Joint DOA Estimation and Phase Calibration for Synchronous CDMA with Decorrelator

A joint direction of arrival (DOA) estimation and phase calibration for synchronous CDMA system with decorrelator are presented. Through decorrelating processing DOAs of the desired users can be estimated independently and all other resolved signal interferences are eliminated. Emphasis is directed to applications in which sensor phases may be in error. It is shown that accurate phase calibration in conjunction with their use in high resolution DOA estimation can be achieved for the decoupled signals.

Automatic IQ Phase Calibration Design in a 2.4GHz Direct Conversion Receiver

An automatic IQ phase calibration method implemented in a 2.4GHz direct conversion receiver is proposed. It uses a delay locked loop （DLL） with a proposed quadrature phase detector to greatly reduce the phase error. The receiver is fabricated in a 0.18μm CMOS process. Measurements show that the IQ phase error can be calibrated within 1°,which satisfies the system requirement.

Method for array gain and phase uncertainties calibration based on ISM and ESPRIT

A new method for array calibration of array gain and phase uncertainties, which severely degrade the performance of spatial spectrum estimation, is presented. The method is based on the idea of the instrumental sensors method （ISM）, two well-calibrated sensors are added into the original array. By applying the principle of estimation of signal parameters via rotational invariance techniques （ESPRIT）, the direction-of-arrivals （DOAs） and uncertainties can be estimated simultaneously through eigen-decomposition. Compared with the conventional ones, this new method has less computational complexity while has higher estimation precision, what＇s more, it can overcome the problem of ambiguity. Both theoretical analysis and computer simulations show the effectiveness of the proposed method.

An Improved Calibration Method of Grating Projection Measurement System

In the traditional fringe projection profilometry system,the projector and the camera light center are both spatially virtual points.The spatial position relationships specified in the model are not easy to obtain,leading to inaccurate system parameters and affectingmeasurement accuracy.This paper proposes a method for solving the system parameters of the fringe projection profilometry system,and the spatial position of the camera and projector can be adjusted in accordance with the obtained calibration parameters.The steps are as follows:First,in accordance with the conversion relationship of the coordinate system in the calibration process,the calculation formula of the vertical distance from the camera light center to the reference plane and the calculation formula of the distance between the projector and the camera light center are given respectively.Secondly,according to the projector calibration principle,the position of the projector light axis perpendicular to the reference plane is gained by comparing the parallel relationship between the reference plane coordinate system and the projector coordinate system’s Z-axis.Then,in order to fulfill the position restriction that the line between the projector light center and the camera light center must be parallel to the reference plane,the camera’s spatial location is adjusted so that the vertical distance between it and the reference plane tends to that between the projector light center and the reference plane.And finally,the three-dimensional(3D)reconstruction of the target object can be finished using the phase height model’s system parameters once the aforementioned position limitations are put into practice.Experimental results demonstrate that the method improves the measurement accuracy,and verifies that it is effective and available in 3D shape measurement.

Impact of Phase Noise on TDMS Based Calibration for Spaceborne Multi-Beam Antennas

For spaceborne multi-beam antennas(MBAs), time division multiplexed switching(TDMS) based calibration receiver can reduce implementation costs effectively and is very suitable for large-scale applications. However, in practice, random phase noise imposed by noisy local oscillators can cause significant performance degradation in TDMS-based calibration systems. Characterization of phase noise effects is therefore crucial for practical applications. In this paper, we analyze the impact of phase noise on the calibration performance for a MBA system. Specifically, we derive the relationship between the probability of correct amplitude/phase estimation and various practical factors involving the signal-to-noise ratio(SNR), the standard deviation of phase noise, the given tolerance region, and the length of the spreading code. The results provide high efficiency for evaluating the calibration performance of the MBAs based on TDMS, especially for precisely anticipating the impact of phase noise. Finally, the accuracy of the derived results is assessed by simulations in different scenarios.

A Precise Calibration Method on Phase Center of Uplink Antenna Array Considering Its Actual Pointing

With regard to the inferior techniques and low accuracy of phase center calibration of an antenna array, this paper proposes a new calibration method considering the actual antenna pointing by introducing a precise engineering surveying technique to measure the real state of antennas. First, an industrial photogrammetric system is utilized to obtain the coordinates of points on antenna panels in different postures, and the actual pointing of the mechanical axis is obtained via least-squares fitting. Then, based on this, the coordinates of antenna rotation center are obtained by seeking the intersection of mechanical axes via using the matrix method. Finally, the mechanical axis in arbitrary postures is estimated based on the inverse-angle weighting interpolation method, and the reliable phase center is obtained by moving a fixed length from the projective center along the mechanical axis. An uplink antenna array including three ? 3 m antennas is taken as experimental object, and all photogrammetric coordinate systems are unified by the engineering control network, with each antenna phase center precisely calibrated via the proposed method. The results of electrical signal synthesis indicate that this method can effectively overcome the influence of gravity deformation and mechanical installation error, and enhance the synthetic signal magnitude of the uplink antenna array.

Experimental demonstration of a fast calibration method for integrated photonic circuits with cascaded phase shifters

With the development of research on integrated photonic quantum information processing,the integration level of the integrated quantum photonic circuits has been increasing continuously,which makes the calibration of the phase shifters on the chip increasingly difficult.For the calibration of multiple cascaded phase shifters that is not easy to be decoupled,the resources consumed by conventional brute force methods increase exponentially with the number of phase shifters,making it impossible to calibrate a relatively large number of cascaded phase shifters.In this work,we experimentally validate an efficient method for calibrating cascaded phase shifters that achieves an exponential increase in calibration efficiency compared to the conventional method,thus solving the calibration problem for multiple cascaded phase shifters.Specifically,we experimentally calibrate an integrated quantum photonic circuit with nine cascaded phase shifters and achieve a high-precision calibration with an average fidelity of 99.26%.

A pressure calibration method for a portable wide-access “panoramic” cell

A simple and convenient pressure calibration method is developed for a newly designed portable wide-access ＇panoramic＇ cell. This cell is adapted to angle-dispersive-mode high-pressure in situ neutron diffraction of reactor neutron sources. This pressure calibration method has established a relationship between the cell pressure and the anvil displace- ment （gasket compression） based on the fixed-point calibration technique. By employing TiZr gasket with a thickness of 3 mm and WC anvil with a culet of 4 mm diameter, the average anvil displacements are 1.31 mm and 2.22 mm for Bi phase transitions （2.55 GPa and 7.7 GPa）, and 1.85 mm for Ba phase transitions （5.5 GPa）, respectively. In this pressure range, the pressure increases quickly with decreasing gasket thickness, and undergoes a linear increase with the anvil displacement. By extrapolating the calibration curve, the cell pressure will achieve 10 GPa when the anvil displacement is around 2.5 ram.

2.7-4.0 GHz PLL with dual-mode auto frequency calibration for navigation system on chip

A 2.7-4.0 GHz dual-mode auto frequency calibration(AFC) fast locking PLL was designed for navigation system on chip(SoC). The SoC was composed of one radio frequency(RF) receiver, one baseband and several system control parts. In the proposed AFC block, both analog and digital modes were designed to complete the AFC process. In analog mode, the analog part sampled and detected the charge pump output tuning voltage, which would give the indicator to digital part to adjust the voltage control oscillator(VCO) capacitor bank. In digital mode, the digital part counted the phase lock loop(PLL) divided clock to judge whether VCO frequency was fast or slow. The analog and digital modes completed the auto frequency calibration function independently by internal switch. By designing a special switching algorithm, the switch of the digital and analog mode could be realized anytime during the lock and unlock detecting process for faster and more stable locking. This chip is fabricated in 0.13 μm RF complementary metal oxide semiconductor(CMOS) process, and the VCO supports the frequency range from 2.7 to 4.0 GHz. Tested 3.96 GHz frequency phase noise is -90 d Bc/Hz@100 k Hz frequency offset and -120 d Bc/Hz@1 MHz frequency offset. By using the analog mode in lock detection and digital mode in unlock detection, tested AFC time is less than 9 μs and the total PLL lock time is less than 19 μs. The SoC acquisition and tracking sensitivity are about-142 d Bm and-155 d Bm, respectively. The area of the proposed PLL is 0.35 mm^2 and the total SoC area is about 9.6 mm^2.

Calibration and Validation of the GR2M Hydrologic Model in the Kouilou-Niari Basin in Southwestern Congo-Brazzaville

The hydrologic simulation of a catchment area, described as the transformation of rainfall into runoff, generally uses hydrologic model. This work opts for the global conceptual hydrologic model GR2M, a monthly time step model, to study the Kouilou-Niari basin, the second most important ones of the Republic of Congo. This includes two parameters to model the hydrologic behavior of a catchment area. The choice of the conceptual model GR2M is justified by the reduced number of parameters and the monthly time scale. The objective of this study is to determine the characteristic parameters of the GR2M model, by a calibrating and a validating procedure. The use of these parameters enables to follow the evolution of the water resources from the climatic variables. It has been first carried out a characterization of some physical, geological and climatic factors governing the flow, by dealing with the main climatic variables which constitute the inputs of the hydrologic model. Then, a hydrologic rainfall-runoff modeling allows to calibrate and validate the model at monthly time scale. Taking into account the number of parameters involved in hydrologic processes and the complexity of the cathment area, this model gives acceptable results throughout the Kouilou-Niari basin. The values of the Nash-Sutcliffe criterion and those of the correlation coefficient obtained are greater than 80% in validation, which explains the performance and robustness of the GR2M model on this basin.

数字示波器相频特性的计量评价

针对数字示波器相频特性校准中,响应波形与激励信号之间相位差获取的难点问题,提出一种借助于脉冲沿幅度触发功能特性的方法,通过设定触发参量与激励信号幅度关系,固定与响应信号波形相对应的激励信号的相位点,从而精确获取被测数字示波器的相移特性,并统一了不同频率下相移特性的参考相位点,顺利获得数字示波器相频响应特性曲线。在一组实验中,验证了所述方法的有效性和可行性,可用于数字示波器相频响应特性的测量评价。

无线电参数综合测试平台机动伴随校准装置的测量不确定度分析

本文结合无线电参数综合测试平台机动伴随校准装置在实际应用中的情况及经验,对其本身的典型测量不确定度来源进行分析,包括频率测量、功率电平测量、相位噪声测量、衰减测量、低频信号输出频率、低频信号输出电压幅度等参数的不确定度进行了分析。

数模混合二维相控阵雷达远场收发校准方法研究

本文提出了一种基于最小系统设计准则的数模混合二维相控阵雷达远场收发校准方法,给出了实现流程、数据分析过程和实测结果。方向图的实测结果显示本文提出的校准方法得到的收发方向图主要技术指标良好且均满足使用要求,在实际工程中具有较好的操作性和推广性。

基于Adam算法的光学相控阵输出光束校准方法

基于微纳集成的光波导相控阵芯片是近年来激光雷达技术领域的研究热点.随着激光雷达系统空间分辨这一实际应用需求的不断提高,作为激光雷达系统中的光束控制器件,光波导相控阵需要扩大阵列规模以提升输出光束的空间分辨率.同时也为光波导相控阵输出光束的优化校准带来了困难,现有算法不仅光束校准质量不高,且校准效率较低.为此,本文将Adam算法应用于光波导相控阵输出光束校准系统中,通过建模仿真比较了Adam算法与现有SPGD算法和GS算法在光束校准层面上的优劣.同时,搭建实验系统实现了高质量的光束校准,根据校准结果,在Adam算法校准下光波导相控阵输出光束的主旁瓣比优于15.98 dB,对16×16光波导相控阵输出光束校准达到收敛所需的迭代次数低于600次.这一算法在光波导相控阵输出光束校准方面的应用,能够提高光波导相控阵的控制精度和效率,拓展光波导相控阵在激光雷达技术、数字全息技术和生物成像技术等方面的应用.

在等电位工作状态下校准多元感应分流器

提出了在等电位工作状态下校准多元感应分流器(multiple inductive current divider,MICD)的1种方法。在校准装置中加入由跟随器和电阻组成的I/V变换器,以使MICD各支路间的电流比例与其工作状态保持一致;用参考电流互感器(CT)提供独立的参考电流,以避免影响支路电流的比例关系。在20、55、400 Hz及1 kHz下对11支路MICD校准所得10:1电流比例的比值差合成标准不确定度优于0.2μA/A,相位差合成标准不确定度优于1.5μrad。

基于反相法的中场校准技术研究

在相控阵天线研制中,阵面校准是非常重要的一环。对比各种校准方法,中场法使用设备少、测试效率高,因而获得了广泛的应用。通常情况下,阵面中的T/R组件内设计有三态开关(发射态、接收态、负载态),中场测试时,通过“逐路通”的方式(逐一选通T/R组件的射频通道,非被测通道处于负载状态),得到所有通道的发射通道(或接收通道)的幅相数据。但在“芯片化”T/R组件组成的阵面中,开关隔离度有限,泄露信号严重干扰被测信号,甚至无法进行正常的故障判断。本文讨论一种基于反相法的中场校准方法,分析了该方法的误差量级,最后通过远场波瓣测试验证了该方法的有效性。

一种大型相控阵雷达外场高精度相位校正方法

针对大型相控阵雷达外场相位校正受风影响无法保证校正精度的难题,本文提出了一种外场高精度相位分级校正方法。采用激光标定法测量标校源风载条件下的晃动曲线和最大晃动速度,根据雷达工作频段及校正精度要求,计算出标校源最大晃动速度条件下的最小保精度校正时间,以最小保精度校正时间作为分级子阵规模划分的依据,通过多级校正完成全阵外场校正。仿真测试结果表明:在5级风载条件下,X波段相位校正精度均方根小于5.8°,最大栅瓣电平降低了9 dB,达到模拟移相器可以实现的精度要求。

双线偏振全数字相控阵天气雷达设计与试验

基于极端灾害性天气对高时空分辨率的探测需求,提出了一种采用平板阵列天线和全数字收发组件,并具有双线偏振功能的S波段相控阵天气雷达系统的实现方法,并对涉及的关键技术进行了研究分析,提出了基于脉内频相扫多波束的扫描策略设计,以及基于机内标定系统的在线标定设计思路。最后采用研制的工程样机开展了强对流天气观测试验,并与CINRAD/SAD雷达的观测数据进行了对比,对比结果表明采用该方法设计的工程样机对强对流天气的观测具有一定优势。

基于相位靶和神经网络的单目相机标定

针对传统基于BP神经网络的标定方法标定精度低,深度方向误差大等问题,提出了一种基于相位靶和径向基函数(RBF)神经网络的单目相机标定方法。采用三步相移法的特征提取方法,并使用多频法计算绝对相位,将相位靶特征点承载的绝对相位转换到三维空间,建立特征点图像坐标与世界坐标之间的对应关系,最后使用RBF神经网络完成二维图像坐标到三维空间坐标的直接映射。实验结果表明,对比传统使用BP神经网络进行标定与棋盘格,圆形标定靶的标定结果,该方法的平均标定误差为0.0980mm,同时在焦距1.4mm,视场220°鱼眼镜头下,仍能保持较高的精度,证明了所提方法的可行性和有效性。

一种相控阵雷达横滚角标校方法

提出了一种相控阵雷达横滚角标校方法,利用相控阵雷达横滚角与目标俯仰角测量误差之间的近似线性关系,结合雷达自带的角度测量误差标定手段,快速地计算得到雷达的横滚角,进而大幅提高相控阵雷达的角度测量精度。实验证明,使用该方法计算得到的横滚角与使用激光测量仪器测得的横滚角结果精度相当,完全能够满足高精度测量雷达的需求。