A pattern reconfigurable antenna switched by MEMS switch

Abstract

This invention discloses a pattern-reconfigurable antenna with feed switching via MEMS switches, belonging to the field of radio frequency (RF) front-end devices. The pattern-reconfigurable antenna comprises a microstrip radiating element, a parasitic guiding element, a composite beam ohmic contact MEMS switch, a 1-to-4 feed network, a DC bias line, test patch pads, a coplanar waveguide, a tapered microstrip line, a dielectric substrate, and a metal ground plane. Two stages of MEMS switches are mounted on the 1-to-4 feed network. When both stages of switches on a feed line are turned on, RF current can flow through that feed line to the corresponding basic radiating element, generating a tilted beam oriented towards that quadrant. Simultaneously turning on the four switches on the front side enables the two basic radiating elements on the front side, generating a tilted beam in the positive direction on the front side. The antenna adopts a single-layer board design, eliminating the need for perforations on the dielectric substrate, resulting in a simple structure and convenient manufacturing. The MEMS switches used have low loss and high isolation, and the surface etching process allows for rapid printing manufacturing.

Description

Technical Field

[0001] This invention relates to a pattern-reconfigurable antenna with a power supply that can be switched via a MEMS switch. It 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] Pattern reconfigurable antennas are a new type of antenna technology that has been widely used in radio frequency communication systems that require control of beam pointing switching. Compared with phased array antennas, they have a simpler structural design, do not require a large number of antenna elements for arraying, and do not require the design of complex array feeding networks. They are often used to achieve low-continuity beam pointing switching and can achieve more efficient electromagnetic wave transmission and reception performance as radio frequency front-end devices.

[0003] 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 in flexibility, efficiency, and adaptability, reducing hardware overhead. Through proper antenna design, they can achieve good matching and radiation characteristics within specific frequency bands, and are expected to be widely used in millimeter-wave communication fields such as wireless communication, satellite communication, the Internet of Things, and radar in the future.

[0004] 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. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention designs a pattern-reconfigurable antenna with a switching feed via a MEMS switch, which can meet the requirement of pattern reconfiguration in the 300GHz terahertz band. The designed antenna element has a low profile, uses a single-layer quartz glass dielectric substrate, and is connected to the radiating element via a 1-to-4 feed network, making it easy to fabricate and test. The designed 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. The pattern-reconfigurable antenna based on this MEMS switch features a large beam deflection angle, high gain, wide beamwidth, and good matching.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] A pattern-reconfigurable antenna with feed switching via MEMS switches includes a dielectric substrate and a metal ground backplane 15; the metal ground backplane is located on the lower surface of the dielectric substrate; the upper surface of the dielectric substrate is provided with a microstrip radiating element, a coplanar waveguide, a 1-to-4 feed network, and a gradient microstrip line.

[0008] The feed port of the coplanar waveguide is connected through a tapered microstrip line and a 1-to-4 feed network; each end of the 1-to-4 feed network is connected to a microstrip radiating unit, and the four microstrip radiating units are arranged in a rectangular array; each microstrip radiating unit has a parasitic attraction unit on one side.

[0009] Composite beam ohmic contact MEMS switches are installed on both the second and fourth branches of the one-to-four feeder network.

[0010] Furthermore, each branch connection of the one-to-four feeder network is provided with a transition gradient structure; the transition gradient structure is provided with a break corresponding to the composite beam ohmic contact MEMS switch.

[0011] Furthermore, the composite beam ohmic contact MEMS switch includes a silicon dioxide beam, a bridge pier, a metal beam, electrodes, and contacts;

[0012] The metal beams, piers, and electrodes are all provided in two sets; the two piers are located on both sides of the fracture, and the adjacent ends of the two metal beams are connected by a silicon dioxide beam, with the contact point close to the lower surface of the silicon dioxide beam; the other end of the metal beam is connected to the corresponding pier, and the electrode is located directly below the corresponding metal beam with a gap greater than zero between them.

[0013] Furthermore, it also includes test patch pads, and the electrodes and piers of the composite beam ohmic contact MEMS switch are connected to the test patch pads via DC bias lines.

[0014] Furthermore, the piers of the two-branch composite beam ohmic contact MEMS switch and the two piers of one of the four-branch composite beam ohmic contact MEMS switches are connected to the same test patch pad.

[0015] The electrodes of each composite beam ohmic contact MEMS switch are connected to the corresponding test patch pads.

[0016] Furthermore, each branch of the one-to-four feeder network is equipped with a patch bridge (23) for the DC bias line to pass through.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] a) Terahertz band radiation loss is low and efficiency is high. An RF MEMS switch with a composite beam structure is used as an RF device loaded onto a 1-to-4 feed network. 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.

[0019] b) Large beam deflection angle, high gain, and wide bandwidth. When the RF switch controls the on / off state of any feeder line, the beam can be directed towards the conducting radiating element. During beam deflection, the radiation gain is 5.87 dB, the beam tilt is 33°, and symmetrical beam deflection can be achieved in all four quadrants. With coplanar waveguide feeding, the relative bandwidth is 22.16%, the operating frequency is 300 GHz, and the matching is good.

[0020] c) Low profile, simple structure, and easy manufacturing. 1µm gold is etched on the quartz glass substrate as the radiating element and feed network. The reflective backplate is a single layer of gold with a dielectric thickness of 100µm. Single-layer board processing is easier to achieve, does not involve substrate via technology, and the gold layer can be achieved through surface processing. The antenna element is simple and can be rapidly printed. Attached Figure Description

[0021] Figure 1 This is a top-view schematic diagram of the complete structure of a reconfigurable antenna whose feed pattern is switched via a MEMS switch.

[0022] Figure 2 This is a top view of the RF MEMS switch structure loaded on the power supply network;

[0023] Figure 3 This is a side view of the structure of an RF MEMS switch;

[0024] Figure 4 This is a front view of the structure of an RF MEMS switch;

[0025] Figure 5This is the S21 curve of the microwave transmission characteristics of an RF MEMS switch;

[0026] Figure 6 It is a beam deflection gain curve of the antenna radiating element;

[0027] Figure 7 This is a curve showing the beam deflection when a single patch of the antenna is selected;

[0028] Figure 8 This is a diagram showing the beam deflection curve when the antenna is selected by dual patches on the front side.

[0029] Figure 9 This is the overall impedance matching S11 curve of the antenna; Detailed Implementation

[0030] 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.

[0031] A pattern-reconfigurable antenna with feed switching via MEMS switches comprises a microstrip radiating element 1, a parasitic guiding element 2, a composite beam ohmic contact MEMS switch 3-8, a 1-to-4 feed network 9, a DC bias line 10, a test patch pad 11, a coplanar waveguide 12, a tapered microstrip line 13, a dielectric substrate 14, and a metal ground plane 15. Its distinguishing feature is that it further includes MEMS switch piers 16, a metal beam 17, a silicon dioxide beam 18, contacts 19, electrodes 20, a silicon nitride insulating layer 21, through holes 22 on the beams, and patch bridging 23.

[0032] The microstrip radiating unit 1 and the parasitic guiding unit 2 are identical in shape and symmetrically positioned. They are connected to a coplanar waveguide via a 1-to-4 feed network. The six MEMS switches are identical in structure and symmetrically positioned, all located at the connection points of the feed network, and feature a gradient design. The gradient structure includes a narrow segment, a gradient segment, and a wide segment connected in sequence; the MEMS switches are located at the break in the narrow segment.

[0033] All feed networks are impedance-matched and can be probe-fed to the coplanar waveguide feed ports using RF probes. The coplanar waveguide 12 has a symmetrical structure with identical spacing, and its feed ports are connected to a 1-to-4 feed network via a tapered microstrip line 13.

[0034] With attachment Figure 1 Taking a reconfigurable antenna with a feed pattern that can be switched by a MEMS switch as an example, it consists of a microstrip radiating element 1, a parasitic guiding element 2, a composite beam ohmic contact MEMS switch 3-8, a 1-to-4 feed network 9, a DC bias line 10, a test patch pad 11, a coplanar waveguide 12, a tapered microstrip line 13, a dielectric substrate 14, and a metal ground backplane 15, and is probe-fed through the port.

[0035] The microstrip radiating element, serving as the antenna body, is directly connected to the feed line. The resonant point can be fine-tuned by adjusting the patch size. A parasitic element on one side of the antenna is excited by a parallel current via a coupled feed. Its length is slightly shorter than the microstrip radiating element, exhibiting capacitive behavior. The current phase of the parasitic element lags behind the current phase on the microstrip radiating patch, acting as a director. The directing effect is amplified by secondary and tertiary directing elements, increasing the beam tilt angle and achieving optimized adjustability. The beam tilt effect of a single radiating element is shown in [reference needed]. Figure 6 .

[0036] The basic principle behind this reconfigurable design is the use of MEMS switches mounted on a 1-to-4 feed network to achieve feed switching. The switches operate in two stages. After the RF signal is fed from the coplanar waveguide port, it passes through a microstrip line tapered matching structure and is transmitted to the first-stage 1-to-2 T-shaped feed structure. The left and right sides are each controlled by two switches in the first stage. The signal passes through one path to reach the second-stage T-shaped feed structure and ultimately to the microstrip radiating patch on the conducting side. The MEMS switches mounted at the T-junctions feature low loss and high isolation, ensuring that energy flows to the intended radiating patch as designed, radiating a beam-deflected radiation pattern in this quadrant. The reconfigurable radiation pattern is achieved based on the principle of switching the feed via RF switches. This antenna can achieve beam deflection in all four quadrants. The beam deflection in a given direction when a switch selects a particular radiating patch is shown in the diagram. Figure 7 Furthermore, when both secondary switches on the upper side are turned on, and the left and right primary switches are also turned on, that is, when both radiating patches on the upper side are simultaneously selected, the antenna radiation pattern tilts forward, and the beam offset is shown in [the diagram]. Figure 8 .

[0037] Appendix Figure 2 The demonstrated RF MEMS switch is a fixed-beam composite material switch, composed of metal beam layers and silica beam layers. The composite beams ensure structural strength and stability, while the symmetrical design of the fixed-beam structure ensures stable processing and testing. The DC bias uses TaN material to lay high-resistance lines, which are bridged at the patch and connected to the electrodes before being led out. A total of six gold pads are designed to provide the electrode drive voltage, and four gold pads are used to ground the switch piers. The specific operation of the switch is as follows:

[0038] As the applied voltage to the PAD electrode is gradually increased, reaching the drive voltage value, the electrostatic force generated by the electrode attracts the upper metal beam to bend downwards. When the voltage is further increased to the pull-in voltage, the deformation reaches its maximum value, the contact and signal line make contact, and the switch is turned on. Adjusting the bias voltage to gradually decrease the electrostatic force, and because an insulating silicon nitride film above the electrode separates the metal beam and the electrode, the metal beam can easily spring back, the contact disengages from the signal line, and the switch is turned off.

[0039] The coplanar waveguide feed structure uses a gradient gap to achieve excellent matching with the gradient microstrip line. The slope of the left and right waistlines of the trapezoidal feed line is consistent. The matching bandwidth can be optimized by optimizing the length of the bottom edge and the bottom angle of the trapezoidal feed line, as well as the linewidth and the length of the connecting part of the microstrip feed line, and the return loss and gain of the antenna element can be adjusted.

[0040] A 1-micron-thick metal ground plane is printed on the lower surface of the dielectric substrate. Without this ground plane, the antenna would radiate to the back lobe, resulting in significant energy leakage. The metal ground plane is used to reflect the beam, directing it towards the upper half-plane. To reduce losses, all metal materials used in the structure are low-resistivity metals, such as aluminum, copper, and gold. The dielectric substrate 10 uses a low-loss material, such as high-resistivity silicon or Rogers 5880. In this example, the metal material is gold, the dielectric substrate is quartz glass with a dielectric constant of 3.78, and a loss tangent of 0.0008.

[0041] The structure of this MEMS-switched, reconfigurable antenna with a feed pattern is illustrated here using one of the following size combinations (the data below are in micrometers):

[0042] when Figure 1 The dimensions of the structure are:

[0043] Microstrip radiating unit 1, length × width = 310 × 200; parasitic leading unit 2, length × width = 200 × 140; parasitic leading unit 2, rectangular defect, length × width = 184 × 40; 1-to-4 feed network 9, wide line section, length × width = 170 × 20; 1-to-4 feed network 9, narrow line section, length × width = 20 × 10; DC bias line 10, width = 5; test patch pad 11, gold PAD size = 100 × 100; structure 12, overall length × width = 620 × 400; coplanar waveguide 12, short side length = 100; tapered microstrip line 13, short side dimension = 20, long side dimension = 70, line length = 1046; patch bridging 23, bridging height = 1.5, bridge thickness = 0.5.

[0044] when Figure 2 The dimensions of the structure are:

[0045] Structure 16 has a length × width of 30 × 10, and structure 22 has a diameter of 6.

[0046] when Figure 3 The dimensions of the structure are:

[0047] Pier 16: Pier height = 1.2; Metal beam 17: Metal beam height = 0.5; Silica beam 18: Silica beam height = 1; Contact point 19: Height = 0.7.

[0048] when Figure 4 The dimensions of the structure are:

[0049] The dielectric substrate 14 has a thickness of 100 μm, the metal ground backplate 15 has a thickness of 1 μm, the metal beam 17 has a size of 50 × 50, the silicon dioxide beam 18 has a length × width of 120 × 50, the contact 19 has a length × width of 50 × 8, the electrode 20 has a length × width of 50 × 25, and the silicon nitride film 21 has a thickness of 0.1 μm.

[0050] When fed by a coplanar waveguide, the center frequency is 300 GHz, which belongs to the terahertz band.

[0051] The simulation diagram of the reflection coefficient of the reconfigurable antenna with a feed pattern switched by a MEMS switch is as follows:

[0052] Figure 9 The image shows the reflection coefficient curve of the antenna, indicating that the S11 of the antenna element is less than -10dB in the frequency range of 280GHz-346.5GHz, with a relative bandwidth of 22.16%, and the antenna has a wide impedance bandwidth.

[0053] At this time, the antenna's beam deflection gain pattern is as follows:

[0054] Figure 7 The image shows the overall radiation gain of the antenna at the center frequency. At this time, two sets of MEMS switches on a certain feed line are in the conducting state, showing that the antenna element gain is 5.87dB and the beam tilt angle is 33°. The antenna has high gain and the beam tilt direction can be symmetrically adjusted in four quadrants, enabling pattern reconfiguration.

[0055] Figure 8 The image shows the overall radiation gain of the antenna at the center frequency. At this time, four MEMS switches (3, 5, 6, and 7) are in the on state, that is, the feed lines of the front dual-radiating patch are selected. The image shows that the antenna element gain is 8.55dB and the forward beam tilt angle is -26.4°. However, since both the left and right patches are connected to the power supply, the beam tilt angles to the left and right are both 0, so the antenna still has a high gain.

[0056] Figure 6 The image shows the radiation gain of the antenna's basic radiating element (microstrip patch and guide element) at the center frequency. It indicates that the gain of the basic radiating element is 7.35 dB and the beam tilt angle is 40°. This element exhibits high gain and good beam tilt capability.

[0057] This antenna unit operates in the terahertz band and can achieve pattern reconfiguration. It has high gain and a simple structure, consisting of only a single-layer plate with a low profile. The coplanar waveguide feeding method has good impedance matching bandwidth and is easy to fabricate.

[0058] The above is just one example. If you want to obtain a reconfigurable antenna with a feed pattern switched by a MEMS switch at different center frequencies, you can adjust different parameters according to the specific implementation method to achieve different operating frequency bands and guiding effects.

Claims

1. A pattern-reconfigurable antenna with feed switching via MEMS switches, comprising a dielectric substrate (14) and a metal ground backplane (15); the metal ground backplane is located on the lower surface of the dielectric substrate; characterized in that, The upper surface of the dielectric substrate is provided with a microstrip radiating unit (1), a coplanar waveguide (12), a one-to-four feed network (9), and a gradient microstrip line (13). The feed port of the coplanar waveguide is connected to a tapered microstrip line (13) and a 1-to-4 feed network; each end of the 1-to-4 feed network is connected to a microstrip radiating unit (1), and the four microstrip radiating units are arranged in a rectangular array; each microstrip radiating unit has a parasitic attraction unit (2) on one side. The one-to-four power supply network is equipped with composite beam ohmic contact MEMS switches on both the second and fourth branches; the composite beam ohmic contact MEMS switches include silicon dioxide beams, bridge piers, metal beams, electrodes, and contacts; The metal beams, piers, and electrodes are all provided in two sets; the two piers are located on both sides of the fracture, and the adjacent ends of the two metal beams are connected by a silicon dioxide beam, with the contact point close to the lower surface of the silicon dioxide beam; the other end of the metal beam is connected to the corresponding pier, and the electrode is located directly below the corresponding metal beam with a gap greater than zero between them.

2. The reconfigurable antenna with a feed pattern that can be switched via a MEMS switch according to claim 1, characterized in that, Each branch connection of the 1-to-4 feeder network is provided with a transition gradient structure; the transition gradient structure is provided with a break corresponding to the composite beam ohmic contact MEMS switch.

3. The reconfigurable antenna with a feed pattern that switches via a MEMS switch according to claim 1, characterized in that, It also includes test patch pads, and the electrodes and piers of the composite beam ohmic contact MEMS switch are connected to the test patch pads via DC bias lines.

4. A pattern-reconfigurable antenna with feed switching via a MEMS switch according to claim 3, characterized in that, The piers of the two-branch composite beam ohmic contact MEMS switch and the two piers of one of the four-branch composite beam ohmic contact MEMS switches are connected to the same test patch pad. The electrodes of each composite beam ohmic contact MEMS switch are connected to the corresponding test patch pads.

5. A pattern-reconfigurable antenna with feed switching via a MEMS switch according to claim 4, characterized in that, Each branch of the one-to-four feeder network is equipped with a patch bridge (23) for DC bias lines to pass through.

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