When it comes to lenses, people usually think of the refractive correction of glasses and the focusing of light in camera lenses - these common lenses achieve precise focusing by bending light. However, the focusing principle of lenses can also be applied to the manipulation of radio waves, thereby forming antennas for transmitting and receiving signals. This cross-disciplinary technology might be beyond the conventional understanding.
一、 The working principle of the lens antenna: Based on refraction for bidirectional control
To understand the working mechanism of the lens antenna, one can start from the optical principle of the eye. The lens of the eye can focus the incident light onto the retina. Similarly, in the lens antenna, if a point source (feed source) is placed at the focus of the lens (the distance from this point to the lens is called the focal length), the spherical wave emitted by it, after refraction or phase adjustment by the lens, will be transformed into parallel rays (collimated light beam), and the wavefront becomes a plane wave. Among them, the rays passing through the central area of the lens have a smaller deflection angle, while the rays passing through the edge area have a larger deflection angle.
This physical process exhibits remarkable reciprocity: it is applicable to both signal transmission (converting the spherical wave emitted by the feed source into plane wave radiation) and signal reception (concentrating the incident plane wave towards the feed source). It is precisely this characteristic that enables the lens to function as an antenna for implementing bidirectional communication capabilities - during transmission, it accomplishes the conversion from spherical wave to plane wave; during reception, it realizes the convergence of the plane wave towards the focal point.
Unlike reflector antennas that operate based on the law of electromagnetic wave reflection (such as typical dish antennas), lens antennas rely on refraction control as the core principle. In terms of structural design and performance, they have developed a unique technical path.
二、 Longbo Lens: A Technological Breakthrough in Gradient Refractive Index
The Longbo Lens is a special type of spherical lens antenna. The core of its technology lies in the gradient refractive index distribution of the dielectric material. This lens typically adopts a multi-layer structure, with each layer of dielectric having a specific dielectric constant, resulting in an overall characteristic of gradually changing dielectric constant from the center of the sphere to the surface.
This gradient distribution enables the propagation path of incident electromagnetic waves to be controllably bent: in the receiving state, electromagnetic waves from different directions can be precisely converged at the corresponding points on the lens surface; in the transmitting state, the beam emitted by the feed source placed on the surface can be collimated and radiated in a specific direction. By virtue of this characteristic, the Longbo lens achieves efficient control of electromagnetic waves from multiple directions, expanding the application scenarios of the lens antenna.
三、 Performance Characteristics of Lens Antenna: Advantages and Limitations Coexist
The technical advantages of lens antennas are quite remarkable: Firstly, the feed source and supporting structure are located behind the lens, which does not obstruct the antenna aperture, ensuring the integrity of signal transmission; Secondly, the design tolerance is relatively large, reducing the precision requirements in the manufacturing process; Thirdly, it can handle a wider beam width than equivalent-sized parabolic reflectors, and the beam can be inclinedly scanned along the antenna axis, demonstrating strong flexibility.
Meanwhile, the lens antenna also has certain limitations: in low-frequency applications, the lenses are often bulky and heavy, which restricts their use in lightweight scenarios; the design process involves complex calculations of refractive index distribution, with a high technical threshold; and under the same performance indicators, the manufacturing cost is usually higher than that of the reflective surface antenna.
四、Application Scenarios and Technical Value
The application scenarios of the lens antenna have a clear technical orientation, and are particularly suitable for broadband antennas and microwave frequency-related fields. Its excellent beam convergence capability has laid an important foundation for the development of more advanced antenna technologies - for example, the parabolic reflector antenna widely used in satellite communications, whose core focusing logic has a close technical connection with the lens antenna.
The cross-disciplinary application of lenses from the field of optics to antenna technology not only demonstrates the universality of physical principles, but also highlights the significant value of breaking traditional frameworks in technological innovation. In the context of the continuous evolution of wireless communication technology, lens antennas, with their unique performance, will still play an irreplaceable role in specific fields.