Coexistence of OFDM‐Based IMT‐Advanced and FM Broadcasting Systems

Coexistence analysis is extremely important in examining the possibility for spectrum sharing between orthogonal frequency‐division multiplexing (OFDM)‐based international mobile telecommunications (IMT)‐Advanced and other wireless services. In this letter, a new closed form method is derived based on power spectral density analysis in order to analyze the coexistence of OFDM‐based IMT‐Advanced systems and broadcasting frequency modulation (FM) systems. The proposed method evaluates more exact interference power of IMT‐Advanced systems in FM broadcasting systems than the advanced minimum coupling loss (A‐MCL) method. Numerical results show that the interference power is 1.3 dB and 3 dB less than that obtained using the A‐MCL method at cochannel and adjacent channel, respectively. This reduces the minimum separation distance between the two systems, which eventually saves spectrum resources.     

一种多频点干扰信号产生方案

在电子对抗领域,通常以同时输出多个载波信号对跳频等抗干扰通信实施干扰。分析了针对跳频通信的各种梳状拦阻式干扰方案的优缺点,设计了一种基于锯齿波线性调频技术的干扰方案。该方案能在保持时域等幅波形的前提下,产生多个离散的梳状谱,有效利用功率放大器的功率容限,适合于通信训练中模拟干扰环境。同时给出了基于数字信号处理器(DSP)、ROM、RAM,以及信号产生软件包组成的数字化多频点干扰信号产生器的实现,并对实现结果进行了分析。     

基于CORDIC算法的DDS调频信号源设计

为了实现可调频信号源的设计,提出了一种基于CORDIC算法的DDS调频信号源的设计方案,本中首先介绍了DDS的工作原理,同时对基于CORDIC算法的相幅变换方法进行了详细叙述,利用计算正弦值的CORDIC算法在FPGA上设计数字调频波信号源,可输出高精度数字调频信号,最后对整体模块进行了仿真和实验,输出中心频率23.5 MHz,带宽1.5 MHz的调频信号,验证了文中提出的方案可行,并且结构简单易于实现.     

一种改进的多符号检测算法

针对再入遥测环境下中信号相位容易受噪声影响,导致传统MSD过程中最大似然值被误判的问题,研究一种改进的多符号检测算法：每次MSD运算较前一次MSD运算有N-2个码元的重叠,即每次滑动两个码元长度的码元滑动策略。仿真和测试结果验证了改进算法的有效性。     

基于DEHT的伪码引信中多分量FM干扰抑制方法研究

在介绍离散进化变换(DET)和离散进化哈夫变换(DEHT)的基本原理基础上,详细分析了伪码引信中基于DEHT的多分量FM干扰抑制方法。接收信号首先通过DEHT估计干扰瞬时相位,并通过递归校正方法减小相位估计误差,利用估计出的干扰瞬时相位设计了一时变级联滤波器,逐个消去FM干扰。对不同干信比(ISR)情况下的干扰抑制前后的相关输出进行了仿真分析。分析结果表明,该方法能有效地去除干扰,相关输出得到显著改善。     

Two-dimensional ferromagnetic materials and related van der Waals heterostructures: a first-principle study

Since the successful fabrication of two-dimensional (2D) ferromagnetic (FM) monolayer CrI₃ and Cr₂Ge₂Te₆, 2D FM materials are becoming an exciting research topic in condensed matter physics and materials fields, as they provide a good platform to explore the fundamental physical properties of magnetic materials under 2D limit. In this review, we summarize the theoretical research progress of intrinsic 2D FM materials and related van der Waals heterostructures (vdWHs) including their electronic structures, magnetism, Curie temperature, valley polarization, and band alignment. Moreover, we also summarize recent researches on the methods that used to regulate the above properties of 2D FM materials and vdWHs, such as defects, doping, strain, electric field and interlayer coupling. These studies show that 2D FM materials have broad application prospects in spintronics and valleytronics. However, there are still many problems waiting to be solved on the way to practical application.     

红外线立体声播放系统

工作于红外线波段的发送和接收设备(俗称无线电红外线耳机),可作为优质音响设备的延伸和功能扩展,本文为该系统的研制简报,并给出了样机的测试结果.     

PCM/FM遥测系统中用于去除多谱勒频率和载波频偏的新方法

本文首先分析了均匀采样二阶DPLL(Digital Phase-Locked Loop)误差传递函数的特性,并基于均匀采样二阶DPLL误差传递函数的高通特性提出了脉冲编码调制/调频(PCM/FM)遥测系统中用于去除多谱勒频率和载波频偏的新方法;然后给出了设计实例和相应的计算机仿真结果;最后给出了有效的实现方法。计算机仿真结果表明,基于均匀采样二阶DPLL误差传递函数的高通特性用于去除多谱勒频率和载波频偏的方法是可行的。     

调频间断连续波雷达信号处理分析与仿真

调频连续波雷达具有诸如低峰值功率,低截获概率以及高距离分辨率等优势.然而,其主要缺点是对收发天线较高的隔离度要求.这通常导致采用两个独立天线用于发射和接收.一些方案采用调频间断连续波技术使得调频连续波雷达可以用一个天线工作提高收发隔离度.本文对调频间断连续波体制雷达信号进行分析,利用二次FFT处理算法解决频谱延展造成虚...     

基于双混沌系统的非线性调频雷达信号及其特性分析

提出了两种双混沌系统的构成方案,通过双混沌系统生成了双混沌信号序列,在此基础之上,利用双混沌信号对正弦波进行调频。双混沌调频(FM)信号具有良好的自相关特性,同时使雷达波形难以辨识。用宽带模糊度函数统计平均方法研究了信号的模糊特性,并对信号的抗干扰性能进行了分析。仿真结果表明,双混沌调频信号具有极佳的距离和速度分辨率,抗干扰能力较强,是一种理想的信号形式。