基于DSP的QPSK调制的设计与实现

设计了一套基于TMS320VC5416型DSP的实验系统,用于实现QPSK的调制。阐述了QPSK算法的基本原理和调制方式及实现QPSK调制硬件的设计方案,最后说明在该系统上现实QPSK的设计流程以及实验波形图。     

基于DSP的QPSK调制的设计与实现

设计了一套基于TMS320VC5416型DSP的实验系统,用于实现QPSK的调制.阐述了QPSK算法的基本原理和调制方式及实现QPSK调制硬件的设计方案,最后说明在该系统上现实QPSK的设计流程以及实验波形图.     

π/4-QPSK调制方式及其与GSMK调制方式的比较

简略介绍了QPSK，π／4－QPSK调制方式及其于此的π／4－QPSK调制方法，就π／4－QPSK的调制电路原理与实现作了概述，并针对π／4－QPSK调制方法的优点及其性能与GMSK技术进行了比较。     

基于System Generator的QPSK数字调制器设计

介绍了QPSK调制的基本原理,给出了QPSK调制器的系统模型设计,该设计是基于System Generator设计平台,在Matlab/Simulink环境下搭建系统模型,再进行功能仿真和验证,完成QPSK调制器的设计。仿真结果表明,所设计的调制器能产生正确QPSK波形,达到了预期效果。     

π/4 QPSK调制器的软件仿真与硬件实现

针对π/4 QPSK(正交相移键控)调制器与QPSK进行了软件仿真比较,实验表明,π/4QPSK具有较高的频谱效率。通过硬件电路实现了π/4 QPSK调制器并用软件仿真对其进行了比较验证,结果证明了硬件实现的可行性及正确性,可用于移动通信实验及程控交换机中。     

卫星数字电视广播信道编码与调制技术的研究

对五种典型的卫星信道编码与调制系统(RS码+1/2卷积码+QPSK、RS码+3/4卷积码+QPSK、RS码+7/8卷积码+QPSK、RS码+2/3 TC-8PSK和RS码+QPSK)进行了性能模拟。结果表明,RS码+卷积码+QPSK类系统较适合卫星数字电视广播。还给出了该类系统中三种典型系统的参数,为制定我国卫星数字电视广播传输标准提供依据。     

π/4QPSK在移动卫星通信中应用分析

本文首先根据移动卫星通信信道存在着各种衰落和频带受限(文中称为带限)及非线性同时存在的特点,讨论了π/4移相四相键控QPSK数字调制解调技术在移动卫星通信中应用情况,并将其与QPSK方式进行了简单的比较。继而又进一步分析了π/4移相QPSK的性能。从而得出在移动卫星通信系统中采用π/4移相QPSK调制方式要优于简单的QPSK调制方式的结论。     

浅谈QPSK调制技术

介绍QPSK原理,给出QPSK矢量图和逻辑编码表,重点概述PHILIPS公司半导体芯片TDA8050A的参数.     

浅谈QPSK调制技术

介绍QPSK原理,给出QPSK矢量图和逻辑编码表,重点概述PHILIPS公司半导体芯片TDA8050A的参数.     

QPSK与16QAM调制在卫星通信中的性能分析

介绍了QPSK与16QAM调制的概念,详细分析了QPSK与16QAM调制的频带利用率和误码性能,总结了卫星通信中采用16QAM调制的优缺点。得出如下结论:16QAM技术可有效地利用带宽,并在带宽利用率上比QPSK更有效,因而采用16QAM调制有利于节省卫星转发器。但是16QAM的功率利用率比QPSK调制方式要低,所以需要配置较大功率的高功放。     

群时延失真对扩频通信性能影响的仿真与分析

首先简要介绍了卫星通信中扩频系统的基本模型和表达式，给出了系统在失真信道中进行计算机仿真的基本模型。然后，利用通信系统仿真软件包ACOLADE，建立了扩频系统在群时延失真信道中的仿真模型，建立了群时延失真信道模型，进行了QPSK、QPSK＋DS、QPSK＋FH等体制在群时延失真信道的特性仿_真分析，最后得出了一些有一定参考价值的分析结果。     

QPSK最佳干扰研究与仿真

由于四相位绝对移相键控（QPSK）的调制方式在卫星通信中占有十分重要的地位,详细的分析了QPSK信号的调制与解调原理,并以此为基础,理论推导出用于QPSK干扰的3种干扰方式的误比特率（BER）,这三种方式包括：连续噪声干扰,单音干扰以及指向性单音干扰。通过分析仿真,得到3种干扰方式的干扰效果,证明了干扰的有效性。     

An analysis and a dynamic testing method of microwave QPSK modulation

Using the clockwise or anticlockwise stepping pulse code signal, the characteristics of general quaternary phase shift keying (QPSK) modulation are analysed. This paper gives the spectrums in several operational conditions and the admittance formulas of related two modulation circuits. Several typical examples of QPSK modulation are calculated. The modulation effect and the phase error can be decided and the QPSK modulator under the dynamic test may be adjusted by using above results. The experimental results are in agreement with the theoretical calculations. An X-band QPSK modulator is also presented. The maximum phase error is less than 4°, the phase accuracy near ±0.1°, the insertion loss less than 4 dB and the data (transfer) rate up to 68 Mb/s.     

Quadrature Overlapped Raised-Cosine Modulation

A variation of an old but neglected pulse shaping technique, raised-cosine, is investigated. By overlapping raised-cosine pulses in each of two data streams and then by quadrature combining them, a simple QPSK/MSK type modulation results. This quadrature overlapped raised-cosine (QORC) modulation exhibits a hybrid structure of QPSK and MSK modulations. The power spectral density of QORC is shown to take on the form of the product of the power spectral densities of MSK and QPSK. The obvious consequences are that the power spectral density main lobe retains the width of the spectral density main lobe of QPSK, but the sidelobes drop off much faster(1/f^{6}). A simple QORC modulator can be implemented similar to an MSK modulator. Several correlation type receivers are investigated and their performances calculated. Computer simulation results are used to compare end-to-end system performance of QORC and staggered QORC (SQORC) with MSK, QPSK, and staggered QPSK (SQPSK) for both linear and nonlinear satellite channels. The performance of QORC and SQORC compares very favorably with QPSK, SQPSK, and MSK. QORC performs particularly well in the presence of a nonlinear channel. The effect of phase equalization of the channel filter was investigated with outstanding performance improvement. The simulation results show that sidelobe regeneration caused by the channel nonlinearity is much less for SQORC than it is for the other modulation formats considered.     

微波四相调制的分析与动态观察法

本文采用步进转动(顺时针或逆时针)的信码作信源,分析了广义四相调制的特性,给出调制信号的频谱和两调相电路间的导纳关系表达式,计算了几种典型四相调制频谱的实例,据此可判定调制的效果和相位误差,并用于动态测试中对四相调制器进行调整,实验表明测得的结果与理论计算是相符的。本文还报道了X波段四相调制器的实验情况,测得其最大相位误差小于4°,相让精度可达±0.1°,插入损耗小于4dB,传送数据率可达 34Mb/s。     

QPSK block-modulation codes for unequal error protection

Unequal error protection (UEP) codes find applications in broadcast channels, as well as in other digital communication systems, where messages have different degrees of importance. Binary linear UEP (LUEP) codes combined with a Gray mapped QPSK signal set are used to obtain new efficient QPSK block-modulation codes for unequal error protection. Several examples of QPSK modulation codes that have the same minimum squared Euclidean distance as the best QPSK modulation codes, of the same rate and length, are given. In the new constructions of QPSK block-modulation codes, even-length binary LUEP codes are used. Good even-length binary LUEP codes are obtained when shorter binary linear codes are combined using either the well-known |u¯|u¯+v¯|-construction or the so-called construction X. Both constructions have the advantage of resulting in optimal or near-optimal binary LUEP codes of short to moderate lengths, using very simple linear codes, and may be used as constituent codes in the new constructions. LUEP codes lend themselves quite naturally to multistage decoding up to their minimum distance, using the decoding of component subcodes. A new suboptimal two-stage soft-decision decoding of LUEP codes is presented and its application to QPSK block-modulation codes for UEP illustrated     

DSSS/QPSK信号盲检测方法仿真

采用功率谱检测法,自相关检测法和高阶累计量检测法对低信噪比下DSSS/QPSK信号进行检测方法。计算机仿真表明,功率谱检测法在信噪比较低时失去了检测能力,而充分利用了伪随机码周期特性的自相关检测法和高阶累计量检测法的检测性能较优,高阶累计量法由于其更好的抑制噪声特性显示出更好的性能。同时,文中比较了DSSS/BPSK信号和DSSS/QPSK信号在相同检测方法下的性能差异。由于调制方式不同,相同的方法对DSSS/QPSK信号的检测性能略低于DSSS/BPSK信号。     

Feasibility study on QPSK optical-heterodyne detection system

The feasibility of a QPSK (quadrature-phase-shift-keying) optical heterodyne detection system for a high-speed and long-span coherent transmission is investigated. The key factors, which are the modulation method and the spectral linewidth requirement for optical light sources, are discussed. Through theoretical analysis and the simulation experiment, it is confirmed that the required beat spectral linewidth for QPSK coherent detection is less than 7.5×10^-5×bit rate. It is also shown that the required spectral linewidth for QPSK differentially coherent detection is less than 2.5×10^-5×bit rate. These results show that the gigabits-per-second range QPSK optical heterodyne detection can be realized with conventional external cavity laser diodes