Convolution-Based Trigonometric Interpolation of Band-Limited Signals

This paper presents a method to obtain a trigonometric polynomial that accurately interpolates a given band-limited signal from a finite sequence of samples. The polynomial delivers accurate approximations in the range covered by the sequence, except for a short frame close to the range limits. Besides, its accuracy increases exponentially with the frame width. The method is based on using a band-limited window in order to reduce the truncation error of a convolution series. It is shown that the polynomial can be efficiently constructed and evaluated using algorithms designed for the discrete Fourier transform (DFT). Specifically, two basic procedures are presented, one based on the fast Fourier transform (FFT), and another based on a recursive update algorithm for the short-time FFT. The paper contains three applications. The first is a variable fractional delay (VFD) filter, which consists of a short-time FFT combined with the evaluation of a trigonometric polynomial. This filter has low complexity and can be implemented using CORDIC rotations. The second is the interpolation of nonuniform Fourier summations, where the proposed method eliminates the need to interpolate any kernel sample. Finally, the third can be viewed as a generalization of the FFT convolution algorithm and makes it possible to interpolate the output of an finite-impulse-response (FIR) filter efficiently.      

超宽带目标时域电磁散射特性测量

建立了一套超宽带时域测量系统,使用该系统对金属球体、导弹缩比模型、飞机缩比模型目标进行了时域电磁散射测量实验,并给出了有效的数据获取及数据处理的方法.经数据处理后的测量数据与理论计算的散射数据相比较,结果完全一致.证明该实验测量系统可以用来对雷达目标电磁散射特性进行高效的测量与分析.     

基于时域eICIC的小区覆盖扩展策略能效优化

为了应对未来5G网络流量爆炸式增长,研究学者提出在宏基站覆盖范围内密集部署小基站,并利用小区覆盖扩展(Cell Range Expansion,CRE)策略实现宏基站与小基站的负载均衡。但是,CRE区域用户会严重受到宏基站的同频干扰,为解决此问题引入几乎空白子帧(Almost Blank Subframe,ABS)策略,提出了一种联合偏置值及ABS比例的迭代优化算法。针对具有偏置值与ABS比例约束的问题,分别对偏置值及ABS比例进行搜索寻找最优解,再通过迭代联合算法进行更新迭代,以实现系统能效的最大化。对提出的迭代联合优化算法进行了仿真分析,进一步验证了所提方案具有较好的能效。     

Detector Time Delay in Band-Limited Systems

The effect of the integration interval in an integrate and dump detector in a band-limited system is analyzed. It is found for optimum performance that the interval must be delayed by τ seconds, which can be approximated by finding the interval giving maximum area under the system pulse response.     

On Sampling of Band-Limited Signals Associated With the Linear Canonical Transform

Sampling is one of the fundamental topics in the signal processing community. Theorems proposed under this topic form the bridge between the continuous-time signals and discrete-time signals. Several sampling theorems, which aid in the reconstruction of signals in the linear canonical transform (LCT) domain, have been proposed in the literature. However, two main practical issues associated with the sampling of the LCT still remain unresolved. The first one relates to the reconstruction of the original signal from nonuniform samples and the other issue relates to the fact that only a finite number of samples are available practically. Focusing on these issues, this paper seeks to address the above from the LCT point of view. First, we extend several previously developed theorems for signals band-limited in the Fourier domain to signals band-limited in the LCT domain, followed by the derivation of the reconstruction formulas for finite uniform or recurrent nonuniform sampling points associated with the LCT. Simulation results and the potential applications of the theorem are also proposed.      

基于时频图像处理方法的多分量信号分离

针对传统时域或频域分析方法对时域、频域交叠但时频域不交叠的多分量信号分离能力不足的问题,提出了一种基于图像处理技术的分离方法.首先对多分量信号进行短时傅里叶变换(STFT),在获取多分量信号时频图像的基础上,引入图像处理技术,实现时频图像二值化,得到多分量信号的二值图像,并利用连通区域标记法对各分量进行定位;最后利用透分量消除法,将定位后的各分量依次提取出来,从而实现时频平面上的各分量分离.仿真实验表明,该方法能够实现多分量信号的有效分离,为后续信号的识别和参数估计奠定了基础.     

Multichannel Sampling of Signals Band-Limited in Offset Linear Canonical Transform Domains

The aim of the multichannel sampling is the reconstruction of a band-limited signal f(t), from the samples of the responses of M linear time invariant systems, each sampled by the 1/Mth Nyquist rate. As the offset linear canonical transform (OLCT) has been found wide applications in signal processing and optics fields, it is necessary to consider the multichannel sampling based on offset linear canonical transform. In this paper, we develop a multichannel sampling theorem for signals band-limited in offset linear canonical transform domains. Moreover, by designing different OLCT filters, reconstruction formulas for uniform sampling from the signal, from the signal and its first derivative or its generalized Hilbert transform are obtained based on the derived multichannel sampling theorem. Since recurrent nonuniform sampling for the signal has valuable applications, reconstruction expression for recurrent nonuniform samples of the signal band-limited in the offset linear canonical transform domain is also obtained by using the derived multichannel sampling theorem and the properties of the offset linear canonical transform.     

微波致热超声信号时频特征及其影响因素

微波致热超声成像是一种兼顾了微波和超声成像两方面长处的新型生物医学成像方法。本文首先给出了一个微波致热超声（Microwave-Induced Thermo-Acoustic,MITA）实验系统,然后结合信号理论和MITA机制,讨论微波脉冲激励源和样品尺寸这两方面因素对MITA信号的时域波形和频域分布的影响。由实验数据和理论分析得出MITA信号时域波形强度与入射微波脉冲宽度和样品截面大小成正比;MITA信号的频率分布除了与激励微波脉冲频谱有关外,更主要的特性是其频谱分布中心与样品厚度所确定的超声波本振频率存在对应关系。     

A Numerical Method for Evaluating the Distortion of Angle-Modulated Signals in a Time Domain

As yet there exists no analytical method of obtaining the exact output distortion of BPF's for an angle-modulated signal input. In this paper, we have introduced a numerical method in which a filtering problem is described by the state space method and then is converted to a time domain difference equation. As a result, evaluation can be carried out quickly and easily.     

Functionally Weighted Lagrange Interpolation of Band-Limited Signals From Nonuniform Samples

A modification of the conventional Lagrange interpolator is proposed in this paper, that allows one to approximate a band-limited signal from its own nonuniform samples with high accuracy. The modification consists in applying the Lagrange method to the signal, but pre-multiplied by a fixed function, and then solving for the desired signal value. Its efficiency lies in the fact that the fixed function is independent of the sampling instants. It is shown in this paper that the function can be selected so that the interpolation error decreases exponentially with the number of samples, for the case in which the sampling instants have a maximum deviation from a uniform grid. This paper includes a low-complexity recursive implementation of the method. Its accuracy is validated in the numerical examples by comparison with several interpolators in the literature, and by deriving upper and lower bounds for its maximum error.     

On Optimal Detection of Band-Limited PAM Signals with Excess Bandwidth

PAM data transmission receivers accomplishing maximum likelihood sequence detection (MLSD) usually require a matched filter prefilter, a sampler at the symbol rate, and a Viterbi algorithm detector. When the channel is unknown or slowly changing, one must use an adaptive matched filter prefilter. We examine an alternative optimum receiver whose optimality is independent of the matched filter prefilter and which is applicable when the channel is effectively band-limited. The sampler in the proposed receiver operates at a rate faster than the data symbol rate, enabling one to replace the matched filter by a fixed low-pass filter and still ensure that the maximum likelihood detector is supplied with a set of sufficient statistics. It is shown that the matched filter is incorporated within a modified Viterbi detector without increasing the number of states in the algorithm, although the Viterbi detector must perform computations at approximately twice the usual rate. Simulations support the optimality of the new receiver and quantitatively indicate the degradation in performance experienced by some adaptive receivers previously proposed.     

时域流信号的多任务稀疏贝叶斯动态重构方法研究

为了解决多任务观测条件下时域流信号动态重构面临的块效应问题,该文基于重叠正交变换(LOT)和稀疏贝叶斯学习的贪婪重构框架先后提出了一种流信号多任务稀疏贝叶斯学习算法及其鲁棒增强型的改进算法,前者将LOT时域滑窗推广到多任务条件下,通过贝叶斯概率建模将未知的噪声精度的估计任务从信号重构中解耦并省略,后者进一步引入了重构不确定性的度量,提高了算法的鲁棒性和抑制误差积累的能力。基于浮标实测数据的实验结果表明,相比多任务重构领域代表性较强的时间多稀疏贝叶斯学习(TMSBL)和多任务压缩感知(MT-CS)算法,本文算法在不同信噪比、观测数目和任务数目条件下具有显著更高的重构精度、成功率和效率。

     

用SQP时域优化高速互连线电路

提出了一个基于特征法传输线网络建模和灵敏度分析的非线性高速互连线电路的时域优化设计方法 .考虑到高速互连线电路设计的特性 ,一般其最优值只是在初值的较小邻域 ,提出用改进的序列二次规划法 SQP优化方法保证了算法的整体收敛性及局部超一次收敛性 .介绍了用于优化内循环的特征法传输线建模和灵敏度分析 .最后 ,用两个例子证明了方法的可行性 .     

用SQP时域优化高速互连线电路

提出了一个基于特征法传输线网络建模和灵敏度分析的非线性高速互连线电路的时域优化设计方法．考虑到高速互连线电路设计的特性,一般其最优值只是在初值的较小邻域,提出用改进的序列二次规划法SQP优化方法保证了算法的整体收敛性及局部超一次收敛性．介绍了用于优化内循环的特征法传输线建模和灵敏度分析．最后,用两个例子证明了方法的可行性．     

一维带限信号正则外推的快速算法

本文给出用离散正则化方法进行一维带限信号外推的快速算法,其基本思想是将正则化方法与离散Fourier变换(DFT)结合起来,而正则参数的选取则基于偏差原理和作者提出的三阶收敛算法来实现.这样,可将计算量由原米的O(n3/3)量级减少到O(12n2)量级(当采样点n为偶数时)乃至O(12/2nlog2n/2)量级(当n=2*,p为正整数时),分析和数值试验表明,新算法具有快速、稳定和抑制高频噪音干扰等优点.     

时频域重叠多信号智能检测方法研究

针对现有基于深度学习理论的信号智能检测方法大多只能对单信号或时频域不重叠的信号进行检测,本文提出了一种基于掩膜区域卷积神经网络(Mask R-CNN)与Criminisi算法的时频重叠多信号智能检测新方法.首先将一维时域信号通过时频变换得到二维时频图像.然后针对时频图中多信号重叠部分像素位置信息缺失这一问题,提出了利用...     

基于能量补偿的时域干扰抵消改善方法

针对时域干扰抵消方法产生的波束畸变和探测盲区问题，提出一种基于能量补偿的时域干扰抵消改善方法.该方法首先根据数据处理带宽和衰减曲线构造能量补偿因子；然后利用时域干扰抵消方法对线列阵拾取数据进行处理，得到相应波束；最后采用能量补偿因子对干扰抵消输出波束进行优化，可以减小波束畸变和探测盲区，达到预期的干扰抵消效果和探测效果.数值仿真和数据处理均表明，本文方法通过构造能量补偿因子改善了时域干扰抵消方法，降低了时域干扰抵消方法形成的"宽凹"或"凸"字型波束对目标探测性能的影响，实现了波束校正，减小了探测盲区，对原衰减区间内的目标实现了有效探测.从根本上解决了时域干扰抵消方法产生的波束畸变和探测盲区问题.     

基于时域聚汇和补偿估计WLFM信号DOA的FRFT-MUSIC算法

本文提出了分数阶付氏变换(FRFT)-MUSIC算法估计多个宽带信号到达角参数(DOA)。该算法通过对到达角的初始估计,在时域内经补偿和聚汇将宽带线性调频信号的时变方向矩阵变换为固定的方向矩阵,然后利用分数阶付氏变换和MUSIC算法实现入射信号DOA估计。本文同时提出了一种对FRFT-MUSIC的组合估计方法以减少计算量。仿真实验证明了算法的有效性。     

Sensing of OFDM Signals in Cognitive Radio Systems with Time Domain Cross‐Correlation

This paper proposes an algorithm to sense orthogonal frequency‐division multiplexing (OFDM) signals in cognitive radio (CR) systems. The basic idea behind this study is when a primary user is occupying a wireless channel, the covariance matrix is non‐diagonal because of the time domain cross‐correlation of the cyclic prefix (CP). In light of this property, a new decision metric that measures the power of the data found on two minor diagonals in the covariance matrix related to the CP is introduced. The impact of synchronization errors on the signal detection is analyzed. Besides this, a likelihood‐ratio test is proposed according to the Neyman–Pearson criterion after deriving probability distribution functions of the decision metric under hypotheses of signal presence and absence. A threshold, subject to the requirement of probability of false alarm, is derived; also the probabilities of detection and false alarm are computed accordingly. Finally, numerical simulations are conducted to demonstrate the effectiveness of the proposed algorithm.