通信工程文献翻译——摘要：本文提出了一个低复杂性均衡器（设计）。这种均衡器可用在偏移正交相移键控（OQPSK调制）中、高斯最小频移键控（GMSK调制）或任何其他交错调制形式中。由于同步和正交分量的相对时间偏移，接收信号必须至少以与它的相应的非正交信号的符号速率的两倍采样，其中符号间隔均衡器（SSE）的使用是可选的。传统方法中QPSK均衡器的数量是本方法的一倍。本研究表明，OQPSK调制也有可能实现一个和符号速率相同的均衡器，而只用线性均衡器（LE）所要求复杂性的一半 。对于判决反馈均衡器（DFE），简化的只是前馈滤波器。

关键词： 均衡器，最小频移键控，判决反馈均衡器，偏移正交相移键控。 

1．引言

数字通信系统中，均衡器的设计的好坏是衡量系统性能的重要指标，在某些情况下，在接收机的复杂数学计算中，均衡器的设计就占了很大一部分。均衡器最常见的类型是 线性均衡器（LE），判决反馈均衡器（DFE） 和最大似然序列估计的均衡器 （MLSE）[1]。在这篇论文中，我们专注于前两种，其设计标准是在传送符号和均衡器输出之间的最小均方误差 （MMSE）。 

一般的任何均衡器可设计成任一个符号间隔均衡器（SSE）或微弱间隔均衡器 （FSE）。SSE间隔时间由符号时间决定，而FSE间隔时间为T/M，（M= 2，3，。。。），其中通常选择M= 2。这是众所周知，FSE的性能SSE得到改善当这两个均衡器都具有相同的时间跨度[2] [3]。由于FSE 以奈奎斯特采样率或更高的速率对接收信号进行采样， 它对采样时间不太敏感的和不 不需要匹配滤波器（MF）。当SSE只能 对失真的接收信号的频率响应特性进行补偿， FSE对在接受信号中的信道失真的补偿在由于符号间隔采样所引起的量化噪声之前[4]。其实，在理想的条件下， 有限长的FSE能够完美平衡FIR通道， 被视为等同于最佳线性接收器， 它是由接着一个SSE的中频组成的。 

如果不看FSE的优点，当大多数信道的能量位于一个单一的主要出口，在以轻微的降低性能的情况下，一个SSE 或许是更好的。当主要考虑的是尺寸，功率消耗和计算复杂性时，当调制形式为QPSK或正交幅度调制（QAM）时，那么FSE和SSE都实现是有可能的。然而，当调制有交错形式，如OQPSK调制，然后最低采样是符号速率......

Abstract—This letter presents a reduced complexity equalizer

for offset quadrature phase-shift keying (OQPSK), Gaussian

minimum shift keying (GMSK), or any other staggered modulation format. Due to the relative time offset of the in-phase and quadrature components, the received signal must be sampled at a rate of at least twice the symbol rate of its corresponding nonstaggered signal, where using a symbol-spaced equalizer (SSE) is an option. The conventional approach doubles the number of equalizer oefficients required relative to QPSK. In this work it is shown that also for OQPSK it is possible to implement an equalizer spaced in symbol rate, with about half the complexity required for the linear equalizer (LE). For the decision feedback equalizer (DFE), savings are achieved only in the feed forward filter.

Index Terms—Equalizers, minimum shift keying, decision feedback equalizer, offset quadrature phase shift keying.

I. INTRODUCTION

IN digital communication systems, equalizer design frequently influences system performance and in some cases is responsible for a large part of the receiver’s computational complexity. The most common types of equalizers are the linear equalizer (LE), the decision feedback equalizer (DFE) and the maximum likelihood sequence estimation equalizer (MLSE) [1]. In this letter we concentrate on the first two types where the design criterion is the minimum mean square error (MMSE) between the transmitted symbols and the equalizer output.

In general any equalizer can be designed as either a symbol spaced equalizer (SSE) or a fractionally spaced equalizer (FSE). The SSE taps are spaced by a symbol time ?? while the FSE taps are spaced by ?? /??, (?? = 2, 3,...), where ?? = 2 is usually selected. It is well known that the FSE has improved performance relative to the SSE when both equalizers have the same time span [2],[3]. Since the FSE samples the received signal at the Nyquist rate or above,it is much less sensitive to the sampling timing and does not require a matched filter (MF). While a SSE can only......