三分量阵列感应实验装置研究

针对国内没有自主研发的三分量感应测井仪器,设计三分量阵列感应的实验装置。使用主控芯片TMS320F2812控制DDS集成芯片AD9833产生6 kHz和18 kHz的正弦波,经功率放大后发送至发射线圈系,接收信号经AD7606采样,由EP4CE6E22C8和TMS320F2812共同完成数据的处理和传输。通过测量水平方向线圈系和垂直方向线圈系的接收信号表明,空气中水平方向的接收电压小于垂直方向的接收电压,实验结果与理论一致,可以用于三分量感应的响应特性研究,同时为实际仪器设计提供实验基础。     

三分量感应线圈系在均匀地层中的响应特性分析

本文根据三正交线圈系结构,对仪器进行单侧布置整个线圈系,根据线圈系结构设计要求,利用感应测井原理,建立发射线圈到接收线圈的响应关系,可得到应用于三分量感应测井仪器探头的响应计算。本方法简单有效,为设计三分量线圈系提供理论基础,并且能够很好地比对实际信号与理论计算的响应一致性,对多分量感应测井仪器的线圈系优化设计具有非常好的参考价值。     

过钻具阵列感应仪器发射电路设计

过钻具阵列感应仪器是一种在过钻具施工工艺中测量地层电导率的阵列感应测井仪器.过钻具阵列感应测井仪器采用泵出工艺,使用电池供电,因此对仪器功耗要求更高.传统感应采用线性功放,效率低,交越失真大.本文利用D类功率放大器工作于开关状态的特点,实际功耗小,效率高,实现低功耗过钻具阵列感应测井仪发射电路.该电路采用DDS技术合成...     

浅谈感应测井仪器中测控电路的设计

在油气储藏评价中,感应测井仪器是一个重要的测量装置,其核心部分是测控电路,主要负责发射信号、接收信号和处理信号,对各个功能模块的运行进行有效控制,并能保证其正常的通信.围绕感应测井仪器的测控电路的设计,本文展开了论述.     

基于多元接收线圈的管道局部缺陷检测方法研究

在管道内部,基于远场涡流技术的局部缺陷定量检测中,当发射线圈处于管道缺陷位置时,接收线圈检测的远场涡流信号中叠加了发射线圈处缺陷造成的伪峰信号,影响了接收线圈处管道缺陷定量分析的正确性.为了实现基于远场涡流检测中局部缺陷正确的定量分析,本文在远场区域设置与发射线圈同轴的多接收线圈以及周向传感器阵列.同轴接收线圈用来获取远场涡流检测信号中的伪峰信号,周向传感器阵列用来检测局部缺陷.该方法通过两个接收线圈获取具有差分特性的两个远场涡流检测信号,然后利用维纳去卷积滤波器实现伪峰信号的获取,同时滤除测试中的噪声;最后,在用于局部缺陷定量分析的涡流信号（由阵列传感器获取）中减去伪峰信号,达到检测管道局部缺陷的目的.该方法通过实验仪器得到验证,在管道局部缺陷的定量检测中具有很好的实用性.     

基于DSP和DDS的三维感应测井高频信号源实现

引言 高频信号源设计是三维感应测井的重要组成部分。三维感应测井的原理是利用激励信号源通过三个正交的发射线圈向外发射高频信号,再通过多组三个正交的接收线圈,得到多组磁场分量,从而准确测量地层各向异性电阻率。     

互质MIMO雷达的非圆信号降维DOA估计方法北大核心CSCD

针对传统互质阵列波达方向估计方法存在的自由度低、阵列孔径小、相位模糊等问题,提出了一种基于互质MIMO雷达的非圆信号降维波达方向(Direction of Arrival, DOA)估计方法。该方法结合了互质阵列与MIMO雷达的优点,利用非圆信号特性对阵列进行扩展,重构接收信号矩阵,然后进行降维处理,并利用噪声特征值的幂级数对噪声子空间进行修正,进一步提高算法精度。最后推导了文中方法的无相位模糊问题。仿真实验表明,文中方法能够有效避免相位模糊,大大提高自由度并扩大阵列孔径,与传统MUSIC算法以及互质阵列MUSIC算法相比,在估计成功率、DOA估计精度等方面均具有更好的性能。     

阵列信号处理实验平台设计

本文针对一维线阵和二维面阵的阵列信号处理算法研究,设计了一种发射阵列和接收阵列上下交错排布的二维稀疏超声相控阵列信号处理实验平台,并给出了实验平台的硬件总体功能设计、发射和接收电路设计及软件架构。相控阵声场特性仿真分析结果表明该实验平台具有较好的波束成形和波达方向估计效果。     

虚拟子阵平滑算法

主动阵列发射正交信号可以极大地扩展阵列的虚拟孔径,阵列的自由度成几何增长。该文利用主动阵列发射同频带时域正交PCM信号构造的虚拟子阵,提出了一种虚拟子阵平滑(VSS)算法,可解决不同目标回波信号相干的问题。该算法避免了接收阵列物理孔径的损失,当接收阵列具有个阵元时,最大可分辨的相干数目为。仿真实验表明VSS算法的有效性,而且该算法只需要较少的阵元发射信号。     

一种混频信号波形发生器的设计与实现

感应测井是重要的地层电阻率测量方法,在石油勘探开发中发挥着越来越重要的作用。三分量感应测井仪中需要一种产生20kHz正弦波和60kHz正弦波的合成波的波形发生器,用以向地层发射感应测井信号。目前感应测井仪中使用的波形发生器都是由RC振荡电路经分频后,     

瞬变电磁测井同轴多匝线圈误差校正模型

受井眼尺寸限制,井下瞬变电磁系统通常采用同轴多匝接收线圈来改善探测性能.但是,线圈匝数的增加在提高信号强度的同时,也引入了模型失配误差.针对该问题,本文在柱状多层非均匀结构基础上,分析了接收与发射线圈间距对感应电动势的影响,并提出了一种瞬变电磁测井同轴多匝线圈误差校正模型.最后,不同收发间距的仿真结果表明,该模型可以有效校正多匝线圈模型失配误差,提高瞬变电磁测井反演精度.     

A 24-GHz Patch Array with a Power Amplifier/Low-Noise Amplifier MMIC

This paper presents an active patch array designed at 24 GHz. It can be used as a front-end component for a phased array. A series resonant array structure is chosen which is compact and easy excite. With 5 elements, the array proved a 12-dB antenna gain. A power amplifier and a low noise amplifier are designed on a single GaAs chip (PALNA). Bias switch is used in the PALNA, which greatly reduces the switch loss in a transceiver and increases the efficiency. 20-dB small signal gain is achieved in both power amplifier and low noise amplifier. The active patch array is built by the combination of the patch array and PALNA. The measured active gain of this antenna is 35-dB for the PA mode and 31-dB for the LNA mode. This active patch array can obtain an EIRP of 34 dBm with a total radiated power of 22dBm and a maximum PAE of 32%. To check the noise performance, we applied sources at both normal temperature and 77K (liquid nitrogen) and extracted the noise figure (3.5 dB) of the active antenna by the Y factor method. The results proved that the active antenna is working efficiently as both a transmitting and receiving antenna.     

逆向调制阵列大气激光通信的误码率分析

为研究逆向调制阵列对大气湍流的抑制作用,提高逆向调制大气激光通信质量。首先,建立了逆向调制阵列接收光束传输模型,分析了光束经大气传输到达逆向调制阵列的信噪比;然后,建立了逆向调制阵列反射光束在大气信道中的传输模型,推导了不同数目反射光束在接收端的光强概率分布模型,分析了在不同湍流环境下采用逆向调制阵列的激光通信误码率;最后,仿真分析了在中等大气湍流条件下传输距离为1 km时,采用三个逆向调制器组成的逆向调制阵列的通信误码率比单个逆向调制器降低4 dB。     

Ultrawideband noise radar based on antenna arrays with signal recirculation

For radar systems using noise sounding signals with orthogonal spectra, which are radiated with the help of a multielement antenna array, a method for recirculation of noise signals in the feedback loop formed by the transmitting element, the target, and the receiving element is considered. The generalized ambiguity function is used to compare the resolutions and the sidelobe levels along the delay (range) coordinate and the angular coordinate for the cases of a linear equispaced transmitting antenna and an individual receiving antenna in the presence and in the absence of recirculation. Sparse and filled antenna arrays are analyzed for the cases of moderately wideband and ultrawideband total noise signals and different distributions of the center frequencies of partial noise signals over the array elements.     

基于LPFT的相控阵雷达信号盲分离

现代电子战中,雷达信号受到严重的干扰,使回波信号的提取愈发困难。跟据相控阵雷达天线阵列的特点,提出了基于局部多项式傅里叶变换(LPFT)的雷达信号盲源分离算法。选取线性调频信号(LFM)雷达信号作为发射信号,将雷达接收信号作为观测信号,应用LPFT进行时频变换,构造时频矩阵,采用联合近似对角化方法对受到干扰的雷达信号进行盲源分离。仿真结果表明,本方法有效得分离出了淹没在噪声和LFM调频干扰中的雷达回波信号。     

Channel Capacity Between Antenna Arrays— Part II: Amplifier Noise Dominates

In this paper (Part II of two), we continue examining the use of space-time coding techniques to achieve very-high spectral efficiencies in highly scattering environments, using multiple transmit and receive antennas. The goal is to increase as much as possible the number of antenna elements, which is particularly difficult at the remote station, which usually has a more limited space allotted to the antenna array than at the base station. Under the assumption that sky noise was the dominant noise source, Part I addressed the channel-capacity effects of mutual impedance between antenna elements in the remote array, and the correlation between the signal and noise fields received by these elements. In Part II, we consider the same effects under the assumption that amplifier noise is the dominant noise source. The question of how closely the receiving array elements can be spaced depends on how precisely the channel can be estimated. This is related to the high-precision requirement experienced with supergain antenna arrays. The supergain connection is made explicit by showing that the optimum channel capacity for the case of a single transmitting element is achieved by using the supergain weights for the receiving array. To indicate the effect of noisy channel estimation, the loss in receiver antenna gain due to noise in weight estimates is computed with a simple simulation model of scattered propagation for the single-transmitting-antenna element case     

Wireless MIMO Sensor Network with Power Constraint WLS/BLUE Estimators

Sensor networks are used in various applications. Sensors acquire samples of physical data and send them to a central node in different topologies to process the data and makes decisions. Multiple Input Multiple Output (MIMO) systems showed good utilization of channel characteristics. In MIMO Sensor Network, multiple signals are transmitted from the sensors and multiple antennas are used at the control node. This provides each receiver the whole combined signal and hence, array processing techniques helps in reducing the effects of noise. In this paper we devise the use of MIMO sensor network and array decision techniques to reduce the noise effect. The proposed Constrained Best Linear Unbiased Estimator (CBLUE) and Constrained Weighted Least Square (CWLS) estimators showed good performance BER when used with MIMO Sensor Network. Most importantly these estimates showed good perturbation results when the estimated channel matrix is not accurate. The condition for good performance was to have the number of receiving antennas at the central node to be equal to the number of transmitting sensors and no significant improve was seen if the number of antennas is greater than the number of transmitting sensors. If the number of sensors is greater than the number of receiving antennas, time or frequency multiplexing is possible to keep good performance for the devised system. Enhancing the BER results in longer battery life at sensor nodes.     

Response of electromagnetic-pulse logging sonde in axiallysymmetrical formation

The time-domain response of an electromagnetic-pulse logging sonde in axially symmetrical formations is obtained using the transmission-line-matrix (TLM) technique. The sonde consists of transmitting and receiving coils that are placed on the axis of the borehole. The formation is assumed to have horizontal layers with or without invasion zones. The transmitting coil emits an electromagnetic pulse of known shape. The receiver transient response was computed using the TLM technique, which calls for dividing the formation into small cells. Each cell is simulated with a matrix of transmission-lines which are connected to those of the adjacent cells     

一种根据扰码特性来提高多径搜索性能的算法

在CDMA系统中，为了对抗多径衰落，使用Rake接收机对接收信号进行处理。在发射端，通过扰码对信号进行加扰处理。Rake接收机对接收的信号进行解扰，相干积分处理，根据功率时堑函数PDP值来计算多径的相位信息。在信噪比比较差的情况下，搜索出来的多径可能是噪声径，这对Rake接收机解调的性能有一定的影响。介绍一种根据扰码自相关特性，来判断搜索出多径是否为噪声径的方法，提高Rake接收机的性能。