Monopole pattern reconfigurable antenna based on RF MEMS switch control

Abstract

The present invention discloses a monopole pattern reconfigurable antenna based on RF MEMS switch control, belonging to the field of RF front-end devices. The antenna comprises a monopole radiating element, parasitic elements located on its left and right sides, a composite beam ohmic contact MEMS switch, a DC bias line, a test patch pad, a coplanar waveguide, a gradient microstrip line, a dielectric substrate, and a metal ground backplane. When the MEMS switch on the parasitic element is on, the parasitic element is slightly shorter than the monopole radiating element and acts as a director. When the MEMS switch is off, the primary director element is split into two at the break, its length being much shorter than the monopole radiating element, and the terminal is open, generating backflow, which offsets the effect of the secondary director element. When one switch is pulled down, the radiation pattern undergoes beam deflection toward the side of the closed switch, with an adjustable deflection angle of up to 41°, a gain of up to 6.14dB, and a beam width of approximately 90°. When both switches are off, the beam deflection is 0°, the radiation pattern points toward the positive Z axis, and the gain is 5.15dB.

Description

Technical Field

[0001] The present invention relates to a monopole pattern reconfigurable antenna based on RF MEMS switch control, which is mainly used in millimeter wave communications in the terahertz frequency band and belongs to the field of radio frequency front-end devices. Background Art

[0002] The reconfigurable pattern antenna is 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, it has a simpler structural design, does not require a large number of antenna units to form an array, and does not require the design of a complex array feed network. It is often used to achieve low-continuity beam pointing switching. As an RF front-end device, it can achieve more efficient electromagnetic wave transmission and reception performance.

[0003] The operating principle of pattern-reconfigurable antennas is based on the reconfiguration of antenna radiating elements or feed paths through RF devices such as PIN diodes, varactor diodes, and RF MEMS switches, stimulating different radiation patterns and thus switching the antenna's beam direction. Reconfigurable antennas offer the advantages of flexibility, efficiency, and adaptability, reducing hardware overhead. Through appropriate antenna design, they can achieve excellent matching and radiation characteristics within specific frequency bands. They hold promise for widespread application in millimeter-wave communications, including wireless communications, satellite communications, the Internet of Things, and radar.

[0004] Currently, conventional reconfigurable antennas are mostly used in low-frequency bands below 10 GHz or in satellite communication bands such as Ku / Ka. Large-scale production in millimeter-wave bands above 100 GHz is generally difficult due to the complexity of high-frequency design and difficult processing techniques. Common reconfigurable antennas typically use PIN diodes as RF switches. However, in the terahertz band of 300 GHz and above, these devices have high losses, which can severely degrade the antenna's radiation performance. Furthermore, the feed network is typically complex, requiring a multi-layer board structure to support power distribution and impedance matching. This also increases the overall size of the antenna, making it difficult to apply to the reconfigurable scenarios required for future terahertz communications. Summary of the Invention

[0005] In order to solve the problems existing in the background technology, the present invention designs a monopole pattern reconfigurable antenna based on RF MEMS switch control, which can meet the demand for realizing pattern reconfiguration in the 300GHz terahertz band. The designed antenna unit has a low cross-section and uses a single-layer quartz glass dielectric plate as a substrate. The feeding method is simple, the process difficulty is low, and it is easy to process and test. The designed composite beam RF MEMS switch has a moderate DC bias voltage, high mechanical strength and stability, high isolation in the disconnected state, and low insertion loss in the on state. The designed monopole pattern reconfigurable antenna based on this MEMS switch has the characteristics of large beam deflection angle, high gain, wide beam, and good matching.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] A monopole pattern reconfigurable antenna based on RF MEMS switch control, comprising a dielectric substrate 10 and a metal ground backplane 11; the metal ground backplane is located on the lower surface of the dielectric substrate, and further comprises a monopole radiating element 1, a parasitic element, a coplanar waveguide 8, and a gradient microstrip line 9;

[0008] The coplanar waveguide 8 is bilaterally symmetrical, and its feeding port 20 is connected to the monopole radiating unit 1 through a gradient microstrip line 9;

[0009] There are two parasitic units, one on the left and one on the right of the monopole radiation unit; each parasitic unit is a ring structure with a break, and a composite beam ohmic contact MEMS switch is provided at the break position;

[0010] The electrodes of the composite beam ohmic contact MEMS switch are connected to the test patch pads located on the upper surface of the dielectric substrate through a DC bias line.

[0011] Furthermore, the break positions of the two parasitic units are symmetrical with respect to the monopole radiation unit.

[0012] Furthermore, the composite beam ohmic contact MEMS switch includes a silicon dioxide beam 14, a bridge pier 12, a metal beam 13, an electrode 16 and a contact 15;

[0013] The metal beams, bridge piers, and electrodes are each provided in two groups; the adjacent ends of the two metal beams are connected by a silicon dioxide beam, with the contacts closely attached to the lower surface of the silicon dioxide beam; the other ends of the metal beams are connected to the corresponding bridge piers, and the electrodes are located directly below the corresponding metal beams with a spacing greater than zero between them;

[0014] There are three test patch pads, namely a left pad, a middle pad and a right pad;

[0015] The bridge pier of the composite beam ohmic contact MEMS switch, the electrode of one composite beam ohmic contact MEMS switch, and the electrode of the other composite beam ohmic contact MEMS switch correspond to and are connected to the three test patch pads respectively.

[0016] Furthermore, a silicon nitride insulating layer 17 is provided on the upper surface of the electrode.

[0017] Furthermore, the DC bias line is a high-resistance line made of TaN material, and a bridge is formed at the contact position between the DC bias line and the parasitic unit.

[0018] Compared with the background technology, the present invention has the following advantages:

[0019] a) Low radiation loss and high efficiency in the terahertz band. An RF MEMS switch with a composite beam structure is used as a radio frequency device and loaded onto the antenna's parasitic element. When disconnected on the microwave transmission line, the switch exhibits an S21 <-20dB, providing high isolation. When on, the switch exhibits an S21 >-0.56dB, exhibiting low terahertz losses. The switch can be effectively controlled on and off via a DC bias, resulting in excellent microwave transmission characteristics and high antenna radiation efficiency.

[0020] b) Large beam deflection angle, high gain, and wide bandwidth. When the RF switch turns on or off the parasitic element on either side, the beam can be steered toward the side where the switch is closed. When beam deflected, the radiation gain is 6.14dB, the beam tilt is 35°, the half-power beamwidth is 88.2°, and the left and right beam deflections are symmetrical. When fed by a coplanar waveguide, the relative bandwidth is 17%, and the operating frequency is 300 GHz, providing excellent matching.

[0021] c) Low profile, small size, and easy manufacturing. A quartz glass substrate is etched with 1µm gold as the radiation unit and feed network. The reflective backplane is a complete layer of gold. The dielectric thickness is 100µm. Single-layer board processing is easier to achieve, without involving substrate through-hole processes. The gold layer can be achieved through surface processing. The feed structure is simple and can be quickly printed and manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a top-down diagram of the complete structure of the monopole pattern reconfigurable antenna based on RF MEMS switch control;

[0023] Figure 2 Schematic diagram of the top view of the RF MEMS switch structure loaded on the parasitic unit;

[0024] Figure 3 yes Figure 1 A side view of the structure;

[0025] Figure 4 yes Figure 2 A front view of the structure;

[0026] Figure 5 This is the S21 curve of the microwave transmission characteristics of the RF MEMS switch;

[0027] Figure 6 It is the gain curve of the antenna when the beam is deflected;

[0028] Figure 7 It is the gain curve when the antenna beam is not deflected;

[0029] Figure 8 It is the impedance matching S11 curve of the antenna; DETAILED DESCRIPTION

[0030] The following is combined with Figure 1-8 The specific embodiments of the present invention are further described in detail with reference to the accompanying drawings and examples.

[0031] The monopole pattern reconfigurable antenna based on RF MEMS switch control comprises a monopole radiating element 1, parasitic elements 2 and 3 located on its left and right sides, composite beam ohmic contact MEMS switches 4 and 5, a DC bias line 6, a test patch pad 7, a coplanar waveguide 8, a gradient microstrip line 9, a dielectric substrate 10, and a metal ground backplane 11. The antenna is characterized by further comprising a MEMS switch pier 12, a metal beam 13, a silicon dioxide beam 14, a contact 15, an electrode 16, a silicon nitride insulating layer 17, a beam through hole 18, and a patch bridge 19.

[0032] The two parasitic patches of the unit have the same shape, symmetrical position, and the same size of fracture design. The two MEMS switches have the same structure and symmetrical position, both located at the corresponding fracture of the parasitic patches, and the patch bridge position of the parasitic unit is the same.

[0033] The feeding network is designed with impedance matching, and an RF probe can be used to probe the coplanar waveguide feeding port 20. The coplanar waveguide 8 has a bilaterally symmetrical structure with the same gap. The feeding port is connected to the monopole radiating element 1 via a gradient microstrip line 9.

[0034] Attach Figure 1 Taking the monopole pattern reconfigurable antenna based on RF MEMS switch control as an example, it consists of a monopole radiating unit 1, parasitic units 2 and 3 located on the left and right sides of the monopole, composite beam ohmic contact MEMS switches 4 and 5, a DC bias line 6, a test patch pad 7, a coplanar waveguide 8, a gradient microstrip line 9, and is probe-fed by port 20.

[0035] The monopole radiating element, serving as the antenna body, is directly connected to the feeder, and the resonant point can be fine-tuned by adjusting the patch size. Parasitic elements on either side are excited by the coupled feed from the monopole patch to generate parallel currents. When the switch is closed, the primary steering element is slightly shorter than the monopole patch, exhibiting capacitive behavior. The current phase of the parasitic element lags behind the current phase of the monopole patch. The monopole on this side acts as a director, and the secondary steering element amplifies the steering effect, increasing the beam tilt angle and achieving optimized adjustability. When the switch is open, the primary steering element, thanks to the high isolation performance of the MEMS switch, is unable to conduct the coupled current smoothly and is split in two at the break design. Its electrical length is much smaller than that of the monopole patch, preventing it from achieving the desired steering effect. The open terminal generates reverse current, weakening and offsetting the steering effect of the secondary steering element, causing the directivity pattern to point towards the side where the switch is closed. This principle enables reconfigurable directivity.

[0036] Attachment Figure 2 The RF MEMS switch on display is a composite switch with a clamped beam, consisting of metal and silicon dioxide beam layers. The composite beam ensures structural strength and stability, and the symmetrical design of the clamped beam ensures stable processing and testing. The DC bias is constructed using TaN material to lay a high-resistance line, which is connected to the electrode through a bridge at the patch and then led out. Two gold pads are designed to provide the electrode drive voltage, and one gold pad is used to ground the switch bridge. The specific operation of the switch is as follows:

[0037] By gradually increasing the applied voltage to the PAD electrode, until the drive voltage is reached, the electrostatic force generated by the electrode pulls the upper metal beam downward, causing it to bend. When the voltage is further increased to the pull-in voltage, the deformation reaches its maximum value, the contact and the signal line make contact, and the switch turns on. By gradually decreasing the bias voltage, the electrostatic force decreases. Because an insulating silicon nitride film above the electrode separates the metal beam from the electrode, the metal beam easily rebounds, the contact detaches from the signal line, and the switch turns off.

[0038] The coplanar waveguide feed structure uses a tapered gap to achieve excellent matching with the tapered microstrip line. The slope of the left and right waistlines of the trapezoidal feed line is consistent. By optimizing the base length and bottom angle of the trapezoidal feed line, as well as the width and length of the microstrip feed line, the matching bandwidth can be optimized and the return loss and gain of the antenna unit can be adjusted. The rectangular defect in the coplanar waveguide is used to adjust the impedance matching of the antenna. The length and width of the defect ground can be optimized, and the resonance point offset can be adjusted without affecting the radiation pattern to optimize the impedance bandwidth.

[0039] A 1-micron-thick metal ground is printed on the bottom surface of the dielectric substrate. Without the metal ground, the antenna would radiate toward the back lobe, resulting in significant energy leakage. The metal ground reflects the beam and directs it toward the upper half plane. To minimize losses, all structural metals are constructed with low-resistivity metals, such as aluminum, copper, and gold. The dielectric substrate 10 is constructed from low-loss materials, such as high-resistance silicon or Rogers 5880. In this example, the metal is gold, and the dielectric substrate is quartz glass, with a dielectric constant of 3.78 and a loss tangent of 0.0008.

[0040] The structure of the monopole pattern reconfigurable antenna based on RF MEMS switch control is described in an embodiment using a size combination (the following data is in micrometers):

[0041] when Figure 1 The dimensions of the structure are:

[0042] The length × width of the monopole radiating element 1 is 240 × 60, the length × width of each level of the parasitic elements 2 and 3 is 210 × 20, the length × width of the connection between the two level guide elements is 55 × 5, the gold PAD size of the test patch pad 7 is 100 × 100, the overall length × width of the coplanar waveguide 8 is 525 × 120, the rectangular defect size is 80 × 80, the gradient inclination angle is approximately 40°, the gradient microstrip line 9 has a short side size of 20, a long side size of 70, and a waistline size of 152;

[0043] when Figure 2 The dimensions of the structure are:

[0044] Structure 12 length × width = 30 × 10, structure 18 diameter = 6;

[0045] when Figure 3 The dimensions of the structure are:

[0046] MEMS switch bridge pier 12 bridge pier height = 1.2, metal beam 13 metal beam height = 0.5, silicon dioxide beam 14 height = 1, contact 15 height = 0.7, patch bridge 19 height = 1.5, bridge deck thickness = 0.5;

[0047] when Figure 4 The dimensions of the structure are:

[0048] The dielectric substrate 10 has a dielectric thickness of 100 μm, the metal backplane 11 has a thickness of 1 μm, the metal beam 13 has dimensions of 50×50 μm, the silicon dioxide beam 14 has a length×width of 120×50 μm, the contact 15 has a length×width of 50×8 μm, the electrode 16 has a length×width of 50×25 μm, and the silicon nitride film of the silicon nitride insulating layer 17 has a thickness of 0.1 μm.

[0049] When feeding the coplanar waveguide, the center frequency is 300 GHz, which belongs to the terahertz frequency band.

[0050] At this time, the reflection coefficient simulation diagram of the monopole pattern reconfigurable antenna based on RF MEMS switch control is as follows:

[0051] Figure 8 The reflection coefficient curve of the antenna is shown in FIG. , which shows that the S11 of the antenna unit is significantly less than -10 dB in the frequency range of 279.64 GHz to 328.38 GHz, and the relative bandwidth is 17%. The antenna has a wide impedance bandwidth.

[0052] At this time, the antenna's beam deflection gain pattern is:

[0053] Figure 6 The figure shows the antenna's radiation gain at its center frequency. The MEMS switch on the left parasitic element is on, indicating a gain of 6.05dB and a beam tilt of -35°. This antenna exhibits high gain and adjustable beam tilt, enabling reconfigurable patterns. Similarly, closing the right MEMS switch allows the beam tilt to reverse to 35° without changing gain or matching, thanks to the complete symmetry of the structural design.

[0054] Figure 7 The figure shows the antenna's radiation gain pattern at the center frequency. At this point, the MEMS switches on the left and right parasitic elements are both off, the steering elements are inactive, the beam is pointing toward the Z axis, and there is no beam tilt. The antenna unit gain is 5.15dB, and the beam tilt angle is 0°. This monopole pattern-reconfigurable antenna, controlled by RF MEMS switches, can reconfigure its pattern in three directions: left, center, and right.

[0055] The antenna unit operates in the terahertz frequency band and can realize the function of reconfigurable radiation pattern. It has high gain and simple structural design. It is composed of only a single-layer board with a low profile. The coplanar waveguide feeding method has a good impedance matching bandwidth and is easy to process and implement.

[0056] The above is only an example. If one wants to obtain a monopole pattern reconfigurable antenna based on RF MEMS switch control at different center frequencies, different parameters can be adjusted according to the specific implementation method to achieve different operating frequency bands and steering effects.

Claims

1. A monopole pattern reconfigurable antenna based on RF MEMS switch control, comprising a dielectric substrate (10) and a metal ground backplane (11); the metal ground backplane is located on the lower surface of the dielectric substrate, characterized in that: It also includes a monopole radiation unit (1), a parasitic unit, a coplanar waveguide (8) and a gradient microstrip line (9); The coplanar waveguide (8) is bilaterally symmetrical, and its feeding port (20) is connected to the monopole radiation unit (1) via a gradient microstrip line (9); There are two parasitic units, one on the left and one on the right of the monopole radiation unit; each parasitic unit is a ring structure with a break, and a composite beam ohmic contact MEMS switch is provided at the break position; The electrodes of the composite beam ohmic contact MEMS switch are connected to the test patch pads located on the upper surface of the dielectric substrate through a DC bias line.

2. The monopole pattern reconfigurable antenna based on RF MEMS switch control according to claim 1, characterized in that: The break positions of the two parasitic units are symmetrical with respect to the monopole radiation unit.

3. The monopole pattern reconfigurable antenna based on RF MEMS switch control according to claim 1, characterized in that: The composite beam ohmic contact MEMS switch comprises a silicon dioxide beam (14), a bridge pier (12), a metal beam (13), an electrode (16) and a contact (15); The metal beams, bridge piers, and electrodes are each provided in two groups; the adjacent ends of the two metal beams are connected by a silicon dioxide beam, with the contacts closely attached to the lower surface of the silicon dioxide beam; the other ends of the metal beams are connected to the corresponding bridge piers, and the electrodes are located directly below the corresponding metal beams with a spacing greater than zero between them; There are three test patch pads, namely a left pad, a middle pad and a right pad; The bridge pier of the composite beam ohmic contact MEMS switch, the electrode of one composite beam ohmic contact MEMS switch, and the electrode of the other composite beam ohmic contact MEMS switch correspond to and are connected to the three test patch pads respectively.

4. The monopole pattern reconfigurable antenna based on RF MEMS switch control according to claim 3, characterized in that: A silicon nitride insulating layer (17) is provided on the upper surface of the electrode.

5. The monopole pattern reconfigurable antenna based on RF MEMS switch control according to claim 1, characterized in that: The DC bias line is a high-resistance line made of TaN material; a bridge is formed at the contact position between the DC bias line and the parasitic unit.

6. The monopole pattern reconfigurable antenna based on RF MEMS switch control according to claim 1, characterized in that: The metal beam is provided with a hollow.

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