Pattern reconfigurable antenna capable of switching feed through MEMS switch

Abstract

The invention discloses a directional diagram reconfigurable antenna capable of switching feed through an MEMS switch, and belongs to the field of radio frequency front-end devices. The directional diagram reconfigurable antenna is composed of a micro-strip radiation unit, a guide parasitic unit, a composite beam ohmic contact type MEMS switch, a one-to-four feed network, a direct current bias line, a test patch bonding pad, a coplanar waveguide, a gradual change micro-strip line, a dielectric substrate and a metal ground backboard. The two-stage MEMS switches are erected on the one-to-four feed network, when the two-stage switches on a certain feeder line are turned on, radio frequency current can flow to the corresponding basic radiation unit through the feeder line to generate an inclined beam facing the quadrant, and the two basic radiation units on the front side can be enabled by simultaneously turning on the four switches on the front side to generate an inclined beam facing the quadrant. And generating an inclined beam in the front side positive direction. The antenna adopts a single-layer board design, the dielectric substrate does not need to be punched, the structure is simple, manufacturing is convenient, the adopted MEMS switch is small in loss and high in isolation degree, and rapid printing and manufacturing can be achieved through the surface etching process.

Description

Technical Field

[0001] The present invention relates to a directional pattern reconfigurable antenna which switches feeding through a MEMS switch, which is mainly used in millimeter wave communication in the terahertz frequency band, etc., 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 designs a directional pattern reconfigurable antenna that switches the feeding through a MEMS switch, which can meet the demand for realizing directional pattern reconfiguration in the 300GHz terahertz frequency band. The designed antenna unit has a low profile, with a single-layer quartz glass dielectric plate as the substrate, and is connected to the radiation unit through a one-to-four feeding network. 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 directional pattern reconfigurable antenna with switched feeding 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 reconfigurable antenna with a directional pattern that switches feeding through a MEMS switch, comprising 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 radiation unit, a coplanar waveguide, a one-to-four feeding network and a gradient microstrip line;

[0008] The feeding port of the coplanar waveguide is connected to a one-to-four feeding network through a gradient microstrip line; the ends of the one-to-four feeding network are connected to microstrip radiating units, and the four microstrip radiating units are arranged in a rectangular array; one side of each microstrip radiating unit is provided with a parasitic unit;

[0009] Composite beam ohmic contact type MEMS switches are provided on the two-branch circuit and the four-branch circuit of the one-to-four feeding network.

[0010] Furthermore, the branch connections of the one-to-four feeding network are all 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] Further, the composite beam ohmic contact MEMS switch includes a silicon dioxide beam, a bridge pier, a metal beam, an electrode and a contact;

[0012] The metal beams, bridge piers and electrodes are each provided with two groups; the two bridge piers are respectively located on both sides of the fracture, the adjacent ends of the two metal beams are connected by a silicon dioxide beam, and the contact 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 with a spacing greater than zero between the two.

[0013] Furthermore, it also includes a test patch pad, and the electrode and the bridge pier of the composite beam ohmic contact MEMS switch are connected to the test patch pad through a DC bias line.

[0014] Further, the bridge pier of the two-branch composite beam ohmic contact MEMS switch and two bridge piers of one of the four-branch composite beam ohmic contact MEMS switches are connected to a test patch pad;

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

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

[0017] Compared with the background technology, the present invention has the following advantages:

[0018] 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 and loaded onto a one-to-four feed network. 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.

[0019] 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 any feed line, the beam can be controlled to point to the side of the radiation unit that is turned on. When the beam is deflected, the radiation gain is 5.87dB, the beam tilt is 33°, and symmetrical beam deflection can be achieved in four quadrants. When fed by a coplanar waveguide, the relative bandwidth is 22.16%, the operating frequency is 300GHz, and the matching is good.

[0020] c) Low profile, simple structure, easy manufacturing. 1um gold is etched on the quartz glass substrate as the radiation unit and 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, does not involve the substrate through-hole process, the gold layer can be achieved through the surface process, the antenna unit is simple, and can be quickly printed and manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a top view of the complete structure of the antenna whose directional pattern can be reconfigured by switching the feeding through the MEMS switch;

[0022] Figure 2 is a top view schematic diagram of the RF MEMS switch structure loaded on the feed network;

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

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

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

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

[0027] Figure 7 It is a graph of the beam deflection when a single patch of the antenna is selected;

[0028] Figure 8 It is the beam deflection curve when the front double patch of the antenna is selected;

[0029] Fig. 9 It is the impedance matching S11 curve of the antenna as a whole; DETAILED DESCRIPTION

[0030] The following is combined with Figure 1-9 The specific implementation modes of the present invention are further described in detail with reference to the accompanying drawings and examples.

[0031] A reconfigurable antenna with a directional pattern that switches feeding through a MEMS switch, comprising a microstrip radiation unit 1, a parasitic unit 2, a composite beam ohmic contact MEMS switch 3-8, a one-to-four feeding network 9, a DC bias line 10, a test patch pad 11, a coplanar waveguide 12, a gradient microstrip line 13, a dielectric substrate 14, and a metal ground backplane 15. The antenna is characterized in that it also includes a MEMS switch bridge pier 16, a metal beam 17, a silicon dioxide beam 18, a contact 19, an electrode 20, a silicon nitride insulating layer 21, a through hole 22 on the beam, and a patch bridge 23.

[0032] The microstrip radiation unit 1 and the parasitic unit 2 are of the same shape and symmetrically located, connected to the coplanar waveguide through a one-to-four feeding network, and the six MEMS switches are of the same structure and symmetrically located, all located at the connection of the feeding network, and have a transition gradient design. The transition gradient structure includes a narrow section, a gradient section, and a wide section connected in sequence; wherein the MEMS switch is located at the break of the narrow section.

[0033] The feeding network is designed with impedance matching, and the coplanar waveguide feeding port can be probe-fed by a radio frequency probe. The coplanar waveguide 12 has a bilaterally symmetrical structure and the same gap, and the feeding port is connected to the one-to-four feeding network through a gradient microstrip line 13.

[0034] Attach Figure 1 Taking the reconfigurable antenna with feeding pattern switched by MEMS switch as an example, it consists of a microstrip radiation unit 1, a parasitic unit 2, a composite beam ohmic contact MEMS switch 3-8, a one-to-four feeding network 9, a DC bias line 10, a test patch pad 11, a coplanar waveguide 12, a gradient microstrip line 13, a dielectric substrate 14, and a metal ground backplane 15, and is probe-fed by the port.

[0035] The microstrip radiating 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 unit on one side of the antenna excites parallel current through coupled feeding. Its length is slightly shorter than that of the microstrip radiating unit and is capacitive. The current phase of the parasitic unit lags behind the current phase on the microstrip radiating patch, acting as a director. The secondary and tertiary steering units amplify the steering effect, increase the beam tilt angle, and achieve optimization and adjustment. The beam tilt effect of a single radiating unit can be seen Figure 6 .

[0036] The basic principle of achieving reconfigurability in this design is to realize feed switching through a MEMS switch installed on a one-to-four feeding network. The switch is divided into two levels of control. After the RF signal is fed from the coplanar waveguide port, it is transmitted to the first-level one-to-two T-type feeding structure through a microstrip line gradient matching structure. The left and right sides are both controlled by the two switches of the first level. After the signal passes through one of the paths, it reaches the secondary T-type feeding structure and finally leads to the microstrip radiation patch on one side. The MEMS switch installed at the T-type transition of this design has the characteristics of low loss and high isolation, which can ensure that the energy flows to the expected radiation patch according to the expected design, and radiates a beam-deflected radiation pattern in this quadrant. The reconfiguration of the radiation pattern is realized based on the principle of switching the feed through an RF switch. The antenna can realize beam deflection in four quadrants. When the switch selects a certain radiation patch, the beam deflection in that direction can be seen. Figure 7 In addition, when the two secondary switches on the upper side are turned on, and the left and right primary switches are also turned on, that is, the two radiating patches on the upper side are simultaneously selected, the antenna radiation pattern tilts forward, and the beam offset is shown in Figure 8 .

[0037] 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 6 gold PADs are designed to drive the electrode voltage, and 4 gold PADs are used to ground the switch bridge. The specific working process of the switch is as follows:

[0038] 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.

[0039] The coplanar waveguide feeding structure adopts a gradient gap to achieve excellent matching with the gradient microstrip line. The slopes of the left and right waistlines of the trapezoidal feed line are consistent. The matching bandwidth can be optimized by optimizing the bottom side length and bottom angle of the trapezoidal feed line, optimizing the line width of the microstrip feed line and the length of the connecting part, and adjusting the return loss and gain of the antenna unit.

[0040] 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.

[0041] The structure of the directional pattern reconfigurable antenna that switches the feeding by the MEMS switch is described in an embodiment by selecting a size combination (the following data is in micrometers):

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

[0043] Microstrip radiation unit 1 length × width = 310 × 200, leading to parasitic unit 2 leading to unit length × width = 200 × 140, leading to parasitic unit 2 rectangular defect length × width = 184 × 40, one-to-four feeding network 9 wide line length × width = 170 × 20, one-to-four feeding network 9 narrow line 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, gradient microstrip line 13 short side size = 20, long side size = 70, line length = 1046, patch bridge 23 bridge height = 1.5, bridge deck thickness = 0.5;

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

[0045] Structure 16 length × width = 30 × 10, structure 22 diameter = 6;

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

[0047] Bridge pier 16 bridge pier height = 1.2, metal beam 17 metal beam height = 0.5, silicon dioxide beam 18 silicon dioxide 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 um, the metal back plate 15 has a thickness of 1 um, 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 thickness of the silicon nitride film 21 is 0.1 um;

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

[0051] At this time, the reflection coefficient simulation diagram of the reconfigurable antenna can be obtained by switching the feed pattern of the MEMS switch:

[0052] Fig. 9 The reflection coefficient curve of the antenna is shown in FIG. 1 , which shows that the S11 of the antenna unit is less than -10 dB in the frequency range of 280 GHz to 346.5 GHz, and the relative bandwidth is 22.16%. The antenna has a wide impedance bandwidth.

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

[0054] Figure 7 The figure shows the radiation gain diagram of the antenna as a whole at the center frequency. At this time, two sets of MEMS switches on a certain feed line are in the on state, showing that the antenna unit gain is 5.87dB and the beam tilt angle is 33°. The antenna has a high gain, and the beam tilt direction can be symmetrically adjusted in four quadrants, which can realize the reconfigurable radiation pattern function.

[0055] Figure 8 The figure shows the radiation gain diagram of the antenna as a whole at the center frequency. At this time, four MEMS switches 3, 5, 6, and 7 are in the on state, that is, the feed line of the front dual radiation patch is enabled, showing that the antenna unit gain is 8.55dB and the forward beam tilt angle is -26.4°. However, since the patches on the left and right sides are both powered on, the beam tilt angles to the left and right are both 0, and the antenna still has a relatively high gain.

[0056] Figure 6 The figure shows the radiation gain diagram of the basic radiating unit (microstrip patch and director vibrator) of the antenna at the center frequency, showing that the gain of the basic radiating unit of the antenna is 7.35dB and the beam tilt angle is 40°. This unit has a higher gain and better beam tilt capability.

[0057] 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.

[0058] The above is only an example. If one wants to obtain a reconfigurable antenna with a directional pattern that switches the feeding at different center frequencies through a MEMS switch, different parameters can be adjusted according to the specific implementation method to achieve different operating frequency bands and steering effects.

Claims

1. A reconfigurable antenna with a directional pattern that switches feeding through a MEMS switch, 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 radiation unit (1), a coplanar waveguide (12), a one-to-four feeding network (9) and a gradient microstrip line (13); The feeding port of the coplanar waveguide is connected to a one-to-four feeding network via a gradient microstrip line (13); the ends of the one-to-four feeding network are connected to microstrip radiation units (1), and the four microstrip radiation units are arranged in a rectangular array; one side of each microstrip radiation unit is provided with a parasitic unit (2); Composite beam ohmic contact type MEMS switches are provided on the two-branch circuit and the four-branch circuit of the one-to-four feeding network.

2. The antenna with reconfigurable directional pattern by switching feeding through a MEMS switch according to claim 1, characterized in that: The branch connection of the one-to-four feeding 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 antenna with reconfigurable directional pattern by switching feeding through a MEMS switch according to claim 2, characterized in that: The composite beam ohmic contact MEMS switch comprises a silicon dioxide beam, a bridge pier, a metal beam, an electrode and a contact; The metal beams, bridge piers and electrodes are each provided with two groups; the two bridge piers are respectively located on both sides of the fracture, the adjacent ends of the two metal beams are connected by a silicon dioxide beam, and the contact 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 with a spacing greater than zero between the two.

4. The antenna with reconfigurable directional pattern by switching feeding through a MEMS switch according to claim 3, characterized in that: The device also includes a test patch pad, and the electrodes and bridge piers of the composite beam ohmic contact MEMS switch are connected to the test patch pad through a DC bias line.

5. The antenna with reconfigurable directional pattern by switching feeding through a MEMS switch according to claim 4, characterized in that: The bridge pier of the two-branch composite beam ohmic contact MEMS switch and two bridge piers of one of the four-branch composite beam ohmic contact MEMS switches are connected to a test patch pad; The electrodes of each composite beam ohmic contact MEMS switch are connected to the test patch pads corresponding to each switch.

6. The antenna with reconfigurable directional pattern by switching feeding through a MEMS switch according to claim 5, characterized in that: Each branch of the one-to-four feeding network is provided with a patch bridge (23) for a DC bias line to pass through.

Images