Radiation Efficiency
The radiation efficiency can be calculated using the radiated power and the
input power accepted by the antenna. Since they are linked directly to the
radiation resistance and loss resistance, the radiation efficiency factor can
also be calculated using the following equation
RL
Rr
RX
From the efficiency point of view, the larger the radiation resistance, the larger the
efficiency
factor. But from the system matching point of view, we need the radiation resistance to
match
with the characteristic impedance of the line and the loss resistance to be zero if possible.
This
is the fundamental requirement for an antenna from the circuit point of view.
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Matching Efficiency
If the input impedance of an antenna is not matched with the feeder impedance,
then a part
of the signal from the source will be reflected back; there is a reflection (mismatch)
loss. This
is characterized by the matching efficiency (also known as reflection efficiency), as
mentioned
earlier, which is defined as the ratio of the input power accepted by the antenna to
the source
supplied power (Ps ):
Thus, the total efficiency of the antenna system (feed and the antenna) is the
product of the two efficiencies:
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EIRP ja ERP
The antenna gain is often incorporated into a
parameter called the effective isotropic radiated power, or
EIRP, which is the amount of power that would have
been radiated by an isotropic antenna to produce the
peak power density observed in the direction of
maximum antenna gain, that is
Another closely related term is the effective radiated
power, ERP, which is also widely used in the
industry. The radiated power is calculated using a
half-wavelength dipole rather than an isotropic
antenna as reference, thus
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Antennit
Kaukokenttä:
Ehto on riittävä UHF-taajuuksilla ja siitä ylöspäin
Matalilla taajuuksilla tarvetta myös näille kahdelle
määrittelylle
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Säteilykuvioparametrit
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Säteilykuvio
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Säteilykuvio
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