Principles of Longbo lens antennas and their applications in 5G communication systems

Principles of Longbo lens antennas and their applications in 5G communication systems

I. Principle of Longbo lens antenna

The Luneburg Lens is a spherical dielectric lens with a gradual refractive index gradient, proposed by Rudolf Karl Luneburg in 1944.

Core structure and refractive index profile

• Shape: Perfect sphere, with structural/material parameters completely symmetrical about the sphere’s center.

• Refractive index: Radial gradient, gradually decreasing from the center to the surface of the sphere.
Ideal formula: n(r) = √(2−(r/R)²)

◦ r: Distance to the center of the sphere; R: Radius of the sphere; n(R)=1 (matched with air).

• Equivalent structure: Similar to an onion, it consists of multiple dielectric rings with different dielectric constants, achieving gradient refraction.

Working principle (reversible optical path)

1. Transmission mode: Spherical waves emitted from a feed source at a certain point on the sphere are refracted by a lens and emerge as parallel plane waves (high-gain narrow beam).

2. Receiving mode: Plane waves incident from any direction are refracted by a lens and precisely focused onto the corresponding point on the spherical surface.

3. Key features: omnidirectional focusing, multi-beam independence, interference-free, high gain, and low sidelobes.
II. Application in 5G communication system

5G requires high gain, multi-beam, wide coverage, large capacity, low interference, cost reduction, and efficiency improvement, which are perfectly matched by the Longbo lens antenna.

1. 5G macro/micro base station coverage

• High-gain narrow beam: It boasts higher gain, longer coverage, and stronger penetration compared to traditional panel antennas.

• Simultaneous multi-beam coverage: Multiple feed sources are arranged on the spherical surface to form independent multi-beams, which do not interfere with each other, doubling the capacity.

• Roof resource reuse: Single antenna supports multiple frequency bands/multiple standards (2G/3G/4G/5G), reducing the number of antennas and saving roof space.

2. Typical 5G scenario applications

• High-speed rail/expressway/tunnel/bridge (narrow and long coverage)

◦ Narrow beam + high gain, achieving long-distance continuous coverage and reducing the number of base stations.

◦ Case: 5G full coverage on the Mudanjiang-Jiamusi High-speed Railway has reduced the number of base stations by 195, saving approximately 92 million yuan in costs over 10 years.

• High-density scenarios (campus/venue/residential area)

◦ Multi-beam precise coverage reduces co-channel interference, enhancing capacity and user experience.

◦ Supports Massive MIMO and collaborates with 5G air interface technology.

• Millimeter-wave 5G (24G/28G/39G, etc.)

◦ Due to the significant path loss of millimeter waves, the Longbo lens offers ultra-high gain to compensate for the loss and enhance coverage.

◦ Supports wide-angle beam scanning (up to 146°), adapting to the flexible coverage requirements of millimeter wave.

• Ultra-long-range coverage in marine/remote areas

◦ With a maximum coverage range of up to 75km, it solves the coverage challenges in maritime areas/remote regions.

• Emergency communication/temporary hotspot

◦ Rapid deployment, multi-beam high capacity, meeting high concurrency scenarios such as music festivals and events.

3. Core value (solving 5G pain points)

• Cost reduction and efficiency enhancement: Reduce the number of base stations and lower deployment/maintenance costs.

• Capacity enhancement: With multi-beam parallelism, the capacity is enhanced by several times.

• Coverage enhancement: Longer range, deeper penetration, and more continuous coverage.

• Interference suppression: Narrow beam + high isolation to reduce co-channel/adjacent channel interference.

• Multi-frequency compatibility: Supports Sub-6G + mmWave, adapts to 5G full-band.

III. Summary

The Longbo lens antenna, which utilizes spherical gradient refractive index to achieve omnidirectional focusing, multi-beam, and high gain, is a key technology for 5G coverage/capacity/cost optimization. It has been widely commercialized in scenarios such as high-speed rail, millimeter wave, high density, and ultra-long range coverage.