gs -sDEV!CE=epson -r60x60 %1

Horn Antenna 10368

Fig 8—A template for a 10368-MHz, 8-dBi horn, suitable for feeding an f/D=0.5 dish.

To achieve maximum gain for a given aperture size and maximum efficiency, the taper must be long enough so that the phase of the wave is nearly constant across the aperture. An optimum horn is the shortest one that approaches maximum gain; several definitions are available. The ffl?Z,„A/VT program uses approximate dimensions from a set of tables by Cozzens to design pyramidal horn antennas with gains from 10 to 25 dB.12 Higher gains are possible, but the length of the horn increases much faster than the gain, so very high gain horns tend to be unwieldy.

Kraus gives the following approximations for beam width in degrees:

A0l and dB gain over a dipole: Gain = 10 log 10 (4.5 • Af:l ■ AHl) where Aj^ is the aperture dimension in wavelengths in the E-plane and A^ is the aperture in wavelengths dimension in the H-plane. The HDL_ANT program uses a more accurate gain

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