Base station antenna: signal hub of mobile communication network

　　Base station antenna: signal hub of mobile communication network

　　Base station antenna is a key device connecting the core network and user terminals in mobile communication systems (2G/3G/4G/5G). It is responsible for converting the electrical signals transmitted by the base station into electromagnetic waves for radiation, and converting the electromagnetic waves sent by the user terminal into electrical signals for transmission back to the base station. Its performance directly determines the network coverage, signal quality, capacity and user experience, and is the core infrastructure for building an efficient communication network.

　　I. Core functions: dual roles of connection and regulation

　　The core role of base station antennas can be summarized into two dimensions: "signal transmission and reception" and "coverage regulation":

　　Signal conversion and transmission: It realizes the transmission conversion of "electrical signal → electromagnetic wave" and the reception conversion of "electromagnetic wave → electrical signal" through internal radiation units, and is the "air interface" of wireless communication.

　　Coverage range control: Accurately control the signal coverage area through directional design (such as beam width and gain) to avoid signal waste or blind spots, and balance coverage breadth and depth.

　　Multi-user concurrent support: through multi-polarization, MIMO (multiple input multiple output) and other technologies, independent channels are provided for multiple users at the same time within a limited spectrum to improve network capacity.

　　Anti-interference optimization: through designs such as suppressing side lobes and improving front-to-back ratio, interference to adjacent base stations or other wireless systems is reduced to ensure communication stability.

　　II. Structural composition: precision collaborative technology integration

　　The performance of base station antennas depends on the collaborative work of various components. Its core structure includes:

　　Radiating unit: a core functional component composed of metal oscillators (such as dipole or microstrip patches), responsible for the energy conversion between electrical signals and electromagnetic waves, and determining the core characteristics of the antenna such as the frequency band and polarization mode.

　　Reflector: a metal flat plate located behind the radiating unit, which enhances the strength of the front signal by reflecting electromagnetic waves, suppresses reverse radiation, and improves the antenna directivity (gain).

　　Feeding network: composed of power dividers, phase shifters, etc., responsible for evenly distributing the base station's RF signal to each radiating unit (when transmitting), or summarizing the signals received by each unit (when receiving), while controlling the phase of each unit to achieve beam steering.

　　Protective cover: Made of weather-resistant materials (such as fiberglass, ABS), it protects internal components from environmental influences such as wind, rain, ultraviolet rays, corrosion, etc., and at the same time needs to meet low-loss wave transmission (attenuation of electromagnetic waves in the working frequency band ≤0.5dB).

　　Installation structure: including pole bracket, tilt adjustment device (mechanical downtilt / electric downtilt), used to fix the antenna and adjust the beam irradiation direction (such as controlling the coverage distance by downtilt to avoid cross-zone interference).

　　III. Main types: technical differentiation based on scene adaptation

　　Base station antennas need to be differentiated according to network standards, coverage environment, and capacity requirements. The main types are as follows:

　　1. Classification by directivity

　　Omnidirectional base station antenna: The beam is 360° omnidirectional, and the gain is usually 3-6dBi. It is suitable for areas with a small coverage radius (≤1km) (such as rural and suburban areas), or as a blind spot antenna to cover local blind spots. Its structure is simple, but the capacity is low (it is difficult to differentiate multiple users through beams).

　　Directional base station antenna: The beam is fan-shaped (the horizontal beam width is usually 65°, 90°, 120°), with a gain of 8-18dBi, which is the current mainstream type. Three pairs of 120° directional antennas can form a base station sector (covering 360°), which is widely used in densely populated areas such as urban areas and suburbs, and can improve signal strength and anti-interference capabilities through narrow beams.

　　2. Classification by polarization mode

　　Single-polarized antenna: Only supports a single polarization direction (such as vertical polarization), needs to be deployed in pairs (transmit and receive separation), and has been gradually replaced by dual-polarized antennas.

　　Dual-polarized antenna: Integrated vertical/horizontal polarization or ±45° cross-polarization radiation unit, can transmit two independent signals at the same time, supports MIMO technology (such as 4G's 2×2 MIMO), doubles the network capacity in the same space, and is the mainstream choice for 4G/5G.

　　Multi-polarization antenna: supports 3 or more polarization directions (such as the combination of circular polarization + linear polarization in 5G Massive MIMO), further improves spatial multiplexing efficiency, and adapts to the polarization loss compensation requirements of high-frequency band (millimeter wave) signals.

　　3. Classification by beam control capability

　　Fixed beam antenna: The beam direction and width are fixed (the coverage angle is adjusted by mechanical downtilt), which is suitable for scenes with stable coverage requirements (such as suburbs), with low cost but poor flexibility.

　　Smart beam antenna (beamforming antenna): The phase of each radiating unit is dynamically adjusted through the phase shifter of the feed network to achieve real-time control of the beam direction and width (such as 5G Massive MIMO). It can track user movement, suppress interference, and significantly improve the edge user rate (3-5 times higher than fixed beam), which is one of the core technologies of 5G network.

　　4. Key technical parameters: core indicators that determine performance

　　The performance of base station antennas is defined by a series of technical parameters, including the following core indicators:

　　Gain: A measure of the antenna's ability to focus energy in a specific direction, measured in dBi. The higher the gain, the longer the signal coverage distance (e.g., the coverage radius of an 18dBi antenna is more than twice that of a 9dBi antenna), but the beam width is narrower.

　　Beam width: divided into horizontal beam width (HBP) and vertical beam width (VBP), which refers to the angle at which the power drops by 3dB in the antenna radiation pattern. For example, a 65° horizontal beam is commonly used in urban areas (to reduce interference between sectors), and a 90°-120° beam is commonly used in rural areas (to expand coverage).

　　Polarization isolation: In a dual-polarization antenna, the isolation capability of two polarized signals (usually ≥30dB). The higher the isolation, the smaller the crosstalk between signals, and the better the MIMO performance.

　　Front-to-Back Ratio: The ratio of the antenna's forward (main beam) and reverse (180° direction) radiation power (usually ≥25dB). The higher the value, the less interference to the rear base station.

　　Frequency band range: The operating frequency band of the target network needs to be covered (such as 1800MHz and 2600MHz for 4G; 3.5GHz and 26GHz for 5G). Multi-band antennas (such as "4G+5G" dual-mode) can reduce base station deployment costs.

　　Voltage standing wave ratio (VSWR): Measures the impedance matching degree between the antenna and the base station RF module (ideally ≤1.5:1). Too high VSWR will lead to increased signal reflection loss (such as 1.25dB when VSWR=2:1).

　　5. Application scenarios: precise adaptation from coverage to experience

　　The selection of base station antennas needs to be deeply bound to the scenarios. Typical applications include:

　　Dense coverage in urban areas: Use dual-polarization smart antennas with high gain (15-18dBi) and narrow beam (65° horizontal), combined with Massive MIMO (64T64R) to increase capacity and cope with high-density users (such as 100,000+ connections per square kilometer).

　　Wide-area coverage in suburban areas: Use directional antennas with medium gain (12-15dBi) and wide beam (90°), control coverage range through electrical downtilt, and balance distance and signal strength.

　　Rural/remote areas: Use omnidirectional antennas (3-6dBi) or wide beam directional antennas (120°) to achieve wide-area coverage at the lowest cost (single base station coverage radius 3-5km).

　　Indoor coverage: Distributed micro base station antennas (small size, low gain 3-8dBi) are deployed in buildings to solve the problem of high-frequency signal (such as 5G millimeter wave) penetration loss and improve indoor speed.

　　Sixth, technological evolution: the leap from "coverage" to "intelligence"

　　The development of base station antennas has always been synchronized with the upgrade of mobile communication technology:

　　2G/3G era: mainly single-polarization, fixed-beam antennas, the core goal is "coverage", and the gain is generally <10dBi.

　　4G era: dual polarization, MIMO (2×2/4×4) become the mainstream, and the electrical downtilt technology is introduced to achieve a balance of "coverage + capacity", and the gain is increased to 12-15dBi.

　　5G era: Massive MIMO (64T64R/128T128R) and intelligent beamforming are standard, supporting Sub-6GHz and millimeter wave dual bands, with a gain exceeding 20dBi. At the same time, AI algorithms are introduced to dynamically optimize beams to achieve precise coverage of "thousands of people with thousands of faces".

　　Future trends: Evolution to "ultra-wideband (covering Sub-6GHz to terahertz), full intelligence (AI-driven real-time beam optimization), and low power consumption (new materials reduce losses)" to provide support for 6G's integrated air-ground network.

　　Summary

　　Base station antennas are the "nerve endings" of mobile communication networks, and their technological progress has directly promoted the leap from "voice calls" to "Internet of Everything". In the 5G and future 6G eras, base station antennas will not only be "transmitters" of signals, but also "sensing nodes" of intelligent networks. Through integration with AI and big data, they will continuously optimize coverage, capacity and energy efficiency, becoming the core infrastructure of the digital society.