Monopole directional diagram reconfigurable antenna based on RF MEMS switch control

Abstract

The invention discloses a monopole directional diagram reconfigurable antenna based on RF MEMS switch control, and belongs to the field of radio frequency front-end devices. The antenna is composed of a monopole radiation unit, parasitic units located on the left side and the right side of the monopole radiation unit, a composite beam ohmic contact type MEMS switch, a direct current bias line, a test patch bonding pad, a coplanar waveguide, a gradient microstrip line, a dielectric substrate and a metal ground backboard. When the MEMS switch on the parasitic unit is switched on, the length of the parasitic unit is slightly smaller than that of the monopole radiation unit, and the parasitic unit plays a role of a director. When the MEMS switch is turned off, the first-stage leading unit is divided into two parts from the fracture, the length of the first-stage leading unit is far smaller than that of the monopole radiation unit, and backflow is generated by the open circuit of the terminal, so that the effect of reducing and offsetting the second-stage leading unit is achieved. When the switch on one side is pulled down, a directional diagram generates beam deflection towards the side where the switch is closed, the adjustable deflection angle can reach 41 degrees, the gain can reach 6.14 dB, the beam width is about 90 degrees, when the switches on the two sides are both switched off, the beam deflection is 0 degree, the directional diagram points to the positive Z axis, and the gain is 5.15 dB.

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 communication 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 need to control 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 feeding network. It is often used to achieve low-continuity beam pointing switching. As a radio frequency front-end device, it can achieve more efficient electromagnetic wave transmission and reception performance.

[0003] The working principle of the reconfigurable antenna is based on the reconstruction of the antenna radiation unit or the feed path through RF devices such as PIN diodes, varactor diodes, and RF MEMS switches, which stimulate different radiation modes and switch the antenna beam direction. Reconfigurable antennas have the advantages of flexibility, efficiency, and adaptability, and can reduce hardware costs. Through reasonable antenna design, good matching and radiation characteristics can be achieved within a specific frequency band. In the future, they are expected to be widely used in millimeter wave communication fields such as wireless communications, satellite communications, the Internet of Things, and radar.

[0004] At present, most conventional reconfigurable antennas are used in low-frequency bands below 10 GHz or satellite communication bands such as Ku / Ka. In millimeter-wave bands above 100 GHz, it is usually difficult to achieve large-scale production due to the complexity of high-frequency design and the difficulty of processing technology. Common reconfigurable antennas usually use PIN diodes as RF switches, but in the terahertz band of 300 GHz and above, the loss of such devices is large, which will seriously degrade the radiation performance of the antenna, and the feeding network is usually more complicated. It is necessary to design a multi-layer board structure to carry the power distribution and impedance matching network, which also increases the overall size of the antenna, making it difficult to apply to the reconfigurable demand scenarios of future terahertz communications. Summary of the invention

[0005] In order to solve the problems existing in the background technology, the present invention is designed to be 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 profile, 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 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, good matching, etc.

[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 also comprises a monopole radiation unit 1, a parasitic unit, 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 radiation unit 1 through a gradient microstrip line 9;

[0009] There are two parasitic units, which are respectively located on the left and right sides 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 type 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 about the monopole radiation unit.

[0012] Further, 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 with two groups; the adjacent ends of the two metal beams are connected by a silicon dioxide beam, and the contact point is closely attached to the lower surface of the silicon dioxide beam; the other end of the metal beam is connected to the corresponding bridge pier, and the electrode is located directly below the corresponding metal beam and there is a spacing greater than zero between the two;

[0014] The test patch pads are provided with three, 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 another 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. The RF MEMS switch with a composite beam structure is used as a radio frequency device to load onto the parasitic unit of the antenna. When the switch is disconnected on the microwave transmission line, S21 <-20dB, with high isolation, and S21>-0.56dB when turned on. The terahertz loss is small, and the switch can be effectively controlled by DC bias. The microwave transmission characteristics are good, and the antenna radiation efficiency is high.

[0020] b) The beam deflection angle is large, the gain is high, and the bandwidth is wide. When the RF switch controls the on and off of the parasitic unit on either side, the beam can be controlled to point to the side where the switch is closed. When the beam is deflected, the radiation gain is 6.14dB, the beam tilt is 35°, the half-power beam width is 88.2°, and the left and right beam deflections are symmetrical. When fed by a coplanar waveguide, the relative bandwidth is 17%, the operating frequency is 300GHz, and the matching is good.

[0021] c) Low profile, small size, easy to manufacture. 1um gold is etched on the quartz glass substrate as the radiation unit and the feeding network. The reflective backplane is a complete layer of gold. The dielectric thickness is 100um. The single-layer board processing is easier to achieve, and does not involve the substrate through-hole process. The gold layer can be realized through the surface process. The feeding structure is simple and can be quickly printed and manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0023] Figure 2 is a top view schematic diagram 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 structural front view of

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

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

[0028] Figure 7 It is the gain curve diagram 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 implementation modes 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 unit 1, parasitic units 2 and 3 located on the left and right sides thereof, composite beam ohmic contact MEMS switches 4 and 5, DC bias line 6, test patch pad 7, coplanar waveguide 8, gradient microstrip line 9, dielectric substrate 10, and metal ground backplane 11. It is characterized in that it also comprises a 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 through hole 18 on the beam, and a patch bridge 19.

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

[0033] The feeding network is designed with impedance matching, and the coplanar waveguide feeding port 20 can be probe-fed by a radio frequency probe. The coplanar waveguide 8 has a bilaterally symmetrical structure and the same gap, and the feeding port is connected to the monopole radiation unit 1 through 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 thereof, 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 radiation unit is directly connected to the feed line as the antenna body, and the resonance point can be fine-tuned by adjusting the size of the patch. The parasitic units on both sides are excited to generate parallel currents through the coupled feeding of the monopole patch. When the switch is closed, the length of the primary steering unit is slightly shorter than the monopole patch, showing capacitive, and the current phase of the parasitic unit lags behind the current phase on the monopole patch. The monopole on this side acts as a director, and the steering effect is amplified through the secondary steering unit, increasing the beam tilt angle and achieving optimization and adjustment; when the switch is disconnected, the primary steering unit benefits from the high isolation performance of the MEMS switch, and the coupling current will not be able to conduct smoothly, and it will be divided into two at the break design. Its electrical length is much smaller than the monopole patch, and the steering effect cannot be achieved. Due to the open circuit of the terminal, reverse reflux is generated, which weakens and offsets the steering effect of the secondary steering unit, and the directional pattern points to the side where the switch is closed. Based on this principle, the directional pattern can be reconfigured.

[0036] Attached Figure 2 The RF MEMS switch on display is a composite switch with a fixed beam, which is composed of a metal beam layer and a silicon dioxide beam layer. The composite beam ensures its structural strength and stability, and the symmetrical design of the fixed beam ensures stable processing and testing. The DC bias uses TaN material to lay a high-resistance line, which is connected to the electrode through a bridge at the patch and led out. A total of 2 gold PADs are designed to drive the electrode voltage, and 1 gold PAD is used to ground the switch bridge. The specific working process of the switch is as follows:

[0037] The applied voltage on the PAD of the electrode is gradually increased. When the driving voltage value is reached, the electrostatic force generated by the electrode attracts the upper metal beam to bend downward. When the voltage is further increased to the pull-in voltage, the deformation reaches the maximum value, the contact and the signal line are in contact, and the switch is turned on. The bias voltage is adjusted to gradually decrease, and the electrostatic force decreases. Since a layer of insulating silicon nitride film above the electrode separates the metal beam and the electrode, the metal beam can easily rebound, the contact is separated from the signal line, and the switch is disconnected.

[0038] The coplanar waveguide feeding structure uses a gradual gap to achieve excellent matching with the gradual microstrip line. The slopes of the left and right waistlines of the trapezoidal feeder are consistent. The matching bandwidth can be optimized by optimizing the bottom length and bottom angle of the trapezoidal feeder, optimizing the line width of the microstrip feeder and the length of the connecting part, and adjusting the return loss and gain of the antenna unit. The coplanar waveguide rectangular defect is used to adjust the impedance matching of the antenna, optimize the length and width of the defect, adjust the resonance point offset without affecting the radiation pattern, and optimize the impedance bandwidth.

[0039] A 1 micron thick metal floor is printed on the lower surface of the dielectric substrate. Without the metal floor, the antenna will radiate to the back lobe, with a large amount of energy leakage. The metal floor is used to reflect the beam and point it to the space of the upper half plane. In order to reduce the loss, the metal material of all structures is a metal with low resistivity, such as aluminum, copper, gold, etc. The dielectric substrate 10 is made of a material with low loss, such as high-resistance silicon, Rogers5880, etc. In this example, the metal material is gold, the dielectric substrate is quartz glass, the dielectric constant is 3.78, and the loss tangent is 0.0008.

[0040] The structure of the monopole pattern reconfigurable antenna based on RF MEMS switch control is described in an embodiment by selecting 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 radiation unit 1 is 240 × 60, the length × width of each level of the parasitic units 2 and 3 is 210 × 20, the length × width of the connection between the two levels of the guiding units is 55 × 5, the size of the gold PAD 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 tilt angle is about 40°, the gradient microstrip line short side size of the gradient microstrip line 9 is 20, the long side size is 70, and the waistline size is 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 um, the metal backing plate 11 has a thickness of 1 um, the metal beam 13 has a size of 50×50, the length×width of the silicon dioxide beam 14 is 120×50, the contact 15 has a length×width of 50×8, the electrode 16 has a length×width of 50×25, and the silicon nitride film thickness of the silicon nitride insulating layer 17 is 0.1 um;

[0049] When the coplanar waveguide is fed, the center frequency is solved to be 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. 1 , 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 radiation gain diagram of the antenna at the center frequency. At this time, the MEMS switch on the left parasitic unit is in the on state, showing that the antenna unit gain is 6.05dB and the beam tilt angle is -35°. The antenna has a high gain and an adjustable beam tilt angle, which can realize the function of reconfigurable radiation pattern. Similarly, when the right MEMS switch is closed, due to the complete symmetry of the structural design, the beam tilt angle can be reversed to 35° without changing the gain and matching.

[0054] Figure 7 The figure shows the radiation gain diagram of the antenna at the center frequency. At this time, the MEMS switches on the parasitic units on the left and right sides are in the off state, the steering unit does not work, the beam points to the Z axis, and there is no beam pointing tilt. It shows that the antenna unit gain is 5.15dB and the beam tilt angle is 0°. The monopole pattern reconfigurable antenna based on RF MEMS switch control can realize the pattern reconfiguration function in three directions: left, middle 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, which are respectively located on the left and right sides 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 type 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 about 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 type 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 with two groups; the adjacent ends of the two metal beams are connected by a silicon dioxide beam, and the contact point is closely attached to the lower surface of the silicon dioxide beam; the other end of the metal beam is connected to the corresponding bridge pier, and the electrode is located directly below the corresponding metal beam and there is a spacing greater than zero between the two; The test patch pads are provided with three, 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 another 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, and 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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