Four-azimuth wave beam reconfigurable antenna with center feed

Abstract

The invention discloses a center feed four-azimuth wave beam reconfigurable antenna, and belongs to the field of radio frequency front-end devices. The antenna is composed of a straight arm, a crank arm, a central square patch, a capacitor loading ring, a shunt feeder line and a composite beam RF MEMS switch loaded at a fracture on the shunt feeder line, the structures are in central symmetry about a feeding point and respectively cover a 90-degree space range, and the feeding structure is connected with the center of a top patch through a microstrip feeder switching metal column. When the MEMS switch on a certain branch feeder line is switched on, current fed in from the center firstly flows to the straight crank arm radiation unit at the near end of the closed switch through the branch and then flows to the radiation unit at the far end, phase lag of the current at the far end is equivalent to superposition of a binary array, deflected wave beams are generated, the deflection angle can reach 50 degrees, the gain is 4.9 dB, and the wave beam width can reach 120 degrees. The structural design in central symmetry can realize the reconfigurability of wave beams in four directions in a space quadrant.

Description

Technical Field

[0001] This invention relates to a center-fed four-directional beam reconfigurable antenna, which is mainly used in millimeter-wave communication in the terahertz band and belongs to the field of radio frequency front-end devices. Background Technology

[0002] The working principle of a reconfigurable antenna is based on the ability to reconfigure the antenna's radiating elements or feed path using radio frequency devices such as PIN diodes, varactor diodes, and RF MEMS switches, thereby exciting different radiation modes and switching the antenna's beam pointing. Reconfigurable antennas offer advantages such as flexibility, efficiency, and adaptability, reducing hardware overhead. With proper antenna design, they can achieve good matching and radiation characteristics within a specific frequency band, and are widely used in millimeter-wave communication fields such as wireless communication, satellite communication, the Internet of Things, and radar.

[0003] Currently, most conventional pattern-reconfigurable antennas are used in low-frequency bands below 10 GHz or in satellite communication bands such as Ku / Ka. In millimeter-wave bands above 100 GHz, the complexity of high-frequency design and the difficulty of manufacturing processes make mass production difficult. Common pattern-reconfigurable antennas typically use PIN diodes as RF switches, but in the terahertz band at 300 GHz and above, these devices have high losses, which severely degrades the antenna's radiation performance. Furthermore, the feed network is usually quite complex, requiring multi-layer board structures to accommodate power distribution and impedance matching networks, which increases the overall size of the antenna and makes it difficult to apply to the reconfigurable requirements of future terahertz communication scenarios.

[0004] In the future application prospects of IoT communication, relay nodes often serve as important hubs for forwarding data communication and need to meet the requirements of multi-directional communication. However, due to the small size of the nodes and the limited pre-stored energy, reconfigurable technology is needed to control the beam direction, maximize the directionality of antenna radiation, and reduce energy loss in non-communication directions. However, there is currently very little research on beam-reconfigurable antennas in the terahertz band, and the beam switching is not flexible enough, with small coverage, low gain, and large sidelobes, which cannot meet the requirements of flexible beam switching in future terahertz communication. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention designs a center-fed, four-directional beam reconfigurable antenna that can meet the beam switching requirements of the four quadrants in the 300GHz terahertz band. This antenna features a low element profile, a simple feeding method, low manufacturing difficulty, and is easy to fabricate and test. Its composite beam RF MEMS switch has a moderate DC bias voltage, high mechanical strength and stability, high isolation in the off state, and low insertion loss in the on state. Therefore, this antenna has the characteristics of large beam deflection angle, high gain, good matching, and flexible switching, and can completely cover the scanning spatial range of the four quadrants.

[0006] To achieve the above effects, the present invention is implemented through the following technical solution: A center-fed four-directional beam reconfigurable antenna includes a radiating layer, an upper dielectric layer, and a metal ground backplane stacked from top to bottom; the radiating layer includes radiating elements, a central square patch, branch feed lines, and a feeding metal post; The central square patch is located on the upper surface of the upper dielectric layer; a circular cutout is provided in the center of the central square patch; the top of the power supply metal pillar penetrates the metal ground backplate and the upper dielectric layer and is located in the first circular cutout, and there is a first annular gap between it and the central square patch, which serves as a capacitor loading ring. The radiating unit has a ring structure; the central square patch is located inside the area enclosed by the radiating unit, and the centers of the two coincide; the central square patch is connected to the radiating unit through a branch feeder; there are four branch feeders, one end of which is connected to the central square patch and the other end is connected to the radiating unit; Each branch feeder is equipped with a break point, and a composite beam RF MEMS switch is installed at the break point.

[0007] Furthermore, the radiating unit includes straight arms and curved arms; the straight arms are provided with four straight arms, each parallel to the edge of the central square patch; one end of the branch feeder is connected to the corner of the central square patch, and the other end is connected to two mutually symmetrical curved arms to form a forked structure; the adjacent ends of the two straight arms are respectively connected to the two curved arms that form the forked structure.

[0008] Furthermore, this also includes microstrip feeders; The lower surface of the metal backplane is also provided with a lower dielectric layer; the microstrip feed line is located on the lower surface of the lower dielectric layer and extends from the center of the lower dielectric layer to the edge of the lower dielectric layer; the inner end of the microstrip feed line is provided with a second circular cutout, and the outer end serves as a power supply port; The power supply metal pillar penetrates the upper dielectric layer, the metal ground backplane, and the lower dielectric layer; the bottom end of the power supply metal pillar is located in the second circular cutout, and there is a second annular gap between it and the microstrip feed line, which serves as a capacitor loading ring.

[0009] Furthermore, the composite beam RF MEMS switch includes a pier, a metal beam, and electrodes; The system has two electrodes, which are located on both sides of the branch feeder. It also has two piers, which are located on the outside of the corresponding electrodes. The top of the two piers is equipped with a metal beam, and a silicon dioxide beam is set in the middle of the metal beam. The bottom of the silicon dioxide beam is equipped with a contact point. The contact point is located directly above the break and is used to realize the connection and disconnection of the branch feeder. A silicon nitride thin film is provided on the top of the electrode.

[0010] The present invention has the following advantages over the prior art: a) Terahertz band radiation loss is low and efficiency is high. A composite beam RF MEMS switch is used as an RF device loaded onto the antenna's branch feed line. When the switch is open on the microwave transmission line, S21 < -20dB, indicating high isolation. When it is on, S21 > -0.56dB, indicating low terahertz loss. The switch can be effectively controlled by DC bias, resulting in good microwave transmission characteristics and high antenna radiation efficiency.

[0011] b) Flexible beam switching: a single antenna can selectively cover any of the four quadrants of space. Four identical RF switches are mounted on the feed lines of the planar quadrant coordinate axes. Closing any switch will cause the antenna beam to point in the opposite direction of that switch. The beam can be dynamically switched as the switches are turned on and off. The switches located on the axis can control the beam to point in the +X, +Y, -X, and -Y directions. The centrally symmetrical structure of the antenna ensures that the beam is the same in any state except for the direction, exhibiting good consistency and complete coverage of the four quadrants of space.

[0012] c) Large beam deflection angle, wide beam, and good antenna matching. When any composite beam RFMEMS switch mounted on the branch feed line is closed, the beam points in the opposite direction to that switch. The radiation gain is 4.9dB, the beam tilt angle is 50°, the half-power beamwidth in the tilt direction is 122° with very small sidelobes, and the beam deflection in all four directions is centrally symmetrical. The conductor metal pillar located at the center is connected to the microstrip feed line, and the inductance introduced by it is canceled out by a capacitor loop, thus improving antenna matching. The input impedance reactance component is approximately 0, and the antenna resonates at 300GHz.

[0013] d) Low profile, small size, and easy manufacturing. 1µm gold is etched on a quartz glass substrate as the radiating unit and feeding network. The metal ground plane is a single layer of gold, and the dielectric layer is 100µm thick. Single-layer board processing is easier to achieve, does not involve substrate via technology, and gold deposition can be achieved through surface processing. The feeding structure is simple and can be rapidly printed. Attached Figure Description

[0014] Figure 1This is a top view schematic diagram of the complete structure of a center-fed four-directional beam reconfigurable antenna. Figure 2 This is a top view of a composite beam RF MEMS switch structure; Figure 3 yes Figure 1 A stacked side view; Figure 4 yes Figure 1 Schematic diagram of the underlying microstrip feeder; Figure 5 yes Figure 2 The front view; Figure 6 This is the S21 curve of the microwave transmission characteristics of the composite beam RF MEMS switch; Figure 7 It is a gain curve of the antenna when the beam is deflected in any direction; Figure 8 It is the planar radiation pattern of the antenna beam deflection; Figure 9 This is the input impedance curve when the antenna beam deflection is working; Figure 10 This is the impedance matching S11 curve of the antenna; Figure 11 This is the Smith chart showing the impedance matching of the antenna. Figure 12 This describes the surface current density distribution of the antenna at time T / 6. Figure 13 This describes the surface current density distribution of the antenna at time T / 3. Detailed Implementation

[0015] The present invention will be further described below with reference to embodiments, which are intended only to provide a better understanding of the invention. Therefore, the specific embodiments described do not limit the scope of protection of the present invention. In addition, the accompanying drawings only show the parts related to the present invention and not the entire structure.

[0016] This embodiment of a center-fed four-directional beam reconfigurable antenna comprises a straight arm 1 of a radiating element, a curved arm 2 of a radiating element, a central square patch 3, a capacitor loading ring, a branch feed line 5, and a composite beam RFMEMS switch 6 loaded at the break point. The above structure is symmetrical about the center of the feed point, each covering a 90° spatial range. The branch feed line 5 is connected to the four corners of the central square patch 3 and is located on the upper surface of the upper dielectric layer 7. The metal ground backplate 11 is located on the lower surface of the upper dielectric layer 7.

[0017] Specific reference Figures 1 to 5There are four straight arms 1, which are parallel to the sides of the central square patch 3. One end of the branch feeder 5 is connected to the corner of the central square patch 3, and the other end is connected to two symmetrical curved arms 2 to form a forked structure. The adjacent ends of the two straight arms 1 are respectively connected to the two curved arms 2 that form the forked structure.

[0018] The microstrip feed line 13 has the same capacitor loading ring, which is connected to the center of the central square patch 3 through the feed metal pillar 12; The microstrip feed line 13 is located on the lower surface of the lower dielectric layer 14 and extends from the center of the lower dielectric layer 14 to the edge of the lower dielectric layer 14. The microstrip feed line 13 has the same capacitor loading ring (formed by the second annular gap 16). One end is connected to the capacitor loading ring at the center of the central square patch 3 through the feed metal pillar 12, and the other end serves as the feed port 15. The feed metal pillar 12 penetrates the upper dielectric layer 7, the metal ground backplane 11 and the lower dielectric layer 7. The composite beam RF MEMS switch 6 includes a silicon dioxide beam 17, a pier 18, a metal beam 19, a through hole 20 on the beam, an electrode 21, a contact 22, and a silicon nitride film 23.

[0019] Two electrodes 21 are provided, and the two electrodes 21 are respectively located on both sides of the branch feeder 5; two piers 18 are provided, and the two piers 18 are respectively located on the outside of the corresponding electrodes 21; a metal beam 19 is provided on the top of the two piers 18, and a silicon dioxide beam 17 is provided in the middle of the metal beam 19; a contact 22 is provided at the bottom of the silicon dioxide beam 17; the contact 22 is located directly above the break and is used to realize the connection and disconnection of the branch feeder 5. A silicon nitride film 23 is provided on the top of the electrode 21; two sets of metal beams 19 are provided; the adjacent ends of the two metal beams 19 are connected by silicon dioxide beams 17, and the contact 22 is in close contact with the lower surface of the silicon dioxide beams 17; the other end of the metal beam 19 is connected to the corresponding pier 18, and the electrode 21 is located directly below the corresponding metal beam 19 and there is a gap greater than zero between them.

[0020] by Figure 1Taking a center-fed four-directional beam reconfigurable antenna as an example, its working principle is illustrated. A high-isolation, low-loss composite beam RF MEMS switch 6 is mounted at the break point of the branch feeder 5. The selection of the branch feeder 5 is controlled by the on / off state of the composite beam RF MEMS switch 6. Specifically, a DC current is applied to the electrode 21 of the composite beam RF MEMS switch 6. As the voltage increases, the electrostatic force gradually increases, attracting the metal beam 19 to bend downwards, and the distance between the electrode and the metal beam 19 gradually decreases. When the DC bias voltage reaches the pull-in voltage of the near-state, the contact 22 bonded by the silicon dioxide beam 17 contacts the branch feeder 5, and the branch feeder 5 is turned on. The design of the composite beam RF MEMS switch 6 achieves isolation between the contact 22 and the metal beam 19, reducing the range of RF signal flow through the switch structure and greatly reducing the insertion loss of the RF switch. Compared with the traditional pure metal beam switch, the loss can be reduced by 1-2dB. When the composite beam RF MEMS switch 6 needs to be turned off, the bias voltage is gradually reduced, the electrostatic force decreases, and because an insulating silicon nitride film 23 above electrode 21 separates the metal beam 19 and electrode 21, the metal beam 19 can easily spring back, the contact 22 disengages from the branch feeder 5, and the switch opens. The composite beam form ensures its structural strength and stability, and the symmetrical design of the fixed beam ensures stable processing and testing. Figure 6 This is the microwave transmission characteristic S21 curve of the composite beam RF MEMS switch 6. Near the 300GHz operating frequency, S21 is -0.565dB when on, indicating low insertion loss. When off, S21 is -21.02dB, showing high isolation. Therefore, the composite beam RF MEMS switch 6 has good RF characteristics and can be used in the terahertz band near the 300GHz operating frequency.

[0021] After the switch is engaged, the branch feed line 5 is turned on. The current fed from the microstrip feed line 13 to the feeding metal pillar 12 into the central square patch 3 will quickly flow through the turned-on branch feed line 5 to the curved arms 2 on both sides, further exciting the current mode on the straight arms 1. Since the composite beam MEMS switches 6 on the other three branch feed lines 5 are open, and the isolation of the composite beam MEMS switches 6 is high, the current on the central square patch 3 cannot quickly flow to the open branches of these three composite beam MEMS switches 6. When the current flows to the four straight arms 1 through the closed branches, it first flows through the two straight arms 1 near the closed composite beam MEMS switches 6, and then flows to the two straight arms 1 far from the closed ones. The phase difference generated between them achieves the superposition effect of array element radiation, producing a tilted and deflected beam. See Appendix Figure 1 Taking the closure of the composite beam MEMS switch 6 in the +Y direction as an example, see attached... Figure 12This describes the surface current density distribution of the antenna at time T / 12. Current is initially induced in the two straight arms 1 near the closed composite beam MEMS switch 6. At time T / 6, the current flows to the two straight arms 1 at the far end, where the current density is stronger, as shown in the attached diagram. Figure 13 As shown. The conduction of the near-end composite beam MEMS switch 6 will cause a phase difference between the near-end and far-end straight arms 1. The far-end phase lags, and the beam points towards the far end of the closed composite beam MEMS switch 6.

[0022] The antenna's feeding structure employs a microstrip feed line 13 to a feeding metal post 12. The feeding metal post 12 is fed into the center of the top central square patch 3 to ensure the central symmetry of the current flow. The direction of the shunt current is controlled by the on / off switching of the composite beam RF MEMS switch 6, ensuring the implementation of the antenna's radiation beam deflection principle. The feeding metal post 12 penetrates the upper dielectric layer 7 and the lower dielectric layer 14, introducing a large inductive component. The antenna's inductive reactance is relatively large and difficult to match. To address this, identical capacitor loading loops are introduced at both ends of the feeding metal post 12 to cancel out the inductive component. By optimizing the radius and spacing of the capacitor loading loops and adjusting the loading capacitance value, the antenna's input impedance is adjusted to a pure resistance near the operating frequency, with the reactance component approximately zero, thus achieving antenna resonance matching.

[0023] The lower surface of the upper dielectric layer 7 is printed with a 1-micron-thick metal backplane 11. Without the metal backplane 11, the antenna would radiate to the back lobe, resulting in significant energy leakage. The metal backplane 11 is used to reflect the beam, directing it towards the space in the upper half-plane. Typically, to reduce losses, the antenna's metal material uses metals with low resistivity, such as aluminum, copper, or gold, while the dielectric substrate often uses low-loss materials, such as high-resistivity silicon or Rogers 5880. In this example, considering the high frequency of the terahertz antenna, conventional processes would result in significant antenna losses. Therefore, a glass substrate process is used to fully utilize its low-loss dielectric characteristics, improving antenna performance. The surface photolithography process offers high precision, enabling the patterning of precision components such as switches. The metal material is gold, and the dielectric substrate of the dielectric layer is quartz glass with a dielectric constant of 3.78 and a loss tangent of 0.0008.

[0024] The structure of this center-fed, four-directional beam reconfigurable antenna is illustrated here using one of the following size combinations (the data below are in micrometers): Figure 1 The dimensions of the structure are: The side length of the central square patch 3 is 80; the spacing of the first annular gap 4, which serves as the capacitor loading ring, is 4; the length × width of the branch feed line 5 is 94 × 8; the length × width of the straight arm 1 of the radiating unit is 80 × 20; the width of the curved arm 2 of the radiating unit gradually changes from 8 to 20, and the central angle is 90°; the side length of the upper dielectric layer 7 is 520. Figure 2The dimensions of the structure are: The length × width of pier 18 is 30 × 10, and the diameter of the through hole 20 on the beam is 6. Figure 3 The dimensions of the structure are: The upper dielectric layer 7 has a thickness of 100, the metal back floor 11 has a thickness of 1, the lower dielectric layer 14 has a thickness of 100, and the feed metal pillar 12 has a radius of 20. Figure 4 The dimensions of the structure are: The side length of the lower dielectric layer 14 is 520; the length × width of the microstrip feed line 13 is 290 × 60. Figure 5 The dimensions of the structure are: The height of the pier 18 of the composite beam MEMS switch 6 is 1.2, the height of the metal beam 19 is 0.5, the height of the silicon dioxide beam 17 is 1, the height of the contact 22 is 0.7, and the thickness of the silicon nitride film 23 is 0.1. When powered by a 50-ohm lumped-port, the center frequency is 300 GHz, which falls within the terahertz band.

[0025] The simulation diagram of the reflection coefficient of the center-fed four-directional beam reconfigurable antenna based on RF MEMS technology is as follows: Figure 10 The image shows the reflection coefficient curve of the antenna, indicating that the S11 of this antenna element is significantly less than -10dB in the frequency range of 290GHz-315GHz. Figure 9 The figure shows the input impedance curve of the antenna. At the operating frequency of 300 GHz, the reactance component is approximately 0, the real impedance is 60 ohms, and the tuning is good. Figure 11 The image shows the Smith chart of the antenna. The chart shrinks well at the center matching point, and the reflection coefficient changes little near the operating frequency band.

[0026] At this time, the antenna's beam deflection gain pattern is as follows: Figure 7 The image shows the radiation gain of the antenna at the center frequency. At this frequency, the antenna element gain is 4.95 dB, the beam tilt angle is 50°, and the half-power beamwidth reaches 120°. This antenna features a wide beam and a large tilt angle, and the beam tilt angle can be reconfigured in four directions. When any of the composite beam MEMS switches 6 is closed, due to the central symmetry of the structural design, the beam tilt angle can be flipped in any direction without changing the gain and matching. Figure 8 The image shows a two-dimensional planar radiation pattern of beam deflection, with a large main lobe beam tilt angle and very small side lobes, exhibiting good radiation characteristics.

[0027] This antenna unit operates in the terahertz band and can achieve pattern reconfiguration. It has a wide beam and excellent tilt angle, and its structural design is simple. It has flexible beam control and can achieve 360° equally divided four-directional coverage scanning. It is easy to manufacture and implement.

[0028] The above is just one example. To obtain a center-fed four-directional beam reconfigurable antenna with different center frequencies, different parameters can be adjusted according to the specific implementation method to achieve different operating frequency bands and guiding effects.

[0029] This invention is not limited to the above embodiments. Without departing from the concept of this invention, it may include more other equivalent embodiments, and the scope of this invention is determined by the scope of the appended claims.

Claims

1. A center-fed four-directional beam reconfigurable antenna, comprising, from top to bottom, a radiating layer, an upper dielectric layer (7), and a metallic ground backplate (11); characterized in that, The radiation layer includes a radiation unit, a central square patch (3), a branch feed line (5), and a power supply metal pillar (12). The central square patch (3) is located on the upper surface of the upper dielectric layer (7); the central square patch (3) has a first circular cutout at its center; the top of the power supply metal pillar (12) penetrates the metal ground backplate (11) and the upper dielectric layer (7) and is located in the first circular cutout, and there is a first annular gap (4) between it and the central square patch (3) as a capacitor loading ring. The radiation unit is a ring structure; the central square patch (3) is located inside the area enclosed by the radiation unit, and the centers of the two coincide; the central square patch (3) is connected to the radiation unit through the branch feed line (5); the branch feed line (5) is provided with four lines, one end of the branch feed line (5) is connected to the central square patch (3), and the other end is connected to the radiation unit; Each branch feeder (5) is provided with a break, and a composite beam RF MEMS switch (6) is provided at the break.

2. The center-fed four-directional beam reconfigurable antenna according to claim 1, characterized in that, The radiation unit includes straight arms (1) and curved arms (2); the straight arms (1) are provided with four straight arms (1), which are parallel to the sides of the central square patch (3); one end of the branch feed line (5) is connected to the corner of the central square patch (3), and the other end is connected to two mutually symmetrical curved arms (2) to form a forked structure; the adjacent ends of the two straight arms (1) are respectively connected to the two curved arms (2) that form the forked structure.

3. The center-fed four-directional beam reconfigurable antenna according to claim 1, characterized in that, It also includes microstrip feeders (13); The lower surface of the metal backplate (11) is also provided with a lower dielectric layer (14); the microstrip feed line (13) is located on the lower surface of the lower dielectric layer (14) and extends from the center of the lower dielectric layer (14) to the edge of the lower dielectric layer (14); the inner end of the microstrip feed line (13) is provided with a second circular cutout, and the outer end serves as a power supply port (15). The power supply metal column (12) penetrates the upper dielectric layer (7), the metal ground backplate (11) and the lower dielectric layer (14); the bottom end of the power supply metal column (12) is located in the second circular cutout, and there is a second annular gap (16) between it and the microstrip feed line (13) as a capacitor loading ring.

4. A center-fed four-directional beam reconfigurable antenna according to claim 1, characterized in that, The composite beam RF MEMS switch (6) includes a pier (18), a metal beam (19), and an electrode (21). Two electrodes (21) are provided, and the two electrodes (21) are located on both sides of the branch feeder (5); two bridge piers (18) are provided, and the two bridge piers (18) are located on the outside of the corresponding electrodes (21); a metal beam (19) is provided on the top of the two bridge piers (18), and a silicon dioxide beam (17) is provided in the middle of the metal beam (19); a contact (22) is provided at the bottom of the silicon dioxide beam (17); the contact (22) is located directly above the break and is used to realize the connection and disconnection of the branch feeder (5); A silicon nitride thin film (23) is provided on the top of the electrode (21).

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