通信工程文献翻译——摘要

尽管长距离卫星通信系统在快速进步，但高频（HF）通信却正在复苏。 国防机构正在将 HF 频谱用于备份通信以及频谱监测应用。 频谱管理组织正在监测 HF 频谱，以控制和实施许可。这些活动通常需要确定传输源的位置、 分离有效信号干扰和噪声，以及理解信号调制系统。 我们的最终目标是通过多个电离层模式与同信道信号和非高斯噪声传播的信号，为真实 HF 信号开发鲁棒的调制识别算法。

调制识别的一个方面是信号识别特征的提取。 本文中，我们的工作为应用各种特征参数得到真实的 HF 信号，并指导哪些功能显示潜在用于在 HF 噪声和多路径存在的 HF 调制类型的鲁棒识别。 它还定义了基于熵参数的调制类型之间的平均间隔距离的测量，并且讨论了 HF 噪声的概率密度函数。

关键词：高频；高频噪声；调制识别；信号特征；熵；一致性；真实信号

1.引言

通过 Guglielmo Marconi 的实验和发明，长距离无线电通信在 20 世纪初变得实用. Marconi 能够展示长距离无线通信，因为电离层中的离子化气体引起高频（HF）信号的折射 （名义上为 2MHz 至 30MHz）。这种折射使得信号能够传播到地平线以外，到达接收器接受不到的较高频率（VHF 及以上）信号。 这一事实使得 HF 频段对于私人和商业利益以及传播到全球的国防部队具有吸引力。 例如，频谱管理机构监测无执照运营人的HF频段， 

军事机构使用 HF 频段进行通信。

常规的 HF 接收机通常以超外差配置和滤波器，振荡器和许多分立组件组成。其功能是将由天线获取的信号下变频到基带，然后解调该信号以提取信息内容。特别通用的 HF 接收机甚至可以具有不止一个的解调器，使得可以处理各种类型......

ABSTRACT

High-frequency (HF) communications is undergoing resurgence despite advances in long-range satellite communication systems. Defense agencies are using the HF spectrum for backup communications, as well as for spectrum surveillance applications. Spectrum management organizations are monitoring the HF spectrum to control and enforce licensing. These activities usually require systems capable of determining the location of a source of transmissions, separating valid signals from interference and noise, and recognizing signal modulation.

Our ultimate aim is to develop robust modulation recognition algorithms for real HF signals, that is, signals propagating by multiple ionospheric modes with cochannel signals and non-Gaussian noise.

One aspect of modulation recognition is the extraction of signal identifying features. This paper continues our work of applying various feature parameters to real HF signals and gives guidance on which features show potential for use in robust recognition of HF modulation types in the presence of HF noise and multi-path. It also defines a measure of mean separation distance between modulation types based on an entropy parameter,and discusses the probability density function of HF noise.

Keywords: HF, HF Noise, Modulation-Recognition, Signal Features, Entropy, Coherence, Real Signals

1. INTRODUCTION

Long distance radio-communications became practical in the early-1900s with the experiments and inventions of Guglielmo Marconi.1 Marconi was able to demonstrate long-distance wireless communications because ionized gases in the ionosphere cause refraction of high-frequency (HF) signals (nominally 2 MHz to 30 MHz).Such refraction enables signals to propagate beyond the horizon to distant receivers unable to be reached by higher frequency (VHF and above) signals. This fact makes the HF band attractive for private and commercial......