射频技术入门之：天线基础

射频技术入门之：天线基础
9
Antenna Basics
Introduction
Antennas are a very important component of communication systems. By
definition, an antenna is a device used to transform an RF signal, traveling
on a conductor, into an electromagnetic wave in free space. Antennas
demonstrate a property known as reciprocity, which means that an
antenna will maintain the same characteristics regardless if it is
transmitting or receiving. Most antennas are resonant devices, which
operate efficiently over a relatively narrow frequency band. An antenna
must be tuned to the same frequency band of the radio system to which it
is connected, otherwise the reception and the transmission will be
impaired. When a signal is fed into an antenna, the antenna will emit
radiation distributed in space in a certain way. A graphical represen