基于Kronecker积的无线通信系统参量分离方法

针对无线通信系统中发射机非线性与多径衰落信道问题,提出了一种根据接收无线信号联合估计无线设备功率放大器(PA)非线性与无线信道单位脉冲响应的方法.首先,根据通信帧训练符号及发射机非线性模型构造卷积矩阵;接着,采用一次最小二乘(LS),根据接收信号估计PA的非线性模型系数与实际发送符号;然后,再采用一次LS,得到无线信道的单位脉冲响应估计;两估计可迭代或直接加取平均进行积累.理论推导与实验结果显示,采用过采样技术,所提方法可应用于单载波或多载波通信,实现PA非线性与无线信道单位脉冲响应的有效分离.新方法在无线通信的物理层射频指纹认证与信号可靠传输中具有应用价值.     

单矢量水听器二维DOA和频率联合估计算法

基于单矢量水听器,利用时延数据构造两个阵形相同的子阵,运用LS-ESPRIT方法,对信号数据矩阵进行特征值分解,提取其特征值和相应的特征向量中包含的频率和角度信息,从而实现单频窄带信号的二维DOA和频率的联合估计。具有较好的估计精度,无需搜索过程并且能够实现三维参数的自动配对。使用MATLAB进行仿真,与基于单矢量水听器的波达方向矩阵法和基于声压阵的LS-ESPRIT方法进行比较,结果表明,该方法具有较好估计性能。     

Exact analysis of the multihop multibranch hybrid AF/DF relaying networks

In this paper, the exact analysis of a multihop multibranch (MHMB) relaying network is investigated wherein each relay can operate in amplify‐and‐forward (AF) or decode‐and‐forward (DF) modes depending upon the decoding result of its received signal. If a relay decodes the received signal correctly, it works in DF mode; otherwise, the relay operates in AF mode. Therefore, we name such relaying network as hybrid amplify‐and‐forward and decode‐and‐forward (hybrid AF/DF) relaying network. We first investigate the signal transmission from source to destination node via n number of relays in a hybrid AF/DF MHMB mode. Then, we obtained the statistical features and analyze the end‐to‐end signal‐to‐noise ratio (SNR). Finally, a comprehensive performance analysis is conducted by using maximal ratio combining (MRC) scheme at the destination node. For comparison, we also obtained the results using selection combining (SC) scheme at the destination node. To the best of our knowledge, very few works in the literature have considered a general system model of MHMB relaying network wherein each relay can operate in AF or DF modes, that is, a hybrid AF/DF relaying network. Accordingly, the analysis of our system model is not only novel and exact, but also is comprehensive and can be employed in the future works.     

遥控赛车解码芯片的ASIC设计

提出了一种遥控赛车解码芯片的设计方阐述了芯片功能原理,对各模块的主要电路进行了设计、分析,其中给出了一些设计巧妙的电路结构,整个设计采用全原理图输入方式,最大程度地简化了电路,最后对整个方案进行了仿真。这种遥控赛车解码芯片可以完成对遥控电路接收端数字基带信号的解码,外围电路简单,大大简化了板级电路的复杂度、成本低,可靠性高。该芯片也适用于其他遥控玩具、防盗系统和电器遥控,应用广泛。整个方案在FPGA中通过了原型验证。     

基于压缩感知和LBG算法的SAR数据压缩与重构方法

针对如何大幅压缩SAR海量数据并获得有效的重构结果以完成SAR场景目标的高分辨成像问题,本文提出利用压缩感知（Compressed Sensing, CS）和Linde-Buzo-Gray （LBG）算法共同完成。对于SAR所接收到的回波信号,首先依据CS理论构造随机高斯噪声观测矩阵对回波信号进行降维处理,然后,利用LBG算法对CS压缩后的数据再进行压缩编码以达到进一步大幅压缩的目的。对于数据重构问题,同样分为两步:一是利用LBG算法编码的逆过程进行解码恢复,二是依据CS理论利用平滑L0（smooth L0, SL0）算法重构原始回波信号。在此基础上,再利用传统频率变标（Frequency Scaling, FS）SAR成像算法进行高分辨成像。仿真结果证明了本文方法的有效性。      

基于空频域稀疏表示的宽频段DOA估计

该文提出一种基于空频域稀疏表示的宽频段波达方向(DOA)估计方法,解决稀疏表示方法在宽带接收机对窄带信号的频率和角度估计中的难题。用空间频率代替频率和方位角的 2 维组合构建过完备字典,字典的长度仅相当于窄带信号DOA估计的字典长度,却能覆盖整个无模糊频段,大大降低了稀疏分解的计算量。该方法首先在频域估计信号的准确频率,根据频域峰值的位置构建频域峰值协方差矩阵。对频域峰值协方差矩阵进行特征分解,利用主特征向量建立稀疏模型估计信号的DOA。算法在低信噪比下具有较高的估计精度,仿真实验和分析验证了该文方法的正确性和有效性。     

An amplify‐and‐forward and decode‐and‐forward mixed relay communication system and its performance analysis

A kind of amplify‐and‐forward (AF) and decode‐and‐forward (DF) mixed relay communication system is proposed in this letter. The source broadcasts the signal to all the relays. Relays that can decode the signal adopt DF scheme to retransmit the signal, while the rest adopt AF scheme for retransmission. The destination employs maximum ratio combining technique to maximize the received signal‐to‐noise ratio. Another situation concerned in this letter is that when the relay cannot decode the source signal, it may retransmit the interference signal with AF scheme. Closed‐form expressions of outage probability are derived. Simulation results show that the analytical curves agree with the simulated ones very well, and the AF‐DF mixed relay system can improve the availability of the relays. Copyright © 2013 John Wiley & Sons, Ltd.     

Estimation of the Communication Link Status in Satcom on-the-Move

In this paper, a method to estimate the satellite link status for the Satcom on-the-move (SOTM) system at Ku band has been proposed and verified by field tests. The objective of this method is to develop a control strategy under blocked and shadowed conditions for the SOTM system that points the antenna line of sight to the satellite using a closed-loop tracking based on the received signal power. This estimation ensures a fast reacquisition of the target satellite after signal blockage and that the transmitted data be cached in time to avoid the real-time collected data lost during blockage. The basic principles of the method can also be applied to the SOTM system at other bands, such as Ka band.     

基于QR分解的LS优化算法研究

本文对基于 QR 分解的 LS 优化算法进行研究，通过构造矩阵的方法，优化 Q 矩阵和 R 矩阵的计算算法，实现了对 LS 算法的优化，减少了算法对时间和空间资源的需求，并对算法进行了时间复杂度和空间复杂度分析，证明了该优化算法的有效性。     

基于非均匀滤波器组的动态信道化滤波

针对中频带宽内存在多个子带信号,其个数、位置和带宽具有时变性的情况,该文提出一种基于非均匀滤波器组的动态信道化滤波的方法:由事先给定的子带信号间的最小保护间隔确定均匀滤波器组的子信道数目并设计相应的余弦调制滤波器组;由子带信号的位置分布求得非均匀处理矩阵,并由此直接合并余弦调制滤波器组的对应的相邻子信道以构成非均匀滤波器组;当信号动态变化时,只要根据新状态下的子带信号位置分布更新非均匀处理矩阵,就能完成新信号的信道化接收;利用不同子带信号的抽取因子之间的大小关系提前部分抽取因子以降低实现过程的运算量。仿真实例验证了新方法的有效性。     

基于深度卷积网络的二维波达方向估计方法

为了提高信号波达方向估计技术的实时性和简便性,设计了一种适用于估计均匀圆阵多信号波达方向的深度卷积网络。由阵列观测数据得到的协方差矩阵被当作是包含实部和虚部两个通道的图像,将其当作是卷积神经网络的输入张量,便可以通过训练网络来提取包含在信号协方差矩阵中的波达方向细微特征,从而实现准确快速地同时对多个入射信号的方向进行估计的目的。仿真结果表明,设计的深度卷积网络能够很好地完成二维信号波达方向估计。相比于现有估计方法,卷积网络给出的结果更加精确,且算法相对稳定。因此,提出的深度卷积网络在多目标方位识别与跟踪领域具有潜在的工程应用价值。     

实现单通道MPSK信号盲分离的MCMC新算法

本文根据单通道接收两路MPSK混合信号在过采样下的基本模型,针对粒子滤波算法在单通道信号盲分离中的性能瓶颈以及高复杂度问题,提出了基于MCMC方法的新算法。该算法对接收信号进行过采样处理,能够利用更多的波形信息,从而有效抑制噪声的影响。新算法利用Gibbs采样估计MPSK调制符号的后验概率,近似实现了贝叶斯最优估计,并利用最小二乘法实现参数的迭代估计。理论分析与仿真实验表明,相对粒子滤波算法,本文提出的新算法在误码率性能以及复杂度方面具有良好的表现。      

直接检测的光正交频分复用传输系统最小均方自适应算法

为了减少直接检测的光正交频分复用(DD-OOFDM)传输系统中色散对系统的影响,传输系统使用了基于频域的最小均方(LMS)自适应均衡技术,由于基于频域的LMS估计方法计算复杂度低且便于信号块处理,相比最小平方(LS)估计方法,可更有效地追踪信道变化,减小相位噪声对传输系统的影响。实验结果表明,经背靠背(BTB)和100km标准单模光纤(SSMF)传输后,使用频域LMS估计方法的信号比使用频域LS估计方法的信号系统接收功率代价在误码率为10×10-2.5和10×10-2.0时分别降低了2dB及2.5dB,频域LMS估计方法比频域LS估计方法对传输系统具有更好的色散补偿效果。     

基于Goertzel算法的亚音频识别方法

对讲机通信中,一般使用亚音频信号（CTCSS）作为识别信号,判断是否对接收到的信号进行解码。提出了Goertzel算法在对讲机的亚音频提取的应用。Goertzel是一种特殊的离散傅里叶变换的方法,对于检测单频率有很好的效果。大幅度降低了亚音频提取的计算量,通过降低算法开销来降低整个系统的成本。相对于传统的使用独立IC识别或者傅里叶变换法,本方法有很大的优势,在生产中得到良好的应用。     

Theoretical Upperbound of the Spurious-Free Dynamic Range in Direct Digital Frequency Synthesizers Realized by Polynomial Interpolation Methods

In this paper, a universal mathematical method is proposed to determine the upperbound of the spurious-free dynamic range (SFDR) in direct digital frequency synthesizers (DDFSs) realized by piecewise polynomial interpolation methods. The Fourier series is used to establish a linear matrix relationship between the frequency spectrum of the interpolated sinusoidal signal and the coefficients of the interpolating polynomials. This matrix relationship can be considered as a linear overdetermined system of equations, which can be solved for the ideal spectrum where the fundamental harmonic has an amplitude of one and the other harmonics are zero. It is shown that the Moore-Penrose pseudoinverse and Chebyshev minimax methods find the coefficients corresponding to the largest signal-to-noise ratio and maximum SFDR designs, respectively. The proposed method is used to show that the maximum SFDR of a DDFS based on the even fourth-order polynomial interpolation is 74.35 dBc. A DDFS based on the aforementioned method is designed and its architecture is optimized to obtain an SFDR of 72.2 dBc. A VLSI implementation of the proposed DDFS is also reported.     

基于均匀圆阵的宽带相干LFM信号定位方法

本文提出一种基于均匀圆阵的宽带相干LFM信号定位方法。首先，算法根据LFM信号在分数阶傅里叶域的能量聚焦性，对接收信号做分数阶傅里叶变换，实现宽带信号的窄带化处理；其次，利用圆阵的虚拟轴向平移形成的相位差构造空间平滑矩阵，完成相干信号的解相干处理；最后，对空间平滑矩阵进行奇异值分解得到相邻阵元接收数据的相位差，结合相位差反演参数估计算法得到二维角度参数估计的闭式解。仿真实验验证了算法对宽带相干LFM信号定位的有效性。     

Automatic classification of multiple signals using 2D matching of magnitude–frequency density features

Signal classification is an important function of modern communication systems in software defined radio applications. The ability to quickly recognize the type of received signals allows a system to automatically adapt the processor to properly decode the signals. Many classification techniques assume that the received signal space is occupied by only one signal, and that the frequency of operation is known. However, in some systems, the receiver may be completely blind to the number and characteristics of signals within the bandwidth of interest. The technique introduced in this study proposes the collapsing of localized magnitude peaks from consecutive short time discrete fourier transform bins into magnitude histograms to create a two dimensional image of the frequency?Cmagnitude density of the received signal space. This image can be a useful visualization tool in the characterization of the signal space in user assisted modes of classification. Alternatively, the process could be automated by utilizing pattern recognition and image processing algorithms. Automatic signal classification is explored in this study.     

基于传播算子的卫星导航系统干扰源直接定位方法

针对现有单星定位技术精确度不足问题,提出一种基于传播算子的卫星导航系统干扰源直接定位方法,解决现有技术无法快速有效地定位中高轨卫星干扰源的问题。对卫星接收信号建模,计算每个时刻的接收信号协方差矩阵,通过对协方差矩阵分块,计算得到传播算子,进而得到导向矢量正交投影子空间的估计;然后建立损失函数,通过搜索得到干扰源位置估计结果。理论分析和仿真结果证明,该算法在复杂度大大降低的同时,定位精确度与传统基于多重信号分类(MUSIC)的直接定位算法相当,远优于现有的测向定位技术,具有重要的工程应用价值。     

Windowing Design Method for Polynomial-Based Interpolation Filters

An efficient implementation for finding digitally the interpolated samples is the Farrow structure. It mimics digitally a hybrid system where a continuous-time (CT) signal is reconstructed using an analog reconstruction filter having a piecewise-polynomial impulse response. The interpolated samples are obtained by sampling reconstructed signal. This paper introduces a generalized design method for polynomial-based interpolation filters and Farrow structure. The proposed method also can be used to calculate the coefficients of Selva interpolator. In this approach, the ideal CT impulse response is truncated by using CT window functions. The obtained windowed impulse response is then approximated using the piecewise Taylor polynomial approximation. Length of the impulse response and degree of the approximating polynomial can be arbitrarily selected, and in this way the transition band width can be controlled. However, if CT fixed-window functions are used, the stopband attenuation is determined by window type and remains approximately constant with increase of length and order of the impulse response. The stopband attenuation can be controlled by using CT dynamic windows such as Kaiser window. The presented windowing design method is an effective tool for calculation of the Farrow structure coefficients, with filter performance that is comparable to the frequency domain design.     

Demodulation and code acquisition using decorrelator detectors forQS-CDMA

A linear detector for a quasisynchronous code-division multiple-access (QS-CDMA) cellular system is presented, which is designed according to a minimum mean-square error (MMSE) criterion. By using a time-averaged version of the interfering signal covariance matrix, it is shown that multiuser interference can be rejected without the need to estimate signal time-of-arrival. Furthermore, unlike previous MMSE receiver designs, estimation of the received signal covariance matrix is not required. An asymptotic form of the MMSE detector, corresponding to a decorrelator implemented using a projection operator, is also obtained. Bit-error rate (BER) results are presented which demonstrate the superiority of the MMSE receiver over the conventional matched-filter detector under strong near-far conditions. An analysis of the expected acquisition time T¯_ACQ is given for the decorrelator detector using a serial search scheme. The results obtained show that T¯_ACQ is far less for a code acquisition method using the decorrelator as opposed to a conventional matched filter