Circularly polarized high-gain lens antenna for improving axial ratio bandwidth and gain bandwidth

Abstract

The invention discloses a circularly polarized high-gain lens antenna for improving axial ratio bandwidth and gain bandwidth, which belongs to the technical field of antenna engineering, is applied to the fields of self-satellite communication and the like, and has the characteristics of wide frequency band (axial ratio bandwidth and gain bandwidth), high gain and easiness in processing. The circularly polarized lens part adopted by the invention is easy to process by means of a 3-D printing technology, and is easy to integrate with a linear polarization feed source. The dielectric lens unit has dual functions of a circular polarizer and a phase shifter, and can improve the gain of the antenna. The phase shifters with different lengths can provide all-phase compensation for the lens antenna, and the circular polarizer can convert linearly polarized waves into circularly polarized waves. Compared with a reported dielectric circularly polarized antenna, the antenna provided by the invention has wider axial ratio bandwidth and gain bandwidth. According to the invention, a lens antenna scheme with low processing complexity, wide band and high gain is realized in the application field of millimeter wave antennas.

Description

Technical Field

[0001] The present invention belongs to the field of antenna engineering technology and relates to a 3-D printed circularly polarized high-gain lens antenna. The antenna has an application background in fields such as satellite communications and has the characteristics of wide bandwidth (axial ratio bandwidth and gain bandwidth), high gain, and easy processing. Background Art

[0002] Millimeter wave technology is gaining attention as a strong contender for fifth-generation (5G) wireless systems, due to its high-speed transmission capability and wide bandwidth. The technology also offers other advantages, such as compact device size and minimal latency. The advent of millimeter wave technology has catalyzed the development of many promising commercial applications, including satellite communications, connected vehicles, digital twins, virtual reality (VR), and the Internet of Things (IoT). Antennas are key components of millimeter wave communication systems and largely determine the transmission quality of the communication system. However, these systems face severe challenges in antenna polarization: the transmitting and receiving antennas must have the same orientation. The mismatch in polarization direction can seriously affect the communication quality. In addition, these systems may also be affected by multipath effects, further reducing communication reliability. These challenges can be overcome by using circularly polarized antennas. With circularly polarized antennas, the strength of the received signal remains relatively unchanged regardless of the antenna orientation. Therefore, current research focuses on optimizing the design of circularly polarized antennas. At the same time, high-gain antennas can also resist the losses along the propagation path, among which transmission array antennas (TAA) and lens antennas are common solutions in this case. Compared with non-dielectric lenses, dielectric lens antennas can achieve high gain and relatively wide gain bandwidth, so they have attracted more and more research interests. Dielectric lens antennas can be manufactured by low-cost and high-precision 3-D printing technology. Some existing literature uses lens antennas composed of dielectric circular polarizers. For example, in the paper "A circularly polarized 3-D printed dielectric transmitarrayantenna at millimeter-wave band", a 3-D printed transmission array antenna operating at 30GHz was proposed, whose unit is composed of dielectric circular polarizers, achieving 17% 3dB axial ratio bandwidth and 13.3% 1dB gain bandwidth; in the paper "High-gain circularly polarized lens antenna for terahertz applications", a lens antenna operating at 300GHz was proposed, which is composed of dielectric circular polarizers and variable-length dielectric rods, achieving at least 44.2% 3dB axial ratio bandwidth and 13.3% 1dB gain bandwidth. Summarizing the reported literature, the 3dB axial ratio bandwidth of circularly polarized dielectric lenses does not exceed 45%, and the 1dB gain bandwidth of 13.3% is still a relatively narrow bandwidth. Both need to be widened and improved. Summary of the invention

[0003] Based on the background technology, the present invention proposes a 3-D printed circularly polarized high-gain lens antenna applied to the field of millimeter wave antennas (such as satellite communications, the Internet of Things, etc.). The unit adopts a composite structure of a dielectric circular polarizer and a phase shifter, and has the characteristics of wide bandwidth (axial ratio bandwidth and gain bandwidth), high gain, and easy processing. It is very consistent with the antenna performance required in the fields of millimeter wave satellite communications, the Internet of Things, etc.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A circularly polarized high-gain lens antenna with improved axial ratio bandwidth and gain bandwidth, the antenna comprising: a linearly polarized pyramidal horn feed and a circularly polarized lens antenna, the circularly polarized lens antenna being located at the horn mouth of the linearly polarized pyramidal horn feed, the circularly polarized lens antenna comprising a bottom plate and a lens array located on the bottom plate, the lens array being composed of a plurality of lens units, each lens unit being a rectangular long strip structure, the axial direction of the lens unit being the same as the axial direction of the linearly polarized pyramidal horn feed; each lens unit having two functions: first, adjusting the phase difference between two orthogonal polarization components by changing the width of a dielectric material so that the phase difference requirement of 90° required for circular polarization is met, and converting electromagnetic waves excited by linear polarization into circular polarization; second, being a phase shifter, compensating for the spatial propagation phase difference generated by the pyramidal horn feed, achieving a nearly uniform phase distribution within the radiation aperture, and realizing the function of improving the gain of the lens antenna.

[0006] Furthermore, the specific structure of the circularly polarized lens antenna is:

[0007] The bottom plate is divided into square grids, each lens unit is located at the center of a square grid, and the polarization angle θ of each lens unit relative to the feed direction is 45°.

[0008] Furthermore, in the entire lens array of the circularly polarized lens antenna, the lens units located at the four corners have the highest heights, and the heights of the lens units decrease from the surrounding areas to the center.

[0009] Furthermore, the lens unit fills up the entire horn mouth of the linear polarization pyramid horn feed.

[0010] Furthermore, the material of the lens unit is consistent with that of the base plate, both of which are 3-D printing material Ultem1010.

[0011] Furthermore, the relative dielectric constant of the lens material is 2.35 and the loss angle is 0.005 at a frequency of 95 GHz; the feed aperture area of ​​the linear polarization pyramid horn is 40×40 square millimeters; and the arrangement period of the lens unit is 1.85 mm.

[0012] The circularly polarized lens part used in the present invention is easy to process with the help of 3-D printing technology and is easy to integrate with the linear polarization feed. Compared with the reported dielectric circularly polarized antenna, it has a wider axial ratio bandwidth and gain bandwidth. The present invention realizes a lens antenna solution with low processing complexity, wide bandwidth and high gain in the field of millimeter wave antenna applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the three-dimensional structure of the 3-D printed circularly polarized high-gain lens antenna of the present invention.

[0014] Figure 2 It is a schematic diagram of the three-dimensional structure of the 3-D printed circularly polarized high-gain lens antenna unit of the present invention.

[0015] Figure 3 The relationship between the size of the 3-D printed circularly polarized high-gain lens antenna unit and the unit number of the present invention.

[0016] Figure 4 It is the transmission coefficient of the 3-D printed circularly polarized high-gain lens antenna unit of the present invention at 95 GHz.

[0017] Figure 5 The transmission amplitude and phase difference of TE wave and TM wave are simulated for the 3-D printed circularly polarized high-gain lens antenna unit of the present invention.

[0018] Figure 6 This is a graph showing how the simulated gain and measured gain of this antenna vary with frequency.

[0019] Figure 7 This is a graph showing the simulated axial ratio and measured axial ratio of the antenna as a function of frequency.

[0020] Figure 8 The following is a comparison of the simulated and measured normalized gain patterns of this antenna at 95 GHz. Figure 8 (a) is the XOZ plane gain pattern, Figure 8 (b) is the gain pattern of the YOZ plane. DETAILED DESCRIPTION

[0021] The schematic diagram of the three-dimensional structure of the high-gain circularly polarized antenna in this embodiment is as follows: Figure 1 , which consists of a linear polarization pyramid horn feed 101 and a circular polarization dielectric lens 102. The 3-D printed lens is fixed to the outer edge of the pyramid horn aperture by surrounding plastic screws.

[0022] The schematic diagram of the three-dimensional structure of the dielectric lens unit in this embodiment is as follows Figure 2, which consists of a medium and air mixture with an adjustable length L. It has the dual functions of a circular polarizer and a phase shifter, which can improve the gain of the antenna. Phase shifters of different lengths can provide full phase compensation for the lens antenna, while the circular polarizer can convert linear polarization waves into circular polarization waves. This lens is made of 3-D printed materials. At a frequency of 95GHz, its relative dielectric constant is 2.35 and its loss angle is 0.005. The lens unit is simulated under two pairs of orthogonal periodic boundary conditions. According to Figure 1 The phase extracted from the simulation of the independent linear polarization illumination source is shown. The phase adapter unit is placed on the illumination source aperture to produce a uniform phase distribution on the lens radiation aperture. To avoid overflow loss, all units of the lens completely cover the feed aperture. The designed feed aperture area is 40×40 square millimeters.

[0023] The relationship between the size of the lens antenna unit and the unit number in this embodiment is as follows: Figure 3 . In order to achieve a wider axial ratio bandwidth and higher gain, specific parameters are selected for the lens unit here. In this embodiment, 17 units are used, and L and w need to be adjusted according to a certain rule at the same time to meet the dual functions of circular polarizer and phase shifter. The lens is arranged on the feed aperture with a polarization angle θ=45° relative to the feed direction. The unit period p=1.85mm.

[0024] In this embodiment, the relationship between the transmission coefficient and the unit number at a frequency of 95 GHz is as follows: Figure 4 . Figure 4 The display unit covers the full transmission phase range of 360°, with a transmission amplitude greater than -1.6dB. At the same time, there is a 90° phase difference between the TE wave and the TM wave. To achieve circular polarization, the two orthogonal electrical components also need to have almost the same amplitude after passing through the unit.

[0025] In this embodiment, the transmission amplitude and phase difference of the simulated TE wave and TM wave are as follows: Figure 5 For simplicity, L is 11.8 mm (unit number 10) as a demonstration example. The simulation results show that TE waves and TM waves have almost the same amplitude. The unit arrangement of air and dielectric mixture produces anisotropy, which makes the two orthogonal electric components produce a 90° phase difference, so that the phase difference remains almost stable at different frequencies, thus meeting the requirements of circularly polarized waves.

[0026] Figure 6 The gain variation of this antenna with frequency is given. The maximum measured gain of left-hand circularly polarized radiation is 28.9dBic, and the 1dB gain bandwidth from 83GHz to 102GHz is 20.5%.

[0027] Figure 7The axial ratio performance of this antenna is given. The 3dB axial ratio bandwidth from 69GHz to 119GHz is 53.2%.

[0028] Figure 8 The simulated and measured gain patterns are shown. The measured results show that the antenna forms an effective radiation main lobe and achieves the functional requirements of high-gain circular polarization.

[0029] A 3-D printed circularly polarized high-gain lens antenna is used as an antenna component in the fields of millimeter wave satellite communications, the Internet of Things, etc. The lens unit is used as a phase shifter and a polarizer at the same time to convert linearly polarized waves into circularly polarized waves. At the same time, the lens can significantly increase the gain of the antenna. The lens structure can be manufactured using 3-D printing technology with an integrated linear polarization feed, thereby reducing the complexity of the antenna structure. The 3-D printed circularly polarized high-gain lens antenna consists of two parts, the first part is a linearly polarized pyramidal horn feed, and the second part is a circularly polarized lens antenna. The radiation structure of the 3-D printed circularly polarized high-gain lens antenna is a circularly polarized lens antenna part, which is a rectangular grid structure composed of 3-D printed dielectric materials and air arranged alternately. It has two functions. The first is similar to a dielectric polarizer. By changing the width of the dielectric material, the phase difference between the two orthogonal polarization components is adjusted to meet the 90° phase difference requirement required to achieve circular polarization, and the electromagnetic wave excited by linear polarization is converted into circular polarization; the second is a phase shifter, which compensates for the spatial propagation phase difference generated by the pyramid horn feed source, so that a nearly consistent phase distribution is achieved within the radiation aperture, thereby realizing the function of the lens antenna to increase the gain. Compared with the existing circularly polarized dielectric antenna unit, the 3-D printed circularly polarized high-gain lens antenna unit has an increased length dimension. On the basis of maintaining the 90° phase difference requirement of the two polarization components required for circular polarization, the length of the unit is adjusted to achieve a phase difference fluctuation range of 80°-100° in the 65GHz-120GHz frequency band. This fluctuation range has a small span, which helps to maintain a lower axial ratio level and cross-polarization level in the frequency band, thereby widening the 3dB axial ratio bandwidth of the antenna to 53.2%, while achieving a 1dB gain bandwidth of 20.5%.

Claims

1. A circularly polarized high-gain lens antenna with improved axial ratio bandwidth and gain bandwidth, the antenna comprising: A linear polarization pyramid horn feed and a circular polarization lens antenna, wherein the circular polarization lens antenna is located at the horn mouth of the linear polarization pyramid horn feed, and the circular polarization lens antenna comprises a bottom plate and a lens array located on the bottom plate, wherein the lens array is composed of a plurality of lens units, each lens unit is a rectangular strip structure, and the axial direction of the lens unit is the same as the axial direction of the linear polarization pyramid horn feed; each lens unit has two functions: first, by changing the width of the dielectric material, the phase difference between the two orthogonal polarization components is adjusted so that the phase difference requirement of 90° required for circular polarization is met, thereby converting the electromagnetic wave excited by linear polarization into circular polarization; The second is the phase shifter, which compensates for the spatial propagation phase difference caused by the pyramid horn feed source, achieves a nearly consistent phase distribution within the radiation aperture, and realizes the function of the lens antenna to increase the gain.

2. A circularly polarized high-gain lens antenna with improved axial ratio bandwidth and gain bandwidth as claimed in claim 1, characterized in that: The specific structure of the circularly polarized lens antenna is: The bottom plate is divided into square grids, each lens unit is located at the center of a square grid, and the polarization angle θ of each lens unit relative to the feed direction is 45°.

3. A circularly polarized high-gain lens antenna with improved axial ratio bandwidth and gain bandwidth as claimed in claim 1, characterized in that: In the entire lens array of the circularly polarized lens antenna, the lens units located at the four corners have the highest heights, and the heights of the lens units decrease from the surrounding areas to the center.

4. A circularly polarized high-gain lens antenna with improved axial ratio bandwidth and gain bandwidth as claimed in claim 1, characterized in that: The lens unit fills the entire horn mouth of the linear polarization pyramid horn feed.

5. The circularly polarized high-gain lens antenna with improved axial ratio bandwidth and gain bandwidth as claimed in claim 1, characterized in that: The relative dielectric constant of the lens material is 2.35 and the loss angle is 0.005 at a frequency of 95 GHz; the feed aperture area of ​​the linear polarization pyramid horn is 40×40 square millimeters; and the arrangement period of the lens unit is 1.85 mm.

6. A circularly polarized high-gain lens antenna with improved axial ratio bandwidth and gain bandwidth as claimed in claim 5, characterized in that: The material of the lens unit is consistent with that of the base plate, both of which are 3-D printing material Ultem1010.

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