As long as radio waves are used, an antenna may be needed to assist in the transmission and reception of radio waves; according to the working frequency band, the antenna can be divided into ultra-long wave, long wave, medium wave, short wave, ultra short wave and microwave from low to high. In the national defense and people's livelihood industries, depending on the wavelength and antenna size, there are big differences. For example, antennas using around 100MHz and WLANs using the 2.4GHz frequency band are used. According to its direction, it can be roughly divided into omni-directional antennas and directional antennas.

The name of the omnidirectional antenna shows that the radiated energy of the electromagnetic field will be the same in every direction. At present, the most common omnidirectional antenna is a dipole antenna. Most of the access points are internal A dipole antenna is built, and its horizontal radiation range is a 360-degree beam. Since the energy in each horizontal direction is equal, it forms a donut-like beam shape from the top of the antenna. If the vertical radiation range is compressed, the transmission distance It will extend as the beam is concentrated, and the beam shape will be close to a pancake. The figure below shows the beam pattern drawn from the top and side of the antenna. If the gain of the dipole antenna is larger, the vertical half-power beam width (HPBW) of the beam is smaller and the transmission distance is larger. Because omnidirectional antennas can cover all horizontal directions, they are usually installed in the center of an open and open environment; if used outdoors, omnidirectional antennas must be installed at the top or high of the building and located in the center of the signal coverage area. In order to communicate with other directional antenna devices to form a point-to-multipoint (Point-to-Multipoint) star topology.

The directional antenna can only be used in a certain position, but the relative transmission distance will be relatively long. There are various styles and shapes of directional antennas, such as Patch antennas, Panel antennas and Yagi antennas, which are often used in wireless areas. Short-distance bridges in the network; for example, two buildings across the road, or a wide-space factory or warehouse are ideal application environments.

In addition, there are highly directional antennas specially used for long-distance communication, which have extremely narrow beam widths and high gain values, which can also be called high-gain directional antennas; for example: dish antennas and lattice ( grid) antenna, usually used for point-to-point communication connection, the transmission distance can be as high as 25 miles; because the beam is very narrow, the antennas must be precisely aimed at each other, and the light of Sight between the antennas must be without any obstacle.