基于相对无模糊相位重构的自动脉内调制特性分析

文章首先分析并给出了相对无模糊相位重构算法，在此基础上构建了基于相位差分峰值幅度比较的BPSK及QPSK调制信号调制方式识别方法和基于最小二乘相位差分直线拟合的LFM信号调制方式识别方法。仿真结果充分验证了相位重构算法和调制方式识别方法的有效性。     

一种PSK信号相位编码调制规律分析方法

通过对PSK信号相位特性的分析,采用相关积累的方法充分利用单个脉冲所提供的相位跳变信息,成功提取出PSK信号相位跳变规律,在此基础上进行了相位编码序列的恢复。根据文章中研究得到的算法进行了仿真实验,仿真结果显示,算法具有良好的低信噪比环境适应能力。     

一种有效的脉内调制信号识别方法

文章在相位重构的基础上分析了各种常见脉内调制信号相位差分序列的特征,并给出了它们的识别方法。采用多重相位差分改善了算法对低信噪比环境的适应能力。本文还根据分析给出了脉内识别的系统框图,最后仿真验证了文中分析结论,给出了不同信噪比下各种调制信号的正确识别率。     

相位编码信号脉内特征分析与识别

首先分析并给出了相对无模糊相位重构算法,在此基础上构建了基于相位差分峰值幅度比较的相位调制信号调制方式识别方法,理论分析了算法的实现过程,进行了仿真试验,仿真结果充分验证了相位重构算法和调制方式识别方法的有效性,并给出了在某电子对抗设备中的实现。     

一维位置敏感探测器的相位响应特性

基于位置敏感探测器(PSD)的相位法探测入射光点的原理,利用RC等效模型得到一维PSD两电极输出电流信号的相位和相位差。分析了相位与调制频率和入射光点位置x的关系,并得出相位差在不同调制频率下的响应特性。在一维PSD上的实验测试结果表明,利用相位差测量的线性关系显著,并且随着调制频率的增大测量灵敏度提高。     

一种PSK信号相位编码调制规律分析方法

通过对PSK信号相位特性的分析，采用相关积累的方法充分利用单个脉冲所提供的相位跳变信息，成功提取出PSK信号相位跳变规律，在此基础上进行了相位编码序列的恢复。根据文章中研究得到的算法进行了仿真实验，仿真结果显示，算法具有良好的低信噪比环境适应能力。     

基于单脉冲相关积累的PSK信号相位编码调制规律分析

文章首先研究了如何通过单脉冲相关积累从PSK信号中提取相位跳变规律,在此基础上给出了相位编码序列恢复方法。为了提高算法的性能,采用多重相关积累对算法进行了改进。根据文章中研究得到的算法进行了仿真实验,仿真结果显示,算法具有良好的低信噪比环境适应能力。     

一种有效的BPSK/QPSK信号调制识别方法

根据不同调制信号相位差分的变化规律,文章提出了基于相位差分峰值幅度比较的BP SK/QPSK调制识别方法。仿真结果验证了调制识别方法的有效性。     

相位测频法在雷达信号脉内特征分析中的应用

以单载频、线性调频、BPSK和FSK信号为例,通过提取信号的瞬时相位,对雷达信号的脉内调制特征进行了分析,介绍了信号瞬时相位的提取方法,然后分别引出相位分析法和相位差分分析法的调制类型识别方法,最后对这两种方法进行了仿真分析。仿真表明,相位测频法是一种有效的雷达信号调制特征分析工具。     

卫星测控侦察中相位编码信号的调制识别

针对卫星测控链路中常用的数字调相信号BPSK、QPSK、OQPSK（偏移QPSK）和UQPSK（非平衡QPSK）的调制识别问题，提出了基于二阶矩和相位差统计特性的分类算法。该方法首先以二倍码速率对复基带信号进行采样，然后利用能量归一化的二阶矩的模和相邻样点相位差绝对值的统计特性，分两个等级实现对这四种信号的分类。分析了载频偏移、相位误差以及成形脉冲对分类算法性能的影响，并通过计算机仿真验证了算法的有效性。     

大动态PCM/FM遥测信号的非相干解调

针对大动态低码率PCM/FM遥测信号的可靠接收问题展开研究,给出了一种基于连续相位调制（CPM）信号原理的载波频偏矫正及差分序列检测的非相干接收方案。针对限幅鉴频、多符号检测及差分序列检测等3种非相干解调算法,介绍了各自应用于PCM/FM信号的算法原理,并比较了3种算法的解调性能及对大动态环境的适应能力。计算机仿真表明,在无残留频偏情况下,2符号相位差分序列检测性能最好;但在0.05倍码速率的残留频偏下,1符号相位差分序列检测的性能更好,优于2符号相位差分序列检测、限幅鉴频检测和多符号非相干检测。对PCM/FM信号的讨论包含了几种典型的非相干解调,对大动态环境下的PCM/FM接收有重要的参考价值。     

Combination of BCM and TCM with 90°, 180°, and 270°phase rotational invariance

Two systematic schemes to combine block-coded modulation (BCM) and trellis-coded modulation (TCM) are proposed. In the first scheme, the signal points which are used in TCM should be partitioned by the proper BCM systems constructed by a multilevel construction method. The asymptotic coding gain will be 6.02-3.01/n dB, where n is the length of the BCM systems. Since the average transmission power can be reduced by using a denser signal lattice, the main idea of the second scheme is to construct the TCM system based on the signal points of a denser lattice formed by a proper BCM system. Hence, we can get a higher coding gain which is a combination of both the distance gain of TCM and the density gain of BCM. Theoretically, the net coding gain of this proposed scheme can reach 5.27 dB in the case of an 8-D constellation and 7.15 dB in the case of a 16-D constellation. For practical implementation, the phase ambiguity problems for both schemes are considered and solved by a differential encoder/decoder     

Comparison Between DPCM and Hadamard Transform Coding in the Composite Coding of the NTSC Color TV Signal

Since differential-pulse-code modulation (DPCM) and orthogonal transform coding (OTC) are the most fundamental methods of high-efficiency coding (bit-reduction method), it is important to clarify the basic coding characteristics of these methods and the difference between them in order to utilize the bit-reduction method effectively. This paper theoretically as well as experimentally compares the coding efficiency of a DPCM having a two-dimensional predictor with that of a two-dimensional Hadamard transform coding method (HTC) in the intrafield coding of the NTSC composite signal. The comparison evidenced that the distinctive difference in coding characteristics between DPCM and HTC depends greatly on the power level of carrier chrominance signals. That is, it is confirmed theoretically and experimentally that the coding efficiency of the HTC is far lower than that of the DPCM in the case of a signal having a high power level carrier chrominance signal such as a color-bar signal.     

雷达信号有意调制的粗分类和细分类识别方法

针对雷达信号脉内有意调制中2类典型调制信号,即相位编码(PSK)信号和调频(FM)信号,提出了一种由粗到细的方法进行脉内识别。首先,对接收到的雷达信号利用其3 dB带宽明显不同的特点,进行类间粗分类,识别出PSK信号和FM信号;然后,针对PSK信号和FM信号类内特征的不同,提出了利用信号的小波脊频特征,来对雷达信号进行类内细分类识别的方法,使PSK信号被细分类为BPSK信号和QPSK信号、FM信号被细分类为LFM信号和NLFM信号,从而完成了典型雷达信号的有意调制的识别。仿真结果表明,在一定信噪比下,此识别方法真实有效。     

Space‐time ring‐TCM codes with CPM based on the decomposed model for transmission over Rayleigh fading channels

Space–time (ST) coding is a proved technique for achieving high data rates in 3G mobile systems that combines coding, modulation and multiple transmitters and receivers. A novel algorithm is proposed for ST ring trellis‐coded modulation (ST‐RTCM) systems with continuous‐phase modulation (CPM) when the channel coefficients are known to the receiver. This algorithm is based on the CPM decomposed model, which exploits the memory properties of this modulation method, resulting in a straightforward implementation of joint ST coding and CPM, which is particularly suitable for ring codes. This new scheme is used to investigate the performance of the delay diversity code with CPM over slow Rayleigh fading channels, in particular with MSK which is one of the most widely used modulation methods of continuous phase. Furthermore, a feedback version of delay diversity allowed by the decomposition is tested in 1REC and 1RC systems. This feedback configuration is seen to provide good results for low signal‐to‐noise ratios. Simulations results are also provided for multilevel ST‐RTCM codes that achieve a higher throughput than MSK‐coded systems. Additionally the serial concatenation of an outer Reed–Solomon code with an ST‐RTCM code is shown, this combination further reduces the error probability and achieves even more reliable communications. Copyright © 2005 John Wiley & Sons, Ltd.     

Analytical Models for Phase-Modulation-Based Microwave Photonic Systems With Phase Modulation to Intensity Modulation Conversion Using a Dispersive Device

Recently, optical phase modulation has been widely used in microwave photonics (MWP) systems, such as radio over fiber systems, photonic microwave filters, optical microwave and millimeter-wave signal generators, and optical subcarrier frequency up-converters. An optical phase-modulated signal can be converted to an intensity-modulated signal in a dispersive optical fiber. Due to the intrinsic nonlinearity of optical phase modulation, for linear applications such as microwave signal distribution and filtering, the modulation index should be kept small to minimize the unwanted modulation nonlinearity. However, for nonlinear applications such as microwave frequency multiplication and subcarrier frequency upconversion, the modulation index should be large to maximize the frequency multiplication and upconversion efficiency. In this paper, for the first time to our knowledge, we develop a thorough theoretical framework for the characterization of phase-modulation-based MWP systems, in which the phase modulation to intensity modulation conversion is realized using a dispersive fiber. Analytical models for the distributions of single-tone and two-tone microwave signals and for microwave frequency multiplication and subcarrier frequency upconversion are developed, which are verified by numerical simulations. The analytical models for single-tone and two-tone transmissions are further confirmed by experiments. The developed analytical models provide an accurate mathematical tool in designing phase-modulation-based MWP systems.     

ADAPTIVE EQUALIZATION WITH RLS-MLSE ASSISTED BY FEC BLOCK CODING FOR FADING MOBILE RADIO CHANNELS

In this paper, we propose an adaptive maximum-likelihood (ML) sequence estimator with RLS channel estimation, which is assisted by forward error control (FEC) coding. The reliable symbols reconstructed in the FEC decoder are used as the feedback signal to the RLS channel estimator. The scheme is compared with decision feedback equalization (DFE) with RLS algorithm, which is assisted by FEC coding. Computer simulations show that in frequency-selective fast fading mobile radio channels, the proposed scheme performs better at moderate Doppler frequencies. It is suitable for four-phase modulation data transmission at the rate of several 10 kb/s in 900 MHz band or in the 1800 MHz band.     

Relation between transmission and throughput of slotted ALOHA localpacket radio networks

A new method for the exact calculation of the throughput of a centralized slotted ALOHA packet radio network over slow Rayleigh-fading channels is presented and the results are compared with the computer simulations. Also, upper and lower bounds on the performance are provided. The effects of capture on the throughput of the system are related to the modulation and coding technique, signal to noise ratio of the received signal, general terminal distribution in the area, and the length of the transmitted packets. The binary phase shift keying (BPSK), coherent and noncoherent binary frequency shift keying (FSK) modulations and BCH coding are considered for the exact calculations. The results of the analysis show that the maximum average throughput of the slotted Aloha packet radio network is around 60% rather than 36% predicted from the simplified analysis. In contrast with some previous reports, it is shown that the throughput of the system is not affected significantly by the use of coding or the change of packet lengths     

一种用于卫星通信的自适应编码调制信号接收方法

针对常规接收方法接收自适应编码调制信号时存在的接收过程易中断、数据不连续等问题,提出了一种适用于卫星信道的自适应编码调制信号接收方法.该方法通过采用统一的解调结构实现对不同调制信号的连续跟踪;利用接收端保存的帧同步字调制波形副本与接收信号中的帧同步字波形的相关结果,对解调方式切换时载波相位跳变值进行估计和补偿,解决了帧同步的连续跟踪问题.与现有方法相比,该方法不需要导频信号,可节省系统开销.     

Analysis and optimization of wavelet-coded communication systems

Since its advent, wavelet coding has been recognized as a promising technique for wireless transmission systems, especially due to its low decoding complexity and good performance over multipath fading. However, this technique requires unusual modulation schemes in order to be fully exploited. A BER analysis of wavelet-coded transmission systems over Rayleigh fading channels is presented in this work. This analysis is used in the design of novel signal constellations for wavelet-coded systems by means of numerical performance optimization. Numerical results obtained from analysis and simulations show that the wavelet-coded systems derived herein have very good performance characteristics over fading channels.