、实用性强的数字多用表自动校准系统.     

多模终端待机低功耗设计

如今的移动通信网络是由多种制式及多个频段融合而成的多模网络,对于商用终端而言,多种难题交织在一起,其中待机时长是必须要解决的一个关键问题.为此,不同于传统增大电池容量的方法,采用降低待机功耗的策略:时域的时隙控制、频域的电流控制、睡眠和唤醒的电源门控制、低频时钟高频化,其中高频时钟校准低频时钟是降低睡眠态功耗的关键措施.这一系列方案的实施,使得终端在多模实际网络环境下的待机电流小于5 mA,终端的待机低功耗达到了有竞争力的商用水平.     

Application of Multivariate Calibration Techniques to HPLC Data for Quantitative Analysis of a Binary Mixture of Hydrochlorathiazide and Losartan in Tablets

New multivariate approaches have been applied to high-performance liquid chromatography (HPLC) with multiwavelength photodiode-array (PDA) detection. Multivariate calibration techniques such as partial least squares (PLS), principal component regression (PCR), classical least squares (CLS), and inverse least squares (ILS) was subjected to HPLC data for simultaneous quantitative analysis of synthetic binary mixtures and a commercial tablet formulation containing hydrochlorothiazide (HCT) and losartan potassium (LST). The combined use of HPLC and multivariate calibrations has been denoted HPLC–CLS, HPLC–ILS, HPLC–PCR, and HPLC–PLS. Successful chromatographic separation of the two active compounds and enalapril maleate, used as internal standard (IS), was accomplished by means of a 4.6 mm i.d. × 250 mm, 5 m particle, Waters Symmetry C₁₈ reversed-phase column and a mobile phase consisting of 60:40 acetate buffer (0.2 M, pH 4.8)–acetonitrile (v/v, 60:40). HPLC data based on the ratio of analyte peak areas to IS peak area were obtained by PDA detection at five-wavelengths (250, 255, 260, 265, and 270 nm). The HPLC–CLS, HPLC–ILS, HPLC–PCR, and HPLC–PLS calibration plots for hydrochlorothiazide and losartan potassium were constructed separately by using the peak-area ratios corresponding to the concentrations of each active compound. The HPLC multivariate calibrations obtained were tested for different synthetic mixtures containing HCT and LST in the presence of the IS. These multivariate chromatographic methods were also applied to a commercial pharmaceutical dosage form containing HCT and LST. The results obtained from the multivariate calibrations were compared with those obtained by use of another, classical HPLC method using single-wavelength detection.Revised: 29 September 2004 and 4 January 2005     

Accurate measurement of sputtered depth for ion sputtering rates and yields: the mesh replica method

For the accurate measurements of crater depths, ion sputtering rates and ion sputtering yields in studies of sputter‐depth profiling using Auger electron spectroscopy (AES) or X‐ray photoelectron spectroscopy (XPS), a proposed mesh replica method has been evaluated. In this method, during ion sputtering, grids of between 50 and 400 mesh (per inch) are placed on the sample to retain unsputtered regions of the original surface to be used as reference. This enables a more accurate measurement of the depth to be made using a stylus profilometer close to the analytical region. The closer‐pitch meshes were thought to offer the prospect of measurements of higher accuracy. Calculations show that sputter deposits from the mesh sides may limit the mesh numbers used to 100 or those of a wider pitch for both stationary and rotated samples. A correlation with published data for stationary samples and new data for rotated samples confirms the calculations. In practice, it is difficult, without a special holder, to have intimate contact between the grid and sample. Such a holder is described. Further calculations concerning the shadowed profiles at the grid bar regions show that the grids may lift off the sample surface by 4–16 µm. This leads to non‐vertical crater walls in each mesh aperture. This effect, however, does not change the above conclusion on the mesh sizes to be used. In this range, the spurious appearance of Auger electrons emitted from the grid material is calculated to be less than 1%. This conclusion applies to the meshes evaluated here, which range in thickness from 13 to 29 µm. Thinner meshes may lead to the applicability of proportionately closer meshed grids in sputter‐profiling applications. Copyright © 2006 John Wiley & Sons, Ltd. The contribution of Martin P. Seah of the National Physical Laboratory is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.     

Determination of Nitrogen in Duplex Stainless Steels by EPMA

 We describe the quantitative determination of low nitrogen contents (< 1 %wt) in highly-alloyed, duplex stainless steels by EPMA using a calibration curve. Five monophasic stainless steels with various nitrogen concentrations were used for the calibration curve, namely, three highly alloyed steels prepared in the laboratory, with nitrogen contents 0.066, 0.565 and 1.016 %wt and two industrial alloys with nitrogen concentrations 0.174 %wt and 0.023 %wt. For these samples, the plot of nitrogen X-ray intensities versus nitrogen contents exhibited an acceptable linear relationship. Average nitrogen contents of the analysed duplex alloys were found to vary in the range < 0.045–0.07 %wt in ferrite and 0.52–0.77 %wt in austenite. These results suggest that the nitrogen solubility limit in ferrite has been reached; on the other hand, nitrogen solubility in austenite increases due to the high manganese and low nickel contents.