Searchback Algorithms for TOA Estimation in Non-coherent Low-rate IR-UWB Systems

Non-coherent ultra-wideband (UWB) receivers offer an attractive low-complexity solution to ranging with UWB radios. They use a simple receiver architecture that can operate at very low sampling rates compared to the Nyquist rate. In this paper, time-of-arrival (TOA) estimation performances of two different searchback algorithms for non-coherent impulse radio UWB systems are analyzed: jump back and search forward (JBSF) and serial backward search (SBS). Average ranging errors for both algorithms are formulated using noise-based ranging thresholds and at sub-Nyquist sampling rates. For JBSF, a lower bound on the average ranging error is obtained using an error-minimizing threshold. Also, a semi-analytic technique for the selection of the searchback window length is presented. For SBS, noise-based threshold selection for both single-cluster and multi-cluster channels are introduced. Computer simulations in IEEE 802.15.4a channels provide insights on the selection of some of the critical parameters for accurate ranging. The simulation results show that JBSF typically performs better than SBS if the inter-cluster delay parameter (K) is not selected appropriately for SBS. In both cases, it is shown that even at sampling rates much smaller than the Nyquist rate, ranging accuracies on the order of 33 cm can be obtained using a non-coherent UWB receiver.

相参雷达与非相参雷达的差异分析

针对相参雷达和非相参雷达的概念进行阐述。通过详细分析两种体制雷达在应用上的主要区别,侧重介绍相参雷达的优点。相参性方面重点介绍多普勒效应具有的特性,从信号接收和信号处理上重点讨论了相参性雷达拥有的速度测量功能,在速度模糊和距离模糊上详细比较了两者的差别。通过实践证明,相参雷达的应用范围比非相参雷达的范围广阔得多,但价格不菲。     

卫星扩频测控相干与非相干测量机制研究

卫星扩频测控体制可采用相干与非相干2种模式实现测速和测距.相干模式通过使用相参应答机进行相干转发,能够获得较高的测量精度;非相干模式则通过卫星从上行信号提取所需信息之后,独立形成下行信号,地面接收后实现解算来完成测量工作.主要针对这2种模式测速与测距的基本原理进行研究.     

短脉冲非相参雷达的补偿相参处理方法研究

为了对短脉冲非相参雷达信号进行相参处理,该文根据其信号特征,建立了参数化信号模型。分析了信号非相参因素,提出了以匹配滤波和参数估计为基础的补偿相参处理算法。通过理论推导证明了对点目标进行补偿相参处理的可行性。并对距离扩展目标进行了理论分析,推导出其获得近似的补偿相参增益所需要满足的条件。并通过仿真验证了理论分析结果。     

用于相干接收的锥形多模干涉合波器

报道了一个新的基于锥形多模干涉的相干光波合波器.对锥形多模波导中的模式行为给出了完整的理论分析,并给出了该锥形合波器在不同结构下的输出特性.在一个绝缘体上硅的基板上实现了该器件.鉴于无后向反射,容易扩展为多口配置,对实验误差有大的允许度和尺寸紧凑等优点,这种锥形多模干涉的合波器是大型光子集成中所用的相干光波合波器的理想选择.     

Tapered Multimode Interference Combiners for Coherent Receivers

报道了一个新的基于锥形多模干涉的相干光波合波器.对锥形多模波导中的模式行为给出了完整的理论分析,并给出了该锥形合波器在不同结构下的输出特性.在一个绝缘体上硅的基板上实现了该器件.鉴于无后向反射,容易扩展为多口配置,对实验误差有大的允许度和尺寸紧凑等优点,这种锥形多模干涉的合波器是大型光子集成中所用的相干光波合波器的理想选择.     

Channel Parameter Estimation for Polarization Diverse Coherent Receivers

A robust in-service estimation of fiber channel parameters from equalizer parameters of a polarization diverse coherent receiver is presented. The equations used for estimation are evolved from a theoretical fiber channel model. The theory is validated based on simulations and data from transmission experiments.     

Multiplier-Free Real-Time Phase Tracking for Coherent QPSK Receivers

This letter presents a hardware-efficient phase estimation algorithm that can replace the common complex estimators for a coherent quadrature phase-shift keying transmission system.     

基于转换矩阵的GPS相干干扰抑制技术

本文首先采用空间平滑技术消除有用的GPS信号与相干干扰信号之间的相关性,然后构造干扰转换矩阵,从而抑制干扰信号,保留有用信号和噪声。最后根据最大输出信噪比原则,获得最佳波束形成器。仿真分析表明该方法可以有效提高输出信号的信号干扰加噪声比,且对信号的DOA估计不敏感。     

Nonsingular Constant Modulus Equalizer for PDM-QPSK Coherent Optical Receivers

Adaptive electronic equalizers using the constant modulus algorithm (CMA) algorithm often converge to a singular coefficient matrix that produces the same signal at multiple outputs. We address this issue in the context of optical communications systems with polarization-division multiplexing and coherent receivers. We study, by computer simulation, the performance of multiuser CMA equalizer, an enhanced CMA equalizer initially proposed for use in wireless multiuser and later multiple-input/multiple-output communications systems. We show that the proposed adaptive electronic equalizer does not exhibit singularities and, therefore, is superior to the commonly used CMA equalizer.     

Automatic PMD Compensation by Unsupervised Polarization Diversity Combining Coherent Receivers

A new automatic scheme to compensate the intersymbol interference caused by fiber polarization mode dispersion (PMD) is introduced. The proposed method makes use of the orthogonal polarization components by combining them through adaptive electronic filters, which are adjusted through a low-complexity unsupervised updating method. The simplicity of the proposed unsupervised method is its most critical feature in terms of enabling real-time and all-hardware implementation. Simulation results are provided for a fiber channel with 40 Gsymbols/s signalling rate and a mean DGD level greater than the symbol period, where it is demonstrated that the PMD can be effectively compensated with a 2 dB signal-to-noise ratio penalty relative to PMD-free channel.      

无线相干光通信空间分集接收合并技术

空间分集接收能补偿大气湍流造成的信道衰落。在给出相干检测分集接收的系统模型和晴朗大气信道模型的基础上,考虑子孔径间信号相关性,分析了等增益合并分集和最大比合并分集的误码率性能,并就中断概率与选择分集进行了比较。分析结果表明,空间分集接收能够明显改善相干光通信系统的性能,并且接收信号间的空间相关性越小分集接收的性能越好,其中最大比合并分集性能相对其他两种合并方式优势明显,选择分集性能最差,但它与等增益合并分集的差距不大,同时选择分集实现相对容易,在工程应用中要综合考虑实现的难易程度和性能。     

高速光通信相干接收系统中偏振模色散均衡算法的分析与优化

在高速光通信系统中,对于偏振模色散对信号失真的影响,利用恒模算法来修正补偿,可以使误码率降低。通过对该算法原理的分析,设计了仿真系统并进行仿真。得出结论：由于硬件的限制,恒模算法的参数并不是越大越好。在选择参数时,要考虑2点：1）可以发送的最大训练系统的长度;2）硬件可支持FIR抽头参数范围。     

Dynamic Range of Single-Ended Detection Receivers for 100GE Coherent PM-QPSK

Recently, coherent polarization-multiplexed quadrature-phase-shift keying has attracted considerable interest. Enabled by progress in ultrafast digital signal processing electronics, it can carry 4 bits per symbol and has been proposed for 100-Gb/s transmission at a reduced 25-GBaud line rate. Several different receiver structures are possible, whose performance, complexity, and design issues are varied. In this letter, we concentrate on a receiver employing single-ended, rather than balanced, detection. We analyzed its performance and found that, by properly tailoring its design parameters, the single-ended receiver may closely approach the performance of the more expensive balanced receiver, over a practically relevant received-signal dynamic range.     

Ultrafast Operation of Digital Coherent Receivers Using Their Time-Division Demultiplexing Function

The digital coherent receiver, which is a combination of a phase-diversity optical homodyne receiver and digital signal processing (DSP), can demodulate any multilevel coded optical signals without relying upon an optical phase-locked loop. However, the maximum symbol rate processed by such a receiver is limited by the speed of electric analog-to-digital converters and digital signal processors. Although real-time operation at 10 Gsymbol/s using an application-specific integrated circuit has recently been demonstrated, it is still difficult to increase the symbol rate beyond 40 Gsymbol/s. In order to cope with this difficulty, we propose a novel scheme, which employs a local oscillator (LO) pulsed at the subharmonic frequency of the symbol rate, enabling time-division demultiplexing of the signal at the digital coherent receiver. We demonstrate that the new type of digital coherent receiver operating at 10 Gsymbol/s can demodulate the aggregate symbol rate of 160 Gsymbol/s. From these results, we can expect ultrafast coherent optical fiber communication in the future.      

一种软件无线电GMSK非相干接收机

本文给出了一种适用于软件无线电的突发模式非相干GMSK接收机。该接收机可以在很短的前导字序列内完成载波和符号同步，采用线性近似的非相干检测算法来对非线性的GMSK。信号实现解调。该接收机采用前馈结构实现快速同步，同时具有较低的计算复杂度和相对优越的性能，适合于在线性软件无线电接收机平台上实现。通过仿真给出了该接收机与几种典型GMSK。接收机的性能比较，并且在实际软件无线电平台上得到验证。     

一种新型的IR-UWB均衡接收机

IR-UWB系统中的密集多径和随机的时延扩展带来了严重的码间干扰,若不采取均衡技术抑制码间干扰,将严重限制系统的性能.针对接收机的位置改变能引起信道模式改变,设计了一个新型的MF-DFE接收机,根据传输速率信息和判决设备得到的信道模式的信息,在快时变的混合信道下,动态的配置判决反馈均衡器的长度进行均衡接收.仿真表明该接收机在快时变的IR-UWB混合信道情况下,在高的传输速率下仍能获得良好的性能.     

相参雷达K分布海杂波背景下非相干积累恒虚警检测方法

相参雷达系统下的非相干积累检测方法,可以提高雷达的目标检测速度,达到实时处理的要求。然而,相参雷达系统下的非相干积累检测方法对参考单元数、脉冲积累数、杂波散斑协方差矩阵以及海杂波模型的形状参数均是非恒虚警(CFAR)的。该文基于块白化的海杂波预白化方法,提出预白化单元平均恒虚警(PWCA-CFAR)检测方法和预白化单元中值恒虚警(PWCM-CFAR)检测方法,并使用了匹配于参考单元数、脉冲积累数、形状参数的自适应门限,确保提出检测方法的恒虚警特性。实验结果表明,当存在异常单元时,PWCM-CFAR检测方法的检测性能优于PWCA-CFAR检测方法。

     

适用于不同相参体制的雷达数字中频接收机

介绍了一种功能完备的雷达数字中频接收机，其具有数字中频处理，数字定相，发射脉冲频谱分析及功率校正，AFC控制等功能。其可用于常规磁控管雷达多普勒改造或提升模拟中频相参多普勒系统性能，也适用于全相参系统接收机中频数字化改造或进一步的性能提升。采用该数字接收机，典型磁控管整机系统的改善因子限制可达40dB以上。该数字接收机性能高，集成度高，适用性广。     

干扰存在背景下MSK相干接收机输出误码率研究

由于非合作接收等因素的影响，相对于通信信号而言，干扰具有一定随机性。本文在研究干扰存在条件下MSK相干解调输出误码率时，将干扰建模成随机参量信号，并推导了针对MSK相干解调的干扰生效条件。讨论了合成矢量图法和数值计算法两种方法，并采用Matlab编程，实现了数值计算法，比较了不同模型下几种干扰样式的优劣。