Terahertz phased array antenna based on circularly polarized antenna elements

Abstract

The application discloses a terahertz phased array antenna based on a circularly polarized antenna unit and belongs to the technical field of radio frequency front ends. The application comprises 16 circularly polarized antenna units integrated on a coplanar waveguide, 16 MEMS four-bit distributed phase shifters and 15 Wilkinson power dividers, is fed by a signal probe, and the signal probe is divided into 16 paths through the 15 Wilkinson power dividers and connected with the circularly polarized antenna units through the MEMS four-bit distributed phase shifters. The MEMS four-bit distributed phase shifters and the circularly polarized antenna units correspond to each other. The application can be applied to various application scenarios as a small-size radio frequency device. The power dividers, phase shifters and high-performance antenna units and other devices involved in the overall structure can work in the terahertz wave band and can be individually applied to other communication systems.

Description

Technical Field

[0001] This invention relates to a terahertz phased array antenna based on circularly polarized antenna elements, which is mainly used in terahertz phased array communication systems and belongs to the field of radio frequency front-end device technology. Background Technology

[0002] In recent years, phased arrays have been widely used in fields such as radar and communication systems.

[0003] Phased arrays are implemented by combining separately manufactured components, antenna elements, phase shifters, power dividers, etc. However, this mixing of components increases the size of the antenna system. Furthermore, this technology introduces parasitic effects, connector losses, and increased packaging costs. In this regard, MEMS (Micro-Electro-Mechanical Systems) is a device miniaturization technology suitable not only for applications such as switches, phase shifters, and tunable capacitors, but also for monolithic manufacturing of the entire transceiver communication system, at a lower cost and eliminating the disadvantages of the aforementioned hybrid systems. Moreover, compared to semiconductor devices, MEMS devices have lower insertion loss and higher linearity in the terahertz band, making them more suitable for terahertz communication systems, reducing losses in the feed line and increasing the radiation gain of the phased array antenna.

[0004] To extend the scanning angle of phased array antennas, circularly polarized antennas with wide beamwidths and wide axial ratios are also very important. Using them as antenna elements of phased array antennas can effectively expand the scanning angle, achieve wide-angle scanning, and meet the requirements of circular polarization in terms of axial ratio.

[0005] A phased array antenna solution for the terahertz band is proposed, using MEMS distributed phase shifters as the phase shifting scheme and wide-beam circularly polarized antennas as antenna elements. Summary of the Invention

[0006] To achieve the solution described in the background art, this invention designs a terahertz phased array antenna based on circularly polarized antenna elements, which can meet the requirements of high radiation gain, wide scanning angle, and small size.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0008] A terahertz phased array antenna based on circularly polarized antenna elements includes 16 circularly polarized antenna elements 12, 16 MEMS four-bit distributed phase shifters 11, and 15 Wilkinson power dividers 13 integrated on a coplanar waveguide, and is fed by a signal probe 14. The signal probe 14 is divided into 16 paths by the 15 Wilkinson power dividers 13, and each path is connected to a circularly polarized antenna element 12 through a MEMS four-bit distributed phase shifter 11. Each MEMS four-bit distributed phase shifter 11 corresponds one-to-one with a circularly polarized antenna element 12.

[0009] The circularly polarized antenna element 12, MEMS four-bit distributed phase shifter 11, Wilkinson power divider 13 and signal probe 14 are all located on the upper surface of the intermediate dielectric layer 18; the lower surface of the intermediate dielectric layer 18 is a metal ground structure 17.

[0010] The circularly polarized antenna element 12 consists of a Wilkinson power divider and a square patch 28. The Wilkinson power divider includes an isolation resistor 23 and two microstrip lines 21 and 22 with a 90° phase difference. The ends of the two microstrip lines are respectively connected to one of the adjacent sides of the square patch. The Wilkinson power divider provides dual-port feeding to the square patch, and the width of the microstrip line portion near the square patch becomes narrower. The square patch 28 has fan-shaped chamfers at the two corners adjacent to the two feeding ports.

[0011] The other adjacent side of the square patch has rectangular branches, both of which are equal in length and width and are connected to the middle of the square patch side.

[0012] Furthermore, the two sector-shaped chamfers are located diagonally opposite the square patch, and the radii of the two sector-shaped chamfers are different.

[0013] Furthermore, the 16 circularly polarized antenna elements 12 are divided into two columns of 8, forming a 2×8 array antenna. The two columns of antenna elements are mirror-symmetrical. The feed points of the two columns of antenna elements are respectively connected to the corresponding MEMS four-bit distributed phase shifters 11. The distributed phase shifters combine the sixteen signals into one through 15 Wilkinson power dividers with the same electrical length, and connect to the signal probe feed port 14.

[0014] The present invention has the following advantages:

[0015] It can operate in the terahertz frequency band and be used in terahertz phased array antenna communication systems.

[0016] b is a circularly polarized antenna array that can achieve high-gain wide-angle beam scanning with high beam scanning resolution; it is a solution for realizing beam scanning phased arrays in the terahertz band.

[0017] c 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] As a small-sized radio frequency device, the d can be applied to a variety of application scenarios.

[0019] The overall structure of the device, including the power divider, phase shifter, and high-performance antenna unit, can all operate in the terahertz band and can be used independently in other communication systems. Attached Figure Description

[0020] Figure 1 This is a top view of the overall structure of an embodiment of the present invention;

[0021] Figure 2 This is a side view of the overall structure of an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the circularly polarized antenna unit structure according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the reflection coefficient S11 curve of a circularly polarized antenna element according to an embodiment of the present invention;

[0024] Figure 5 This is the radiation pattern of the circularly polarized antenna element in an embodiment of the present invention on two mutually perpendicular elevation planes at its operating frequency;

[0025] Figure 6 This is a graph showing the axial ratio of the circularly polarized antenna element at its operating frequency on two mutually perpendicular elevation planes according to an embodiment of the present invention.

[0026] Figure 7 This is an axial ratio curve of the circularly polarized antenna element at maximum gain according to an embodiment of the present invention;

[0027] Figure 8 This is the beam scanning radiation pattern of the phased array antenna at the operating frequency according to an embodiment of the present invention. Detailed Implementation

[0028] The following is in conjunction with the appendix Figure 1-8 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] The terahertz phased array antenna based on circularly polarized antenna elements includes 16 circularly polarized antenna elements, 16 MEMS four-bit distributed phase shifters, and 15 Wilkinson power dividers, which are integrated on a coplanar waveguide and fed by a signal probe. They are located on the upper surface of the intermediate dielectric layer, and the lower surface of the intermediate dielectric layer is a metallic ground structure.

[0031] Furthermore, the circularly polarized antenna element comprises a Wilkinson power divider and a square patch. The Wilkinson power divider includes two microstrip lines (21 and 22) with a 90° phase difference and an isolation resistor, providing dual-port feeding to the square patch. The width of the microstrip line narrows near the patch. The square patch has equal length and width, with circular chamfers of different radii at its two corners adjacent to the two feeding ports. Two small rectangular protrusions of equal length and width are located on the rectangular side opposite the two ports, positioned at the center of the square patch's side length.

[0032] Furthermore, the terahertz phased array antenna has 16 circularly polarized antenna elements divided into two columns of eight, forming a 2×8 array antenna. The second column of antenna elements is obtained by central symmetry from the first column. The feed points of the two columns of antenna elements are respectively connected to 16 MEMS four-bit distributed phase shifters. The distributed phase shifters are then combined into one signal by passing through 15 Wilkinson power dividers with the same electrical length, and connected to the signal probe feed port.

[0033] Furthermore, in the terahertz phased array antenna, the antenna portion is fed by a microstrip line; the distributed phase shifter, Wilkinson power divider, and feed port are integrated on a coplanar waveguide.

[0034] Reference Figures 1 to 3 In this embodiment, the phase shifter unit includes a probe feed port 14, a Wilkinson power divider 13, a MEMS four-bit distributed phase shifter 11, a circularly polarized patch antenna unit 12, an intermediate dielectric layer 18, and a bottom metal ground 17. The metal ground structure 17 is located at the bottom, with the dielectric layer 18 on top of it, and the other structures are all located on the top layer of the device.

[0035] The probe feed port 14 divides the input signal into 16 signals of equal phase and amplitude via a coplanar waveguide transmission line and 15 Wilkinson power dividers. These 16 signals are then fed into 16 MEMS distributed phase shifters. Signals with the same phase undergo phase changes as they pass through phase shifters in different states, and are then fed into 16 circularly polarized antenna elements. The phased array antenna achieves beam scanning by controlling the phase of the antenna elements.

[0036] To increase the beam scanning angle and improve the radiation gain of the phased array, a Wilkinson power divider dual-fed patch antenna is used for the circularly polarized antenna. To expand the axial ratio beamwidth and bandwidth of the antenna elements, two circular chamfers of different sizes are cut into the square patch, and rectangular stubs of equal size are added to both sides. Changing the circular chamfers, rectangular stubs, and patch size all affect the matching effect, beamwidth, axial ratio characteristics, and other performance characteristics of the antenna elements.

[0037] To reduce losses, metals with low resistivity, such as aluminum, copper, and gold, are used as the metallic materials, and materials with low losses in the terahertz frequency band, such as quartz glass, are used as the dielectric substrate 18.

[0038] The structure of the power divider, phase shifter, circular chamfering of antenna elements, rectangular stubs, patch size, and other parameters have a significant impact on the beam scanning angle, scanning resolution, radiation gain, and axial ratio characteristics of a phased array antenna. Specifically:

[0039] a) The structural dimensions of the Wilkinson power divider 13 directly affect line loss. Optimizing it to a suitable size can significantly improve the radiation gain of the phased array.

[0040] b) The structural design of the MEMS distributed phase shifter 11 affects the feed phase step of the antenna element, which in turn affects the scanning resolution of the phased array antenna. This patent uses a four-bit distributed phase shifter, which can achieve 16 states with a phase shift step of 22.5°.

[0041] c) The size of the antenna element patch 12 affects the antenna operating frequency. The longer the side length of the square patch, the lower the operating frequency.

[0042] d) The dimensions of the two circular chamfers 24 and 26 of antenna element 12 affect the axial ratio characteristics. After optimization, a wide axial ratio bandwidth and a wide axial ratio beamwidth can be achieved.

[0043] e) The dimensions of the two rectangular stubs 25 and 27 of antenna element 12 affect the matching effect. After optimization, a wide impedance bandwidth can be achieved.

[0044] Therefore, selecting the appropriate antenna element size and designing a MEMS distributed phase shifter are of great significance for improving the performance of the phased array antenna. At the same time, different requirements correspond to different structures.

[0045] This terahertz phased array antenna is illustrated using one of the following size combinations; the data below are in micrometers:

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

[0047] Structure 15 = 19120, Structure 16 = 10230;

[0048] when Figure 3 The dimensions of the structure are:

[0049] Structure 24 = 10, Structure 25 = 30, Structure 26 = 65, Structure 27 = 20, Structure 28 = 524;

[0050] The dielectric layer 18 has a thickness of 50, and the metal layer has a thickness of 1.

[0051] The operating center frequency of the phase shifter is 140 GHz.

[0052] The simulated S11 curve of the antenna element at this time is as follows:

[0053] Figure 4 The image shows the S11 curve of the circularly polarized antenna element, indicating that the return loss S11 of the antenna is less than -16dB in the frequency range of 130-150GHz.

[0054] At this point, the radiation patterns of the circularly polarized antenna element in the two vertical elevation planes are as follows:

[0055] Figure 5 The image shows the radiation patterns of the antenna at azimuth angles of 0° and 90°. It shows that the maximum gain at the operating frequency reaches 5dB, the half-power beamwidth exceeds 90°, the right-hand circular polarization gain is about 24dB higher than the left-hand circular polarization gain, and the front-to-back ratio reaches 23dB.

[0056] At this point, the axial ratio curves of the circularly polarized antenna element on the two vertical elevation planes are:

[0057] Figure 6 The image shows the axial ratio characteristics of the antenna on two elevation planes at azimuth angles of 0° and 90°. It can be seen that at the operating frequency, the 3dB axial ratio beamwidth on both elevation planes exceeds 180°.

[0058] Figure 7 The display shows its axial ratio frequency curve at maximum gain. It can be seen that the axial ratio of this antenna is less than 3dB at maximum gain from 135GHz to 150GHz.

[0059] At this time, the beam scanning gain pattern of the phased array antenna is:

[0060] Figure 8 The beam scanning pattern of the phased array antenna at the operating frequency is shown. It is found that by changing the phase shifter state, beam scanning from -45° to +45° can be achieved; and the maximum gain relative to the energy input of each antenna element exceeds 13dB, with the maximum gain of the middle beam exceeding 15dB.

[0061] The above is just one example. To obtain phased array 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 terahertz phased array antenna based on circularly polarized antenna elements, characterized in that, The system includes 16 circularly polarized antenna elements (12), 16 MEMS four-bit distributed phase shifters (11), and 15 Wilkinson power dividers (13) integrated on a coplanar waveguide, all fed by a signal probe (14). The signal probe (14) is divided into 16 paths by the 15 Wilkinson power dividers (13), each connected to a circularly polarized antenna element (12) via a MEMS four-bit distributed phase shifter (11). Each MEMS four-bit distributed phase shifter (11) corresponds one-to-one with a circularly polarized antenna element (12). The circularly polarized antenna unit (12), MEMS four-bit distributed phase shifter (11), Wilkinson power divider (13) and signal probe (14) are all located on the upper surface of the intermediate dielectric layer (18); the lower surface of the intermediate dielectric layer (18) is a metallic ground structure (17); The circularly polarized antenna unit (12) consists of a Wilkinson power divider and a square patch (28). The Wilkinson power divider includes an isolation resistor (23) and two microstrip lines (21 and 22) with a phase difference of 90°. The ends of the two microstrip lines are respectively connected to one of the adjacent sides of the square patch. The Wilkinson power divider provides dual-port feeding to the square patch, and the width of the microstrip line portion near the square patch becomes narrower. The square patch (28) has fan-shaped chamfers at the two corners adjacent to the two feeding ports. The other adjacent side of the square patch has rectangular branches, both of which are equal in length and width and are connected to the middle of the square patch side.

2. The terahertz phased array antenna based on circularly polarized antenna elements according to claim 1, characterized in that, The two sector-shaped chamfers are located at opposite corners of the square patch, and the radii of the two sector-shaped chamfers are different.

3. The terahertz phased array antenna based on circularly polarized antenna elements according to claim 1, characterized in that, Sixteen circularly polarized antenna elements (12) are divided into two columns of eight, forming a 2×8 array antenna. The two columns of antenna elements are mirror symmetrical. The feed points of the two columns of antenna elements are connected to the corresponding MEMS four-bit distributed phase shifters (11). The distributed phase shifters combine the sixteen signals into one through 15 Wilkinson power dividers with the same electrical length and connect to the signal probe feed port (14).

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