Electromagnetic Field Theory

Microwaves

Application Note of Electromagnetic Wave Propagation:
Microwaves are EM waves whose frequencies range from approximately 300 MHz to 1000 GHz.
About Microwaves
  • The signal from
  1. An AM radio station is about 1 MHz.
  2. An FM station is about 100 MHz.
  • Microwave oven operates at 2.4 GHz.
  • Satellite television receiver operates at about 4 GHz.
  • Police radar works at about 22 GHz.
  • Microwaves behave more like rays of light than ordinary waves.
  • Microwave spectrum provides more communication channels than the radio an TV bands.
Microwave System consists of:
  • Transmitter including a microwave oscillator, waveguides, and transmitting antenna.
  • Receiver including a receiving antenna, transmission line or waveguide and microwave amplifiers.
Use of microwaves:
  • Telecommunications
    • The transmission of analog or digital information from one point to another.
    • Microwaves propagate along a straight line like light rays and are not bent by the ionosphere.
    • Communication satellite is a microwave relay station that is used to link two or more ground based transmitters and receivers.
    • The satellite receives signals at one frequency, amplify them and transmits at another frequency.
  • Radar System
    • Radar is used to detect aircraft, guide supersonic missiles, observe and track weather patterns and control flight traffic at airports.
    • Radar is also used in burglar alarms, garage door openers and police speed detectors.
  • Heating
    • Microwave energy is more easily directed, controlled and concentrated than low frequency EM waves.
    • When the magnetron oscillates, microwave energy is extracted from the resonant cavities.
    • The reflections from the stationary walls and the motion of the stirring fan cause a microwave energy to be well distributed. Thus the microwave enables the cooking process to be fast.
    • Microwave heating properties also are used in physical diathermy and in drying potato chips, paper, cloth etc.
  • Radio astronomy
  • Land Surveying
  • Meteorology
  • UHF Television
  • Medicine
  • Identification Systems
Paramjeet Singh Jamwal
Lecturer
Guru Nanak Education Trust Group Of Institutions, Roorkee
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