In professional satellite communications transmitters, it is common for a single antenna to work with two orthogonal polarizations simultaneously, so that the available bandwidth for the signal on the link is doubled (military antennas). To do this, standing next to one ortho-mode transducer feeder, which has a circular waveguide port connected to the horn and two orthogonal rectangular waveguide ports, each of which works in a different polarization.
This parameter is defined as the ratio between the maximum radiated power in a geometric direction and power radiated in opposite direction. When this relationship is reflected in dB scale, the ratio F / B (Front / Back) is the difference in dB between the maximum radiation level and radiation level of 180 degrees. This parameter is especially useful when interference back is critical in choosing the antenna that we use.
Beamwidth: The angular range of directions in which the radiation of a beam takes a value 3 dB below the maximum. The direction in which the radiated power is halved. Ratio at the secondary main lobe (SLL): The ratio in dB between the maximum value of main lobe and the maximum value of secondary lobe. Front-back ratio (FBR): The ratio in dB between the value of maximum radiation and the same direction and opposite direction.
Comparing an antenna yagi with a satellite, the antenna yagi have a F / B ratio of about 15 dB (depending on model and manufacturer) while for the parabolic relationship F / B is> 35dB (depending on model and manufacturer) . This is observed as "good" antenna on rejection of signals by the rear. The higher the paramentro in parabolic antennas will be better. The 15 dB of antenna yagui it can also be interpreted as the attenuation that would have on the system, if for example a bounced capture of a building, by the rear of the wave. Radiation resistance - when power is supplied to an aerial, radiating part of it and part is converted into heat dissipating. When talking about radiation resistance, it is made taking into account that cannot be measured directly.
A transmitter with more than about 3 items are usually less sensitive in a circle slice perpendicular towards the main direction of a jet and therefore one can put antennas in close proximity to a base station. The distance between the antennas should be at least 1 / 2-1 of main wavelengths used. Further away than about 10 wavelengths (far field) affects largely the antenna radiation pattern, but it can affect radio propagation or radio broadcast.
The antenna location should have unrestricted access to just above the the sky. Earth would reflect more or less of radio waves. This depends on: mast placed as high as possible so that there are no obstructions between the transmitter and receiver. Satellite or interstellar radio propagation (Earth to satellite, space shuttle) or (satellite, space shuttle to Earth). There must be no obstructions between the satellite and ground transmitters.
The dimensions are generally a maximum wavelength. It is widely used in the bands of MF, HF, VHF and UHF. You can find wire antenna arrays. Examples of wire antennas are: the vertical monopole, the dipole and its evolution, the Yagi, loop antenna and the helical antenna is a special type of antenna that is used primarily on VHF and UHF. It describes a helix conductor, thereby producing a circular polarization.
The characteristics of an antenna depends on the relationship between the dimensions and the wavelength of a signal transmitted or received radio frequency. If the masts dimensions are much smaller than the wavelength are called elementary antennas, whether they have dimensions of order of a half wavelength resonating and if its size is much larger than the wavelength are directives.
This parameter is defined as the ratio between the maximum radiated power in a geometric direction and power radiated in opposite direction. When this relationship is reflected in dB scale, the ratio F / B (Front / Back) is the difference in dB between the maximum radiation level and radiation level of 180 degrees. This parameter is especially useful when interference back is critical in choosing the antenna that we use.
Beamwidth: The angular range of directions in which the radiation of a beam takes a value 3 dB below the maximum. The direction in which the radiated power is halved. Ratio at the secondary main lobe (SLL): The ratio in dB between the maximum value of main lobe and the maximum value of secondary lobe. Front-back ratio (FBR): The ratio in dB between the value of maximum radiation and the same direction and opposite direction.
Comparing an antenna yagi with a satellite, the antenna yagi have a F / B ratio of about 15 dB (depending on model and manufacturer) while for the parabolic relationship F / B is> 35dB (depending on model and manufacturer) . This is observed as "good" antenna on rejection of signals by the rear. The higher the paramentro in parabolic antennas will be better. The 15 dB of antenna yagui it can also be interpreted as the attenuation that would have on the system, if for example a bounced capture of a building, by the rear of the wave. Radiation resistance - when power is supplied to an aerial, radiating part of it and part is converted into heat dissipating. When talking about radiation resistance, it is made taking into account that cannot be measured directly.
A transmitter with more than about 3 items are usually less sensitive in a circle slice perpendicular towards the main direction of a jet and therefore one can put antennas in close proximity to a base station. The distance between the antennas should be at least 1 / 2-1 of main wavelengths used. Further away than about 10 wavelengths (far field) affects largely the antenna radiation pattern, but it can affect radio propagation or radio broadcast.
The antenna location should have unrestricted access to just above the the sky. Earth would reflect more or less of radio waves. This depends on: mast placed as high as possible so that there are no obstructions between the transmitter and receiver. Satellite or interstellar radio propagation (Earth to satellite, space shuttle) or (satellite, space shuttle to Earth). There must be no obstructions between the satellite and ground transmitters.
The dimensions are generally a maximum wavelength. It is widely used in the bands of MF, HF, VHF and UHF. You can find wire antenna arrays. Examples of wire antennas are: the vertical monopole, the dipole and its evolution, the Yagi, loop antenna and the helical antenna is a special type of antenna that is used primarily on VHF and UHF. It describes a helix conductor, thereby producing a circular polarization.
The characteristics of an antenna depends on the relationship between the dimensions and the wavelength of a signal transmitted or received radio frequency. If the masts dimensions are much smaller than the wavelength are called elementary antennas, whether they have dimensions of order of a half wavelength resonating and if its size is much larger than the wavelength are directives.
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