Error Propagation in a Practical Six-Port Device

In this contribution the various influences on the accuracy of the phase measurement unit of a near range precision radar are investigated. The front-end is a monostatic design operating at 34–36.2 GHz. The hardware configuration enables different modes of operation including FM-CW and a single frequency mode with phase and frequency measurement. To achieve a highly accurate distance measurement, attention must be paid to various error sources. Due to the use of a six-port it is rather complicated to determine the corresponding error propagation. In the following the results of investigations on how to achieve an exceptional accuracy of 0.1 mm are described. Especially the error propagation through the six-port is analyzed in detail.     

On the Application of Six-Port Technology (SPT) in Ultrasonic Imaging for Medical Diagnosis

In this paper, an introduction of six-port technology to ultrasonic imaging for medical diagnosis is presented for the first time. Calculations are made to explore the possibilities and advantages of this application. Analysis shows that the introduction of six-port technology for medical ultrasonic imaging to detect the phase information of the reflected signal will improve the measurement accuracy and simplify the instrumentation of imaging technologies used in medical diagnosis.     

Uncertainty analysis for a phase-detector based phase noise measurement system

Phase noise is an important parameter to characterise the frequency stability of oscillators and synthesised signal generators. Accurate measurement of phase noise is required for various applications in radar, communication and navigation systems. A single-channel phase-detector based phase noise measurement system is described. The system’s measurement errors and uncertainties have been analysed in details. The expanded uncertainty is about 2.7 dB for calibrating phase noise of a signal generator at 0.001–1.6 GHz for frequency offsets from 1 Hz to 100 kHz. The uncertainty budget for measuring a signal generator’s phase noise at 640 MHz is also presented.     

Frequency Dependence of the Soil Electromagnetic Properties Derived from Ground-Penetrating Radar Signal Inversion

The accuracy at which the subsurface electromagnetic properties can be identified from full wave inversion of ground penetrating radar (GPR) signals relies on the appropriateness of the model describing their frequency dependence. In this paper, we focus on the characterization of the frequency dependence of the dielectric permittivity and electric conductivity of a sandy soil subject to different water contents from inversion of GPR measurements. Based on previous studies of Lambot et al. the methodology relies on an ultrawide band (UWB) stepped-frequency continuous-wave (SFCW) radar combined with an off-ground monostatic transverse electromagnetic (TEM) horn antenna. Forward modeling of the radar signal is based on linear system transfer functions for describing the antenna, and on the exact solution of Maxwells equations for wave propagation in a horizontally multilayered medium representing the subsurface. Model inversion, formulated by the classical least-squares problem, is carried out iteratively using advanced global optimization techniques. The frequency dependence of the electromagnetic properties of the sandy soil is characterized by performing inversions of the radar signal in different and subsequent limited frequency bands, in which the electromagnetic parameters are assumed to be constant. We observed that over the entire frequency band considered in this study (1–3 GHz), the dielectric permittivity of the sand remains constant with frequency, whatever the water content is. In contrast, the electric conductivity increases significantly from 1GHz to 3 GHz, and this effect increases with water content. The frequency dependence of the electric conductivity may be adequately described using a simple linear relationship. This approach is advantageous since it limits the number of parameters to be optimized in the inverse modeling procedure.     

基于矢量调制法的矢性物理量测量仪器

依据调制解调原理和线性系统理论，矢量调制法使用机械转动方法，将输入信号在进入传感器之前调制成为正弦波，由于线性传感器的频率保持性和叠加特性，对传感器输出信号解调，将得到准确的输入响应，由此去除常见的传感器偏置、偏置的漂移、干扰与噪声。基于矢量调制法原理，开发了一套使用矢量传感器构造的新原理测量仪器，并详细叙述了该仪器的物理实现方法和算法原理，对影响测量精度的主要因素给出量化分析结果。作为应用实例，说明了VMM测量仪器在寻北仪、三维矢性物理量测量中的原理和方法。理论分析和实验测量表明，矢量调制法物理意义明确，操作方便简单，抑制测量误差效果明显。VMM测量仪器显著地提高了矢性物理量的测量精度，可以广泛用于矢性物理量的精确测量。     

基于平面线圈的高分辨力时栅角位移传感器

针对现有时栅角位移传感器采用漆包线绕制工艺加工线圈,导致线圈布线不均且容易随时间发生变化进而影响测量精度的问题,提出一种基于PCB技术的新型时栅角位移传感器。该传感器通过在PCB基板的不同层上布置特定形状的激励线圈和感应线圈,形成两个完全相同并沿圆周空间正交的传感单元;当在两传感单元的激励线圈中分别通入时间正交的两相激励电流后,通过导磁定子基体和具有特定齿、槽结构的导磁转子对传感单元内的磁场实施精确约束,使两传感单元的感应线圈串联输出初相角随转子转角变化的正弦感应信号;最后通过高频时钟脉冲插补初相角实现精密角位移测量。利用有限元分析软件对传感器进行了建模和仿真。根据仿真模型制作了传感器实物,开展了验证实验,并对实验中角位移测量误差的频次和来源进行了详细分析。经过标定和补偿,最终获得了整周范围内误差在-2.82″~2.02″的时栅角位移传感器。理论推导、仿真分析和实验验证均表明,该传感器不仅能实现精密角位移测量,还能在激励线圈和感应线圈空间极距和信号质量不变的情况下,将位移测量的分辨力从信号源头提高1倍,且结构简单稳定、极易实现,特别适用于环境恶劣的工业现场。     

A Frequency-to-Time Sound-Velocity Transducer

The transducer described is intended to control the sound velocity in sea water and is based on the principle of the tracking balancing of the probing duration by an acoustic pulse of the studied medium at a given basic distance by the pulse period divisible by the pulse period of the frequency-controlled oscillator. The transducer has a high measurement accuracy, which is achieved by the practical exclusion of a random error component caused by amplitude fluctuations of the received signal as a result of abnormalities of the acoustic transparency of the studied medium caused by various disturbing factors. The acoustic base-line distance of the converter is 0.1 m, the measurement range is 1400–1600 m/s, the output signal is a frequency of 140–160 kHz, the absolute basic error is ±0.035 m/s, and the output signal rise time does not exceed 0.6 s.     

Piezoelectric based resonant mass sensor using phase measurement

The paper presents design, development and testing of a resonant sensor to measure mass in the range of 0-12 g. The sensor is built using cantilever structure with piezoelectric excitation, sensing and microcontroller based closed loop electronics. The sensor measures the unknown mass by measuring the shift in resonance frequency of the cantilever beam. The shift in resonance frequency for a change in mass is detected by measuring the phase difference between the piezoelectric sensor output and actuator input using microcontroller. The proposed measurement system is simple and accuracy is found to be ±1.2% of full scale deflection.     

A measuring method for large antenna assembly using laser and vision guiding technology

In this paper a new conception of a measuring method is proposed to assist precision automatic assembly of large radar antenna. Different from conventional 6-DOF tracking methods, the measuring system decomposes the measurement task into several independent steps. The measuring system consists of a camera, two laser distance meters, two position sensitive detectors (PSD) and an inclination angle sensor. The camera is adopted to guide antenna position and orientation adjustment over a large space. Laser meters and PSD sensor is used to precisely measure the position and orientation of radar antenna. To improve the practicability of measuring system, a robust vision measurement method is proposed. The mathematical models and practical calibration methods for measurement are elaborated. The preliminary experimental results agree with the methods currently being used for orientation and position measurement. The measuring method provides an alternative choice for the metrology in precision assembly. By using the method proposed in this paper, the measuring system can achieve a measurement accuracy of approximately 1 mm, which meets the accuracy requirement of large radar antenna automatic assembly application. Besides, the measuring method provides an alternative solution for large scale metrology which take the environmental impact into account.     

Measurement of the Parameters of the Dielectric Windows of the Linear Collider TESLA Cavities

A setup for measuring the permittivity and the loss parameter of ceramic samples is described. The setup operation is based on a conventional method for measuring changes in the frequency and Q-factor values of cavities caused by insertion of experimental samples into the cavity. Cylindrical ceramic samples with the permittivity = 8–10 and loss parameter tan = (2–4) × 10^–4 were studied. A cylindrical E ₀₁₀ cavity with a cutoff waveguide attached to one of the faces of the cavity was selected, because it provided sufficient accuracy of measurement and could be effectively used for testing series of samples of various sizes and shapes at a fixed frequency of 1300 MHz. It was shown that the permittivity of various samples could be determined with an accuracy of 1.5%, whereas the loss parameter could be determined with an accuracy of 7%.     

Resolution Enhancement with Model-Based Frequency Estimation Algorithms in Radar Signal Processing

In this work we present results on the improvement of resolution capability and accuracy for radar signal evaluation by means of model-based frequency estimation algorithms. In frequency modulated continuous wave radar sensors, which are widely used in industrial contactless distance measurement applications, the usage of the Fourier Transformation for signal evaluation is very common. Nevertheless, using the Fast Fourier Transformation, the resolution capability for closely spaced targets is limited and directly related to the employed signal bandwidth. Model-based frequency estimation algorithms, developed during the last decades, can essentially improve target resolution and distance accuracy. These improvements are shown on simulation data as well as on measured data. Model order estimation, still a challenge when applying model-based evaluation techniques, is tackled by an adaptive approach.     

数字信号处理技术在科氏质量流量计中的应用

科氏质量流量计是目前应用范围最广、发展速度最快的流量计之一。数字信号处理技术是科氏质量流量计的核心技术,直接决定其测量精度、测量稳定性等性能指标;而流量传感器输出信号的数学模型是信号处理的依据和基础。国内外学者提出了多种信号处理方法,但是,没有根据不同的信号模型和不同的应用场合对各种信号处理方法进行比较和评价。为此,根据不同数字信号处理方法的特征量提取原理,分析了其具有的优缺点。针对科氏质量流量计单相流、批料流与气液两相流测量这3种典型应用场合中存在的关键技术问题,依据随机游动信号模型、突变信号模型和自回归滑动平均(ARMA)信号模型,分别从计算精度、响应速度、收敛性、抗干扰能力和对参数变化的敏感度等方面,对不同信号处理方法进行考核和对比,确定了3种典型应用场合下,解决关键技术问题,性能最佳的数字信号处理方法。     

A high-speed precision digital phase meter with direct calculation of the signal phase

A programmed phase meter for the detection of small phase deviations is described. The device is designed for a remote vibration meter. The application of digital signal processing ensures the detection of differential or simple phase deviations at a specified carrier frequency of 10.7 MHz with a sensitivity of 10^–5 rad.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 88–91.Original Russian Text Copyright © 2005 by Goncharenko.     

A miniaturised sensor for deep hole diameter measurement

A miniaturised displacement senor for deep hole measurement is reported in this paper. By exploiting the induced eddy current effects detected by chip coils, the sensor generates a ’digital’ signal. The sensor chip coil can be manufactured by the similar processes to those used for manufacturing a printed circuit board (PCB) which allows them to be miniaturised. The paper elaborates on the construction and mechanism by which the displacement is directly transferred to a frequency output. It also reports on the transducer, which uses two contact probes for transmitting the displacement to a noncontact sensing element. Experimental results demonstrate the stability, linearity, measurement range and accuracy of the sensor system.     

Frequency-to-Time Converter for Measuring Sound Velocity in Liquids

The measuring converter is based on the principle of tracking the balancing of the separated informative value of the interval probed by an acoustic pulse in the studied medium at a given basic distance by a pulse period divisible by the period of pulses of a frequency-controlled generator. A high accuracy is reached by excluding an inconclusive (spurious) time delay of the acoustic and electric signals in the acoustic converter and electronic operational units. The acoustic base-line distance of the measuring converter is 0.1 m, the measurement range is 1400–1600 m/s, the output signal has a frequency of 140–160 kHz, the absolute basic error is ±0.015 m/s, and the time to reach a steady-state output signal is 0.6 s.     

A microwave interferometer for steady-state plasma density measurements

An interferometer for a wavelength of 8 mm, capable of homodyne frequency conversion for measuring the electron density of a steady-state plasma from a high-frequency ion source, is described. An original method for generating a reference intermediate-frequency signal using a cavity resonator is applied in the interferometer. The unambiguously measured phase shifts range from 1.5° to 360°, and the error in measuring the phase shift is 5%.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 98–100.Original Russian Text Copyright © 2005 by D. Nagornyi, A. Nagornyi, Voznyi.     

Accurate ultrasound speed measurement using an MLS-modulated continuous wave

The continuous wave shows greater potential than the pulse signal to achieve high-accuracy ultrasound speed measurement thanks to its stronger noise resistance. However, the accuracy of ultrasound speed measurement would deteriorate if echoes exist in the received continuous wave. This paper presents an applicable method using the maximum length sequence-modulated continuous wave. The present method improves the accuracy of ultrasound speed measurement further by resisting echoes. The time delay between the received signal and the transmitted signal is estimated accurately by combining the cross-correlation, parabolic interpolation and phase shift technique. Moreover, both the inherent delays induced by physical system and the path length of ultrasound are expediently corrected through least square estimation. As a result, accurate time of flight and ultrasound speed measurement are achievable. For example, the standard deviation of ultrasound speed measurement in distilled water is less than 0.003 m/s, and the deviation between the ultrasound speed measurement and the reference is less than 0.04 m/s.     

Optical deflection measuring system

A system for accurate real-time measurement of deflections was developed. A stable laser source is, by means of a single-mode fiber, coupled to an optical head located at one end of deformed structure. A detector circuit with a quadrant detector and processing electronics, located at the other end of the structure, communicates the resolved 2D position of the incident beam over a common digital bus. Experiments using interferometers were conducted in a climate-controlled chamber to evaluate system performance and verify the accuracy. A resolution of 0.1  m is attainable in dynamic measurements. The system was calibrated and tested to yield measurement accuracy of ± 0.8  m for ± 2σ probability over the measurement range of ± 300  m. Drift of the system in the experimental setup was determined to be less than 2  m for measurement in both degrees of freedom within the 10 h period under constant environmental conditions.     

嵌入式容栅传感技术及轴功率测试研究

针对旋转轴功率测试存在的传感器信号引线困难、安装空间受限、信号易受干扰的问题,设计了一种嵌入式容栅扭矩、转速传感器和测试系统.测试时在轴的两端分别安装容栅传感器,轴在受到扭矩时产生扭角,则两容栅的输出信号会产生一个相位差,通过测量相位差的变化得到扭矩.容栅传感器的差动结构提高了灵敏度减小了误差,容栅的嵌入式安装,将对被测轴的影响降到了最低.实验证明容栅传感器可靠性高,可以在环境要求严格的情况下长时间使用,并且无需通过滑环、无线或红外进行供电和信号的传输,克服了以上方式安装复杂、信号易受干扰的缺点.     

地面机动雷达水平及方位传感器的使用和标定

随着车载高机动雷达天线车自动控制技术的提高,对水平传感器及定向装置等测量仪的系统精度要求也随之提高。要充分发挥测量仪的性能指标,避免不正确使用造成的精度损失,系统标定非常重要。文中基于机动式车载雷达的实际工程运用,阐述了目前常用的水平传感器及定向装置的安装需求和标定方法,详细描述了标定的具体步骤,探讨了系统固定误差的消除途径,通过水平度和方位角度两个方面的说明,给出此类测量仪的正确使用方法,以实现预期的精度指标。