An electrical device which has power to changes become radio waves and vice versa is called antenna. There are some different kinds of antenna that belonged in three groups. There are omni-directional, directional, and semi-directional that propagates in different directions. Because of the different groups, there are many types of antennas for example dipole antenna, directional antenna, micro-strip antenna, sector antenna, yagi antenna, parabolic antenna, and grid antenna.
One of the types of antenna is dipole antennas. Dipole antennas usually called rubber ducky, are antennas that belonged in omni-directional groups. Dipole antennas have characteristic that are propagate radio frequency (RF) energy in 360 degrees with horizontal direction. Dipole antenna has forms very easy to build. It consists of two slice of wire-cut to the proper length or can be encapsulated. The function of dipole antennas are usually implementated in many enterprise and home production.
Directional and semi-directional groups are antennas that focus to radiate power into tight beams. The common characteristic of directional and semi-directional antennas are reciprocal, and in the transmitting antenna used in receiving antenna. The directional and semi-directional antennas are used in long distance like satellite.
A patch antenna is including in a semi-directional antenna group. This antenna also famous as micro-strip antenna. And the characteristic of this antenna is commonly rectangular and enclosed in a plastic enclosure, beam-width of patch antenna approximately 30 until 190 degrees and the common gain is 9 dB. One of another semi-directional antenna group is sector antennas. Sector antennas have characteristic namely sector antenna supply a pie-form or sector radiation pattern and are commonly set a sectorized array, beam-width of sector antenna approximately 60 until 180 degrees but commonly 120 degrees. The implementation of sector antennas is usually used in cellular communication.
One of directional antenna type is yagi antenna. To form a directional array, yagi antenna uses several elements. The signs of yagi antenna consist of single driven element in-circuit transmitter or receiver with a transmission line and additional parasitic elements, yagi antenna also has beam-width between 30 to 80 degrees, and supply excess of 10 dB passive again. Yagi antenna is usually used in fixed-frequency applications, like as rooftop terrestrial television antenna, radio amateurs, and broadcasting stations.
The most famous type of directional antenna is parabolic antenna or usually called as dish antenna. The characteristic of this antenna is using a parabolic reflector, a curved surface with the cross-sectional form a parabola, to direct the radio waves. High directivity is one of the advantage parabolic antennas. And another characteristic parabolic antenna is narrow beam-width, commonly not exceeding 25 degrees. Implementations of parabolic antenna are microwave relay links which carry telephone and television signals range nearby cities, wireless WAN or LAN links for data communications, satellite communications, spacecraft communication antenna, and radio telescopes. Variation of the dish is called grid antenna. Grid antenna belongs to directional antenna. A parabolic reflector will give a large solid surface to the wind. The wind condition can be high or moderate will cause the dish deform. To prevent this condition, the reflector perforated becomes a grid. The characteristic grid antenna such as beam-width and gain are as same as with parabolic antenna.
Based on three groups of antennas, the application of antennas varies according the characteristics and function antennas.
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