Polarization, as one of the key parameters of the antenna, needs to be considered before selection. In this issue, we start from antenna polarization, let's talk about the comparison between single polarization and dual polarization, as well as their practical applications and detailed selection.
First of all, let's summarize the meaning of antenna polarization very simply. The antenna radiates transverse electromagnetic waves in the far field, and the direction of the electric field vector is perpendicular to the magnetic field, and at the same time perpendicular to the direction of propagation. Therefore, when radio waves propagate in space, the direction of their electric field changes according to a certain law, and this phenomenon is called the polarization of radio waves.
After explaining the definition of antenna polarization, let's talk about single-polarization antennas and dual-polarization antennas, which are quite different in many ways.
A single-polarization antenna is a special form of antenna, and its function of receiving and transmitting signals is to separate two antennas, and one antenna contains only one polarization mode.
This type of antenna requires two antennas to work at the same time when receiving and transmitting signals, so it requires more installation space and maintenance work. In some cases, the performance gains of a single-polarized antenna may be more pronounced than a dual-polarized antenna.
Dual-polarized antenna is a new antenna technology that combines two antennas with +45° and -45° polarization directions orthogonal to each other and operates in transceiver duplex mode at the same time. The most prominent advantage of this type of antenna is the saving of the number of antennas for a single directional base station. Dual-polarized antennas combine transmit and receive functions on a single antenna, while transmitting signals independently in both horizontal and vertical directions. Compared with single-polarization antennas, dual-polarization antennas have a wider signal coverage and are simpler to install and maintain.
Here we will compare single-polarized antennas and dual-polarized antennas from 4 angles to see where they differ greatly.
Single-polarization antennas: Two antennas are required to transmit and receive signals, which are responsible for signal transmission in the horizontal and vertical directions.
Dual-polarized antenna: Transmitting and receiving functions are integrated on a single antenna, which can transmit signals independently in the horizontal and vertical directions.
Since a single-polarized antenna requires additional space to fit the two antennas that receive and transmit, it has higher space requirements than dual-polarized antennas. In addition, single-polarized antennas also require more work in routine maintenance, such as regular inspection and calibration of two pairs of antennas.
In open areas, such as mountainous areas or plain rural areas, the coverage effect of a vertical single-polarized antenna may be better than that of other non-vertically polarized antennas, because the mobile phone perpendicular to the ground is easier to match with the vertically polarized signal. In the urban environment, due to the obstruction of the building, the electromagnetic waves are reflected many times through the surface of the building, which is easy to rotate the polarization. Therefore, in urban environments, there is not much difference in the coverage effect of vertically polarized antennas and ±45° dual-polarized antennas.
In power-constrained systems, such as suburban or rural areas where coverage needs to be increased and fading overcome, the performance improvement of dual-polarized antennas may not be as significant as that of single-polarized antennas. Specifically, the performance improvement of 10λ single-polarized antennas is less than 5% compared with dual-polarized antennas, and the performance gap between the two is not large.