Interdecadal Variations of Phase Delays Between Two Nino Indices at Different Time Scales

Phase delays between two Nino indices-sea surface temperatures in Nino regions 1+2 and 3.4 (1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that there are two types of period bifurcations in the Nino indices and that period bifurcation points exist only in the region where the wavelet power is small. Interdecadal variation features of phase delays between the two indices vary with different time scales. In the periods of 40-72 months, the phase delay changes its sign in 1977: Nino 1+2 indices are 2-4 months earlier than Nino 3.4 indices before 1977, but 3-6 months later afterwards. In the periods of 20-40 months, however, the phase delay changes its sign in another way: Nino 1+2 indices are 1-4 months earlier before 1980 and during 1986-90, but 1-4 months later during 1980-83 and 1993-2001.

Method for differential phase delay resolution of phase referencing VLBI technique and its experimental verification

The phase referencing Very Long Baseline Interferometry(VLBI)technique is a newly developed tool to measure the angular position of a deep space exploration probe in the plane-of-the-sky.Through alternating observations between the probe and a nearby reference radio source,their accurate relative angular separation can be obtained from the radio images generated by this technique.To meet the requirements of the current orbit determination software,differential delay should be firstly derived from those radio images.A method to resolve the differential phase delay from the phase referencing VLBI technique is proposed in this paper,and as well the mathematical model for differential phase ambiguity resolution is established.This method is verified with practical measurement data from the Chang’E-3 mission.The differential phase delay between the Chang’E-3 lander and rover was derived from the phase referencing VLBI measurements,and was then imported into the Shanghai astronomical observatory Orbit Determination Program(SODP)to calculate the position of the rover relative to the lander on the lunar surface.The results are consistent with those acquired directly from radio images,indicating that the differential phase ambiguity has been correctly resolved.The proposed method can be used to promote applications of the phase referencing VLBI technique in future lunar or deep space explorations,and more accurate orbit determination becomes promising.

Group delay and phase delay in GNSS systems

GNSS signals have previously been modulated using binary phase shift keying but this modulation scheme is being replaced by binary offset carrier(BOC)modulation.Research has considered how the BOC signals might be affected differently when passed through a surface acoustic wave(SAW)filter.The concern has been that because of the split spectrum nature of the BOC signals,the upper and lower side-lobes will be delayed significantly differently.This was suggested because SAW filters have nonlinear phase characteristics and therefore different frequencies are delayed differently.It was suggested that this difference in delay will result in greater distortion of the correlation triangle.A delay magnification effect was also mentioned when analyzing the delay of a BOC signal.It was not understood why the theoretical delay calculations did not match up with the actual results in both hardware and simulation.This paper clarifies some of the confusion and explains why the“delay magnification”applies to phase delay but not group delay.This paper also takes a look at how the code phase delay can vary with frequency and correlator spacing as a result of the SAW filter properties.

A new method for resolving phase ambiguity in radio interferometry using Earth rotation synthesis

As a key technique in deep space navigation, radio interferometry can be used to determine the accurate location of a spacecraft in the plane-of-sky by measuring its signal propagation time delay between two remote stations. To improve the measurement accuracy, differential phase delay without phase ambiguity is usually desired. Aiming at the difficulties of resolving phase ambiguity with few stations and narrowband downlink signals, a new method is proposed in this work by taking advantage of the Earth rotation. The high accurate differential phase delay between the spacecraft and a calibrator can be achieved not only in the in-beam observation mode but also in the out-of-beam observation mode. In this paper we firstly built the model of phase ambiguity resolution. Then, main measurement errors of the model are analyzed, which is followed by tests and validations of the model and method using the tracking data of the Cassini mission and Chang'E-3 mission. The results show that the phase ambiguities can be correctly resolved to generate a 10-picosecond level accuracy differential phase delay. Angular measurement accuracy of the Cassini reaches the milli-arc-second level, and the relative position accuracy between the Chang'E-3 rover and lander reaches the meter level.

大型宽带相控阵天线子阵级延时器误差分析及补偿

子阵级使用延时器是改善宽带相控阵天线波束性能常用的技术途径。在对延时器电性能误差特性分析的基础上,提出采用次级子阵延时器联合TR通道移相器和衰减器分级补偿天线系统内部射频链路的时延、幅度和相位误差的方法。通过采用两级子阵延时架构的一维大型天线阵列模型的仿真验证,表明该方法不仅可实现大带宽大扫描角大型相控阵天线的方向图高精度控制,同时降低了大时延量延时器的研制难度。

宽带相控阵天线实时延时器分级应用研究

提出了一种在宽带相控阵天线中分级使用实时延时器的方案。作为阵元级和子阵级延时器应用的折中方案,该方案对波束指向偏移的校正通过高位加低位延时器的组合应用,并选取适当高、低位延时器的数量比例来实现。在获得较好波束校正性能的同时,该方案简化了天线系统的整体复杂度,具有良好的工程可实现性。

宽带相控阵天线波束指向频响分析和实时延迟器应用

分析了直线和平面宽带相控阵天线扫描波束指向随工作频率改变而产生漂移的现象,给出了阵列单元或子阵采用实时延迟器后,这种指向漂移得以改善的估计。结果表明,漂移为原先的1/M(M为子阵列)。

A Fiber Optic Sensor for 2,4-dichlorophenol Analysis based on Optical Composite Oxygen-sensitive Film

A novel fiber optic sensor based on optical composite oxygen-sensitive film was developed for determination of 2,4-dichlorophenol(DCP).The optical composite oxygen-sensitive film consists of tris(2,2’-bipyridyl)dichloro ruthenium(II)hexahydrate(Ru(bpy)3Cl2)as the fluorescence indicator and iron(III)tetrasulfophthalocyanine(Fe(III)PcTs)as bionic enzyme.A lock-in amplifier was used for detecting the lifetime of the composite oxygen-sensitive film by measuring the phase delay of the sensor head.The different variables affecting the sensor performance were evaluated and optimized.Under the optimal conditions(i e,pH 6.0,25℃,Fe(III)PcTs concentration of 5.0×10^-5 mol/L),the linear detection range,detection limit and response time of the fiber optic sensor are 3.0×10^-7-9.0×10^-5 mol/L,4.8×10^-8 mol/L(S/N=3),and 220 s,respectively.The sensor displays high selectivity,good repeatability and stability,which have good potentials in analyzing DCP concentration in practical water samples.

宽带相控阵天线子阵延时随机配置优化研究

针对宽带相控阵天线中子阵级配置实时延时器的拓扑结构,提出了一种对子阵延时量化误差引起的天线波束指向偏差的修正方案。该方案通过随机配置延时修正量,并以波束指向偏差及增益下降为评价标准,优化各实时延时器延时修正量化参数,从而达到修正天线带内指向色散的目的。该方案在获得较好波束校正性能的同时,一定程度上简化了天线系统的整体复杂度,具有良好的工程可实现性。

PHOTOACOUSTIC VISCOELASTICITY IMAGING OF BIOLOGICAL TISSUES WITH INTENSITY-MODULATED CONTINUOUS-WAVE LASER

In this paper,a novel photoacoustic viscoelasticity imaging(PAVEI)technique that provides viscoelastic infornation of biological tissues is presented.We deduced the proocess of photoacoustic(PA)ffct on the basis of thermal viscoelasticity theory and est ablished the relationship between the PA phase delay and the vicoelasticity for soft solids.By detecting the phase delay of PA signal,the viscoelasticity distribution of absorbers can be mapped.Gelatin phantoms with diferent densities and different absorption cofficients were used to verify the dependence of PA VEI measurements.Moreover,tissue mimicking phantoms mixed with fat and collagen at different concentrations were used to testify the feasibility of this technique with reli able contrast.Finally,the PAVEI was sucossfully applied to discrimination between biological tissue constituents.Our experimental results demonstrate that this novel technique has the potential for visualizing the anatomical and biomechanical properties of biological tissues.

子阵级应用延迟线对相控阵天线带宽改善的分析

采用频率无关移相器的相控阵天线的波束指向会随频率发生变化,实时延迟线是提高宽带相控阵天线指向精度的重要方法。分析了平面相控阵天线波束指向随频率改变而产生漂移的现象,理论分析和仿真结果均表明,当频率改变时,平面相控阵天线的波束指向仅在俯仰角面发生漂移,而在方位角的指向不变。详细讨论采用子阵分割技术,并在子阵级别用实时延迟线,单元内采用移相器的混合波束控制技术。结果表明,这种方法可以有效扩展相控阵天线的带宽。

A new high-precision gravity solid tidal model for Precision Gravity Measurement Facility

It is significant for establishing gravity datum to construct precise gravity solid tidal model,A simple method with relatively low performance is to interpolate tidal parameters from the global gravity solid tide models.A competitive approach is to determine local gravity solid tidal model by harmonic analysis using long-time serial gravity observations.In this paper a new high-precision gravity solid tidal model for Precision Gravity Measurement Facility is estimated from two co-site gravimeters in the cave laboratory using modern international standard data processing techniques,whose accuracy is evaluated further by comparing with previous publications.The results show that:(1)the determined gravity solid tidal models from two co-site gravimeters are in good agreement with each other,of which the maximum differences for amplitude factors and phase delays don’t exceed 0.01700%and 2.50990°,respectively.(2)the performance of the obtained gravity solid tidal model is 0.00411 for amplitude factors and 0.24120°for phase delays,which is a little better than that of previous publications using superconducting gravity data from Wuhan station.(3)our results and methods are corrective and effective.(4)our model is tiny different from that provided by Wuhan station,which implies that it is necessary to construct a gravity solid tidal model for Precision Gravity Measurement Facility,rather than just adopting existing models at Wuhan station.Our results are helpful in realizing the goal of Precision Gravity Measurement Facility.

CATIA AIDED RADOME ANALYSIS USING GEOMETRIC OPTICS METHOD

In this paper, the Geometric Optics (GO) method using the approximate ray paths coupled with the Computer Aided Tri-dimensional Interface Application (CATIA) meshing modeling are implemented to analyze the performance of electric large three-dimensional dielectric radome-enclosed antenna of arbitrary contour shape. The surfaces of the radome are approximated by planar triangular patches, the influences of various number of patches on power transmission coefficient and Insertion Phase Delay (IPD) via an ogive and a conical radome are discussed by the hybrid method. The simulation results indicate that computational error from planar triangular patches can limit in one percent, meeting the engineering application requirements.

A Fiber Optic Sensor for Determination of 2,4-dichlorophenol based on Iron(Ⅱ) Phthalocyanine Catalysis

A new fi ber optic sensor based on the oxidation of 2,4-dichlorophenol（DCP） catalyzed by iron（II） phthalocyanine（Fe（II）Pc） was developed for the determination of DCP. The optical oxygen sensing fi lm containing fl uorescence indicator Ru（bpy）3Cl2 was used to detect the consumption of oxygen in solution. Moreover, a lock-in amplifier was used to determine the lifetime of the sensor head by detecting its phase delay change. The results reveal that the sensor has a linear detection range of 1.0×10^-6- 9.0×10^-5 mol/L and a response time of 5 min. The sensor also has high selectivity, good repeatability and stability. It can be used effectively to determine DCP concentration in real samples.

大型宽带相控阵天线多级子阵延时应用研究

在采用子阵延时方案的大型宽带相控阵天线系统设计中,子阵划分结构和实时延时器使用方式将直接决定系统的宽带性能、工程实现复杂度以及研制成本。本文基于阵列方向图合成的基础理论模型,推导得出多级子阵延时方案与传统单级子阵延时方案具有相近的阵列辐射性能。通过一维大型线阵多级子阵方案的应用示例,说明多级子阵延时方案可显著降低系统总体复杂度,在此基础上分析并总结阵列宽带性能与子阵规模和时延步进量之间的关系。

平面相控阵天线两维扫描波束指向漂移

揭示了平面相控阵天线宽带工作时,两维扫描波束指向漂移的规律。理论分析表明:在球坐标系下,φ方向不发生漂移,θ方向的漂移与直线相控阵天线一维扫描时相同。全空域立体扫描波瓣的仿真验证了上述结论。文章也给出了阵列单元或子阵设置数字延迟器后,扫描波束指向漂移改善的分析结果。

An aquifer model with a parameter characterizing the inhomogeneity of media

A fissured aquifer model used in petroleum engineering has been studied by the author. It is found that thefissure-induced inhomogeneity which appeared in reservoir media can be expressed by a delay timeτ whichcharacterizes the process of transition from unsteady to steady seepage flow. Comparison between the fissured aquifer model mentioned above and corresponding homogeneous media is given in this paper. The expression of the characteristic delay timeτis independently derived by using the fissured porous media modeland by solving the characteristic time of an one-dimensioned diffusion equation in turn. The result shows thatthe τ value is in direct proportion to L2. L is the average size of aquifer rock blocks cut by fissures network.The larger the L value, the longer the fissures is and the less the density of fissure is. For identifying the inhomogeneity manifestation of aquifer, a criterion related with the characteristic time of external force action isproposed. In addition, a suggestion on the in-situ measurement of the new aquifer parameter, the 1 value, isgiven.

地质雷达测控系统的FPGA实现

超宽带地质雷达测控系统的关键是等效时间采样系统的实现,而等效时间采样需要一个精确的可编程延时器。利用Cyclone III、IV的锁相环(PLL)模块的动态相位调整功能,实现了最小步长125 ps的可编程延时器,可完成高达8 GS/s的等效采样,并开发了相应的测控模块。测控模块通过Avalon总线与软核NIOS II连接,在NIOS II的控制下实现地质雷达的扫描控制。该设计具有结构紧凑、性能稳定、成本低廉等优点,适用于低频段地质雷达。试验测试证明了系统的可行性。

基于压缩感知的光控相控阵波束形成方法

针对光控相控阵在实现宽带宽角扫描时,所需要的光真延时器数目过多问题进行研究,提出了基于压缩感知的光控相控阵方向图形成方法。首先通过公式推导详细分析了影响光控相控阵波束偏移的因素,其次给出光真延时器稀疏排布方式,在此基础上基于压缩感知理论恢复出光控相控阵的方向图。所提方法能够在大幅减少光真延时器数目的条件下实现宽带宽角扫描。最后利用仿真实验验证了所提方法的有效性。

宽带相控阵天线延迟线分析

采用频率无关移相器的相控阵天线的波束指向会随频率发生变化,实时延迟线是提高宽带相控阵天线波束指向精度的重要方法。分析了子阵级采用延迟线,单元级使用移相器的宽带相控阵天线副瓣特性,发现当工作频率改变时,由于阵列存在周期相位误差导致天线副瓣电平抬高。针对此问题,提出单元级精细延迟线方案,消除周期相位误差对天线副瓣的影响。仿真结果表明,这种方法在扩展相控阵天线带宽的同时,明显改善了天线的副瓣特性。