What is antenna array and antenna array type
An antenna array, also called a phased array, is a group of antennas composed of two or more antennas. These antennas combine signals with each other to achieve higher performance than a single antenna. The antenna array can improve the overall overall gain, achieve diversity reception, cancel interference, adjust to a specific direction, measure the source direction of the input signal, and maximize the signal to interference noise ratio (SINR). The array antenna is usually composed of more than one dipole, but it can also be composed of active dipoles. The antenna elements in the array radiate separately, and the radiation of all the elements are added together to form a radiation beam with high gain, high directivity, high performance, and minimum loss. Similar to dipoles, active oscillators can also be used as transmitters and receivers. When connected to a transmission line, the active vibrator directly obtains power from the transmission device, or acts as a receiver, directly transmitting the received power to the receiving device. The application areas of array antennas include satellite communications, wireless communications, radar communications, and astronomy research.
Antenna array type
The antenna array can be classified according to the radiation pattern and the type of vibrator used. When the distance between the placement position of the parasitic oscillator and the active oscillator is close enough to cause coupling, the corresponding driver of the parasitic oscillator will generate the largest amount of emitted radiation. The parasitic oscillator that can increase the power from the driver is called the director, and the parasitic oscillator that can maximize the radiation energy to the active oscillator is called the reflector. When all the elements in the antenna array are active elements, the array is also called an active array or a connection array. Interestingly, once the array contains one or more parasitic oscillators, the entire system is called a parasitic array. Multi-element arrays can be classified according to their directionality. For example, an array that radiates in two opposite directions is called a bidirectional array, and an array that radiates in only one direction is called a unidirectional array.
One, active array
A collinear array is a unidirectional high-gain antenna containing two or more half-wave dipoles, which are arranged head to tail on the same straight line or axis to form a parallel or collinear structure . The main purpose of this type of array is to increase the radiated power and to achieve a highly directional beam by avoiding power loss in other directions. The advantages of collinear array antennas include improved directivity and reduced power loss.
The pendent array is a bidirectional array that improves emission performance by radiating electromagnetic waves in a specific direction. The design element of this type of array includes two or more half-wave dipoles, all of which have the same size and are equally spaced along the same straight line or axis to form collinear points with the same source. The radiation pattern of the vertical array antenna is perpendicular to the above-mentioned axis, the radiation beam is narrow, and the gain is high.
Similar to the pendant array, the endfire array also uses two half-wave dipoles separated by half a wavelength, and has a bidirectional radiation pattern. Compared with the pendant array, the end-fire array has a narrower beam width, lower gain, and higher directivity. The radiation direction of the endfire array is parallel to the array plane and perpendicular to the vibrator, and the radiation direction of the vibrator is toward the end of the array, that is, the radiation direction of the array is consistent with the radiation direction of the vibrator.
Second, the parasitic array
Yagi Uda Array
The most commonly used antenna in home TV reception has the characteristics of high gain and high directivity. This type of antenna has multiple guides, and the directivity of the antenna can be improved by setting the guides. The disadvantage of the Yagi-Uda antenna is that it is easily affected by noise and the ambient atmosphere.
Log periodic array
The impedance of a log-periodic array antenna is a log-periodic function of frequency. Similar to the Yagi-Uda antenna, the log-periodic antenna has the advantage of maintaining constant radiation resistance, standing wave ratio, gain, and directivity ratio within the required operating frequency range. Log periodic antennas include planar log periodic antennas, trapezoidal log periodic antennas, tooth-shaped log periodic antennas, V-shaped log periodic antennas, slot log periodic antennas, dipole log periodic antennas, and LPDA (log periodic even Polar array) and other types.
Wound rod array
The basic structure of this type of antenna is two identical half-wave dipoles placed at right angles to each other and fed in phase. After stacking multiple pole-around antennas along the vertical axis, the gain can be increased. This structure is called a stacked array. The working mode of the pole-around antenna is divided into two types: normal and axial, and the polarization mode is different under different working modes. In the normal mode, the antenna radiated wave is horizontally polarized, and the polarization direction is perpendicular to the antenna axis. In the axial mode, the radiated wave is a circularly polarized wave around the antenna axis.
Super wound rod array
The super winding rod array is the so-called batwing antenna, in which the dipole in the winding rod antenna is replaced by 4 plates, and 1 to 8 stacked arrays can be set on a single winding rod. The advantage of this type of array is that the gain and directivity are better than those of ordinary whirling antennas, but at the same time there is a certain power loss.