What Is an Antenna Array?
The directivity of a single antenna is limited. In order to be suitable for various occasions, two or more single antennas working at the same frequency will be fed and spaced to form an antenna array according to certain requirements. It is also called an antenna. Array. The antenna radiation unit constituting the antenna array is called an array element.
Antenna array
- (1) Strengthen and improve
- The working principle of the antenna array can be seen as the superposition of electromagnetic waves (electromagnetic fields). For several columns of electromagnetic waves, when they reach the same area,
- The antenna array can also be classified according to the connection method of the antenna elements. All elements of the phased array are connected to
- Phased array
- (1) In-line array
- An in-line array is a type of vertical array in which the axes of the antenna elements are placed along the same straight line. Taking a half-wave dipole in-line array as an example, all antenna elements have no energy radiation in the direction of the main axis of the array, so there is no signal in this direction; but all antenna elements on one side of the array have energy radiation (the phase must be considered problem).
- When installing an in-line array antenna, the main axis is usually placed vertically. They are omnidirectional in the horizontal direction, but the radiation angle in the vertical plane is small. Therefore, they are suitable for making good base stations for mobile radio systems. Many cellular radio systems and PCS systems use in-line arrays for base stations.
- (2) Perpendicular array
- The antenna units are arranged in multiple columns in the same direction, and the main axis of the array is perpendicular to the main axis of the unit, which can also form a vertical array. Although the antenna elements in the secondary array are not aligned, they are still in phase. The difference from in-line arrays is their polarization. Taking a dipole antenna array as an example, the distance between adjacent antenna elements is half a wavelength, and the feeders are cross-connected. Straight arrays are vertically polarized antennas, while vertical arrays are horizontally polarized.
- (3) Endfire array
- Taking a dipole antenna as an example, the feeders of the adjacent antenna elements in the perpendicular array are cross-connected to parallel connections so that the phase difference between the two antennas adjacent to each antenna element is 180 degrees. The radiation of one antenna element is offset by the adjacent radiation in the vertical direction, and all the radiation from the antenna element will be superimposed in the direction away from the end point of the antenna. This antenna installation generally has its main axis level and its radiation in one direction. The polarization direction of this antenna depends on the polarization direction of the antenna unit used.
- (4) Wound antenna
- Wrap antenna
- Taking the dipole antenna element as an example, the wound-rod antenna obtains omnidirectional performance in the horizontal plane, and the polarization mode is horizontal. The feed phase difference of the dipole antenna is 90 degrees.
- Wand antennas are often used for FM broadcast reception. In this application, the wand antenna does not require a rotor to show proper performance in all directions.
- (5) Log-periodic dipole antenna array
- The array element of this antenna is a dipole antenna. The length of the longest dipole antenna element is a half wavelength of the lowest operating frequency, and the shortest antenna element length is less than the half wavelength of the highest operating frequency. The parallel feeder is connected to the narrow end of the antenna, and power can be fed to other dipole antennas by the cross-connected network.
- Log Periodic Dipole Antenna Array
- Yagi-Uda antenna array