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A batwing or super turnstile antenna is a type of radio antenna named for its distinctive shape which resembles a bat wing or bow tie. Stacked arrays of batwing antennas are used as television broadcasting antennas due to their omnidirectional characteristics. Batwing antennas typically generate a horizontally polarized signal. The advantage of the "batwing" design for television broadcasting is that it has a wide bandwidth.
Design and characteristics
Batwing antennas are essentially a type of crossed dipole antenna, a variant of the turnstile antenna. The typical arrangement consists of two pairs of identical elements offset at right angles that are mounted vertically around a common mast. Element “wings” on opposite sides are fed as a dipole. To generate an omnidirectional pattern, the two element pairs are fed so they are 90° out of phase. The antenna radiates horizontally polarized radiation in the horizontal plane, changing to circularly polarized waves in the axial direction (into the sky and down toward the earth). Each group of four elements at a single level is typically referred to as a bay.
To reduce power radiated in the unwanted axial directions, in broadcast applications multiple bays fed in phase are stacked vertically with a spacing of approximately one wavelength, to create a collinear array. This generates an omnidirectional radiation pattern with increased horizontal directivity (more of the energy radiated in horizontal directions and less into the sky or down at the earth), suitable for terrestrial broadcasting.
The most notable characteristic of a batwing antenna is its wide bandwidth of approximately 35% at a VSWR of 1.1:1. This makes the antenna design suitable for broadcasters who wish to use a single antenna to transmit multiple television signals.
- Markley, Don. "Television antenna systems." 'Broadcast Engineering.' 1 Apr 2004.
- Milligan, Thomas A. 'Modern antenna design.' Wiley-IEEE Press, 2005. ISBN 978-0-471-45776-3
- Sclater, Neil. 'Electronics technology handbook.' McGraw-Hill Professional, 1999. ISBN 0-07-058048-0
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