About antenna parameters: detailed explanation of dBi and polarization

　　About antenna parameters: detailed explanation of dBi and polarization

　　1. dBi: unit for measuring antenna gain

　　"dBi" is the decibel number relative to an isotropic radiator, which is used to describe the ability of an antenna to focus energy in a specific direction (based on an ideal omnidirectional uniform radiating antenna).

　　High dBi (such as 12dBi): Energy is focused in a narrow beam, with a longer reading distance but a narrower coverage area (similar to a focused flashlight, with a long range but a small illumination range).

　　Low dBi (such as 9dBi): Energy is spread to a wide beam, with a wider coverage area but a shorter reading distance (similar to a lantern, with a large illumination range but a limited range).

　　2. Polarization: the propagation direction of radio waves

　　Polarization defines the vibration direction of electromagnetic waves when they leave the antenna, and is mainly divided into two categories:

　　Linear polarization

　　Electromagnetic waves propagate in a single plane (vertical or horizontal).

　　Advantages: wider reading range (10-20% higher than circular polarization) and low energy loss.

　　Disadvantages: Reading reliability decreases if the tag is tilted or misaligned.

　　Applicable scenarios: when the tag direction is fixed and consistent.

　　Circular polarization

　　Electromagnetic waves rotate during propagation, covering all possible directions.

　　Advantages: high fault tolerance, stable reading regardless of the tag angle.

　　Disadvantages: slightly shorter reading range than linear polarization.

　　Applicable scenarios: when the tag direction is random or unknown.

　　Summary: Linear polarization is selected for controllable tag direction, and circular polarization is selected for random direction.

　　3. 9dBi antenna: ideal choice for general use

　　9dBi antenna balances coverage and reading distance, suitable for scenarios where tags are dispersed or have variable directions, and is a "universal model" that combines practicality and flexibility.

　　Core advantages:

　　Wide coverage, tags can be read from multiple angles;

　　Strong adaptability, can still work efficiently when the tag position is uncertain;

　　Reduce blind spots and reduce the probability of missing misaligned tags.

　　Best application scenarios:

　　Retail inventory tracking, warehouse shelves and aisles, access control, short-distance logistics (such as conveyor belts).

　　Polarization recommendation: Circular polarization is preferred because the tag direction is mostly random; if the tag direction is uniform, linear polarization can also be applied.

　　4. 12dBi antenna: Professional choice for long-distance focusing

　　The 12dBi antenna is designed for long-distance reading. The signal is focused into a strong and narrow beam, which is suitable for scenarios where a specific area needs to be accurately covered, but the coverage range is narrow.

　　Core advantages:

　　Long reading distance meets the needs of long-distance scanning;

　　Accurate positioning, suitable for monitoring specific entrances or areas;

　　Strong anti-interference, narrow beam reduces interference from irrelevant tags.

　　Best application scenarios:

　　Outdoor vehicle/fleet tracking, port gate cargo scanning, large industrial plants, truck/container tracking on specific routes.

　　Polarization recommendation: Linear polarization is preferred when the distance is long and the tag direction is controllable (such as vehicle gates); if the tag direction may change, circular polarization is more reliable, but the reading range will be slightly shortened.