CN119651142A - Monopole pattern reconfigurable antenna based on RF MEMS switch control - Google Patents

Abstract

The invention discloses a monopole pattern reconfigurable antenna based on RF MEMS switch control, and belongs to the field of radio frequency front-end devices. The device consists of monopole radiating units, parasitic units positioned on the left side and the right side of the monopole radiating units, a composite Liang Oum contact MEMS switch, a direct-current bias line, a test patch pad, a coplanar waveguide, a gradual change microstrip line, a dielectric substrate and a metal ground backboard. When the MEMS switch on the parasitic element is turned on, the parasitic element length is slightly less than the monopole radiating element, and the parasitic element acts as a director. When the MEMS switch is turned off, the first-stage guiding unit is divided into two parts at the fracture, the length of the first-stage guiding unit is far smaller than that of the monopole radiating unit, and the terminal is opened to generate reflux, so that the effect of counteracting the second-stage guiding unit is reduced. When the switch on one side is pulled down, the directional diagram deflects a beam towards one side of the closed switch, the adjustable deflection angle can reach 41 degrees, the gain can reach 6.14dB, the beam width is about 90 degrees, when the switches on two sides are opened, the beam deflection is 0 degree, the directional diagram points to the positive Z axis, and the gain is 5.15dB.

Description

Monopole pattern reconfigurable antenna based on RF MEMS switch control

Technical Field

The invention relates to a monopole pattern reconfigurable antenna based on RF MEMS switch control, which is mainly applied to millimeter wave communication and the like in a terahertz frequency band, and belongs to the field of radio frequency front-end devices.

Background

The directional diagram reconfigurable antenna is a novel antenna technology, is widely applied to a radio frequency communication system needing to control beam directional switching, has simple structural design, does not need a plurality of antenna units for array formation and does not need to design a complex array feed network compared with a phased array antenna, is commonly used for realizing low-continuity beam directional switching, and can realize more efficient electromagnetic wave transmitting and receiving performance as a radio frequency front-end device.

The working principle of the directional diagram reconfigurable antenna is based on the fact that the antenna radiation unit or the feed path is reconfigured through radio frequency devices such as PIN diodes, varactors and RF MEMS switches, different radiation modes are excited, and therefore the beam direction of the antenna is switched. The reconfigurable antenna has the advantages of flexibility, high efficiency and adaptability, hardware cost can be reduced, good matching and radiation characteristics can be realized in a specific frequency band through reasonable antenna design, and the reconfigurable antenna is hopefully widely applied to millimeter wave communication fields such as wireless communication, satellite communication, internet of things and radar in the future.

At present, most conventional pattern reconfigurable antennas are applied to satellite communication bands below 10GHz or Ku/Ka and the like, and millimeter wave bands above 100GHz are generally difficult to realize large-scale production due to complexity of high-frequency design and difficulty of processing technology. Common pattern reconfigurable antennas generally adopt PIN diodes as radio frequency switches, but in terahertz frequency bands of 300GHz and above, the loss of the devices is large, the radiation performance of the antennas can be seriously degraded, and in general, a feed network is also complex, a multi-layer board structure is required to be designed to bear power distribution and impedance matching networks, so that the overall size of the antenna is increased, and the antenna is difficult to be applied to the reconfigurable demand scene of future terahertz communication.

Disclosure of Invention

In order to solve the problems in the background art, the design of the invention is a monopole pattern reconfigurable antenna based on RF MEMS switch control, and the requirements of pattern reconfiguration in the 300GHz terahertz frequency band can be met. The designed antenna unit has low section, uses a single-layer quartz glass dielectric plate as a substrate, has simple feeding mode and low process difficulty, and is easy to process and test. The designed composite beam RF MEMS switch has moderate DC bias voltage, high mechanical strength and stability, high isolation in the off state and low insertion loss in the on state. The designed monopole pattern reconfigurable antenna based on the MEMS switch has the characteristics of large beam deflection angle, high gain, wide beam, good matching and the like.

In order to solve the technical problems, the invention is realized by the following technical scheme:

The monopole pattern reconfigurable antenna based on RF MEMS switch control comprises a dielectric substrate 10, a metal ground backboard 11, a monopole radiating unit 1, a parasitic unit, a coplanar waveguide 8 and a gradual change microstrip line 9, wherein the metal ground backboard is positioned on the lower surface of the dielectric substrate;

The coplanar waveguide 8 is bilaterally symmetrical, and a feed port 20 of the coplanar waveguide is connected with the monopole radiating unit 1 through a gradual microstrip line 9;

each parasitic unit is of an annular structure, a fracture is arranged on the parasitic unit, and a composite Liang Oum contact MEMS switch is arranged at the fracture position;

The electrodes of the composite Liang Oum contact MEMS switch are connected with a test patch pad positioned on the upper surface of the dielectric substrate through direct-current bias wires.

Further, the fracture positions of the two parasitic elements are symmetrical with respect to the monopole radiating element.

Further, the composite Liang Oum-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 beam, the bridge pier and the electrode are all provided with two groups, the adjacent ends of the two metal beams are connected through the silicon dioxide beam, and the contact is clung to the lower surface of the silicon dioxide beam;

The number of the test patch bonding pads is three, namely a left bonding pad, a middle bonding pad and a right bonding pad;

the bridge pier of the composite Liang Oum contact type MEMS switch, the electrode of one composite Liang Oum contact type MEMS switch and the electrode of the other composite Liang Oum contact type MEMS switch are respectively corresponding to and connected with the three test patch pads.

Further, the upper surface of the electrode is provided with a silicon nitride insulating layer 17.

Furthermore, the direct-current bias line is a high-resistance line paved by TaN materials, and bridging is carried out at the contact position of the direct-current bias line and the parasitic unit.

Compared with the background technology, the invention has the following advantages:

a) The terahertz frequency band has small radiation loss and high efficiency. The RF MEMS switch with the composite beam structure is used as a radio frequency device to be loaded on a parasitic unit of an antenna, S21< -20dB is high in isolation degree when the switch is disconnected on a microwave transmission line, S21< -0 > 56dB is high in isolation degree when the switch is conducted, terahertz loss is small, the on-off of the switch can be effectively controlled through direct current bias, the microwave transmission characteristic is good, and the radiation efficiency of the antenna is high.

B) The beam deflection angle is large, the gain is high, and the bandwidth is wider. When the radio frequency switch controls the on-off of any parasitic unit on one side, the beam can be controlled to point to one side of the switch which is closed. When the beam deflects, the radiation gain is 6.14dB, the beam inclination is 35 degrees, the half-power beam width is 88.2 degrees, and the beam deflection is symmetrical. When the coplanar waveguide feeds, the relative bandwidth is 17%, the working frequency point is 300GHz, and the matching is good.

C) Low profile, small size and convenient manufacture. The quartz glass substrate is etched with 1um gold as a radiation unit and a feed network, the reflective backboard is a complete layer of gold, the thickness of a medium is 100um, the processing of a single-layer board is easier to realize, the substrate through hole process is not involved, the gold-forming layer can be realized through the surface process, the feed structure is simple, and the rapid printing manufacturing can be realized.

Drawings

FIG. 1 is a schematic top view of the complete structure of a monopole pattern reconfigurable antenna based on RF MEMS switch control;

FIG. 2 is a schematic top view of the RF MEMS switch structure loaded on a parasitic element;

FIG. 3 is a side view of the structure of FIG. 1;

FIG. 4 is a front elevational view of the structure of FIG. 2;

FIG. 5 is a graph of RF MEMS switch microwave transmission characteristics S21;

Fig. 6 is a graph of gain at beam deflection for an antenna;

fig. 7 is a graph of gain when the beam of the antenna is undeflected;

Fig. 8 is an impedance matching S11 graph of the antenna;

Detailed Description

The following describes in further detail the embodiments of the present invention with reference to figures 1-8 and examples.

The monopole pattern reconfigurable antenna based on RF MEMS switch control comprises a monopole radiating unit 1, parasitic units 2 and 3 positioned on the left side and the right side of the monopole radiating unit, composite Liang Oum contact MEMS switches 4 and 5, a direct-current bias line 6, a test patch pad 7, a coplanar waveguide 8, a gradual change microstrip line 9, a dielectric substrate 10 and a metal ground backboard 11. The MEMS switch bridge is characterized by further comprising an MEMS switch bridge 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.

The two parasitic patches of the unit are identical in shape, symmetrical in position and provided with fracture designs with the same size, the two MEMS switches are identical in structure and symmetrical in position and are located at corresponding fracture positions of the parasitic patches, and the bridging positions of the parasitic patches of the unit are identical.

The feeding network is designed by impedance matching, and can feed probes to the coplanar waveguide feeding port 20 through a radio frequency probe. The coplanar waveguide 8 has a structure with bilateral symmetry and the same gap, and the feed port is connected with the monopole radiating element 1 through the gradual microstrip line 9.

Taking the monopole pattern reconfigurable antenna based on RF MEMS switch control of fig. 1 as an example, the antenna is composed of a monopole radiating unit 1, parasitic units 2 and 3 positioned on the left side and the right side of the monopole radiating unit, composite Liang Oum contact MEMS switches 4 and 5, a direct-current bias line 6, a test patch pad 7, a coplanar waveguide 8 and a gradual microstrip line 9, and is fed by a probe through a port 20.

The monopole radiating unit is directly connected with the feeder line as an antenna main body, and the resonance point can be finely adjusted by adjusting the size of the patch. The parasitic elements on both sides are excited by the coupling feed of the monopole patch to produce parallel currents. When the switch is turned off, the first-stage steering unit benefits from the high isolation performance of the MEMS switch, coupling current cannot be smoothly conducted and is divided into two parts at a fracture design position, the electric length of the first-stage steering unit is far smaller than that of the monopole patch, the steering effect cannot be realized, reverse reflux is generated due to open terminal, the steering effect of the second-stage steering unit is weakened and counteracted, the directional diagram points to one side of the switch closure, and the directional diagram is reconfigurable based on the principle.

The RF MEMS switch shown in the figure 2 is a clamped beam composite material switch, and consists of a metal beam layer and a silicon dioxide beam layer, wherein the composite beam ensures the structural strength and stability, and the symmetrical design of the clamped beam ensures the stability of processing and testing. The direct current bias adopts TaN material to lay high-resistance wire, and is connected with the electrode through bridge at the patch and led out, 2 gold PADs are designed for driving voltage to the electrode, and 1 gold PAD is used for grounding the switch bridge pier. The specific working process of the switch is as follows:

when the voltage is further increased to the actuation voltage, the deformation reaches the maximum value, the contact is contacted with the signal line, and the switch is turned on. The bias voltage is adjusted to be gradually reduced, the electrostatic force is reduced, and the metal beam and the electrode are separated by a layer of insulating silicon nitride film above the electrode, so that the metal beam can rebound easily, the contact is separated from the signal line, and the switch is disconnected.

The coplanar waveguide feed structure adopts a gradual change gap to realize excellent matching with gradual change microstrip lines, the slopes of left and right waist lines of the trapezoid feeder lines are consistent, the line width and the length of a joint part of the microstrip feeder lines are optimized to optimize matching bandwidth by optimizing the bottom edge length and the bottom angle of the trapezoid feeder lines, and the return loss and the gain of an antenna unit are adjusted. The rectangular defect of the coplanar waveguide is used for adjusting the impedance matching of the antenna, the length and width dimensions of the defect ground can be optimized, the resonance point offset is adjusted under the condition that the radiation pattern is not influenced, and the impedance bandwidth is optimized.

The lower surface of the dielectric substrate is printed with a metal floor with the thickness of 1 micrometer, and under the condition that no metal ground is arranged, the antenna can radiate to the rear lobe, a large amount of energy is leaked, and the metal ground is used for reflecting the beam and pointing to the space of the upper half plane. To reduce the loss, the metal materials of all structures are metals with small resistivity, such as aluminum, copper, gold, etc., and the dielectric substrate 10 is a material with small loss, such as high-resistance silicon, rogers5880, etc. In this example, the metal material was gold, the dielectric substrate was quartz glass, the dielectric constant was 3.78, and the loss tangent was 0.0008.

The structure of the monopole pattern reconfigurable antenna based on RF MEMS switch control is described herein as being an example of a combination of dimensions (in microns for the following data):

when the dimensions of the structure of fig. 1 are:

The length×width=240×60 of the monopole radiating element 1, the length×width=210×20 of each stage of the parasitic elements 2,3, the length×width=55×5 of the connection point of the two stages of the parasitic elements, the test patch PAD 7 gold PAD size=100×100, the overall length×width=525×120 of the coplanar waveguide 8, the rectangular defect size=80×80, the gradient inclination angle is about 40 °, the gradient microstrip line short side size=20, the long side size=70, and the waistline size=152 of the gradient microstrip line 9;

when the dimensions of the structure of fig. 2 are:

structure 12 length x width = 30 x 10, structure 18 diameter = 6;

When the dimensions of the structure of fig. 3 are:

MEMS switch pier 12 bridge 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;

When the dimensions of the structure of fig. 4 are:

Dielectric substrate 10 dielectric thickness=100 um, metal back floor 11 thickness=1 um, metal beam 13 dimensions=50×50, silicon dioxide beam 14 length×width=120×50, contact 15 length×width=50×8, electrode 16 length×width=50×25, silicon nitride insulating layer 17 silicon nitride film thickness is 0.1um;

When the coplanar waveguide feeds, the solution center frequency is 300GHz, and the coplanar waveguide belongs to the terahertz frequency band.

The reflection coefficient simulation diagram of the monopole pattern reconfigurable antenna based on the RF MEMS switch control is as follows:

The reflection coefficient curve of the antenna is shown in fig. 8, which shows that the S11 of the antenna unit is significantly smaller than-10 dB in the frequency range of 279.64GHz-328.38GHz, the relative bandwidth is 17%, and the antenna has a wider impedance bandwidth.

The beam deflection gain pattern of the antenna at this time is:

The radiation gain diagram of the antenna at the center frequency is shown in fig. 6, at this time, the MEMS switch on the parasitic element on the left side is in an on state, which shows that the gain of the antenna element is 6.05dB, the beam tilt angle is-35 °, the antenna has a higher gain, and the beam tilt angle is adjustable, so that the function of reconstructing the directional diagram can be realized. Similarly, when the right MEMS switch is closed, due to the perfect symmetry of the structural design, the beam tilt angle can be changed to 35 ° reversely under the condition that the gain and the matching are not changed.

The radiation gain diagram of the antenna at the center frequency is shown in fig. 7, where the MEMS switches on the left and right parasitic elements are all in an off state, the director is inactive, the beam is directed to the Z-axis, and no beam is directed to tilt. The antenna element gain is shown to be 5.15dB at this point and the beam tilt angle is 0. The monopole pattern reconfigurable antenna based on RF MEMS switch control can realize the pattern reconfigurable function of three directions of left, middle and right.

The antenna unit works in the terahertz frequency band, can realize the function of directional diagram reconstruction, has higher gain, has simple structural design, is only composed of a single-layer plate, has low profile, has better impedance matching bandwidth in a coplanar waveguide feeding method, and is easy to process and realize.

The foregoing is merely an example, and if a monopole pattern reconfigurable antenna based on RF MEMS switch control at different center frequencies is desired, different parameters may be adjusted according to the specific embodiment to achieve different operating frequency bands and guiding effects.

Claims (6)

1. The monopole pattern reconfigurable antenna based on RF MEMS switch control comprises a dielectric substrate (10) and a metal ground backboard (11), wherein the metal ground backboard is positioned on the lower surface of the dielectric substrate, and the monopole pattern reconfigurable antenna is characterized by further comprising a monopole radiating unit (1), a parasitic unit, a coplanar waveguide (8) and a gradual change microstrip line (9);

the coplanar waveguide (8) is bilaterally symmetrical, and a feed port (20) of the coplanar waveguide is connected with the monopole radiating unit (1) through a gradual microstrip line (9);

each parasitic unit is of an annular structure, a fracture is arranged on the parasitic unit, and a composite Liang Oum contact MEMS switch is arranged at the fracture position;

The electrodes of the composite Liang Oum contact MEMS switch are connected with a test patch pad positioned on the upper surface of the dielectric substrate through direct-current bias wires.

2. A monopole pattern reconfigurable antenna based on RF MEMS switch control according to claim 1, wherein the break locations of the two parasitic elements are symmetrical about the monopole radiating element.

3. The monopole pattern reconfigurable antenna based on RF MEMS switch control of claim 1, wherein the composite Liang Oum-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 beam, the bridge pier and the electrode are all provided with two groups, the adjacent ends of the two metal beams are connected through the silicon dioxide beam, and the contact is clung to the lower surface of the silicon dioxide beam;

The number of the test patch bonding pads is three, namely a left bonding pad, a middle bonding pad and a right bonding pad;

the bridge pier of the composite Liang Oum contact type MEMS switch, the electrode of one composite Liang Oum contact type MEMS switch and the electrode of the other composite Liang Oum contact type MEMS switch are respectively corresponding to and connected with the three test patch pads.

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

5. The monopole pattern reconfigurable antenna based on RF MEMS switch control of claim 1, wherein the DC bias line is a high resistance line laid by TaN material and bridging at the contact position with the parasitic element.

6. The monopole pattern reconfigurable antenna based on RF MEMS switch control of claim 1, wherein the metal beam is provided with a hollow.