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Pyramidal horn (fig. a) – a horn antenna with the horn in the shape of a four-sided pyramid, with a rectangular cross section. They are a common type, used with rectangular waveguides, and radiate linearly polarized radio waves. [12] Sectoral horn – A pyramidal horn with only one pair of sides flared and the other pair parallel. It produces ...
A spiral antenna is a type of radio frequency antenna shaped as a spiral, [1]: 14‑2 first described in 1956. [2] Archimedean spiral antennas are the most popular, while logarithmic spiral antennas are independent of frequency: [3] the driving point impedance, radiation pattern and polarization of such antennas remain unchanged over a large bandwidth. [4]
It is also possible to depict the directive gain of the antenna as a function of the direction. Often the gain is given in decibels. The graphs can be drawn using Cartesian (rectangular) coordinates or a polar plot. This last one is useful to measure the beamwidth, which is, by convention, the angle at the −3dB points around the max gain.
Here, the gain and effective area of antenna 2 are fixed, because the orientation of this antenna is fixed with respect to the first. Now for a given disposition of the antennas, the reciprocity theorem requires that the power transfer is equally effective in each direction, i.e.
Typically, the boresight gain of an antenna is related to the beam width. [26]: 257 For a rectangular horn, Gain ≈ 30000/BW h.BW v, where BW h and BW v are the horizontal and vertical antenna beamwidths, respectively, in degrees. For a circular aperture, with beamwidth BW c, it is Gain ≈ 30000/BW c 2.
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In electromagnetics, an antenna's gain is a key performance parameter which combines the antenna's directivity and radiation efficiency. The term power gain has been deprecated by IEEE. [1] In a transmitting antenna, the gain describes how well the antenna converts input power into radio waves headed in a specified direction. In a receiving ...
The longer the effective length, the greater is the voltage appearing at its terminals. However, the actual power implied by that voltage depends on the antenna's feedpoint impedance, so this cannot be directly related to antenna gain, which is a measure of received power (but does not directly specify voltage or current). For instance, a half ...