EnglishViews: 0 Author: Site Editor Publish Time: 2025-10-29 Origin: Site
Antenna Gain: "Energy Focusing Technique" for Passive Devices
Antenna is the core component of wireless communication system, and its "gain" characteristic often raises questions: as a passive device,The antenna itself does not amplify the signal power, so why is there "gain"?In fact, antenna gain does not describe power amplification, but rather the ability of the antenna to concentrate energy in a particular direction.
1. The essence of gain: energy redistribution
The essence of antenna gain is to enhance the signal strength in the specified direction by sacrificing the radiation ability in other directions.It's like replacing a light bulb with a flashlight: the total energy is the same, but the light is focused by a reflector, which illuminates farther away.
Definition of gain: under the condition of equal input power,The ratio of the signal power densities produced at the same point in space by an actual antenna and an ideal radiating element.
There are two keys to understanding antenna gain:
As a passive device, the antenna does not add power, but redistributes energy;
The antenna gain is a relative value with respect to a reference antenna.
2. Gain and directionality: two sides of the same coin
The antenna gain is closely related to the pattern: the narrower the main lobe and the smaller the side lobe of the pattern, the higher the gain.
Omnidirectional antenna: 360 ° radiation in the horizontal plane and beam limitation in the vertical plane
Directional antenna: focuses energy into a narrow beam
According to the law of conservation of energy, when the gain of the antenna is positive in some directions, the gain in other directions is negative.
3.Quantized representation of gain
Unit | Reference Datum | Conversion relation | Application scenario |
dBi | Ideal point source antenna (isotropic antenna, theoretical model) | dBi = dBd + 2.15 | Theoretical calculation, general comparison |
dBd | Half-wave dipole antenna (practically manufacturable standard antenna) | dBd = dBi - 2.15 | Actual antenna performance label |
For example, a 0 dBd antenna is equivalent to 2.15 dBi; the GSM directional base station antenna gain is about 18 dBi, and the omnidirectional base station antenna gain is about 11 dBi.
4. Common Methods to Improve Antenna Gain
The core idea is to reduce the lobe width in the vertical plane, while taking into account the radiation requirements in the horizontal plane. The mainstream technologies include:
Increase the size of the antenna: such as parabolic antenna, the gain is positively related to the aperture.The formula is G (dBi) = 10L G { 4.5 × (D/λ0) ² } (D is the diameter of the paraboloid and λ0 is the central working wavelength).The higher the gain.
Adopt an antenna array, namely arranging a plurality of antenna unit according to a rule (such as a vertical four-element array) to enable electromagnetic waves to be superposed in that same phase in a target direction,A single half-wave oscillator (2.15 dBi) can be raised to 8.15 dBi.
Application of modern technologies: smart antennas concentrate radiation energy through arrays, and MIMO technology combines multiple antennas to optimize signal transmission.The gain of that system can be indirectly improve.
In practical engineering, the selection of antenna gain needs to consider many factors, such as coverage requirements, equipment size and installation environment.Although high-gain antenna can expand the coverage distance, it also brings the problem of beam narrowing, which requires precise alignment.
Professional Communication Products
ZHENGZHOU LEHENG ELECTRONIC TECHNOLOGY CO.,LTD
Tel:86-371-60911368
Email:info@global-antenna.com
Website:https://www.asialeren.com
