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When considering an antenna's directional pattern, gain with respect to a dipole does not imply a comparison of that antenna's gain in each direction to a dipole's gain in that direction. Rather, it is a comparison between the antenna's gain in each direction to the peak gain of the dipole (1.64). In any direction, therefore, such numbers are 2 ...
Ruze's equation is an equation relating the gain of an antenna to the root mean square (RMS) of the antenna's random surface errors. The equation was originally developed for parabolic reflector antennas, and later extended to phased arrays. The equation is named after John Ruze, who introduced the equation in a paper he wrote in 1952. [1]
Left: with a low gain feed antenna, significant parts of its radiation fall outside the dish. Right: with a higher gain feed, almost all its radiation is emitted within the angle of the dish. The radiation pattern of the feed antenna has to be tailored to the shape of the dish, because it has a strong influence on the aperture efficiency, which ...
Friis' original idea behind his transmission formula was to dispense with the usage of directivity or gain when describing antenna performance. In their place is the descriptor of antenna capture area as one of two important parts of the transmission formula that characterizes the behavior of a free-space radio circuit. [2]
An antenna designer must take into account the application for the antenna when determining the gain. High-gain antennas have the advantage of longer range and better signal quality, but must be aimed carefully in a particular direction. Low-gain antennas have shorter range, but the orientation of the antenna is inconsequential.
The free space loss is easily calculated using Friis transmission equation which states that the loss is proportional to the square of the distance and the square of the frequency. Additionally losses are incurred in most radio links, including atmospheric attenuation by gases, rain, fog and clouds.
Isotropic gain is the ratio of the power density (signal strength in watts per square meter) received at a point far from the antenna (in the far field) in the direction of its maximum radiation (main lobe), to the power , received at the same point from a hypothetical lossless isotropic antenna, which radiates equal power in all directions ...
Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: =.