1.射频无线 通信系统介绍

1.射频和无线通信系统介绍

概述

This tutorial is part of the National Instruments Measurement Fundamentals series. Each tutorial in this series teaches you a specific topic of common measurement applications by explaining the theory and giving practical examples. This tutorial covers an introduction to RF, wireless, and high-frequency signals and systems.

本教程是测量NI基础系列的一部分。本系列教程中的每一个指南结合理论解释和实际的例子教你常用的测量应用。本教程介绍介绍了射频，无线和高频信号与系统。

For the complete list of tutorials, return to the NI Measurement Fundamentals Main page, or for more RF tutorials, refer to the NI RF Fundamentals Main subpage.

对于教程的完整清单，请返回NI Measurement Fundamentals Main page,或更多的射频教程，请参阅NI RF Fundamentals Main subpage.

目录

1.Marconi and the First Wireless Transmissions 马可尼和第一次无线传输

2.What is RF?射频是什么？

3.Why Operate at Higher Frequencies? 为什么工作在更高的频率？

4.Frequency Shifting through Frequency Mixing通过混频移频

5.Looking for more RF Basics? 寻找更多的射频基础知识？

6.Relevant NI Products

7.Conclusions结论

Marconi and the First Wireless Transmissions

Radio Frequency (RF) and wireless have been around for over a century with Alexander Popov and Sir Oliver Lodge laying the groundwork for Guglielmo Marconi’s wireless radio developments in the early 20th century. In December 1901, Marconi performed his most prominent experiment, where he successfully transmitted Morse code from Cornwall, England, to St John’s, Canada.

在亚历山大波波夫爵士和奥利弗洛奇奠定了20世纪初马可尼无线电台的基础时，射频（RF）和无线已经出现了一个世纪。在1901年12月，马可尼进行他最杰出的实验，在那里他成功从英国康沃尔发送莫尔斯码到加拿大圣约翰。

What is RF? 什么是射频？

RF itself has become synonymous with wireless and high-frequency signals, describing anything from AM radio between 535 kHz and 1605 kHz to computer local area networks

(LANs) at 2.4 GHz. However, RF has traditionally defined frequencies from a few kHz to roughly 1 GHz. If one considers microwave frequencies as RF, this range extends to 300 GHz. The following two tables outline the various nomenclatures for the frequency bands. The third table outlines some of the applications at each of the various frequency bands.

RF本身已成为无线和高频信号的代名词，它包括了535kHz~1605kHz的调幅无线电到2.4 GHz的计算机局域网（LAN）之间的任何频率。然而，传统定义的RF从几kHz的频率至大约1GHz。如果把微波频率考虑作为射频，这个范围扩展到300GHz。以下两个表概述了各频段的术语。第三表列出了在不同频段的一些应用。

T able 1: Frequency Band Designations

Table 1 shows a relationship between frequency (f) and wavelength (λ). A wave or sinusoid can be completely described by either its frequency or its wavelength. They are inversely proportional to each other and related to the speed of light through a particular medium. The relationship in a vacuum is shown in the following equation:

where c is the speed of light. As frequency increases, wavelength decreases. For reference, a 1 GHz wave has a wavelength of roughly 1 foot, and a 100 MHz wave has a wavelength of roughly 10 feet.

表1显示了频率（f）和波长（λ）的关系。波或正弦波可以完全由其频率或波长描述。他们成反比关系，并与通过特定媒介的光速有关。在真空的关系如公式如下：。其中c是光速。随着频率的增加，波长减小。作为参考，1 GHz的波具有波长约为1英尺，100 MHz的波有大约10英尺的波长。

T able 2: Microwave Letter Band Designations