Antenna gain is essential for microwave communication---since it helps both transmitting and receiving, it is doubly valuable.
Antenna gain is an indicator of how well an antenna focuses RF energy in a preferred direction. Antenna gain is expressed in dBi (the ratio of the power radiated by the antenna in a specific direction to the power radiated in that direction by an isotropic antenna fed by the same transmitter). Antenna manufacturers normally specify the antenna gain for each antenna they manufacture .
The relationship between antenna gain and effective area is
G = 4πAe / λ 2 = 4π f 2Ae / c2
Where
G = Antenna Gain
Ae = Effective area
λ = Carrier wavelength
f = Carrier frequency
c = Speed of light ( 3 × 108 m/s)
The hypothetical isotropic antenna is a point source that radiates equally in all directions. Any real antenna will radiate more energy in some directions than in others. Since it cannot create energy, the total power radiated is the same as an isotropic antenna driven from the same transmitter: in some direction it radiates more energy than an isotropic antenna, so in others it must radiate less energy. The gain of an antenna in a given direction is the amount of energy radiated in that direction compared to the energy an isotropic antenna would radiate in the same direction when driven with the same input power. Usually we are only interested in the maximum gain-----the direction in which the antenna is radiating most of the power .
An antenna with a large aperture has more gain than smaller one; just as the captures more energy from a passing radio wave, it also radiates more energy in that direction. Gain may be calculated as
GdBi = 10 log10( η 4π/ λ 2 A)
With reference to an isotropic radiator; η is the efficiency of the antenna.
Labels:
Microwave antenna
Antenna gain is an indicator of how well an antenna focuses RF energy in a preferred direction. Antenna gain is expressed in dBi (the ratio of the power radiated by the antenna in a specific direction to the power radiated in that direction by an isotropic antenna fed by the same transmitter). Antenna manufacturers normally specify the antenna gain for each antenna they manufacture .
The relationship between antenna gain and effective area is
G = 4πAe / λ 2 = 4π f 2Ae / c2
Where
G = Antenna Gain
Ae = Effective area
λ = Carrier wavelength
f = Carrier frequency
c = Speed of light ( 3 × 108 m/s)
The hypothetical isotropic antenna is a point source that radiates equally in all directions. Any real antenna will radiate more energy in some directions than in others. Since it cannot create energy, the total power radiated is the same as an isotropic antenna driven from the same transmitter: in some direction it radiates more energy than an isotropic antenna, so in others it must radiate less energy. The gain of an antenna in a given direction is the amount of energy radiated in that direction compared to the energy an isotropic antenna would radiate in the same direction when driven with the same input power. Usually we are only interested in the maximum gain-----the direction in which the antenna is radiating most of the power .
An antenna with a large aperture has more gain than smaller one; just as the captures more energy from a passing radio wave, it also radiates more energy in that direction. Gain may be calculated as
GdBi = 10 log10( η 4π/ λ 2 A)
With reference to an isotropic radiator; η is the efficiency of the antenna.
0 comments:
Post a Comment