Supergain antennas: possibilities and problems

In principle, any desired amount of gain can be developed from an antenna of arbitrary size. The phenomena of high gain from very small antennas is called "supergain". To see why this statement might be so, the author recalls the construction used in optics, known as Huygens' principle. This states that every point on a wavefront can be regarded as a source of radiation. At the end of a short period of time, the envelope of all of these individual wavelets forms the new wavefront. For example, this construct explains why a shadow is not perfectly sharp, and why interference fringes form. End fire antennas, dipole antennas, Yagi antennas and quad antennas are examined.<
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