Millimeter wave polarization and directional diagram reconfigurable antenna

Abstract

The invention discloses a millimeter wave polarization and directional diagram reconfigurable antenna, and belongs to the field of radio frequency front-end devices. The antenna is composed of symmetrical rectangular radiation patches, and a semicircular defect, a quarter circle defect, a rectangular branch load, an orthogonal bidirectional feed network, a T-shaped power dividing feed network, a composite beam ohmic contact type MEMS switch, a direct current bias line, a test patch bonding pad, a coplanar waveguide, a gradient matching structure, a dielectric substrate and a metal ground backboard which are located on the radiation patches. When the single-side MEMS switch on the T-shaped power dividing feed network is switched on, energy flows to the radiation unit on the side, and the leftward or rightward wave beam inclination effect can be achieved. When the MEMS on the two sides are both switched on, the radiation pattern points to the Z positive axis, no beam deflection exists, and therefore the pattern reconfigurable function in the left direction, the middle direction and the right direction can be achieved. When a switch on the orthogonal bidirectional feed network is closed, the size of the long line can realize 90-degree phase delay, and two orthogonal degenerate modes are synthesized into a circularly polarized wave to cover a complete half-power beam width.

Description

Technical Field

[0001] The present invention relates to a millimeter wave polarization and directional pattern reconfigurable antenna, which is mainly used in a communication system in a millimeter wave 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] Antenna polarization refers to the direction of the electric field vector when the antenna transmits or receives electromagnetic waves. In communication systems, antenna polarization affects the propagation characteristics and reception effect of the signal. Choosing the right polarization method can improve the transmission efficiency of the signal and reduce interference. For example, satellite communications often use circular polarization to resist signal attenuation caused by multipath propagation, while in some terrestrial wireless communications, linear polarization may be selected to adapt to specific environmental conditions. Reconfigurable technology enables antennas to switch between multiple polarization radiation modes to meet the application requirements of different scenarios. At present, polarization reconfigurable antennas usually use RF switches to control the switching of multiple polarization modes, including switching between left-hand / right-hand circular polarization, switching between linear polarization and circular polarization, switching between horizontal polarization and vertical polarization, etc.

[0005] At present, conventional polarization and directional pattern reconfigurable antennas are mostly used in low-frequency bands below 10 GHz or satellite communication bands such as Ku / Ka. In the millimeter wave band 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

[0006] In order to solve the problems existing in the background technology, the present invention designs a millimeter-wave polarization and radiation pattern reconfigurable antenna, which can meet the requirements of realizing the reconfiguration of radiation pattern and polarization in the millimeter-wave frequency band of 140GHz. 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 composite beam RF MEMS switch used 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 millimeter-wave polarization and radiation pattern reconfigurable antenna based on this MEMS switch has the characteristics of large beam deflection angle, high gain, wide circular polarization axis ratio, etc., and can realize the reconfiguration of circular polarization and linear polarization.

[0007] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0008] A millimeter wave polarization and pattern reconfigurable antenna, comprising two symmetrically arranged rectangular radiation patches, a dielectric substrate 19 and a metal ground backplane 20, wherein the metal ground backplane 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 thereof 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 at adjacent edges;

[0009] The upper surface of the dielectric substrate 19 is also provided with a T-type power division feeding network and a coplanar waveguide; the feeding port of the coplanar waveguide is connected to the T-type power division feeding network 8 through a gradient matching structure 18; both ends of the T-type power division feeding network are connected to an orthogonal bidirectional feeding network; the two ends of the orthogonal bidirectional feeding network are respectively connected to the other adjacent edge of the corresponding rectangular radiation patch;

[0010] A composite beam ohmic contact type MEMS switch is arranged at the connection break of the T-type power division feeding network and the orthogonal bidirectional feeding network and at the break of one branch of the orthogonal bidirectional feeding network.

[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, a test patch pad is also provided on the upper surface of the dielectric substrate; the motor and the bridge pier of the composite beam ohmic contact MEMS switch are connected to the test patch pad through corresponding DC bias lines.

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

[0015] Further, the bridge piers of each composite beam ohmic contact MEMS switch are connected to the same test patch pad;

[0016] At the connection break between the T-type power splitter feeding network and the orthogonal bidirectional feeding network, the composite beam ohmic contact MEMS switch corresponds to the test patch pad one by one, and its electrode is connected to the corresponding test patch pad;

[0017] At a break in one of the branches of the orthogonal bidirectional feeding network, the composite beam ohmic contact MEMS switch of the same branch corresponds to a test patch pad, and its electrodes are all connected to the corresponding test patch pad.

[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 circular polarization axis ratio range is wide, the beam deflection angle is large, and the gain is high. The RF switch on the orthogonal dual-feed network controls the polarization mode of the antenna. When disconnected, the antenna is single-feed polarized, and when closed, it is dual-feed circularly polarized radiation. The RF switch on the T-type centimeter feed network can control the beam pointing. The beam is tilted to the side where the switch is closed, with a tilt angle of 30.5° and a radiation gain of 6.27dB. The left and right beams are symmetrical when deflected, radiating circularly polarized waves. The E-plane / H-plane single-side radiation 3dB axis ratio range exceeds 120°, and the comprehensive 3dB axis ratio range exceeds 90°, covering the complete half-power beam width.

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

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

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

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

[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 circular polarization axis ratio range curve when the antenna is orthogonally fed bidirectionally;

[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] A millimeter wave polarization and pattern reconfigurable antenna comprises symmetrical rectangular radiation patches 1, 2, semicircular defects 3, quarter-circular defects 4, rectangular branch loading 5, orthogonal bidirectional feeding networks 6, 7, T-type power splitter feeding network 8, composite beam ohmic contact MEMS switches 9, 14, DC bias line 15, test patch pad 16, coplanar waveguide 17, gradient matching structure 18, dielectric substrate 19, and metal ground backplane 20. It also comprises MEMS switch bridge pier 21, metal beam 22, silicon dioxide beam 23, contact 24, electrode 25, silicon nitride insulating layer 26, and through hole 27 on the beam.

[0032] The two rectangular radiation patches have the same shape and size, and are symmetrically positioned. They both have defect loading designs of the same size and position. The six RF MEMS switches have the same size and structure, and are symmetrically positioned. They are located at the beginning and end of the orthogonal bidirectional feeding network and the beginning of the T-type power divider feeding network. The switch installation positions are symmetrical, and the bias line bridge positions are the same.

[0033] The feeding network is designed with impedance matching, and the coplanar waveguide feeding port can be probe-fed by the radio frequency probe. The coplanar waveguide 17 has a bilaterally symmetrical structure and the same gap, and the feeding port is connected to the T-type power splitter feeding network 8 through a gradient matching structure 18.

[0034] Attach Figure 1 Taking a millimeter-wave polarization and radiation pattern reconfigurable antenna as an example, it consists of symmetrical rectangular radiation patches 1, 2, a semicircular defect 3, a quarter-circular defect 4, a rectangular branch loading 5, an orthogonal bidirectional feeding network 6, 7, a T-type power divider feeding network 8, a composite beam ohmic contact MEMS switch 9, 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 by the coplanar waveguide port.

[0035] The rectangular radiation patch 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 switches 9 and 10 on the T-type power splitter feeding network can control the feeding direction to achieve the reconfigurable directional pattern of left and right beam deflection. The switches 11 and 14 on the orthogonal bidirectional feeding network can control the radiation switching of circular polarization and linear polarization. When the switch is disconnected, the energy cannot pass smoothly through the feed line to the other end. The loading of the dual switches ensures higher isolation and ensures that there is no degradation caused by additional branch loading when disconnected.

[0036] The dimensions of the orthogonal bidirectional feeding network have been strictly 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 to synthesize circularly polarized waves. At the same time, the beam deflection can be controlled by controlling the switch on the T-type power divider feeding network, which can achieve circularly polarized beam radiation with a tilt angle of 30.5°.

[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 4 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:

[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 uses a gradual gap at the end 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, the line width of the microstrip feeder and the length of the connecting part to adjust the return loss and gain of the antenna unit. The signal line of the coplanar waveguide and the metal ground on both sides can be tested with the GSG RF probe to facilitate RF testing.

[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 millimeter wave polarization and directional pattern reconfigurable antenna 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] Rectangular radiation patches 1, 2 length × width = 520 × 520, semicircular defect 3 radius = 40, quarter-circular defect 4 radius = 50, rectangular branch loading 5 length × width = 40 × 40, orthogonal bidirectional feeding network 6, 7 line width = 20, T-type power splitter feeding network 8 length × width = 142 × 20, DC bias line 15 line width = 5, test patch pad 16 gold PAD size = 100 × 100, coplanar waveguide 17 overall length × width = 600 × 230, triangular defect size = 35 × 30, gradient matching structure 18 gradient microstrip line short side size = 5, long side size = 70, total length = 135;

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

[0045] The length×width of the bridge pier 21 is 30×10, and the diameter of the through hole 27 on the beam is 6;

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

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

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

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

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

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

[0052] Figure 8 Shown in FIG. 1 is the reflection coefficient curve of the antenna, which shows that the S11 of the antenna unit is significantly less than -10dB in the frequency range of 136.6GHz-142.6GHz.

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

[0054] Figure 6 The figure shows the radiation gain diagram of the antenna at the center frequency. At this time, the right MEMS switch 9 of the T-type power splitter feeding network is in the on state, showing that the antenna unit gain is 6.27dB and the beam tilt angle is -30.5°. The antenna has a high gain and 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 30.5° without changing the gain and matching. In addition, the left and right radiating units are mirror-symmetrical, which can realize left-handed and right-handed circular polarization reconfiguration while controlling the beam deflection.

[0055] At this time, when the MEMS switches 11-12 on the orthogonal bidirectional feeding network are all closed, the antenna is in a dual-feed state, and the two orthogonal degenerate modes synthesize a circularly polarized radiation wave and retain the beam deflection of the directional pattern. The 3dB axial ratio range is shown in Figure 7 The 3dB axial ratio range of E-plane / H-plane single-sided radiation exceeds 120°, and the comprehensive 3dB axial ratio range exceeds 90°, covering the complete half-power beamwidth.

[0056] When the MEMS switches 11-12 on the orthogonal bidirectional feeding network are all disconnected, the antenna is in a single-feed state, and a single mode excites its linearly polarized wave, and the beam deflection of the directional pattern is still retained. Similarly, the other side can also achieve 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-type power splitter feeding network are both in the on state, the antenna radiates toward the Z axis without beam deflection in the left and right directions, and radiates linearly polarized waves.

[0058] The antenna unit operates in the millimeter wave frequency band and can realize the reconfigurable functions of the radiation pattern and polarization. It has a high gain and a 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.

[0059] The above is only an example. If one wants to obtain a millimeter-wave polarization and radiation pattern reconfigurable antenna at different center frequencies, different parameters can be adjusted according to the specific implementation method to achieve different operating frequency bands and beam tilt effects.

Claims

1. A millimeter wave polarization and pattern reconfigurable antenna, comprising two symmetrically arranged rectangular radiation patches, characterized in that: It also includes a dielectric substrate (19) and a metal ground back plate (20), wherein 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 adjacent edges; The upper surface of the dielectric substrate (19) is also provided with a T-type power division feeding network and a coplanar waveguide; the feeding port of the coplanar waveguide is connected to the T-type power division feeding network (8) via a gradient matching structure (18); both ends of the T-type power division feeding network are connected to an orthogonal bidirectional feeding network; and both ends of the orthogonal bidirectional 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 break of the T-type power division feeding network and the orthogonal bidirectional feeding network and at the break of one branch of the orthogonal bidirectional feeding network.

2. The millimeter wave polarization and pattern reconfigurable antenna according to claim 1, 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.

3. The millimeter wave polarization and pattern reconfigurable antenna according to claim 2, characterized in that: A test patch pad is also provided on the upper surface of the dielectric substrate; the motor and the bridge pier of the composite beam ohmic contact MEMS switch are connected to the test patch pad through corresponding DC bias lines.

4. The millimeter wave polarization and pattern reconfigurable antenna according to claim 2, characterized in that: The quarter circle defect is located at a corner between two branch connection edges of the orthogonal bidirectional feeding network.

5. The millimeter wave polarization and pattern reconfigurable antenna according to claim 3, characterized in that: The bridge piers of each composite beam ohmic contact MEMS switch are connected to the same test patch pad; At the connection break between the T-type power splitter feeding network and the orthogonal bidirectional feeding network, the composite beam ohmic contact MEMS switch corresponds to the test patch pad one by one, and its electrode is connected to the corresponding test patch pad; At a break in one of the branches of the orthogonal bidirectional feeding network, the composite beam ohmic contact MEMS switch of the same branch corresponds to a test patch pad, and its electrodes are all connected to the corresponding test patch pad.

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