Basic Antenna Types

  • The following discussion of antenna types assumes an “adequate” ground plane is present.

    1/4 Wave
    A single radiating element approximately 1/4 wavelength long. Directivity 2.2 dBi, 0 dBd.

    Loaded 1/4 Wave
    The loaded 1/4 wave antenna looks electrically like a 1/4 wave antenna but the loading allows the antenna to be physically smaller than a 1/4 wave antenna. Quite often this is implemented by placing a loading coil at the base of the antenna. Gain depends upon the amount of loading used. Directivity 2.2 dBi, 0 dBd.

    1/2 Wave
    A single radiating element 1/2 wavelength long. Directivity 3.8 dBi, 1.6 dBd. A special design is the end fed 1/2 wave.

    5/8 Wave
    A single radiating element 5/8 wavelength long. Directivity 5.2 dBi, 3.0 dBd.

    Collinear
    Two or three radiating elements separated by phasing coils for increased gain. Four styles are common:
    1. 5/8 over 1/4: top element is 5/8 wave and bottom element is 1/4 wave. Directivity 5.4 dBi, 3.2 dBd.
    2. 5/8 over 1/2: top element is 5/8 wave and the bottom is 1/2 wave. Directivity 5.6 dBi, 3.4 dBd.
    3. 5/8 over 5/8 over 1/4: the top 2 elements are 5/8 wave and the bottom element is 1/4 wave. Directivity 7.2 dBi, 5.0 dBd.
    4. 5/8 over 5/8 over 1/2: the top 2 elements are 5/8 wave and the bottom element is 1/2 wave. Directivity 7.6 dBi, 5.4 dBd.
    Using more than three radiating elements in a base-fed collinear configuration does not significantly increase gain. The majority of the energy is radiated by the elements close to the feed point of the collinear antenna so there is only a small amount of energy left to be radiated by the elements which are farther away from the feed point.

    Please note the directivity is given above for common antenna configurations. The gain depends upon the electrical efficiency of the antenna. Here is where the real difference between antenna manufacturers is seen. If you cut corners in building an antenna, the gain may be significantly lower than the directivity. Larsen uses low-loss materials to minimize the difference between the gain and the directivity in our antennas.

    Whip
    The vertical portion of the antenna assembly acting as the radiator of the radio frequency.



  • Dipole 
    An antenna - usually 1/2 wavelength long - split at the exact center for connection to a feed line. Dipoles are the most common wire antenna. Length is equal to 1/2 of the wavelength for the frequency of operation. Fed by coaxial cable.

  • Sleeve Dipoles are realized by mean of the addition of a metallic tube on a coaxial structure.

  • Printed Dipoles have a radiation structure supported by a printed circuit.

    Embedded Omni
    These antennas are generally integrated on a base for applications such as access points. This structure could be externally mounted (ex: sleeve dipole) or directly integrated on the PC board of the system (ex: printed dipole).

    Yagi
    A directional, gain antenna utilizing one or more parasitic elements. A yagi consists of a boom supporting a series of elements which are typically aluminum rods. Named after one of the Japanese inventors (Yagi and Uda).

    Panel

  • Single Patch describes an elementary source obtained by means of a metallic strip printed on a microwave substrate. These antennas are included in the radiating slot category.

  • Patch Arrays are a combination of several elementary patches. By adjusting the phase and magnitude of the power provided to each element, numerous forms of beamwidth (electric tilt, sectoral, directional ...) can be obtained.

  • Sectoral antennas can be depicted like a directive antenna with a beamwidth greater than 45°. A 1 dB beamwidth is generally defined for this kind of radiating structure.

    Omni-ceiling Mount
    Omni-ceiling mount antennas are used for the propagation of data in an in-building environment. In order to provide good coverage, these antennas are vertically polarized and present an omnidirectional pattern in the horizontal plane and a dipolar pattern in the vertical plane.

    Parabolic
    An antenna consisting of a parabolic reflector and a radiating or receiving element at or near its focus.

  • Solid Parabolics utilize a dish-like reflector to focus radio energy of a specific range of frequencies on a tuned element

  • Grid Parabolics employ an open-frame grid as a reflector, rather than a solid one. The grid spacing is sufficiently small to ensure waves of the desired frequency cannot pass through, and are hence reflected back toward the driven element.
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