A terahertz broadband wide-angle pattern reconfigurable antenna

Abstract

The application provides a terahertz broadband wide-angle pattern reconfigurable antenna, and belongs to the field of radio frequency MEMS. The antenna comprises a tilted beam radiation unit, a tapered balun, a feed network, a MEMS switch network and a voltage bias line group; the feed network comprises one microstrip main feed line and four microstrip branch lines; three voltage bias line groups and one microstrip main feed line are distributed in a cross shape, the outer end of the microstrip main feed line is connected with the tapered balun, and the inner end of the microstrip main feed line is connected with the four microstrip branch lines through a two-stage bifurcation structure; the four tilted beam radiation units are connected with one microstrip branch line respectively; the MEMS switch network comprises three groups of switch structures, and the voltage bias line group at each bifurcation structure is used for controlling the opening and closing of the switch structure at the bifurcation structure, so as to realize the on-off of the corresponding microstrip line in the feed network. The application has the advantages of simple structure, convenient manufacturing, fast manufacturing and integration, and azimuth beam scanning.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of radio frequency MEMS, and particularly relates to a terahertz directional diagram reconfigurable antenna based on a MEMS switch network. BACKGROUND

[0002] The MEMS switch is widely applied in radio frequency systems below the millimeter wave frequency band due to high isolation, small insertion loss and other advantages; in the terahertz frequency band, the solid-state semiconductor switch is still immature, and the mechanical switch is too large in size, so that the application potential of the MEMS switch is multiplied; the directional diagram reconfigurable antenna has wide and important application requirements in satellite communication systems, broadband network systems and radar systems in civil and military fields due to the advantages of switchable beam pointing and large coverage space angle. There are more researches on the MEMS switch in the world, but there are fewer achievements in the terahertz frequency band, and the research is still in the initial stage. The directional diagram reconfigurable antenna can change the maximum radiation direction itself without adjusting the signal amplitude and phase, which provides a new dimension for the terahertz front-end design and enhances the large-angle scanning capability; however, the directional diagram reconfigurable antenna has the disadvantages of complex antenna structure, difficult processing, great influence of bias circuit and wide-angle scanning in one-dimensional direction for most antennas.

[0003] There are few achievements of the terahertz frequency band MEMS switch and the directional diagram reconfigurable antenna, the terahertz MEMS switch has large structure size, poor high-frequency isolation and large loss, for example, N. Scott Barker and other persons from the University of Virginia, USA, designed a terahertz cantilever beam switch based on a coplanar waveguide by using silicon and fused quartz in 2022; the MEMS switch array working in the terahertz frequency band and its related radio frequency applications have not been truly realized, Mehmet Unlu and other persons from Turkey published a conference paper on the antenna pointing control by using the MEMS switch in 2017, the paper is only based on the simulation results, and the beam sidelobe is high and the coverage angle range is small.

[0004] Due to the disadvantages of large structure size, poor high-frequency isolation and large loss of the current terahertz MEMS switch, it is difficult to meet the requirements of the application in the antenna and other radio frequency devices. The reconfigurable antenna in the terahertz frequency band still cannot realize the large-angle beam coverage. SUMMARY

[0005] Therefore, the application provides a terahertz wideband wide-angle directional diagram reconfigurable antenna, which can meet the requirements of full coverage in the horizontal plane and basic coverage in the upper half of the pitch plane in the terahertz frequency band, and has the characteristics of wide bandwidth, multiple reconfigurable beams, low sidelobe, high polarization purity, easy design and implementation and the like.

[0006] The application is achieved in the following manner:

[0007] A terahertz broadband wide-angle beam reconfigurable antenna comprises four inclined-beam radiating units, a tapered balun, a feed network, a MEMS switch network and three voltage biasing line groups; the feed network is composed of microstrip lines, including a microstrip main feed line, a first-level bifurcation structure, two second-level bifurcation structures and four microstrip branch lines; the three voltage biasing line groups and the microstrip main feed line are in a cross shape, the outer end of the microstrip main feed line is connected with the tapered balun, the inner end of the microstrip main feed line is connected with the four microstrip branch lines through the two second-level bifurcation structures, and the three voltage biasing line groups extend to the bifurcation structures respectively; the four inclined-beam radiating units are distributed in the four 90-degree angles of the cross formed by the three voltage biasing line groups and the microstrip main feed line, and the four inclined-beam radiating units are connected with the microstrip branch lines respectively; the MEMS switch network comprises three switch structures, and the three switch structures are located at the three bifurcation structures in the feed network respectively, and the voltage biasing line groups at each bifurcation structure are used to control the opening and closing of the switch structure at the bifurcation structure, so as to realize the on-off of the corresponding microstrip lines in the feed network.

[0008] Further, the line width and the interval of the grounded coplanar waveguide part of the tapered balun change simultaneously, the terminal of the tapered balun is surrounded by the metallized via formed by the TGV process, and the grounded coplanar waveguide part of the tapered balun is finally output as a microstrip main feed line.

[0009] Further, the four inclined-beam radiating units have the same structure, and the length and the slot width are independently designed.

[0010] Further, the outer ends of the three voltage biasing line groups are connected with a group of biasing contacts respectively.

[0011] Further, the width of the microstrip line in the feed network is linearly narrowed before entering the switch structure.

[0012] Further, the MEMS switch network comprises six switch structures in total, two switch structures are arranged at each bifurcation structure, and all the switch structures are distributed in an axisymmetric manner about the microstrip main feed line; each voltage biasing line group comprises four voltage biasing lines, and each switch structure is connected with two voltage biasing lines.

[0013] Further, the switch structure comprises an elastic metal-dielectric composite film bridge, a pull-down electrode, a silicon nitride isolation layer, a first metal pier, and a second metal pier; each of the two ends of the elastic metal-dielectric composite film bridge has a crane-shaped arm, the elastic metal-dielectric composite film bridge is of an asymmetric structure, the main body of which is a dielectric part, and a metal layer is attached to the lower surface of the middle part and the lower surface of one end of the bridge, thereby forming two metal-dielectric overlapping parts, wherein the metal layer of the middle part is provided with a metal contact point for conducting the corresponding microstrip line, the crane-shaped arm of one end of the elastic metal-dielectric composite film bridge is connected to the first metal pier through the metal layer, and the crane-shaped arm of the other end without the metal layer covers the second metal pier through a folding arm; the pull-down electrode is located below the metal layer at the bridge surface and is used to pull down the bridge surface so that the metal contact point contacts the microstrip line, and the pull-down electrode is covered with the silicon nitride isolation layer; the two voltage bias lines connected to the switch structure are connected to the first metal pier and the pull-down electrode of the switch structure, respectively.

[0014] Further, the pull-down electrode is isosceles trapezoidal, and the corresponding side waist is parallel to the gradually changing profile of the linear narrowing of the adjacent microstrip line.

[0015] The present application has the following advantages:

[0016] 1. The MEMS switch of the present application still has high isolation characteristics in the terahertz frequency band, and through the series equivalent inductance, wideband low-loss characteristics and miniaturization characteristics can also be achieved, which is convenient for high-density integration.

[0017] 2. The present application can realize azimuthal beam scanning, and through the single-port design, large-angle coverage in the elevation plane and quadrant scanning in the full azimuthal plane are realized.

[0018] 3. The present application has a simple structure and is easy to manufacture, and only a single layer of fused quartz substrate and two layers of planar microstrip structure are used, so that rapid manufacturing and integration can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic diagram of the overall structure of the embodiment of the present application;

[0020] Figure 2 is a schematic diagram of the MEMS switch network of the embodiment of the present application;

[0021] Figure 3 is an oblique view of the MEMS switch structure of the embodiment of the present application;

[0022] Figure 4 is a pull-down simulation diagram of the MEMS switch of the embodiment of the present application;

[0023] Figure 5 is an S parameter curve diagram of the MEMS switch of the embodiment of the present application;

[0024] Figure 6 , Figure 7 is the S parameter curve of the switch network of the embodiment of the application;

[0025] Figure 8 is the standing wave ratio curve of the reconfigurable antenna of the application;

[0026] Figure 9 is the two-dimensional elevation pattern of each deflection state of the embodiment of the application. DETAILED DESCRIPTION

[0027] In order to make the technical problems to be solved by the application, the technical solutions and the beneficial effects clearer, the application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not used to limit the application.

[0028] A terahertz broadband angle pattern reconfigurable antenna, comprising a test balun for a terahertz frequency band, a broadband MEMS switch network and a tilted beam radiation unit, all structures are distributed on the top and bottom two layers of a fused quartz substrate; the test balun comprises a line width and a gap step-graded ground coplanar waveguide, and a transition section of the ground coplanar waveguide to a microstrip; the MEMS switch network is symmetrically distributed between the balun interface and the antenna interface, and the switch itself and the network as a whole have broadband and low loss characteristics in the terahertz frequency band;

[0029] Each MEMS switch comprises a metal pier, a metal-dielectric asymmetric composite film bridge, a pull-down electrode, a metal contact point, a voltage bias line and a bias contact point; the pull-down electrode and the metal contact point are respectively located on the two sides of the film bridge, wherein the metal part of the film bridge is connected to the corresponding metal pier by a crane-shaped arm, the dielectric part of the film bridge is coincided with the metal part at one end and is fixed on the other metal pier by a folding arm at the other end; the two high resistance lines of the voltage bias line are connected to the metal pier and the pull-down electrode at one end, and are connected to the bias contact point at the other end; the metal contact point is located at the center position of the metal-dielectric composite film bridge, and guides the signal path when pulled down;

[0030] The terahertz MEMS switch array network is a radio frequency structure composed of six MEMS switches described above, and a certain route is realized by a specific switch combination; the switch network input end is connected to the step-graded test balun, and the output end is connected to the tilted beam radiation unit; the step-graded test balun is located on one side of the antenna structure, and the top and bottom layers are grounded through the metallized via realized by the TGV process; the step-graded test balun comprises an impedance step-graded section and a transition section of the ground coplanar waveguide to the microstrip main feeder; the tilted beam radiation unit is a quasi-Yagi structure, and the parameters of the unit on one side of the balun and the unit on the opposite side are different, and are tuned respectively.

[0031] Further, the radiation units are four, each of which is connected with the test balun through the MEMS switch group of the corresponding line, and only one radiation unit works at each time.

[0032] Further, the dielectric material of the membrane bridge is silicon dioxide or silicon nitride.

[0033] The following is a more specific example:

[0034] As Figures 1-3 shown, a terahertz broadband wide-angle pattern reconfigurable antenna includes a tapered balun 1, a microstrip main feed line 4, a MEMS switch network 5, a voltage bias line group 10, 12, 14, a bias contact 11, 13, 15, and a tilted beam radiation unit 6, 7, 8, 9. The on-off of the feed line can be controlled separately by applying voltage to the voltage bias line group 10, 12, 14; the four radiation units have basically the same structure and are symmetric about the feed line axis, one end is connected to the MEMS switch network, and the length 16 and slot width 17 of the four radiation units can be independently changed.

[0035] The pattern reconfigurable antenna unit has a unique feed structure (i.e. tapered balun 1), including a ground and line width simultaneously tapered ground coplanar waveguide structure 3 and a transition structure from ground coplanar waveguide to microstrip main feed line 4. The top ground is connected to the bottom ground through the metalized via 2; the end ground of the ground coplanar waveguide is truncated by the metalized via, the top ground no longer extends and presents a circular arc transition, and finally outputs the microstrip main feed line 4.

[0036] The MEMS switch network 5 includes three groups of unique terahertz MEMS switches 24 and 25, 26 and 27, 28 and 29, and the corresponding microstrip main feed line deformation network. The microstrip main feed line 4 is connected with the secondary microstrip main feed line 18 and 19 through the switches 24 and 25, respectively; the secondary microstrip main feed line is connected with the tertiary transmission line 20, 21, 22, 23 through the switches 26 and 27, 28 and 29; the end of the secondary microstrip main feed line 18, 19 is the same as the end of the microstrip main feed line 4, both have a linearly decreasing line width, and the end is divided into two, and after passing through the switch contact point, it is linearly widened; the on-off of each group of MEMS switches is selected by its voltage bias line group 10, 12, 14.

[0037] The six MEMS switch structures in the MEMS switch network 5 are identical and axially symmetric about the microstrip main feed line 4, each comprising a metal bridge 30 and 31, an elastic metal-dielectric composite membrane bridge (metal-dielectric overlapping part 32 and dielectric part 33), a pull-down electrode 34, a silicon nitride isolation layer 35, a metal contact point 36, and voltage bias lines 37 and 38. The elastic metal-dielectric composite membrane bridge is an asymmetric structure and mainly supported by dielectric, with one end of the overlap connected to the metal bridge by a crane-shaped arm, and the other end of the dielectric covered with the metal bridge by a folding arm. The pull-down electrode 34 is located on one side of the elastic metal-dielectric membrane bridge, and the metal contact point 36 is located in the center of the membrane bridge. The voltage bias line 37 is connected to the metal bridge 30, and the voltage bias line 38 is connected to the pull-down electrode 34, and the voltage between the two lines generates a pull-down force on the composite membrane bridge.

[0038] The following is another embodiment:

[0039] Referring to Figures 1-3 A terahertz broadband wide-angle pattern reconfigurable antenna is composed of a tapered balun 1, a MEMS switch network 5, a high-impedance voltage bias line group 10, 12, and 14, a bias contact 11, 13, and 15, a tilted beam radiation unit 6-9, and a dielectric substrate 40.

[0040] Among them, the four tilted beam radiation units 6-9, the MEMS switch network 5, and the three groups of high-impedance voltage bias line groups 10, 12, and 14 are axially symmetric about the microstrip main feed line 4; the tilted beam radiation unit 6-9 of this embodiment is a segmented metal patch with a radial length 16 of about one-half of the waveguide wavelength at the resonant frequency, the initial segment is a sector with a certain angle and radius, and the remaining segments are rings with the same angle and different radii; each tilted beam radiation unit is connected to the microstrip main feed line 4 through the MEMS switch network 5. The size 16 of the tilted beam radiation unit 6-9 and the spacing 17 of the last segment are used to adjust the resonant frequencies of the antenna in each reconfiguration state; when 16 increases, the first resonant frequency of the antenna unit decreases, and when 16 decreases, the first resonant frequency increases; when 17 increases, the second and third resonant frequencies of the antenna unit increase, and when 17 decreases, the second and third resonant frequencies decrease; the mutual coupling between the radiation unit and the feed line, the deflection angle of the maximum radiation direction in the deflection state, and the gain characteristics at that angle are also related to the resonant frequencies.

[0041] In this embodiment, the tapered balun 1 is particularly optimized, using a five-order Chebyshev impedance transformation and simultaneously tapering the ground and line width (as shown in structure 3), and using the TGV process to realize a metalized via on fused quartz at the end of the grounded coplanar waveguide (as shown in structure 2), further realizing the transition from the grounded coplanar waveguide to the microstrip main feed line 4.

[0042] The details of the MEMS switch network 5 are as follows Figure 2As shown, the microstrip main feed line 4 performs the first line selection through switches 24 and 25. The voltage bias line group 14 can control the closure of any one of the switches, and the signal enters one of the secondary microstrip main feed lines 18 and 19. The end of the secondary microstrip main feed line is the same as the end of the microstrip main feed line 4, with a linearly decreasing linewidth, and the end is split into two. The linewidth only becomes linearly wider after passing the switch contact point. Through the selection of voltage bias line group 10 or 12, the signal finally enters any one of the three-stage transmission lines 20, 21, 22, and 23.

[0043] A typical MEMS switch structure in this embodiment is as follows: Figure 3 As shown, it is driven by DC voltage. Each of the three sets of voltage bias lines (positions 10, 12, and 14) has four high-resistance lines for applying voltage, connecting the metal bridge 30 of the two MEMS switches to the pull-down electrode 34. When voltage is applied to the bias lines, the composite membrane bridge, combining silicon dioxide or silicon nitride material with metal, is pulled down by electrostatic force. The two ends of the metal contact point 36 are bridged to the microstrip main feed line 39, and the switch is turned on. When the voltage is set to zero, the electrostatic force of the metal is released, the metal-dielectric membrane bridge recovers by elastic force, and the switch is turned off. The MEMS switch in this embodiment has the following characteristics: the pull-down of the metal contact is achieved by the pull-down electrode on one side of the membrane bridge, which is asymmetrical. Due to the unbalanced pull-down force, the metal-dielectric side of the membrane bridge is connected to the metal bridge 30 by a crane-shaped arm, and the dielectric side of the membrane bridge is covered by a folded arm on the metal bridge 31 to balance the pull-down force.

[0044] The antenna operates as follows: When MEMS switch 24 is on and 25 is off, half of the MEMS switch network is disabled. If 26 is on and 27 is off, the tilted beam radiator 6 in the four radiating elements operates, with the beam pointing towards the bisector of the fan-shaped opening angle and deviating significantly from the normal direction perpendicular to the paper. Conversely, if 26 is off and 27 is on, the beam points towards the bisector of the fan-shaped opening angle of the tilted beam radiating element 9. The other radiating elements operate on the same principle. Current flows from the microstrip main feed line 4 of the MEMS switch network 5 into the secondary feed line, then from the secondary feed line through selection into the tertiary feed line, and finally feeds into the corresponding radiating element, forming a beam covering the corresponding quadrant. (See appendix...) Figure 1 In the displayed overall antenna structure, a metal ground plane of the same size as the dielectric substrate 40 is used to reflect the beam, pointing it towards the upper half-plane space. That is, the main beam is deflected towards the upper half-space of the radiating structure. The deflection angle is related to the resonant characteristics of the radiating element and the size of the metal ground plane. The smaller the outer ring in the radiating element, the larger the deflection angle between the main beam and the plane containing the microstrip main feed line. When the size of the metal ground plane is within a certain range, the main beam has the maximum deflection angle.

[0045] When two of the six MEMS switches are on and the rest are off, it is a deflection state; when all the switches are off, the antenna will not work. Therefore, there are four deflection states in total.

[0046] In order to reduce the loss, the metal material adopts a metal with small resistivity, such as gold, and the dielectric substrate 40 adopts a material with small loss, such as fused quartz glass.

[0047] The structure of the MEMS feed network has an important influence on the performance of the reconfigurable antenna, which is specifically manifested as follows:

[0048] 1) The distance between the two switches in the same switch group affects the isolation of the network and directly affects the beam, so that the antenna beam is distorted if the distance is too large, and it is difficult to process if the distance is too small;

[0049] 2) The line width variation strategy of the microstrip one-to-two affects the reflection coefficient and isolation of the network, thereby affecting the beam shape and antenna impedance matching;

[0050] 3) The length of the secondary microstrip main feed line between the switch groups affects the reflection coefficient of the network and the coupling between the radiation unit and the feed, and the antenna performance in different deflection states is basically consistent through optimization;

[0051] When the MEMS switch network is formed, the structural characteristics of the MEMS switch have an important influence on the final network performance and the final realization of the antenna beam switching, which is specifically manifested as follows:

[0052] 1) The distance between the pull-down electrode and the feed line directly affects the isolation of the switch, and the pull-down electrode finally presents a parallel state with the gradually changing edge of the feed line width, so that the switch is miniaturized and high-isolation, thereby improving the network isolation and reducing the antenna beam sidelobe;

[0053] 2) The length of the metal part where the contact is located affects the isolation of the switch when it is off, and the width affects the impedance matching when it is on, so both states need to be considered to achieve the best performance of the switch and the network, thereby achieving the best antenna reflection coefficient and beam;

[0054] 3) The form of the switch membrane bridge will determine the contact state of the contact when the pull-down electrode is pulled down, and the miniaturization and high-isolation of the switch are realized through the asymmetric membrane bridge design. In the direct contact type switch, the contact needs to be in full contact with the microstrip feed line in the pull-down state to achieve the effect of on and off.

[0055] Because the radiation unit is coupled with the feed line, the voltage bias line, etc. in the specific implementation, the performance of the antenna in different deflection states is different, so it is of great significance to design a reasonable MEMS switch form, MEMS network structure and radiation unit to improve the performance of the directional diagram reconfigurable antenna. The final structure parameters of the antenna are the result of comprehensive optimization.

[0056] The following selects a size combination for illustration (the following data unit is microns):

[0057] When Figure 1 The size of the structure is:

[0058] Structure 16 = 653, structure 17 = 25, structure 3 has a gradual line width = 35, 34, 30, 27, 26, 23, and a gradual interval = 5, 8, 10, 13, 20, 25;

[0059] When Figure 2 The size of the structure is:

[0060] Structure 41 = 113, structure 42 = 91, structure 43 = 41, structure 44 = 46;

[0061] When Figure 3 The size of the structure is:

[0062] Structure 45 = 25, structure 46 = 10;

[0063] The total thickness of the medium substrate 40 is 50, and the metal layer thickness of the microstrip main feeder and the metal ground is 1.

[0064] At this time, the electrostatic force simulation diagram of the MEMS switch in the reconfigurable antenna is as follows:

[0065] Figure 4 The structure change of the MEMS switch in the embodiment under the potential difference of 100 V is shown in the figure, and the switch film bridge can pull down the contact point by 0.8 microns, so that the microstrip main feeder is turned on.

[0066] At this time, the S parameters of the MEMS switch in the on and off states are:

[0067] Figure 5 The S parameters of the MEMS switch in different working states are shown in the figure, and the four curves are the reflection coefficient and the transmission coefficient of the switch in the on and off states. The results show that the reflection coefficient of the switch in the on state is less than-15 dB in the frequency band of 320-350 GHz, and the in-band insertion loss is less than 0.8 dB; while the switch in the off state has an isolation of more than 16 dB, realizing high isolation in the terahertz frequency band.

[0068] At this time, the S parameters of the MEMS switch network in each switching state are:

[0069] Figure 6 , Figure 7 The S parameter characteristics of the switch network of the above-mentioned MEMS switch are shown in the figure. Figure 6For the S parameters of the structure 23, it can be seen that the reflection coefficient is good in the 200-350 GHz band, all less than -15 dB, and the insertion loss of the on-path is less than 1 dB, and the isolation of the rest of the off-paths is about 20 dB; Figure 7 For the S parameters of the structure 20, the results show that the reflection coefficient of the microstrip main feed line 4 is still better than -15 dB in the band, and the insertion loss of the on-path is slightly larger, but also about 1 dB, and the isolation of the rest of the paths is greater than -17 dB. Since the antenna is symmetrical about the feed line axis, only the above two states can be investigated.

[0070] At this time, the reflection coefficient of the terahertz directional pattern reconfigurable antenna based on the MEMS switch network is:

[0071] Figure 8 The reflection coefficients of the connected radiation units in the above two network states are shown in FIG. 8. When the tilt-beam radiation units 6 and 9 are working, the standing wave ratio of the whole antenna in the 300-370 GHz band is less than 2, and even less than 1.5 in the working state of the tilt-beam radiation unit 9. Due to the feed line coupling, the performance is slightly worse in the working state of the tilt-beam radiation unit 6, and the standing wave ratio is less than 1.5 in the 330-350 GHz band after optimization.

[0072] At this time, the radiation pattern of the terahertz directional pattern reconfigurable antenna based on the MEMS switch network is:

[0073] Figure 9 The beam scanning diagrams in the elevation plane at 330 GHz, 340 GHz and 350 GHz in the above two antenna states are shown in FIG. 9. The black curve represents the linearly polarized radiation beam curve in the working state of the tilt-beam radiation unit 9, and the gray curve represents the tilt-beam radiation unit 6. In different states, the antenna forms a deflected beam at a 45°, 135° azimuth angle, the beam deflection angle can reach 45°, the 3 dB beam can cover up to 80°, and the beam can basically cover the upper half space.

[0074] It can be seen that the directional pattern reconfigurable antenna controlled by the MEMS switch network can realize a reconfigurable wide-angle tilt-beam in the terahertz band.

[0075] The above is only an example. If a beam reconfigurable antenna at a different center frequency is needed, different parameters can be adjusted according to the specific implementation, such as adjusting the radiation unit, the size of the switch contact and the size of the switch network to adjust the working center frequency, adjusting the beam deflection angle and adjusting the impedance matching, etc. The reconfigurable antenna can also be realized by other radiation units that can realize a deflected beam.

[0076] In the application, the MEMS switch unit is formed by a metal-dielectric composite beam to form a high-isolation asymmetric structure, the switch has a small size and a low pull-down voltage by combining the crane arm and the folding arm, the corresponding microstrip line is conducted by the electrostatic force generated by the potential difference between the bottom electrode and the beam metal part and the metal contact on the beam; when one of the MEMS switch lines on the top layer is conducted and the other lines are turned off, the linearly polarized antenna beam is directed to the conducted side. The mutual coupling influence caused by the compact switch network is avoided by tuning the antenna unit itself; the reconfigurable switch unit has high isolation, the reflection coefficient is less than-15 dB in the 280-360 GHz frequency band, the in-band insertion loss is less than 0.6 dB, and the isolation is greater than 14 dB; the switch network has a wideband characteristic, the reflection coefficient is less than-15 dB in the 200-350 GHz frequency band, the overall insertion loss is about 1 dB under different switching states, the isolation between the disconnected line and the input end is greater than 17 dB; the final directional diagram reconfigurable antenna can realize a deflection angle of more than 45 degrees away from the normal direction at the center frequency, and the beam width covers 80 degrees away from the normal direction. Compared with other terahertz antenna units, the application can realize the directional diagram reconfigurable and large-angle beam coverage, and the planar microstrip structure can realize rapid manufacturing.

Claims

1. A terahertz broadband wide-angle beam pattern reconfigurable antenna, characterized in that, It comprises four inclined-beam radiation units (6, 7, 8, 9), a tapered balun (1), a feed network, a MEMS switch network (5) and three voltage biasing line groups (10, 12, 14); the feed network is composed of microstrip lines, including a microstrip main feed line (4), a first-level bifurcation structure, two second-level bifurcation structures and four microstrip branch lines; the three voltage biasing line groups (10, 12, 14) and the microstrip main feed line (4) are distributed in a cross shape, the outer end of the microstrip main feed line (4) is connected with the tapered balun (1), the inner end of the microstrip main feed line (4) is connected with the four microstrip branch lines through the two-level bifurcation structures, among the three voltage biasing line groups, the first voltage biasing line group extends to the first-level bifurcation structure, the second voltage biasing line group extends to one of the second-level bifurcation structures, and the third voltage biasing line group extends to the other second-level bifurcation structure; The four inclined-beam radiation units (6, 7, 8, 9) are distributed in the four 90-degree angles of the cross formed by the three voltage biasing line groups (10, 12, 14) and the microstrip main feed line (4), and the four inclined-beam radiation units (6, 7, 8, 9) are respectively connected with a microstrip branch line; the MEMS switch network (5) comprises three groups of switch structures, among the three groups of switch structures, the first group of switch structures is located at the first-level bifurcation structure in the feed network, the second group of switch structures is located at one of the second-level bifurcation structures in the feed network, and the third group of switch structures is located at the other second-level bifurcation structure in the feed network, and the voltage biasing line group at each bifurcation structure is used for controlling the opening and closing of the switch structure at the bifurcation structure, so as to realize the on-off of the corresponding microstrip line in the feed network; The MEMS switch network comprises a total of 6 switch structures, two switch structures are arranged at each bifurcation structure, and all the switch structures are distributed in an axial symmetry about the microstrip main feed line (4); each voltage biasing line group comprises four voltage biasing lines, and each switch structure is connected with two voltage biasing lines.

2. The THz wide-beam angle pattern reconfigurable antenna according to claim 1, wherein, The line width and the spacing of the grounded coplanar waveguide part of the tapered balun (1) change simultaneously, the terminal of the tapered balun (1) is surrounded by the metallized via formed by the TGV process, and the grounded coplanar waveguide part of the tapered balun (1) is finally output as the microstrip main feed line (4).

3. The THz wide-beam angle pattern reconfigurable antenna according to claim 1, wherein, The four inclined-beam radiation units (6, 7, 8, 9) have the same structure, and the length and the slot width are independently designed.

4. The THz wide-beam angle pattern reconfigurable antenna according to claim 1, wherein, The outer ends of the three voltage biasing line groups (10, 12, 14) are respectively connected with a group of biasing contacts.

5. The THz wide-beam angle pattern reconfigurable antenna according to claim 1, wherein, The width of the microstrip line in the feed network is linearly narrowed before entering the switch structure.

6. The THz wide-beam angle pattern reconfigurable antenna according to claim 1, wherein, The switch structure comprises an elastic metal-dielectric composite film bridge, a pull-down electrode (34), a silicon nitride isolation layer (35), a first metal pier (30), and a second metal pier (31); each end of the elastic metal-dielectric composite film bridge has a crane-shaped arm, the elastic metal-dielectric composite film bridge is of an asymmetric structure, the main body of the elastic metal-dielectric composite film bridge is a dielectric part (33), the middle lower surface and the lower surface of one end of the dielectric part (33) are covered with a metal layer, thereby forming two metal-dielectric overlapping parts (32), wherein the metal layer of the middle part is provided with a metal contact point (36) for conducting the corresponding microstrip line, the crane-shaped arm of one end of the elastic metal-dielectric composite film bridge is connected to the first metal pier (30) through the metal layer, and the crane-shaped arm of the other end without the metal layer covers the second metal pier (31) through a folding arm; the pull-down electrode (34) is located below the metal layer at the bridge surface and is used for pulling down the bridge surface so that the metal contact point (36) contacts the microstrip line, and the pull-down electrode (34) is covered with the silicon nitride isolation layer (35); two voltage bias lines connected to the switch structure are connected to the first metal pier and the pull-down electrode (34) of the switch structure.

7. The THz wide-beam angle pattern reconfigurable antenna according to claim 6, wherein, The pull-down electrode (34) is isosceles trapezoidal, and the corresponding side waist is parallel to the gradually changing profile of the linear narrowing of the adjacent microstrip line.

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