球坐标系下多普勒雷达目标跟踪滤波器

将仅仅考虑位置量测的三维去偏一致转换量测卡尔曼滤波算法进行推广,以解决包含多普勒量测且斜距和多普勒的量测误差相关的雷达目标跟踪问题。首先利用斜距和多普勒量测的乘积构造伪量测,以减小多普勒量测和目标运动状态之间的强非线性程度;然后利用嵌套条件方法得到了转换量测误差前两阶矩的一致性估计;最后根据转换量测是目标运动状态二次函数的特性,用二阶EKF最优地实现了非线性跟踪滤波。Monte-Carlo仿真结果表明采用新算法可以明显改善跟踪滤波器的性能。     

Choice of PRF for error-tolerant range destaggering of radar targets

High and medium PRF radars perform ranging by means of multiple PRFs chosen according to the Chinese remainder theorem. Unfortunately this theory does not cope with errors in range measurements. A new rule for the choice of the PRFs is proposed which is tolerant of a prescribed error amplitude in range measurements.     

Fast convergent robust range estimator for surface-to-air missiles

To cope with the intermittent unavailability of ground radar measurements due to jamming, a linear robust range estimation scheme utilising seeker measurements only is devised. Aside from the conventional approaches, it directly extracts range information from Doppler mismatch and line-of-sight rate measurements. The proposed filter shows good estimation performance and fast convergence with very small computational load     

基于约束最大后验估计的水下航行器组合定位算法

针对水下航行器声学/航位推算组合定位系统,利用声信标与水下航行器间的几何定位结构关系,构建获得水下声学距离量测等式与不等式约束条件,通过最大后验(MAP)估计准则与标准扩展Kalman滤波(EKF)方法相结合,设计出声学距离量测约束下的水下航行器组合定位算法,实现了水声距离量测与航位推算信息的有效融合.数值仿真试验结果...     

A Technique for Extending the Dynamic Range of the Dual Six-Port Network Analyzer

The dynamic range of the six-port type of automatic network analyzer is typically limited to measuring two-port devices with a transmission coefficient S/sub 12/ in the range of 0 to -60 dB. The following describes a subcarrier approach for extending the dynamic range of the dual six-port network analyzer. The subcarrier is generated by inserting a 10-kHz, biphase modulator ahead of one of the six-ports. With the subcarrier approach, measurements of S/sub 12/ in the range of -60 to -100 dB can be made. Test results are presented showing measurements of S/sub 12/ =-80 db with a precision of +-0.05 dB or better, and an accuracy of +-0.16 dB or better at 3 GHz. Measurement results are also presented showing the dynamic range achievable with thermistor and barretter detectors. Key Words: barretter power detectors; diode power detectors; impedance measurements; microwave network analyze; six-port network analyze; thermistor power detectors.     

一种光子相关器动态范围自适应调整方法与实现

目前广泛应用的光子相关光谱(PCS)颗粒测量系统中, 光子相关器动态范围的设置需要与实际待测颗粒的光强自相关函数曲线衰减区间相匹配, 这样, 相关器才能给出具有最佳分辨率的自相关函数曲线。然而, 在实际测量过程中, 待测颗粒体系的粒度分布范围通常是未知的, 因此需要对参数进行多次修正才能得到最佳的分辨率效果。对此, 提出一种可根据被测颗粒体系的粒度分布范围变化, 自适应修正测量参数进行光子相关器动态范围调整的方法。该方法通过初始采样时间的选择和相关通道采样时间的再分配, 实现测量过程中的相关器动态范围调整, 使其与待测颗粒体系的光强相关函数曲线衰减区间相匹配, 从而保证在任意颗粒系的测量中都能得到分辨率最佳的自相关函数曲线。     

基于量测预测联合估计的单站只测角跟踪

提出用于单站只测角系统的修正最佳线性无偏估计(BLUE)滤波器。针对BLUE 滤波器用于雷达目标跟踪时需要完备的非线性观测集合来构建转换量测及单站只测角系统只提供方位观测,无法直接应用普通BLUE滤波器跟踪目标的问题,构造了基于目标状态预测的预测斜距,并在分析预测斜距误差统计特性后,用斜距预测和方位观测组成转换量测,推导出可应用于单站只测角系统的BLUE滤波模型。所提改进算法在性能和运算量上有明显优势,有很好的应用潜力。     

激光捷联导引头线性区扩展方法研究

当激光捷联导引头工作在设计的线性区外时,在确定的激光导引头参数条件下,通过对激光探测器输出电信号的综合处理与运用,从软件算法方面可将激光导引头线性区向外大范围扩展。当目标回光剩余光斑占有两个象限时,经计算、标定,其测量结果较准确,扩展后的测量结果与线性区内测量结果呈准线性分布,当目标剩余光斑仅占有一个象限时,其质心相对于导引头视轴的距离可精确确定,但其给出的俯仰、方位位置存在较大偏差,通过限定角度,可以给出目标粗略角度位置。     

一种新的加权最小二乘测距定位方法

三站二维定位问题是最小定位问题，一般只利用几何关系就能获得定位估计，但由于未利用距离测量的统计信息，定位精度较差。该文先将点到点的距离测量转化为点到线的距离估计，再在此基础上推导出一种新的加权几休定位方法，其中加权的确定利用了距离测量的统计信息。仿真实验表明，在测距误差较小时新方法具有更高的定位精度。     

Performance of a small loop antenna in the 3-10 MHz band

The performance of a typical small loop antenna of 1 m diameter is presented at frequencies in the range 3.6-10.1 MHz. It is argued that the antenna may reasonably describe as electrically small in this frequency range. Measurements of the antenna's bandwidth and, hence, Q factor are presented, along with direct measurements of the radiated field at various distances with a carefully measured RF input power. The radiation efficiency of the loop is derived from the measurements, and is compared with theoretical predictions of the efficiency based on classical electromagnetics. Close agreement is demonstrated between measurements and predictions. Consistency with the Chu bandwidth limit is also demonstrated for this antenna.     

A Cooperative Localization Algorithm for UWB Indoor Sensor Networks

This paper deals with range-based localization in ultra wideband sensor networks, allowing for the possibility of large range measurement errors because of a failure to detect the direct paths between some nodes. A novel algorithm is proposed that uses only partial knowledge of the service area topology, particularly of the positions of objects which are capable of causing undetected direct path (UDP) propagation conditions. Although the spirit of the proposed approach, because of the lack of information on the range error statistics, is to remove measurements performed under UDP conditions from the computation of the location estimate, these measurements are used implicitly by the algorithm to contribute to the erroneous trial locations being discarded. A cooperative stage is included that allows the probability of localization of a target with an insufficient initial number of accurate range measurements to increase. The proposed algorithm outperforms a variety of alternative positioning techniques, and thus illustrates the capability of this topology knowledge to mitigate the UDP problem, even in the absence of any knowledge about the range error statistics.     

Characterization of Scattering Parameters Near a Flat Phantom for Wireless Body Area Networks

In this paper, the scattering parameters of two dipoles placed closely to a flat, homogeneous, biological tissue are characterized in the 2.4-GHz band. The impact of the presence of a flat phantom and of the height of a dipole above the phantom on the reflection coefficient is analyzed through measurements and simulations. The effect of the type of tissue on the reflection coefficient is also investigated by performing simulations for a range of relative permittivity and conductivity combinations spanning the whole range of human tissues at 2.4 GHz. A semiempirical path loss model, validated by measurements and simulations, is presented for wireless communication, for antenna heights from 2 mm up to 5 cm and antenna separations from 10 to 50 cm. Also, the influence of the relative permittivity and conductivity on the path loss is modeled, leading to a range of possible values and lower and upper boundaries for the path loss as a function of the antenna height. The combination of the range with the boundaries results in a best-case and worst-case path loss model for wireless body area networks. The models are validated with measurements on the torso of a human.     

Nighttime Variations of Extremely Low Frequency (ELF) Signal Strengths in Connecticut

A limited amount of extremely low frequency (ELF) horizontal magnetic field strength measurements have been taken in Connecticut during the past 3 years. The transmission source for these 1.6 Mm range measurements was the U. S. Navy ELF Wisconsin Test Facility. The principal result obtained from these measurements is that there are considerable variations in the ELF nighttime propagation parameters.     

Pattern measurements of reflector antennas in the compact range andvalidation with computer code simulation

The measurements were performed at the University's compact range facility. They demonstrated: (1) the excellent dynamic range that can be achieved with antenna pattern measurements in a compact range facility; and (2) the excellent validation achieved for the calculated patterns of two 8-ft diameter reflector antennas. The compact range has a rolled edge modification to its reflector and uses a pulsed radar system to eliminate the clutter interference such that a dynamic range of more than 80 dB can be obtained. The measured far field patterns of two 8-ft reflector antennas, a prime focus fed antenna and a Cassegrain antenna, at 11 GHz were compared with those calculated by Ohio State University's Reflector Antenna Code. The computer code simulation's approach is also briefly described     

带多普勒量测的序贯SCKF雷达目标跟踪算法

为提高非线性观测条件下雷达目标的跟踪性能,将序贯处理方法引入均方根容积卡尔曼滤波( SCKF),提出一种带多普勒量测的序贯均方根容积卡尔曼滤波( SSCKF-D)雷达目标跟踪算法,该算法通过建立伪量测去除径向距离和径向速度量测误差方差之间的相关性。基于SCKF算法,按照量测精确度的高低顺序对方位角、俯仰角、径向距离和伪量测序贯处理。 Monte Carlo仿真表明,与SCKF和带多普勒量测的均方根容积卡尔曼滤波( SCKF-D)算法相比,SSCKF-D算法跟踪精度更高,较后者提高20%以上,收敛速度更快,更适用于空间目标跟踪。     

Design of a Tunable Differential Ring Oscillator With Short Start-Up and Switching Transients

Timing measurements such as jitter and skew in the range of picoseconds, for circuits with multigigahertz clocks or multigigabit-per-second serial communication interfaces are common. A Vernier-oscillator-based time-to-digital converter (TDC) is a circuit that allows picosecond-timing measurements by means of two tunable oscillators. In such a circuit, the oscillator jitter, tuning response, start-up transient, and frequency switching transient play an important role in the TDCs measurement time and accuracy. In this work, we discuss the design of an optimized, differential CML-based ring oscillator and its impact on a TDC design. Simulation results from the new oscillator show that the oscillator's short start-up and frequency switching transients have negligible effects on the accuracy of the TDC measurements. TDC simulation results show that, using two of these oscillators, accurate timing measurements in the range of 10 to 900 ps can be achieved with best-case accuracy of ~2 ps.     

Material dispersion in lightguide glasses

Material dispersion measurements are reported on six characteristic lightguide glass compositions. The measurements were made on bulk specimens and cover the wavelength range from 0.8 to 1.5 ?m. It is observed that in these silicate glasses the wavelength at which material dispersion is zero is in all cases greater than 1.2?m.     

Characterization of Submillimeter Wave Absorbers from 200–600 GHz

This paper presents measurements of both specular and non-specular scattering from several submillimeter wave absorber materials designed for antenna testing and from low-cost carpet materials. The frequency range is 200–600 GHz in specular scattering, and 300–400 GHz in non-specular scattering measurements. The constructed bistatic test bench allows testing of the full continuous angular range of 0°–90°. The measurement results show large differences in performance of different materials. It is shown that reflectivities below ?50 dB over limited angular ranges are possible with a correct alignment of the material. Also, low-cost carpet materials have lower than ?15 dB reflectivities in most angles, and may be useful in non-critical parts of the antenna test range. The results can be used to optimise the absorber placement inside an antenna range, concerning both best performance and lowest cost.     

A novel ToA location algorithm using LoS range estimation for NLoS environments

One of the main problems facing accurate location in wireless communication systems is nonline-of-sight (NLoS) propagation. In this paper, we propose a novel location technique that estimates the true, or line-of-sight (LoS), ranges based on NLoS range measurements. This approach utilizes a constrained nonlinear optimization approach, when range measurements are available from three base stations (BSs) only. Bounds on the NLoS error and the relationship between the true ranges are extracted from the geometry of the cell layout and the measured range circles to serve as constraints. Simulations studying the performance of the algorithm for different NLoS error distributions and BS configurations show that the location accuracy is significantly improved over traditional algorithms, even under highly NLoS conditions.     

Design of target support columns using EPS foam

When making RCS measurements on a ground-bounce range, EPS foam columns are frequently used as target supports for test bodies and air vehicles. Since background subtraction is rarely used to suppress foam-column scattering in large-scale RCS measurements, the columns must be structurally sound while maintaining a minimized RCS signature over the aspect angles, and radar frequency band, of interest. The goal is to devise a column that is unnoticeable in the measured data, yet strong enough to support a specified weight. The major factor that contributes to EPS foam-column scattering is shaping, and finding the optimal shape for a particular test is not trivial. Part 1 of this paper describes methods in the design and construction of EPS foam columns. Subjects include determination of EPS material properties, mathematical specification of column geometries, accurate and efficient computation of column mechanics and scattering, and effective optimization of column parameters. Part 2 of this paper shows comparisons of predicted column RCS to column measurements performed at NRTF. These comparisons give credibility to the concept of foam-column modeling and ground-bounce range scattering simulations, and give range engineers confidence in the foam-column design process.