دانلود کتاب آنتن ( Antennas )

Antennas

This text is for the course on antennas offered to the senior/graduate level by most
electrical engineering departments. It will also appeal to practicing engineers working
on antenna development. The text explains both the basic theory of antennas and its
application to practical designs. It provides comprehensive coverage and is replete
with interesting worked examples and challenging problem sets. The revision represents
a thorough updating of material and now includes BASIC programs which can be used
for antenna design and computational techniques.

In radio engineering, an antenna is the interface between radio waves propagating through
space and electric currents moving in metal conductors, used with a transmitter or receiver.

In transmission, a radio transmitter supplies an electric current to the antenna’s terminals, and
the antenna radiates the energy from the current as electromagnetic waves (radio waves).
In reception, an antenna intercepts some of the power of a radio wave in order to produce an
electric current at its terminals, that is applied to a receiver to be amplified. Antennas are
essential components of all radio equipment.
The first antennas were built in 1888 by German physicist Heinrich Hertz in his pioneering
experiments to prove the existence of waves predicted by the electromagnetic theory of
James Clerk Maxwell. Hertz placed dipole antennas at the focal point of parabolic reflectors
for both transmitting and receiving. Starting in 1895, Guglielmo Marconi began development
of antennas practical for long-distance, wireless telegraphy, for which he received a Nobel Prize.

The words antenna and aerial are used interchangeably. Occasionally the equivalent term “aerial”
is used to specifically mean an elevated wire antenna. The origin of the word antenna relative to
wireless apparatus is attributed to Italian radio pioneer Guglielmo Marconi. In the summer of 1895,
Marconi began testing his wireless system outdoors on his father’s estate near Bologna and soon
began to experiment with long wire “aerials” suspended from a pole.

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