通信工程文献翻译——摘要：本文主要工作目的有两个。首先，提出全面可替代方法来理解QPSK原理。这个主要注重的是QPSK调制器怎样通过其中的四种可能相来代表每对要传输的比特。这种方法是完全基于相量分析的，不是很精确。本工作的第二个目标是，复杂的QPSK调制方案，可以用简单的组件在Simulink里实现，避免各种复杂的数学模块障碍。在第二部分的实现方案中，证实了在第一部分的方法的可行性。结果表明，尽管略有不可避免的轻微延迟，但该数据在一个无噪声信道的另一端收到的数据完全匹配。本QPSK方法可以用来作为实验室里直接为大学生提供新的数字通信技术的培训。

关键词：解调器；Matlab Simulink的仿真；调制器；正交相移键控

1．引言

最重要的是要发送的数据是被一个更高频率的载波调制，在这个庞大的通讯扩展时代，对调制技术的改进，以提高通信系统在带宽效率，信号完整性，功耗能量和传输的安全性也很重要。

为此，三个基本的数字调制方式的很多变化，如幅移键控（ASK），移相键控（PSK）和移频键控（FSK））已经成熟，这些新变化之一是正交相移键控，即QPSK。

QPSK调制是一种载波一次被两比调制的相移键控形式，选择四种可能的载波相移键控之一，在相同的带宽下，QPSK允许传输信号的信息量是普通PSK的两倍。对很多人来说，QPSK的应用在包括卫星的MPEG2视频，电缆调制解调器，视频会议传输和蜂窝电话系统。它的一个变形，交错正交相移键控（O-QPSK）也将在最近被批准通过了IEEE 802.15.4标准，商业上称为无线局域网。

这里描述一QPSK发射机调制器怎样选择代表它能适应的载波的四相移键控，来传输四个可能二进制对的方法，其中的4相移也可以适用于载波。

人们常常认为，像QPSK这样调制方案只能用数学建模或使用基于数学模块的硬件或软件来实现。举例来说，Matlab是块级仿真环境，Simulink，它提供了一个工具箱库，这个工具箱库可直接用于通过一个使用QPSK调制的数字信号来调制载波信号，这种块通常会被建立在一个漫长的程序代码上，这个程序代码是基于对QPSK如何工作的数学分析上的。虽然对于用户来说这样的组件能够用QPSK调制有效地调制载波信号，但不知道在这个库的后面的程序是怎样运行的，因此无法修复任何因系统不完善而发生的错误，获得这种复杂的组件或通过许可的软件或硬件相关联的成本可能是相当高。该方法提供了如何在Simulink中显示简单的块，如开关，触发器，多路复用器，加法器和乘法器可以被用来建立一个QPSK调制器，用户可以在这个系统上的显示屏上的每一个点绘制这些符号。除了教育用途之外，作为本科生数字通信技术的新的实验室训练，它能实现为用户显示信号发生了什么，发生的地点和方式，这种方法可以用硬件来实现一个简单的QPSK调制解调器。

2．QPSK调制原理

2.1QPSK的运行

在QPSK调制中的术语‘正交’意味着在......

Abstract The work reported in this paper serves two purposes. First, an alternative comprehensive approach is proposed for the understanding of the mechanism behind QPSK. This focuses on how a 

QPSK modulator decides to represent each pair of bits to be transmitted, by which of its four possible phase shifts. This approach is based entirely on the analysis of phasors and is completely mathematicsless. The second part of this work proposes a method by which complex modulation schemes, like QPSK, can be implemented using only fi rst degree components in Simulink, avoiding all the hurdles of mathematically complicated blocks. The implementation, in the second part, confi rms the viability of the approach in the fi rst part of this work. Results show that the data received on the other end of a noiseless channel exactly matches the data sent despite a slight unavoidable delay. The proposed method for implementing QPSK can be used directly as a laboratory exercise for undergraduate students new to digital communication techniques.

Keywords Demodulator; MATLAB Simulink simulation; Modulator; Quadrature Phase Shift Keying Just as it is important that data to be transmitted is carried by a modulated higher frequency carrier, it is also important in this era of vast communication expansion that modulation techniques are improved to enhance communication systems’ performance in terms of bandwidth effi ciency, signal integrity, power consumption and transmission security.

For this purpose, many variations of the three basic digital modulation schemes (Amplitude Shift Keying (ASK), Phase Shift Keying (PSK) and Frequency shift keying (FSK)) have been developed.1 One of these new schemes is the Quadrature Phase Shift Keying, QPSK.

QPSK is a form of Phase Shift Keying in which the carrier is modulated by two bits at once, selecting one of four possible carrier phase shifts. QPSK allows the transmitted signal to carry twice as much information as ordinary PSK but using the same bandwidth. Among many, some of the applications where QPSK is adopted include satellite transmission of MPEG2 video, cable modems, ideoconferencing 

and cellular phone systems. A variation of it, the Offset Quadrature Phase Shift Keying (O-QPSK) has also bee adopted in the recently ratifi ed IEEE 802.15.4 standard commercially known as ZigBee.

The method presented here describes how the modulator of a QPSK transmitter chooses to represent any of the four possible pairs of binary bits it can transmit at once by which of the 4 phase shifts it can apply to the carrier.

It is often thought that complicated modulation schemes like QPSK can only be modeled mathematically or implemented using mathematically-based blocks either......