06-05-2017, 03:56 PM
An antenna is a transducer that converts the radio-frequency electric current into electromagnetic waves that radiate into space. In bidirectional communication, the same antenna can be used for transmission and reception.
It is a source or radiator of electromagnetic waves or an electromagnetic wave sensor. It is a transition device or transducer between a guided wave and a wave of free space or vice versa. It is an electrical conductor or a conductors system that radiates EM energy or collects EM energy from the free space. It is an impedance matching device, coupling EM waves between the transmission line and the free space or vice versa.
Some types of antenna
Wire, dipolar, loop and helical antennas
Aperture antennas-Horns and reflectors
Array Antennas-Yagi, Periodic Record
Patch Antennas - Microstrips, PIFAs
Beginning
Under time-varying conditions, the Maxwell equations predict EM energy radiation from the current source (or accelerated charge). This occurs at all frequencies, but is insignificant as long as the size of the region of origin is not comparable to the wavelength. While Tr.lines are designed to minimize this loss of radiation, radiation in the free space becomes the primary purpose in the case of antennas. For the harmonic variation of the steady state, we usually focus on the time-changing current. For transients or pulses, we focus on accelerated charge. Radiation is perpendicular to acceleration. The radiated power is proportional to the square of
I L or Q V
It is a source or radiator of electromagnetic waves or an electromagnetic wave sensor. It is a transition device or transducer between a guided wave and a wave of free space or vice versa. It is an electrical conductor or a conductors system that radiates EM energy or collects EM energy from the free space. It is an impedance matching device, coupling EM waves between the transmission line and the free space or vice versa.
Some types of antenna
Wire, dipolar, loop and helical antennas
Aperture antennas-Horns and reflectors
Array Antennas-Yagi, Periodic Record
Patch Antennas - Microstrips, PIFAs
Beginning
Under time-varying conditions, the Maxwell equations predict EM energy radiation from the current source (or accelerated charge). This occurs at all frequencies, but is insignificant as long as the size of the region of origin is not comparable to the wavelength. While Tr.lines are designed to minimize this loss of radiation, radiation in the free space becomes the primary purpose in the case of antennas. For the harmonic variation of the steady state, we usually focus on the time-changing current. For transients or pulses, we focus on accelerated charge. Radiation is perpendicular to acceleration. The radiated power is proportional to the square of
I L or Q V
Where ,
I = Time that changes the current in Amps / sec
L = Current element length in meters
Q = Charging in Coulombs
V = rate of change of time
