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Antenna and wave Propagation

by Ranjit KumarRanjit Kumar
Type: NoteInstitute: West Bengal University of technology Offline Downloads: 3Views: 394Uploaded: 2 months ago

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Ranjit Kumar
Ranjit Kumar
Chapter 1 Introduction • Antennas are devices that launch energy into space around them in the form of electromagnetic waves. • Or, in the reverse process, extract energy from an existing electromagnetic wave. These properties are used for: - Telecommunications, broadcasting - Active Remote Sensing: electromagnetic waves are transmitted to "illuminate" an object, and returning echoes are detected and analysed. - Passive Remote Sensing - Energy Transmission: medical applications, satellites. - Electronic Warfare: enemy communications are disrupted. • An antenna is also defined as a transducer, an element between a transmission line and the free space where the electromagnetic wave propagates. 1-1
• An antenna is designed to radiate or receive energy with specific properties (defined by the polarization and the wavelength of the electromagnetic wave). • Antennas are made in various shapes and sizes: The dimensions of an antenna are usually measured in units of the wavelength λ (lambda) of the electromagnetic wave that is sent (or received). 1-2
The Electromagnetic Spectrum Visible light belongs to a family of waves called the Electromagnetic Waves. Properties: - An electromagnetic (EM) wave consists of electric and magnetic field that oscillate at the same frequency. - The visible part of the EM spectrum covers a very narrow frequency range. - The velocity of an EM wave propagating in vacuum is constant, and equal to the speed of light, c. - The wavelength λ of an EM wave is related to its oscillation frequency f by λ =c/f 1-3

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