A Digital Hall Magnetometer

A digital Hall magnetometer with residual-voltage compensation and a sensitivity threshold of 4·10^–4 Oe·Hz^–1/2 for a PKhE602817 type sensor is described. An algorithm for compensating the residual voltage by a factor of more than 300 is proposed.     

一种全天候高分辨力的成像遥感方式—合成孔径侧视雷达

遥感成像所采用的电磁波波长愈长，受外界的干优越少，但影像分群力越低。合成孔径侧视雷达采用微波作为成像媒体，故能全天候运作，且能达到很高的分辨力，目前可达到0．7米，这是藉助于两种新技术实现的：合成孔径的天线和脉冲压缩技术。本文简明介绍了这种遥感成像系统的原理。     

一种新型宽带激振器的设计

研制一种新型宽频带激振器,在原有振动测试系统的基础上,将电动式激振与压电式激振这两种方式点结合起来。通过对其进行空载加速度频响测试和力频响测试,实现从20Hz至20kHz较宽范同内的激振,验证了这种新型宽带激振器的可行性。     

宽带信号多路径定位

1引言 声场的多途结构中蕴藏着比平面波模型更多的关于目标位置的信息.在射线模型中目标的位置信息完全蕴藏在到达路径的相对时延中.近年来,R.J.Vaccaro和Jian Li发展了基于单传感器的多路径时延估计算法,而M.Wax则致力于已知信号的多路径时延和到达角的联合检测与估计.这些算法均假设接收的多路径信号是发射信号的延迟加权叠加,且权重是标量,这与实际水声环境有一定差别,因为声线在海洋波导中传播时不可避免地要与海底、海面多次接触,并且海洋本身就是一个时变空变的不均匀体,因此会给每条声线带来一定的信号畸变,这些畸变具有随机性无法准确预知,更不是用一个权重参量所能完全表征的.以上这些算法都是波形意义上的迭代搜索算法,对信号的畸变非常敏感,因此在以下的分析中我们不予采用,而是采用更为宽容的相关处理.     

Lock-On Magnetometer Utilizing a Superconclucting Sensor

A magnetometer utilizing a superconducting quantum interference device (SQUID) as a magnetic flux sensor is described. Its unique capabilities include: sensitivity of about an order of magnitude better than that of heretofore published magnetometers of other types, measurement range extending to zero field, and appreciable frequency response at high sensitivity (12 c/s bandwidth at 10.7 ?Gs full scale). The SQUID is a null detector in a feedback circuit in which unknown field changes are measured in terms of bucking field changes. Some limitations and design considerations are discussed. A recording of micropulsations of the earth's magnetic field is shown.     

Algorithmic Correction of Magnetometer Device Errors

Measurement Techniques - The problems of using gradient measurements in magnetic exploration are considered. In many cases, to solve various geological problems, information on the intensity of the...     

Optimum Broad-Band Steps for a Sliding Load

The broad-band (2-18 GHz) optimum steps of a commercial sliding load have been determined by simulation on a digital computer. The influence of the load, which is slided, is taken into account. The results have been tested through a sliding short and by measuring a very good fixed load. An equivalent directivity greater than 59 dB has been obtained.     

激光泵浦的铯-氦磁力仪的信号特征

研究了基于激光泵浦的铯-氦磁力仪的磁共振信号特征。通过使用窄线宽激光对铯原子进行泵浦,得到了12.3 A/T的电流-磁场转换因子,与基于放电灯泵浦的铯-氦磁力仪相比,转化效率增大13.5倍。实验发现通过间接泵浦,可消除“光致展宽”。通过分析线宽的实验值和理论值,得到实验值线宽的最大展宽来自于脉冲激励的结论。通过测量光源、磁场、光电传感器和电路的本底噪声,确定了该磁力仪最大的噪声源为光源和磁场,以磁场分辨力为优化目标得到了最佳光强,铯-氦磁力仪的磁场分辨力可以达到0.05 nT。     

A High-Temperature Superconducting Magnetometer with Double Modulation

A high-temperature superconducting magnetometer with double modulation at frequencies of 50 kHz and 5 MHz, which uses the nonlinear properties of a ceramic superconductor, is described. The magnetometer has a noise level of 2.3 nA/(m·Hz^1/2) in the 0–14.5 kHz frequency band.     

Broad-Band Discriminators for ATE Measurement of Sideband Noise

Techniques for measurement of carrier noise sidebands are analyzed relative to their applicability to automated test equipment. Resonant cavity discriminators are shown to be useful for narrow-band high sensitivity requirements at microwave frequencies. Interferometer discriminators cover the 10 MHz to 18 GHz spectrum with only four bridges. Two transmission lines provide -120 dBc/Hz sensitivity. If four lines are used the sensitivity is -130 dBc/Hz. Techniques for further improvement are also described.     

Improving the Sensitivity of Superconductor-Based DC Magnetometer

In this study we report on some critical factors affecting the sensitivity of a magnetic field sensor whose working principle is based on a linear DC field dependence of the second harmonic of the AC response in polycrystalline type-II superconductors. DC-fields down to 2?nT in magnitude could be detected by finding optimal conditions. The optimal sensor design was determined by studying superconductor cores having different geometries and coil configurations. The optimal AC-field frequency, which is required for excitation of the specimen, was found to be 50?kHz. The second harmonic signal changes quite linearly with the DC-field up to 0.1?Oe.     

两种非屏蔽SERF原子磁强计实现方法及其比较

本文介绍了SERF(无自旋交换弛豫)态原子磁强计基本原理和检测方法,阐述了双光束交叉调制法和单光束分频调制法,这两种现有的地磁场下SERF态原子磁强计获得三轴磁场信息的检测方法.对两种方法在光路配置、零位偏置和灵敏度等方面的特性进行了比较,总结了双光束交叉调制法在y轴锁零控制方面存在的难度,得出了单光束分频调制的z轴方向灵敏度会随磁场减小而下降,同样导致锁零精度下降的结论.     

Equivalent Magnetic Noise Limit of Low-Cost GMI Magnetometer

We present a noise analysis of a giant magnetoimpedance (GMI) sensor using a peak detector at the optimal magnetic field working bias point of a sensor wire, by considering internal noise sources (intrinsic GMI device associated noise sources and conditioning electronic noise sources). An expression is obtained for the theoretical expected noise for known electronic design parameters and physical characteristics of the GMI wire. The most significant contributions to noise in a GMI measurement, using two basic oscillators (either a simple discrete RC oscillator or quartz oscillator) along with a peak detector, are presented. We discuss the expected extrinsic equivalent magnetic noise limit.      

A Broad-Band Impedance Indicator Employing a Phase-Shift Keying Modulator

A novel homodyne scheme for implementing a broad-band impedance indicator is proposed. It features a simple form made possible by using a modified quarternary phase-shift keying as a subcarrier modulation method. This method allows both the amplitude and the phase of a signal to be detected simultaneously by one single-ended mixer. A prototype indicator has assured the swept-frequency measurement over the band ranging from 8.6 to 10.4 GHz with the amplitude and phase errors of less than 5 percent and 5°, respectively. The capabilities are demonstrated by presenting examples of measurement.     

Broad-Band Microwave Voltmeter Using Thermoelectric Effects of Hot Carriers

The performance, especially of the minimum detectable voltage, the dynamic range, and the frequency characteristics on the microwave voltmeter based on the thermoelectric effects of hot carriers in a semiconductor placed in the strip line are described. Parasitic reactance of whisker and mount may be neglected in comparison with spreading resistance of not less than 500 ?, so that broad-band microwave voltmeter can be obtained. The VSWR was less than 1.2 within the range of frequency from 1 to 12.4 GHz. Making use semiconductor of low resistivity and small diameter point contact diode, a highly sensitive voltmeter is obtained. It was found that the dynamic range depends on the resistivity and the diameter of the electrode.     

具有高测量重复性的脉冲磁场磁强计

脉冲磁场磁强计是一种新的、高效率、全象限的永磁材料测量仪器.对脉冲磁场磁强计的磁场产生、信号采集和数据处理等原理分别进行了阐述.由于磁体不必与极头构成闭合回路,在采用珀尔帖效应精确控制测试线圈的环境温度以后,脉冲磁场磁强计的测量重复性(重复9次)由原来的0.326%(Br)、1.860%(HCj),提高到了恒温慢速测量模式下的0.0819%(Br)、0.080 8%(HCj).     

Broad-Band Calorimeter for Precision Measurement of Millimeter- and Submillimeter-Wave Power

A millimeter-wave dry calorimeter has been developed for power levels of 0.1 to 100 mW. The estimated instrument error for power levels of 10-100 mW is less than 0.3 percent. The required time for final reading is only about 40 s, which makes the instrument very useful for general laboratory power measurement. The VSWR is less than 1.15 over the whole waveguide band 60-90 GHz. The construction is simple compared to other designs with comparable accuracy.