超宽带冲击脉冲正交解调接收机幅相误差分析与校正算法

对脉冲体制的超宽带正交解调接收机幅相误差模型进行了深入分析。并基于冲击脉冲信号形式,提出新的正交解调接收机幅相误差分析与校正算法。弥补了现有的基于线性调频信号形式而提出的超宽带正交解调误差校正算法的不足,其更普适于各种超宽带信号形式。在实际系统中获得了理想的效果。     

一种超宽带等效采样接收机的设计与实现

脉冲超宽带雷达回波信号由于带宽大而难以直接采样,通常采用等效时间采样方法来进行模数转换。传统的等效采样接收机大都是基于改变ADC采样时钟的时延来实现等效采样,采样时钟对触发信号会产生亚稳态时序,不可避免地会出现数据误对齐,必须添加辅助的在线或离线校正设计。针对这一问题,设计了一种基于FPGA内置延迟线的超宽带等效采样接收机,FPGA产生延时可调的发射触发信号去控制波形产生系统,基于高速采样保持器和ADC完成回波接收,实现了超宽带射频信号的等效采样,而无数据误对齐问题。接收机的等效采样速率为12.8GS/s,-3dB采样带宽为6.4GHz,满足脉冲超宽带雷达的应用需求。     

超宽带穿墙雷达取样脉冲产生器设计

在超宽带穿墙雷达接收机系统中,其关键的等效采样技术需要一种极窄脉宽高电压的脉冲触发采样门电路来对接收信号进行采样。介绍了超宽带取样脉冲产生技术,讨论并分析了几种常用超宽带脉冲产生方法的特点及其局限性。提出了新型的肖特基二极管脉冲整形网络,设计并实现了应用于等效采样接收机系统的新型亚纳秒取样脉冲产生器,很好地结合了雪崩晶体管与脉冲整形网络的优势,在显著减小脉宽的同时保持了较高的脉冲幅度。通过仿真分析和制作测试,获得了脉冲底宽为400 ps、幅度为6.46 V和波动水平为-14.7 dB的单极性窄脉冲,实测结果与设计数值一致性良好。这种简单高效廉价的电路十分符合超宽带穿墙雷达等效采样接收机取样脉冲的设计。     

基于变换采样的超宽带接收机设计

为了实现以较低的采样率对超宽带(UWB)脉冲信号进行采样以及在带宽和系统复杂度之间取得均衡,设计了一种基于变换采样的超宽带接收机系统.设计的接收机在AD芯片之前加入了跟踪保持放大器,提高了系统的模拟带宽(5GHz),通过采样时钟的较小延时实现了较高的等效采样率(8 GHz).主要用来接收带宽1 GHz以及以上的超宽带信号,利用VHDL进行编程,通过Chipscope抓取信号进行验证.测试表明,该系统能接收1 GHz以及以上带宽超宽带信号,达到了设计要求,可以用于超宽带通信与测距.     

ALOHA脉冲超宽带网络的性能分析

脉冲超宽带(IR-UWB)系统的脉冲宽度极窄,脉冲占空比极低,使用跳时和时间分集传送。该文分析了分布式脉冲超宽带网络中采用ALOHA 方式共享信道时帧传送失败的原因,推导出帧传送失败的概率,通过分析数据帧产生-缓冲-传送的M/G/1 排队过程,得到了网络吞吐、帧传送延时的公式。仿真结果说明,ALOHA脉冲超宽带网络的吞吐,帧传送延时和网络稳定性能远远优于ALOHA 载波调制技术网络。     

全新的高稳定穿墙雷达接收机前端设计

在穿墙雷达(TWR)接收超宽带(UWB)回波信号的过程中,高速信号采集是其中的关键所在。首先基于传统等效采样方法,改进了其采样模式,能极大地提高等效采样的实时性,并减小精密延时电路的延时时间范围。其次利用跟踪保持芯片设计了一种新型等效采样接收机前端实现方案,不仅能降低等效采样技术对取样脉冲的要求,而且能充分发挥跟踪保持芯片高重复频率、高稳定和高度集成的优势。通过分析和仿真论证,实现了10GHz的等效采样频率,理论分析与仿真测试结果一致性良好。这种高度集成、简单高效的电路在超宽带穿墙雷达接收机中具有很好的应用前景。     

网络、滤波、滤波器、限幅器、斩波器

0608992超宽带非周期信号等效采样的研究〔刊,中〕/李熹//电测与仪表.—2005,42(12).—45-49,38(D)对超宽带窄脉冲信号需要进行高速采样才能有效采集,等效采样是一种实现超高速采样的有效手段。经过了时间间隔调制的超宽带脉冲串信号已经不是周期信号,而传统的等效采样一般都是以被采集信号的周期为前提的。提出了一种对于超宽带非周期信号等效采样的新方法,并对设计出的电路进行测试,得出了理想的测试结果。参50608993基于FIR滤波器组的DFT算法=DFTalgorithmbasedon FIR filter banks〔刊,英〕/E.V.Papoulis and T.Stathaki//Elect…     

脉冲探地雷达小型化控制与采集系统设计

根据脉冲探地雷达低成本、高精度和小型化的要求,研制了一种基于微控制器的超宽带(UWB)探地雷达信号控制与数据采集系统。文中分析了延时式等效时间采样原理,阐述了系统总体结构,描述了触发脉冲生成电路和回波数据采集通道的工作原理和设计方法,给出了底层固件的开发流程以及系统软件功能。研制的高集成度嵌入式控制与采集系统,降低了探地雷达系统整体成本,提高了系统的实时性和可靠性。     

一种适用于超宽带脉冲信号检测的改进CUSUM算法

将最快检测技术应用于超宽带脉冲信号检测中,具体采用改进的CUSUM(Cumulative Sum)算法来检测超宽带脉冲信号。首先分析了经过多径信道衰减后的超宽带脉冲信号概率分布特性,进一步提出了适用于超宽带脉冲信号检测的改进CUSUM算法。理论分析和仿真证明了所提改进算法性能优越且实现复杂度低。该算法克服了块检测算法的信噪比门限效应,且具有最优的检测延迟性能,相同虚警限制下其检测性能明显优于能量检测算法。     

脉冲超宽带技术在航天测控系统中的应用

针对当前航天测控系统安全性不足的问题,将脉冲超宽带技术应用于航天测控系统中,构建了一种新的脉冲超宽带测控体制。建立了基本的脉冲超宽带测控信号模型,对脉冲超宽带测控系统的性能和传输链路进行了分析。给出了脉冲超宽带测控系统结构框图,介绍了系统工作过程。针对并行信号捕获方法资源消耗大的不足,提出了两步并行捕获方法。分析表明,脉冲超宽带技术可用于航天测控系统中,完成测距测速和数据传输任务。脉冲超宽带测控系统可有效提高测控系统的隐蔽性和抗干扰能力,同时提高测距精度。在信号捕获方面,与并行捕获方法相比,两步并行捕获方法的硬件资源消耗得到大大降低,同时还可保证较快的捕获速度,但会产生一定的信噪比损失。     

Characterization of the Arterial System in the Time Domain

The impulse response function and the input impedance of the systemic arterial tree emphasize different aspects of this system. The impulse response function is calculated via inverse Fourier transformation of the input impedance. The effects of truncation of the impedance are reduced by subjecting the data to a Dolph-Chebyshev filter. The impulse response functions of a windkessel model, a uniform tube model, and of the arterial system of the dog, are given. The impulse response functions of the windkessel model and of the arterial system of the control dog show a sharp initial peak followed by an exponential decay (equal decay time as that of the diastolic pressure tracing). The height of the decay extrapolated to time zero is related to total arterial compliance. Total arterial compliance calculated in this way agrees with the value calculated from the ratio of the time constant of the diastolic pressure decay and peripheral resistance. The presence of peaks in the impulse response function indicates a distinct reflection site as shown in the uniform tube model and found in the dog with balloon occlusion of the descending aorta. The measurement of the time intervals between these peaks and the start of excitation together with the pulse wave velocity enable us to calculate the distance between the location of the reflecting site and the heart.     

基于平坦度的激光雷达强度图像的滤波算法

激光雷达是一种比较新的获取地面信息的方法，这种方法得到的数据不仅包括不规则间距的三维数据点云，还包括激光强度信息。现有的激光雷达数据处理方法大都是将三维数据点进行处理得到数字地面模型（DTM），对于激光强度信息的处理方法的研究比较少。针对激光雷达数据中像素级融合了三维信息和强度信息的特点，提出了一种基于高程信息平坦度的均值滤波算法。先将激光雷达的强度信息转换为灰度图像，然后在对各像素进行均值滤波处理时，融合了对应的激光雷达距离信息中该像素邻域内的高程信息。运用此算法和传统均值算法对激光雷达数据进行了处理，并且使用多种指标对处理结果进行了比较。结果表明，该算法既保持了传统均值滤波的优点，又改进了对弱边缘目标的保护。     

Iterative site-based modeling for wireless infrared channels

We describe an iterative site-based method for estimating the impulse response of wireless infrared channels. The method can efficiently account for multiple reflections of any order. A simple geometrical model of indoor environments is presented which includes interior features such as partitions, people, and furniture, thus permitting accurate evaluation of shadowing effects. For a reflection order of three, the iterative method is over 90 times faster than the existing recursive technique. A computer implementation is described and used to demonstrate the efficiency and accuracy of the method     

声场脉冲响应的分段模拟方法

计算脉冲响应是封闭空间声场模拟技术的重要工作。针对脉冲响应各部分的特点，改变仅利用某一种模型模拟整个脉冲响应的传统做法，把声线跟踪法、虚源法和统计学方法结合起来，对脉冲响应进行分段模拟研究。算法设计过程中，对扩散反射和镜面反射都作了考虑，并研究了“混响尾巴”的计算方法以及提高计算效率的具体途径。仿真实践表明，所棕方法能在保证一定精度的前提下使计算效率得到有效提高。     

基于频率步进原理的声表面波射频标签的辨识

为降低声表面波(SAW)射频标签(RFID)系统对硬件模数转换器和天线开关速度及隔离度的要求,提出了频率步进原理声表面波射频标签的辨识。采用基于自回归模型的功率谱估计方法对回波信号进行了时频变换,通过对加入了噪声的系统回波信号进行仿真实验,验证了发射频率步进脉冲信号取代传统窄脉冲的可行性以及算法的高精度。同时也讨论了阅读器与标签之间不同距离、温度影响和相位噪声对标签解码的影响,提出了解决思路。     

Modeling of nondirected wireless infrared channels

We show that realistic multipath infrared channels can be characterized well by only two parameters: optical path loss and RMS delay spread. Functional models for the impulse response, based on infrared reflection properties, are proposed and analyzed. Using the ceiling-bounce functional model, we develop a computationally efficient method to predict the path loss and multipath power requirement of diffuse links based on the locations of the transmitter and receiver within a room. Use of our model is a simple, yet accurate, alternative to the use of an ensemble of measured channel responses in evaluating the impact of multipath distortion     

Frequency-Domain Shuttle-Pulse Measurement of Losses and Mode Conversion

A new method for measuring losses and mode conversion at microwave frequencies is presented. The method consists of producing the impulse response of single- or double-cavity resonant circuits in the frequency domain. To obtain this response, the input reflection coefficient of the circuit to be measured is first changed into a function of time by a swept-frequency technique, and then Fourier-transformed by means of a spectrum analyzer system. High generality of application and repeatability as well as measurement simplicity and definition are the main features of the new method. The examples of application presented include measurement of microstrip-line attenuation constants up to X-band and characterization of mode conversion coefficients in overmoded circular waveguide at millimeter-wave frequencies.     

Nonlinear suppression of autoregressive impulse noise in on-off binary communications

A novel method is proposed to combat an impulse noise in on-off binary communication. The method is based on modeling of the impulse noise using the autoregressive model. This approach does not require explicit a priori knowledge of the impulse noise statistics. The performance of the resulting algorithm is analyzed using computer simulation. It is shown that essentially power-independent reception may be achieved under conditions of impulse noise. It is also shown that the proposed technique greatly improves the system performance even when the Gaussian noise is added to the receiver input mixture. However, the improvement diminishes as the impulse-noise-to-Gaussian-noise ratio decreases.     

Design and characterization of finite-length fiber gratings

A rigorous analysis of the response of fiber Bragg gratings of finite length is presented. For the discrete grating model, we find necessary and sufficient conditions for the response to be realizable as a grating of finite length. These conditions are used to develop a general method for designing gratings with a prescribed length. The design process is divided into two parts. First, we find a realizable reflection spectrum which approximates the target spectrum. Once the spectrum is found, one can determine the associated grating profile by straightforward layer-peeling inverse-scattering or transfer matrix factorization methods. As an example, a dispersionless bandpass filter is designed and compared to the results when the layer-peeling algorithm is applied directly to a windowed impulse response. We also discuss potential applications to grating characterization including regularization and finding the absolute reflection spectrum from a measured, normalized version.