At the same time, the effective area isĪs we can see, the effective aperture is only 67% of the collecting area of the antenna. The collecting area of the antenna A = πD²/4 = π70²/4 = 3848 m². An antenna with more elements and a longer boom will have more gain and a larger effective aperture.Īntenna gain is G = 69.5 dBi or 9,000,000. Note also that the bigger the antenna gain, the higher its effective area. Note that unlike in any dish antenna where the effective aperture is always smaller than the physical area, the effective aperture of a Yagi antenna extends symmetrically above and below the plane of its elements and extends symmetrically beyond the physical length of the antenna elements. However, for wire antennas (dipoles, monopoles, Yagi-Uda antennas), the effective area is much larger than the physical area of the antenna.Įffective aperture (area) of a Yagi-Uda antenna. Note that for aperture antennas like dish or horn antennas, the effective area is closely related to (but always less than) the physical area.
Now, replacing the factor Aη with A e, we will haveįrom this formula, which is used in this calculator, we can see that for a given antenna aperture, the gain increases with the square of the wavelength or if the wavelength is constant, then the gain is proportional to the aperture size. However, some of this power is always lost in the form of thermal energy, which is used for heating the antenna itself and its feeder. If the antenna efficiency is 1 (or 100%), then all the power delivered to the antenna is radiated or if this is a receiving antenna, then all the power gathered by the antenna goes to the receiver. Here A e is the effective antenna aperture (area), which is defined as the physical aperture multiplied by the antenna efficiency. Where λ is the wavelength and η is the antenna efficiency, which is always less then unity: The relation between the antenna gain and area is given by the following formula, which takes into account the antenna efficiency: So, the narrower the width of the beam, the higher the antenna gain.
The antenna gain G is directly proportional to the antenna aperture A and is increased by means of focusing radiation in only one direction while reducing radiation in all other directions. Where P d is the surface power density or specific power (power per unit area) of the incident electromagnetic energy and A is the aperture area. Consider an aperture antenna as a receiving antenna. From this area, an antenna directed towards the source of the signal absorbs the energy of an incident electromagnetic wave. The antenna effective aperture is the area of the equivalent flat antenna with a uniform amplitude-phase distribution having the same maximum value of directivity as the given antenna.
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