A millimeter wave polarization and pattern reconfigurable antenna

Abstract

The application discloses a millimeter wave polarization and pattern reconfigurable antenna and belongs to the field of radio frequency front-end devices. The millimeter wave polarization and pattern reconfigurable antenna is composed of symmetrical rectangular radiation patches, a half-circle defect, a quarter-circle defect and a rectangular branch loading located on the radiation patches, an orthogonal two-way feeding network, a T-shaped power division feeding network, a composite beam ohmic contact type MEMS switch, a direct current bias line, a test patch pad, a coplanar waveguide, a gradual matching structure, a dielectric substrate and a metal ground back plate. When unilateral MEMS switches on the T-shaped power division feeding network are turned on, energy flows to the radiation unit on the side, and the beam tilting effect to the left or the right can be realized. When the MEMS on both sides are turned on, the radiation pattern is directed to the Z positive axis, and there is no beam deflection, and accordingly, the pattern reconfigurable function of three directions, i.e. left, middle and right, can be realized. When the switches on the orthogonal two-way feeding network are turned on, the size of the long line can realize 90° phase delay, two orthogonal degenerate modes are combined to form circularly polarized waves, and complete half-power beam width is covered.

Description

TECHNICAL FIELD

[0001] The application relates to a millimeter wave polarization and pattern reconfigurable antenna, mainly applied to a communication system in a millimeter wave frequency band, and belongs to the field of radio frequency front-end devices. BACKGROUND

[0002] The pattern reconfigurable antenna is a new type of antenna technology, which has been widely applied in radio frequency communication systems requiring control of beam pointing switching. Compared with phased array antennas, the pattern reconfigurable antenna has a simple structure design, does not need a large number of antenna elements for arraying, and does not need a complex array feeding network to be designed. The pattern reconfigurable antenna is often used to realize low-continuity beam pointing switching and can realize more efficient electromagnetic wave transmission and reception performance as a radio frequency front-end device.

[0003] The working principle of the pattern reconfigurable antenna is based on the fact that the antenna radiating element or the feeding path is reconfigured by using radio frequency devices such as PIN diodes, varactor diodes and RF MEMS switches, different radiation modes are excited, and the beam pointing of the antenna is switched. The reconfigurable antenna has the advantages of flexibility, efficiency and adaptability, can reduce hardware overhead, and through reasonable antenna design, good matching and radiation characteristics can be realized in a specific frequency band. The reconfigurable antenna has the potential to be widely applied to the fields of millimeter wave communication such as wireless communication, satellite communication, Internet of Things and radar in the future.

[0004] Antenna polarization refers to the direction of the electric field vector when the antenna transmits or receives electromagnetic waves. In a communication system, antenna polarization affects the propagation characteristics and reception effect of signals. Selecting a suitable polarization mode can improve the transmission efficiency of signals and reduce interference. For example, circular polarization is often used in satellite communication to resist signal attenuation caused by multipath propagation, while linear polarization may be selected in some ground wireless communication to adapt to specific environmental conditions. The reconfigurable technology enables the antenna to switch between multiple polarization radiation modes to meet the application requirements of different scenarios. Currently, polarization reconfigurable antennas usually use radio frequency switches to control the switching of multiple polarization modes, including the switching of left-handed / right-handed circular polarization, the switching of linear polarization and circular polarization, the switching of horizontal polarization and vertical polarization, and the like.

[0005] Most of the conventional polarization and pattern reconfigurable antennas are currently applied to low-frequency bands below 10 GHz or satellite communication bands such as Ku / Ka. It is usually difficult to realize mass production in the millimeter wave frequency band above 100 GHz due to the complexity of high-frequency design and the difficulty of processing technology. Common reconfigurable antennas usually use PIN diodes as radio frequency switches. However, at a terahertz frequency of 300 GHz and above, the loss of such devices is large, which seriously degrades the radiation performance of the antenna. In addition, the feeding network is also relatively complex, and a multi-layer board structure needs to be designed 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 communication. SUMMARY

[0006] In order to solve the problems in the background art, the application designs a millimeter wave polarization and pattern reconfigurable antenna, which can meet the requirements of pattern and polarization reconfiguration at a millimeter wave frequency of 140 GHz. The antenna unit profile is low, a single layer of quartz glass dielectric plate is used as the substrate, the feeding mode is simple, the process difficulty is low, and it is easy to process and test. The composite beam RF MEMS switch is applied, the direct current bias voltage is moderate, the mechanical strength and stability are high, the isolation is high in the off state, and the insertion loss is low in the on state. The millimeter wave polarization and pattern reconfigurable antenna based on the MEMS switch has the characteristics of large beam deflection angle, high gain, wide circular polarization axial ratio, and can realize the reconfiguration of circular polarization and linear polarization.

[0007] In order to solve the above technical problems, the application is realized by the following technical scheme:

[0008] A millimeter wave polarization and pattern reconfigurable antenna, comprising two symmetrically arranged rectangular radiation patches, further comprising a dielectric substrate 19 and a metal ground back plate 20, the metal ground back plate 20 is located on the lower surface of the dielectric substrate 19, and the rectangular radiation patch is located on the upper surface of the dielectric substrate 19; one edge of the rectangular radiation patch is provided with a semicircular defect 3, one corner is provided with a quarter circular defect 4, and the other edge is provided with a rectangular branch loading 5; the semicircular defect 3 and the rectangular branch loading are located on the adjacent edges;

[0009] The upper surface of the dielectric substrate 19 is further provided with a T-shaped power division feeding network and a coplanar waveguide; the feeding port of the coplanar waveguide is connected with the T-shaped power division feeding network 8 through a gradual matching structure 18; both ends of the T-shaped power division feeding network are connected with a quadrature dual-directional feeding network; both ends of the quadrature dual-directional feeding network are connected to the other adjacent edges of the corresponding rectangular radiation patch.

[0010] A composite beam ohmic contact type MEMS switch is arranged at the connection fracture of the T-shaped power division feeding network and the quadrature dual-directional feeding network and the fracture of one branch of the quadrature dual-directional feeding network.

[0011] Further, the composite beam ohmic contact type MEMS switch comprises a silicon dioxide beam, a pier, a metal beam, an electrode and a contact;

[0012] The metal beam, the pier and the electrode are each provided with two groups; the two piers are respectively located on the two sides of the fracture, the adjacent ends of the two metal beams are connected through the silicon dioxide beam, and the contact is tightly attached to the lower surface of the silicon dioxide beam; the other end of the metal beam is connected to the corresponding pier, and the electrode is located directly below the corresponding metal beam with a spacing greater than zero between them.

[0013] Further, the medium substrate upper surface is also provided with a test patch pad; the motor and the pier of the composite beam ohmic contact MEMS switch are connected with the test patch pad through the corresponding direct current bias line.

[0014] Further, the quarter-circle defect is located at the corner between the two branch connection edges of the orthogonal bidirectional feed network.

[0015] Further, the pier of each composite beam ohmic contact MEMS switch is connected on the same test patch pad.

[0016] At the connection break of the T-shaped power division feed network and the orthogonal bidirectional feed network, the composite beam ohmic contact MEMS switch corresponds to the test patch pad, and the electrode is connected on the corresponding test patch pad.

[0017] At the branch break of the orthogonal bidirectional feed network, the composite beam ohmic contact MEMS switches of the same branch correspond to a test patch pad, and the electrodes are connected on the corresponding test patch pad.

[0018] Compared with the background art, the present application has the following advantages:

[0019] a) The terahertz band radiation loss is small, and the efficiency is high. The RF MEMS switch with a composite beam structure is loaded on the parasitic unit of the antenna as a radio frequency device. When the switch is disconnected on the microwave transmission line, S21<-20dB, the isolation is high, when S21>-0.56dB, the terahertz loss is small, the switch on-off can be effectively controlled by direct current bias, the microwave transmission characteristic is good, and the antenna radiation efficiency is high.

[0020] b) The circular polarization axial ratio range is wide, the beam deflection angle is large, and the gain is high. The RF switch on the orthogonal feed network controls the polarization mode of the antenna. When the switch is disconnected, the antenna is single-feed line polarized, and when the switch is closed, the antenna is double-feed circularly polarized. The RF switch on the T-shaped power division feed network can control the beam pointing. When the switch is closed to one side, the beam is inclined at an angle of 30.5°, and the radiation gain is 6.27dB. When the left and right beams are deflected, they are symmetrical, the radiation is circularly polarized wave, the E / H plane single-side radiation 3dB axial ratio range is more than 120°, and the comprehensive 3dB axial ratio range is more than 90°, covering the complete half-power beam width.

[0021] c) The profile is low, the size is small, and the manufacturing is convenient. The 1um gold etched on the quartz glass substrate is used as the radiation unit and the feed network, the reflective back plate is a complete gold layer, the medium thickness is 100um, the single-layer plate is easier to process, no substrate via hole process is involved, the gold layer can be realized through surface process, the feed structure is simple, and rapid printing manufacturing can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1It is a complete structure top view schematic diagram of a millimeter wave polarization and pattern reconfigurable antenna;

[0023] Figure 2 It is a structure top view schematic diagram of RF MEMS switch loaded on the feed network;

[0024] Figure 3 It is a structure side view of the MEMS switch;

[0025] Figure 4 It is a structure front view of the MEMS switch;

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

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

[0028] Figure 7 It is a circular polarization axial ratio range curve diagram when the antenna is orthogonally bidirectional fed;

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

[0030] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings. Figures 1-8 and examples.

[0031] A millimeter wave polarization and pattern reconfigurable antenna, comprising symmetrical rectangular radiation patches 1, 2, a half-circle defect 3, a quarter-circle defect 4, a rectangular branch loading 5 on the radiation patch, an orthogonally bidirectional feed network 6, 7, a T-shaped power division feed network 8, a composite beam ohmic contact MEMS switch 9, 14, a direct current bias line 15, a test patch pad 16, a coplanar waveguide 17, a gradual matching structure 18, a dielectric substrate 19, a metal ground back plate 20. It also comprises a MEMS switch pier 21, a metal beam 22, a silicon dioxide beam 23, a contact 24, an electrode 25, a silicon nitride insulating layer 26, and a beam through-hole 27.

[0032] The two rectangular radiation patches are the same in shape and size, symmetrical in position, and are designed with the same size and position of defects, the six RF MEMS switches are the same in size and structure, symmetrical in position, located at the beginning and end of the orthogonally bidirectional feed network and the beginning of the T-shaped power division feed network, the switch is erected in a symmetrical position, and the bias line is bridged in the same position.

[0033] All the feeding networks are impedance-matched and can be probe-fed to the coplanar waveguide feeding ports using RF probes. The coplanar waveguide 17 has a symmetrical structure with identical gaps, and its feeding ports are connected to the T-type power divider feeding network 8 via a gradient matching structure 18.

[0034] With attachment Figure 1 Taking a millimeter-wave polarization and pattern reconfigurable antenna as an example, it consists of symmetrical rectangular radiating patches 1 and 2, a semi-circular defect 3 and a quarter-circular defect 4 located on the radiating patches, a rectangular stub loading 5, orthogonal bidirectional feed networks 6 and 7, a T-type power divider feed network 8, composite beam ohmic contact MEMS switches 9 and 14, a DC bias line 15, a test patch pad 16, a coplanar waveguide 17, a gradient matching structure 18, a dielectric substrate 19, and a metal ground backplane 20, and is probe-fed through the coplanar waveguide port.

[0035] The rectangular radiating patch serves as the antenna body and is directly connected to the feed line. The resonant point can be fine-tuned by adjusting the patch size. Switches 9 and 10 on the T-shaped power divider feed network can control the feed direction to achieve reconfigurable left and right beam deflection. Switches 11 and 14 on the orthogonal bidirectional feed network can control the switching between circular and linear polarization radiation. When the switches are open, energy cannot smoothly reach the other end through the feed line. The dual-switch loading ensures higher isolation and prevents degradation caused by additional stub loading when the switch is open.

[0036] The dimensions of the orthogonal bidirectional feed network are rigorously designed. The long line with switch loading has a 90° phase delay compared to the short line. Two orthogonal degenerate modes are excited at the microstrip patch and synthesized to obtain a circularly polarized wave. At the same time, the beam deflection can be controlled by controlling the switch on the T-type power divider feed network, which can achieve circularly polarized beam radiation with a tilt angle of 30.5°.

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

[0038] The applied voltage on the PAD of the electrode is gradually increased, and when the driving voltage value is reached, the electrostatic force generated by the electrode attracts the upper metal beam to bend and deform downward. When the voltage further rises to the attraction voltage, the deformation reaches a maximum value, the contact and the signal line are in contact, and the switch is turned on. Adjust the bias voltage to gradually decrease, the electrostatic force decreases, and because the upper layer of the electrode is separated from the metal beam by an insulating silicon nitride film, the metal beam can easily spring back, the contact is separated from the signal line, and the switch is turned off.

[0039] The end of the coplanar waveguide feed structure adopts a gradually changing gap to achieve excellent matching with the gradually changing microstrip line. The slopes of the left and right waist lines of the trapezoidal feed line are consistent. The matching bandwidth can be optimized by optimizing the length of the bottom side and the angle of the bottom corner of the trapezoidal feed line, and by optimizing the width of the microstrip feed line and the length of the joint part. The return loss and gain of the antenna unit can be adjusted. The GSG radio frequency probe can be used to measure the signal line and the metal ground on both sides of the coplanar waveguide, which facilitates radio frequency testing.

[0040] The lower surface of the dielectric substrate is printed with a 1-micron-thick metal floor. Without the metal floor, the antenna will radiate to the rear lobe, and a large amount of energy will be leaked. The metal floor is used to reflect the beam and point to the upper half of the plane. In order to reduce the loss, the metal material of all structures is selected to have a small resistivity, such as aluminum, copper, gold, etc. The dielectric substrate 10 is made of a material with small loss, such as high-resistance silicon, Rogers 5880, etc. In this example, the metal material is gold, and the dielectric substrate is quartz glass with a dielectric constant of 3.78 and a loss tangent of 0.0008.

[0041] The structure of the millimeter wave polarization and pattern reconfigurable antenna is selected here to illustrate an embodiment with a size combination (the following data is in microns):

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

[0043] The rectangular radiation patch 1, 2 is 520 x 520 long x wide, the semicircular defect 3 is 40 in radius, the quarter-circle defect 4 is 50 in radius, the rectangular branch loading 5 is 40 x 40 long x wide, the orthogonal bidirectional feed network 6, 7 is 20 in line width, the T-shaped power division feed network 8 is 142 x 20 long x wide, the DC bias line 15 is 5 in line width, the test patch pad 16 is 100 x 100 in gold PAD size, the coplanar waveguide 17 is 600 x 230 in overall length x width, the triangular defect size is 35 x 30, the gradually changing microstrip line of the gradually changing matching structure 18 is 5 in short side size, 70 in long side size, and 135 in total length.

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

[0045] The pier 21 is 30 x 10 long x wide, and the beam upper through hole 27 is 6 in diameter.

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

[0047] The height of the bridge 21 = 1.2, the height of the metal beam 22 = 0.5, the height of the silicon dioxide beam 23 = 1, and the height of the contact 24 = 0.7;

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

[0049] The thickness of the dielectric substrate 19 = 100 um, the thickness of the metal ground plate 20 = 1 um, the size of the metal beam 22 = 50 x 50, the length x width of the silicon dioxide beam 23 = 120 x 50, the length x width of the contact 24 = 50 x 8, the length x width of the electrode 25 = 50 x 25, and the thickness of the silicon nitride film 26 = 0.1 um;

[0050] When the coplanar waveguide is fed, the central frequency is 140 GHz, which belongs to the millimeter wave frequency band.

[0051] At this time, the reflection coefficient simulation diagram of a millimeter wave polarization and pattern reconfigurable antenna is as follows:

[0052] Figure 8 The reflection coefficient curve of the antenna is shown in the figure, and it is shown that the S11 of the antenna unit is significantly less than -10 dB in the frequency range of 136.6 GHz-142.6 GHz.

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

[0054] Figure 6 The radiation gain diagram of the antenna at the central frequency is shown in the figure, at this time, the right MEMS switch 9 of the T-shaped power division feeding network is in the on state, and it is shown that the gain of the antenna unit is 6.27 dB, and the beam tilt angle is -30.5°. The antenna has high gain and can realize the function of pattern reconfiguration. Similarly, when the right MEMS switch is closed, due to the complete symmetry of the structure design, the beam tilt angle can be reversed to 30.5° without changing the gain and matching. In addition, the left and right radiation units are mirror symmetric, which can realize the reconfiguration of left-handed and right-handed circular polarization while controlling the beam deflection.

[0055] At this time, when the MEMS switches 11-12 on the orthogonal bidirectional feeding network are both closed, the antenna is in a double-fed state, two orthogonal degenerate modes are combined to synthesize circularly polarized radiation waves, and the beam deflection of the pattern is preserved, and the 3dB axial ratio range is shown in Figure 7 , the 3dB axial ratio range of E / H single surface radiation is over 120°, and the comprehensive 3dB axial ratio range is over 90°, covering the complete half-power beam width.

[0056] When the MEMS switches 11-12 on the orthogonal two-way feed network are both open, the antenna is in a single feed state, a single mode excites its linearly polarized wave, and the beam deflection of the pattern is still retained. Similarly, the other side can also realize the radiation of circularly polarized and linearly polarized waves with beam deflection.

[0057] When the MEMS switches 9-10 on the left and right sides of the T-shaped power division feed network are both in the on state, the antenna radiates towards the Z axis without left-right directional beam deflection, and radiates linearly polarized waves.

[0058] The antenna unit working in the millimeter wave frequency band can realize the functions of reconfigurable pattern and polarization, has high gain, and the structure design is simple, only composed of a single layer plate, the profile is low, the coplanar waveguide feed method has good impedance matching bandwidth, and is easy to process and realize.

[0059] The above is only an example, if a millimeter wave polarization and pattern reconfigurable antenna with different center frequencies is needed, different parameters can be adjusted according to the specific implementation to achieve different working frequency bands and beam tilting effects.

Claims

1. A millimeter-wave polarization and pattern reconfigurable antenna comprising two rectangular radiating patches symmetrically arranged, characterized in that, Also include a dielectric substrate (19) and a metal ground back plate (20), the metal ground back plate (20) is located in the lower surface of the dielectric substrate (19), the rectangular radiation patch is located in the upper surface of the dielectric substrate (19); One edge of the rectangular radiation patch is provided with a semicircle defect (3), one corner is provided with a quarter circle defect (4) and the other edge is provided with a rectangular branch loading (5); The semicircle defect (3) and the rectangular branch loading are located in the adjacent edge; The upper surface of the dielectric substrate (19) is also provided with a T-shaped power division feeding network and a coplanar waveguide; The feeding port of the coplanar waveguide is connected with the T-shaped power division feeding network (8) through a gradual matching structure (18); Both ends of the T-shaped power division feeding network are connected with a quadrature dual-direction feeding network; Both ends of the quadrature dual-direction feeding network are respectively connected to the other adjacent edge of the corresponding rectangular radiation patch; A composite beam ohmic contact type MEMS switch is arranged at the connection fracture of the T-shaped power division feeding network and the quadrature dual-direction feeding network and the fracture of one branch of the quadrature dual-direction feeding network.

2. The millimeter-wave polarization and pattern reconfigurable antenna according to claim 1, wherein, The composite beam ohmic contact type MEMS switch comprises a silicon dioxide beam, a bridge pier, a metal beam, an electrode and a contact point; The metal beam, the bridge pier and the electrode are each provided with two groups; Two bridge piers are respectively located on the two sides of the fracture, the adjacent ends of the two metal beams are connected through the silicon dioxide beam, and the contact point is tightly 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 has a spacing greater than zero between the two.

3. The millimeter-wave polarisation and pattern reconfigurable antenna according to claim 2, characterised in that, The upper surface of the dielectric substrate is also provided with a test patch pad; The motor and the bridge pier of the composite beam ohmic contact type MEMS switch are connected with the test patch pad through the corresponding direct current bias line.

4. The millimeter-wave polarisation and pattern reconfigurable antenna according to claim 2, characterised in that, The quarter circle defect is located at the corner between the two branch connection edges of the quadrature dual-direction feeding network.

5. The millimeter-wave polarisation and pattern reconfigurable antenna according to claim 3, characterised in that, The bridge pier of each composite beam ohmic contact type MEMS switch is connected to the same test patch pad; At the connection fracture of the T-shaped power division feeding network and the quadrature dual-direction feeding network, the composite beam ohmic contact type MEMS switch corresponds to the test patch pad one by one, and the electrode thereof is connected to the corresponding test patch pad; At the fracture of one branch of the quadrature dual-direction feeding network, the composite beam ohmic contact type MEMS switch of the same branch corresponds to one test patch pad, and the electrodes thereof are connected to the corresponding test patch pad.

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