A circularly polarized antenna with a terahertz wide axial ratio beam

Abstract

The application discloses a circularly polarized antenna of a terahertz wide axial ratio beam, and belongs to the technical field of radio frequency front-end devices. The antenna is stacked in the following order from the bottom layer to the top layer: a feed network layer, a second dielectric layer, a metal slot layer sandwiched between the first dielectric layer and the second dielectric layer, a first dielectric layer, and an antenna metal layer located at the top layer. The first dielectric layer and the second dielectric layer are two quartz glass substrates with different thicknesses. The metal slot layer in the middle is etched with cross-shaped slots with gradually changing widths. The feed network is composed of an input port, a microstrip transmission line, a first-stage power divider, a second-stage power divider, an M-type microstrip line, and a hook-shaped impedance matching structure. Four-port feeding is realized through the feed network, and there is a 90-degree phase difference between the feeding points. The M-type microstrip line applied in the feed network also expands the axial ratio beam width of the antenna. The application has the characteristics of simple structure, convenient design, wide axial ratio beam, large radiation range, and application to a terahertz system.

Description

Technical Field

[0001] This invention relates to a circularly polarized antenna with a wide axial ratio beam in terahertz, which is mainly used in terahertz satellite communication systems and belongs to the field of radio frequency front-end device technology. Background Technology

[0002] With the increasing prevalence of wireless devices, data traffic has entered a new period of rapid development. Currently, many applications are gradually migrating from computers to wireless devices such as mobile phones, which are convenient for real-time portability and operation. However, this has also led to a rapid increase in data traffic and a shortage of bandwidth resources. Statistics show that data rates in the market are likely to reach Gbps or even Tbps in the next 10 to 15 years. Therefore, to improve data transmission rates, a feasible solution is to develop a new frequency band: terahertz electromagnetic waves. Terahertz antennas, as the radio frequency front-end of communication systems, have also received widespread attention from researchers. Circularly polarized antennas, due to their low attenuation in rain and snow, strong ionospheric penetration capability, and immunity to the Faraday effect generated by the Earth's magnetic fields at the poles, can be applied in terahertz satellite communications. The beamwidth of a circularly polarized antenna with an axial ratio of less than 3dB, together with its half-power beamwidth, determines its beam range and also determines the beam scanning performance of the phased array when it is used as an antenna element. Recent research on wide-beam antennas has yielded numerous results, but these primarily focus on expanding the half-power beamwidth. Research on the axial ratio beamwidth performance of circularly polarized antennas is relatively limited, with most antennas exhibiting a narrow axial ratio beamwidth. For instance, Yang Cheng et al.'s 2021 paper published in IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS proposed a wide-bandwidth, wide-beam circularly polarized antenna, but it lacked a wide axial ratio beamwidth. Similarly, Chao Shu et al.'s 2022 paper published in IEEE TRANSACTIONSON ANTENNAS AND PROPAGATION proposed a wide-bandwidth, well-isolated, and high-gain dual-circularly polarized antenna, but it also did not discuss the axial ratio beamwidth issue.

[0003] Due to the drawback of most wide-beam antenna elements having a narrower circular polarization axis ratio and beamwidth, it is currently difficult to meet the requirements for phased array antennas and various radio frequency communication equipment applications. Summary of the Invention

[0004] To address the problems existing in the background technology, this invention designs a wide-axis-ratio circularly polarized antenna in the terahertz band, which can meet the requirements of wide-axis-ratio beam and wide half-power beam. The designed circularly polarized antenna achieves the characteristics of simple structure, convenient design, large beamwidth, and wide operating bandwidth.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] A terahertz wide-axis ratio beam circularly polarized antenna includes a feed network, a first dielectric layer, a second dielectric layer, a metal slot layer, and an antenna metal layer; the stacking order of the antenna from bottom to top is: feed network layer, second dielectric layer, metal slot layer sandwiched between the first dielectric layer and the second dielectric layer, first dielectric layer, and antenna metal layer located on top.

[0007] The antenna metal layer is a square patch of gold with the same length and width, located in the middle of the top layer of the antenna.

[0008] Furthermore, the first dielectric layer and the second dielectric layer are two quartz glass substrates with different thicknesses.

[0009] Furthermore, the power supply network comprises an input port, a microstrip transmission line, a first-stage power divider, a second-stage power divider, an M-shaped microstrip line, and a hook-shaped impedance matching structure. The input port is connected to the input terminal of the first-stage power divider via a microstrip transmission line. The two output terminals of the first-stage power divider are respectively connected to the input terminals of the two second-stage power dividers via microstrip transmission lines. The output terminals of the second-stage power dividers are connected to four hook-shaped matching structures via microstrip transmission lines, with an M-shaped microstrip line structure positioned between one of the output terminals and the hook-shaped matching structure.

[0010] Furthermore, the hook-shaped matching structure consists of three metal microstrip transmission lines of different widths, with their ends connected at 90 degrees to each other. The connection points are cut with chamfers, and four hook-shaped matching knots are located at the center of the bottom layer, each of which can be obtained by rotating the other.

[0011] Furthermore, the power divider is a Wilkinson power divider consisting of microstrip lines and isolation resistors, which is a 1-to-2 splitter.

[0012] Furthermore, a cross-shaped slit is etched on the intermediate metal slit layer, and the width of the cross slit in the middle is greater than the width at the end. The width of the slit gradually decreases from the center of the cross to the end of the cross, and the cross is located at the center of the metal layer.

[0013] The four-port feeding method, with a 90-degree phase difference between the feed points, is achieved through a feeding network. The combination of four-port feeding and cross-slot coupling feeding increases the axial beamwidth of the circularly polarized antenna. The M-type microstrip line used in the feeding network also extends the axial beamwidth of the antenna.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] a) It can operate in the terahertz frequency band and be used in terahertz communication systems.

[0016] b) As a circularly polarized antenna, it has a large operating bandwidth and a large beamwidth, and at the same time has a wide beam with an axial ratio of ≤3dB and a regular radiation pattern.

[0017] c) It has a simple structure and is easy to manufacture. As a terahertz radio frequency device, it meets the process manufacturing requirements and can be applied.

[0018] d) As a low-profile antenna element, it can be applied to a variety of application scenarios. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the antenna metal layer structure according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the metal gap layer structure according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the power supply network layer structure according to an embodiment of the present invention;

[0022] Figure 4 This is a structural side view of an embodiment of the present invention;

[0023] Figure 5 This is a reflection coefficient S11 curve diagram of an embodiment of the present invention;

[0024] Figure 6 This is a radiation pattern according to an embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the axial ratio beam in two azimuth planes at 325GHz according to an embodiment of the present invention;

[0026] Figure 8 This is a schematic diagram of the axial ratio beam at a frequency near 325GHz in an embodiment of the present invention;

[0027] Figure 9 This is a schematic diagram of the axial ratio bandwidth in the direction of maximum radiation according to an embodiment of the present invention; Detailed Implementation

[0028] The following is in conjunction with the appendix Figure 1-9 The embodiments and examples will further illustrate specific implementations of the present invention in detail.

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Reference Figures 1 to 4This embodiment includes a feed network 15, a first dielectric layer 12, a second dielectric layer 14, a metal slot layer 13, and an antenna metal layer 11. The antenna is stacked in the following order from bottom to top: feed network layer 15, second dielectric layer 14, metal slot layer 13 sandwiched between the first dielectric layer and the second dielectric layer, first dielectric layer 12, and antenna metal layer 11 located on the top layer. The antenna is fed through a microstrip feed port 16.

[0031] Appendix Figure 1 The antenna metal layer 11 is a square patch of gold with the same length and width, located in the middle of the top layer of the antenna. Changing the side length 21 of this square metal patch will change the antenna operating frequency; the larger the patch, the lower the operating frequency.

[0032] Appendix Figure 2 The intermediate metal slot layer 13 has cross-shaped slots etched on it, with the width of the slot in the middle being greater than that at the ends. The slot width gradually decreases from the center of the cross to the ends, and the cross is located at the center of the metal layer. The side length 31 of the cross slot affects the antenna's operating frequency; the longer the side length, the lower the operating frequency. The cross slots serve as a coupling feed. The bottom feed network 15 distributes one signal into four signals with a 90-degree phase progression via a power divider. The four branches of the cross slots correspond to the four output feed points 54, 55, 56, and 57 (i.e., hook-shaped structures on the feed network) of the feed network, located above the feed points, coupling electromagnetic waves to the top-layer square patch 11. The gradually changing slot width affects the antenna's coupling feed effect; changing the gradually changing width 32 and 33 of the slots within a certain range improves the antenna's impedance matching effect, and also improves the axial ratio performance due to the increased radiation efficiency of the four feed points.

[0033] Appendix Figure 3 The feed network 15 consists of an input port, a microstrip transmission line, a first-stage power divider, a second-stage power divider, an M-shaped microstrip line, and hook-shaped impedance matching structures. The input port 16 is connected to the input of the first-stage power divider 51 via a microstrip transmission line. The two outputs of the first-stage power divider are connected to the inputs of the two second-stage power dividers 52 and 53 via microstrip transmission lines. The outputs of the second-stage power dividers 52 and 53 are connected to four hook-shaped matching structures 54, 55, 56, and 57 via microstrip transmission lines. One of the outputs is connected to hook-shaped matching structure 54 via an M-shaped microstrip line structure 48. Each hook-shaped matching structure should be 90 degrees electrical length apart from the microstrip transmission line at the signal input port 16, resulting in a 90-degree phase progression for the input signal at the upper cross-shaped slot 13. With a fixed electrical length, a well-planned microstrip line transmission path reduces coupling effects between different feed points and increases the axial ratio beamwidth; that is, optimizing the feed network distribution optimizes the axial ratio beamwidth characteristics.

[0034] The hook-shaped matching structure consists of three metal microstrip transmission lines 43, 44, and 45 with different widths. Their ends are connected at 90-degree angles to each other, with chamfered corners at the connection points. Four hook-shaped matching junctions are located at the center of the bottom layer, and each can be obtained by rotating the other. Changing the length and width of the microstrip transmission lines 43, 44, and 45 affects the coupling efficiency with the upper metal gap 13; optimizing the length and width of the microstrip transmission lines 43, 44, and 45 reduces reflected signals and optimizes radiation efficiency.

[0035] The power dividers 51, 52, and 53 are Wilkinson power dividers consisting of microstrip lines and isolation resistors, which are divided into two by one.

[0036] Appendix Figure 4 The first dielectric layer 12 and the second dielectric layer 14 are two quartz glass substrates with different thicknesses.

[0037] To reduce losses, metals with low resistivity, such as aluminum, copper, and gold, are used as the metallic materials, and the dielectric substrates 12 and 14 are made of materials with low losses in the terahertz frequency band, such as quartz glass.

[0038] The patch size, metal slot structure size, and feed network structure have a significant impact on the antenna's operating bandwidth and axial ratio beamwidth, specifically as follows:

[0039] a) Changing the side length 21 of the square metal piece 11 will change the antenna operating frequency. The larger the piece, the lower the operating frequency.

[0040] b) The side length 31 of the cross-shaped slot 13 will affect the antenna operating frequency. The longer the side length, the lower the operating frequency.

[0041] c) Changing the gradient width 32 and 33 of the slot 13 within a certain range will improve the impedance matching effect of the antenna. At the same time, due to the increased radiation efficiency of the four feed points, the axial ratio performance will also be improved.

[0042] d) Optimizing the distribution of the feed network 15 will optimize the axial ratio beamwidth characteristics;

[0043] e) Optimizing the length and width of microstrip transmission lines 43, 44, and 45 will reduce reflected signals and optimize radiation efficiency;

[0044] Therefore, selecting appropriate patch size, metal slot structure size and feed network structure is of great significance for improving the performance of circularly polarized antennas. At the same time, different requirements correspond to different structures.

[0045] This terahertz wide-axis-ratio beamwidth circularly polarized antenna is illustrated here using one of the following size combinations (the data below are in micrometers):

[0046] when Figure 1The dimensions of the structure are:

[0047] Structure 21 = 142, Structure 22 = 700

[0048] when Figure 2 The dimensions of the structure are:

[0049] Structure 31 = 190, Structure 32 = 20, Structure 33 = 17;

[0050] when Figure 3 The dimensions of the structure are:

[0051] Structure 41 = 95.5, Structure 42 = 45, Structure 43 = 55, Structure 44 = 45, Structure 45 = 164, Structure 46 = 64, Structure 47 = 124.5, Structure 48 = 121, Structure 49 = 78;

[0052] The first dielectric layer 12 has a thickness of 50, the metal layer has a thickness of 1, and the second dielectric layer 14 has a thickness of 30.

[0053] The antenna's center frequency is 325 GHz.

[0054] The simulation diagram of the reflection coefficient of the circularly polarized antenna at this time is as follows:

[0055] Figure 5 The image shows the reflection coefficient curve of the wide-axis ratio circularly polarized antenna, indicating that the S11 is significantly less than -10dB in the frequency range of 317-364GHz and significantly less than -15dB in the frequency range of 321-355GHz.

[0056] The simulated radiation pattern of the antenna at this time is:

[0057] Figure 6 The image shows the gain patterns of the wide-axis ratio circularly polarized antenna in the E and H planes at the center frequency, indicating that its half-power beamwidth exceeds 90 degrees and its shape is normal.

[0058] The simulated axial ratio diagram of the antenna at this time is as follows:

[0059] Figure 7 The image shows a schematic diagram of the axial ratio beam of the wide axial ratio circularly polarized antenna in two azimuth planes at the operating frequency. It shows that the beam width is greater than 120 degrees in both the E-plane and H-plane when the axial ratio is less than 3dB.

[0060] Figure 8 The image shows a schematic diagram of the axial ratio beam of the wide axial ratio circularly polarized antenna at seven frequencies near its operation. It shows that in the 0-degree azimuth plane, the beamwidth of the beam with an axial ratio of less than 3dB is greater than 200 degrees.

[0061] Figure 9The diagram shows the axial ratio bandwidth of this wide-axis ratio circularly polarized antenna in the direction of maximum radiation, indicating that its axial ratio is less than 3dB in the direction of maximum gain from 312GHz to 340GHz.

[0062] The above is just one example. To obtain wide-axis ratio circularly polarized antennas with different center frequencies, different parameters can be adjusted according to the specific implementation method and applied to different communication systems.

Claims

1. A circularly polarized antenna with a terahertz wide-axis ratio beam, characterized in that: The layers stacked from bottom to top are: feed network layer, second dielectric layer, metal slot layer, first dielectric layer and antenna metal layer. The antenna metal layer includes a square patch of equal length and width, located at the center of the upper surface of the first dielectric layer; Both the first dielectric layer and the second dielectric layer are quartz glass substrates, and they have different thicknesses. The main body of the metal gap layer is a thin metal plate. A cross-shaped gap is etched in the center of the thin metal plate. The width of the gap in the middle is greater than the width at the end. The gap width gradually narrows from the center of the gap to the end of the gap. The power supply network layer consists of an input port, a microstrip transmission line, a first-stage power divider, a second-stage power divider, an M-shaped microstrip line, and a hook-shaped impedance matching structure. The input port is connected to the input terminal of the first-stage power divider via a microstrip transmission line. The two output terminals of the first-stage power divider are respectively connected to the input terminals of the two second-stage power dividers via microstrip transmission lines. The output terminals of the second-stage power dividers are connected to four hook-shaped matching structures via microstrip transmission lines. One of the output terminals of one of the second-stage power dividers is connected to the hook-shaped matching structure through the M-shaped microstrip line. The hook-shaped matching structure consists of three sequentially connected metal microstrip transmission lines. Adjacent metal microstrip lines are perpendicular to each other and have chamfered corners on the outside of the connection points. The four hook-shaped matching structures surround the center of the bottom layer and are rotationally symmetrical. Both the first-stage power divider and the second-stage power divider are Wilkinson power dividers consisting of microstrip lines and isolation resistors, which are divided into two stages.

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