tailieunhanh - Lò vi sóng RF và hệ thống không dây P1

BRIEF HISTORY OF RF AND MICROWAVE WIRELESS SYSTEMS The wireless era was started by two European scientists, James Clerk Maxwell and Heinrich Rudolf Hertz. In 1864, Maxwell presented Maxwell's equations by unifying the works of Lorentz, Faraday, Ampere, and Gauss. He predicted the propagation of electromagnetic waves in free space at the speed of light. He postulated that light was an electromagnetic phenomenon of a particular wavelength and predicted that radiation would occur at other wavelengths as well. His theory was not well accepted until 20 years later, after Hertz validated the electromagnetic wave (wireless) propagation | RF and Microwave Wireless Systems. Kai Chang Copyright 2000 John Wiley Sons Inc. ISBNs 0-471-35199-7 Hardback 0-471-22432-4 Electronic CHAPTER ONE Introduction BRIEF HISTORY OF RF AND MICROWAVE WIRELESS SYSTEMS The wireless era was started by two European scientists James Clerk Maxwell and Heinrich Rudolf Hertz. In 1864 Maxwell presented Maxwell s equations by unifying the works of Lorentz Faraday Ampere and Gauss. He predicted the propagation of electromagnetic waves in free space at the speed of light. He postulated that light was an electromagnetic phenomenon of a particular wavelength and predicted that radiation would occur at other wavelengths as well. His theory was not well accepted until 20 years later after Hertz validated the electromagnetic wave wireless propagation. Hertz demonstrated radio frequency RF generation propagation and reception in the laboratory. His radio system experiment consisted of an end-loaded dipole transmitter and a resonant square-loop antenna receiver operating at a wavelength of 4 m. For this work Hertz is known as the father of radio and frequency is described in units of hertz Hz . Hertz s work remained a laboratory curiosity for almost two decades until a young Italian Guglielmo Marconi envisioned a method for transmitting and receiving information. Marconi commercialized the use of electromagnetic wave propagation for wireless communications and allowed the transfer of information from one continent to another without a physical connection. The telegraph became the means of fast communications. Distress signals from the . Titanic made a great impression on the public regarding the usefulness of wireless communications. Marconi s wireless communications using the telegraph meant that a ship was no longer isolated in the open seas and could have continuous contact to report its positions. Marconi s efforts earned him the Nobel Prize in 1909. In the early 1900s most wireless transmission occurred at very long .