1. Antenna gain
Antenna gain refers to the ratio of the radiation power density of the antenna in a certain specified direction to the radiation power density of the reference antenna (usually an ideal radiation point source) at the same input power. The parameters that represent antenna gain are dBd and dBi.
The physical meaning of gain can be understood as follows: to generate a signal of a certain size at a certain point at a certain distance, if an ideal non-directional point source is used as the transmitting antenna, an input power of 100W is required, while when a directional antenna with a gain of G=13dB (20 times) is used as the transmitting antenna, the input power is only 100/20=5W. In other words, the gain of an antenna, in terms of its radiation effect in the maximum radiation direction, is the multiple of the input power amplified compared with the non-directional ideal point source.
Antenna gain is used to measure the ability of an antenna to send and receive signals in a specific direction and is one of the most important parameters for selecting an antenna. Gain is closely related to the antenna pattern. The narrower the main lobe of the pattern and the smaller the side lobe, the higher the gain. The relationship between the main lobe width and antenna gain is shown in Figure 1-1.
Figure 1-1
Under the same conditions, the higher the gain, the farther the radio wave propagates. However, in actual implementation, the antenna gain should be reasonably selected based on the matching of the beam and the coverage target area. For example, when the coverage distance is close, in order to ensure the coverage effect of the near point, a low-gain antenna with a wider vertical lobe should be selected.
2. Related concepts
·dBd: relative to the gain of a symmetrical array antenna,
·dBi: relative to the gain of a point source antenna, the radiation in all directions is uniform. dBi=dBd+2.15
Lobe angle: the angle formed by 3dB below the main lobe peak in the antenna pattern, please refer to the lobe width for details, ideal radiation point source: refers to an ideal isotropic antenna, that is, a simple point radiation source, with the same radiation characteristics in all directions in space.
3. Calculation formula
Antenna gain =10lg(antenna radiation power density/reference antenna radiation power density)
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Post time: Dec-06-2024
