1OH6KVP

Radiation EfficiencyThe 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

From the efficiency point of view, the larger the radiation resistance, the larger the efficiencyfactor. But from the system matching point of view, we need the radiation resistance to matchwith the characteristic impedance of the line and the loss resistance to be zero if possible. Thisis the fundamental requirement for an antenna from the circuit point of view.

RL Rr

RX

2OH6KVP

Matching Efficiency

If the input impedance of an antenna is not matched with the feeder impedance, then a partof the signal from the source will be reflected back; there is a reflection (mismatch) loss. Thisis characterized by the matching efficiency (also known as reflection efficiency), as mentionedearlier, which is defined as the ratio of the input power accepted by the antenna to the sourcesupplied power (Ps ):

Thus, the total efficiency of the antenna system (feed and the antenna) is the product of the two efficiencies:

3OH6KVP

EIRP ja ERPThe 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 isAnother 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

4OH6KVP

Antennit

Ehto on riittävä UHF-taajuuksilla ja siitä ylöspäin

Kaukokenttä:

Matalilla taajuuksilla tarvetta myös näille kahdelle määrittelylle

5OH6KVP

Säteilykuvioparametrit

6OH6KVP

Säteilykuvio

7OH6KVP

Säteilykuvio