CN116154471A

CN116154471A - Terahertz wide-bandwidth angle pattern reconfigurable antenna

Info

Publication number: CN116154471A
Application number: CN202310358689.4A
Authority: CN
Inventors: 杨光耀; 张乃柏; 王子莱; 宋瑞良; 刘宁
Original assignee: CETC 54 Research Institute
Current assignee: CETC 54 Research Institute
Priority date: 2023-04-06
Filing date: 2023-04-06
Publication date: 2023-05-23

Abstract

The invention provides a terahertz wide-bandwidth angle diagram reconfigurable antenna, and belongs to the field of radio frequency MEMS. The antenna comprises an inclined beam radiation unit, a gradual change balun, a feed network, an MEMS switch network and a voltage bias line group; the feed network comprises a microstrip main feed line and four microstrip branch lines; the three voltage bias line groups and one microstrip main feeder are distributed in a cross shape, the outer end of the microstrip main feeder is connected with a gradual change balun, and the inner end of the microstrip main feeder is transited to four microstrip branch lines through a two-stage bifurcation structure; the four inclined beam radiation units are respectively connected with a microstrip branch line; 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 switching of the switch structure, so that the on-off of the corresponding microstrip line in the feed network is realized. The invention has simple structure and convenient manufacture, can realize rapid manufacture and integration, and can realize the scanning of azimuth beams.

Description

Terahertz wide-bandwidth angle pattern reconfigurable antenna

Technical Field

The invention belongs to the field of radio frequency MEMS (micro electro mechanical systems), and particularly relates to a terahertz pattern reconfigurable antenna based on an MEMS switch network.

Background

The MEMS switch is widely applied to radio frequency systems below millimeter wave frequency bands due to the advantages of high isolation, small insertion loss and the like; in the terahertz frequency band, the solid-state semiconductor switch is still immature, and the volume of the mechanical switch is too large, so that the application potential of the MEMS switch is doubled; the reconfigurable antenna based on the directional diagram switching has wide and important application requirements in satellite communication systems, broadband network systems and radar systems in the fields of civil use, military use and the like due to the advantages of switchable beam directions, large coverage space angles and the like. Worldwide, there are many studies on MEMS switches, but few results in the terahertz frequency band, and studies are still in the beginning. The directional diagram reconfigurable antenna can complete the change of the maximum radiation direction under the condition of not adjusting the signal amplitude and the phase, provides a new dimension for terahertz front end design, and enhances the large-angle scanning capability of the antenna; however, the disadvantage of the pattern reconfigurable antenna is that the antenna structure is complex, the processing is difficult, the influence of the bias circuit is large, and most antennas can only realize wide-angle scanning in one-dimensional direction.

The existing terahertz frequency band MEMS switch and pattern reconfigurable antenna have the advantages of being flexible in result, large in structure size, poor in high-frequency isolation and large in loss, and a terahertz cantilever beam switch based on a coplanar waveguide is designed by using silicon and fused quartz in 2022, for example, N.Scott Barker et al of university of Virginia; the MEMS switch array and the related radio frequency application thereof operating in the terahertz frequency band are not really realized, and the Mehmet un et al of turkish scholars in 2017 published a conference paper for regulating and controlling the antenna pointing by using the MEMS switch, which is only based on the simulation result, and has high beam sidelobes and small coverage angle range.

The current terahertz MEMS switch has the defects of larger structural size, poor high-frequency isolation and large loss, and the current terahertz MEMS switch is difficult to meet the requirements of application on radio frequency devices such as antennas. While the terahertz band reconfigurable antenna cannot realize wide-angle beam coverage at present.

Disclosure of Invention

In view of the above, the invention provides a terahertz wide-bandwidth angular pattern reconfigurable antenna which can meet the requirements of full coverage of a horizontal plane and basic coverage of a pitching plane under a terahertz frequency band, and has the characteristics of wide bandwidth, multiple reconfigurable beams, low back lobe, high polarization purity, convenience in design and implementation and the like.

The purpose of the invention is realized in the following way:

a terahertz wide-bandwidth angular pattern reconfigurable antenna comprises four oblique beam radiating units, a gradual change balun, a feed network, an MEMS switch network and three voltage bias line groups; the feed network is composed of microstrip lines and comprises a microstrip main feed line, a primary bifurcation structure, two secondary bifurcation structures and four microstrip branch lines; the three voltage bias line groups and one microstrip main feeder are distributed in a cross shape, the outer end of the microstrip main feeder is connected with a gradual change balun, the inner end of the microstrip main feeder is transited to four microstrip branch lines through a two-stage bifurcation structure, and the three voltage bias line groups respectively extend to a bifurcation structure; the four inclined beam radiation units are distributed in four 90-degree included angles of a cross formed by the three voltage bias line groups and a microstrip main feeder line, and are respectively connected with a microstrip branch line; the MEMS switch network comprises three groups of switch structures, the three groups of switch structures are respectively positioned at three bifurcation structures in the feed network, 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 that the on-off of the corresponding microstrip line in the feed network is realized.

Further, the line width and the distance of the grounded coplanar waveguide part of the graded balun are changed at the same time, the terminal of the graded balun is surrounded by a metallized via hole formed by a TGV process, and the grounded coplanar waveguide part of the graded balun is finally output into a microstrip main feeder.

Further, the four oblique beam radiating elements are identical in structure, and are independently designed in length and slot width.

Further, the outer ends of the three voltage bias line groups are respectively connected with a group of bias contacts.

Further, the microstrip line in the feed network is linearly narrowed in width before entering the switching structure.

Further, the MEMS switch network comprises 6 switch structures in total, two switch structures are arranged at each bifurcation structure, and all the switch structures are axisymmetrically distributed relative to the microstrip main feeder line; each voltage bias line group comprises four voltage bias lines, and each switch structure is connected with two voltage bias lines.

Further, the switch structure comprises an elastic metal-dielectric composite film bridge, a pull-down electrode, a silicon nitride isolation layer, a first metal bridge pier and a second metal bridge pier; the elastic metal-medium composite film bridge is integrally of an asymmetric structure, a main body of the elastic metal-medium composite film bridge is a medium part, the lower surface of the middle part of the medium part and the lower surface of one end of the medium part to the bridge deck are respectively adhered with metal layers, so that two metal-medium overlapped parts are formed, wherein the metal layers in the middle part are provided with metal contact points for conducting corresponding microstrip lines, one end of the elastic metal-medium composite film bridge, which is covered with the metal layers, is connected with a first metal bridge pier through the metal layers, and the other end of the elastic metal-medium composite film bridge, which is not covered with the metal layers, is covered with a second metal bridge pier through the folding arms; the pull-down electrode is positioned below the metal layer at the bridge deck and is used for pulling down the bridge deck so as to enable the metal contact point to contact the microstrip line, and the metal contact point is covered with the silicon nitride isolation layer; two voltage bias lines connected with the switch structure are respectively connected with the first metal bridge pier and the pull-down electrode of the switch structure.

Further, the pull-down electrode is isosceles trapezoid, and the corresponding side waist is parallel to the linearly narrowed gradual change profile of the adjacent microstrip line.

The invention has the beneficial effects that:

1. the MEMS switch still has high isolation characteristic in the terahertz frequency band, and can realize broadband low-loss characteristic and miniaturization characteristic through series equivalent inductance, thereby being convenient for high-density integration.

2. The invention can realize azimuth beam scanning, and adopts a single-port design to realize the large-angle coverage of a pitching plane and the quadrant scanning of an omnibearing plane.

3. The invention has simple structure and convenient manufacture, and can realize rapid manufacture and integration by only utilizing a single-layer fused quartz substrate and a two-layer planar microstrip structure.

Drawings

FIG. 1 is a schematic overall structure of an embodiment of the present invention;

FIG. 2 is a schematic diagram of a MEMS switch network in accordance with an embodiment of the invention;

FIG. 3 is an oblique view of a MEMS switch structure of an embodiment of the invention;

FIG. 4 is a pull-down simulation of a MEMS switch in accordance with an embodiment of the present invention;

FIG. 5 is a graph of S-parameters of a MEMS switch in accordance with an embodiment of the present invention;

FIGS. 6 and 7 are graphs of S-parameters of a switching network according to an embodiment of the present invention;

FIG. 8 is a standing wave ratio plot of a reconfigurable antenna of the present invention;

fig. 9 is a two-dimensional pitch pattern for each yaw state in an embodiment of the invention.

Description of the embodiments

In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

A terahertz wide bandwidth angular pattern reconfigurable antenna comprises a test balun for terahertz frequency bands, a broadband MEMS switch network and an inclined beam radiation unit, wherein all structures are distributed on the top and bottom layers of a fused quartz substrate; the test balun comprises a grounded coplanar waveguide with gradually changed line width and gap steps, and a transition section from the grounded coplanar waveguide to the microstrip; the MEMS switch network is symmetrically distributed between the balun interface and the antenna interface, and the switch and the whole network have broadband and low-loss characteristics in terahertz frequency bands;

each MEMS switch comprises a metal bridge pier, a metal-medium asymmetric composite membrane 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 positioned at two sides of the membrane bridge, wherein the metal part of the membrane bridge is connected with the metal bridge pier at the corresponding side by utilizing the crane-shaped arm, one end of the medium part of the membrane bridge is overlapped with the metal part, and the other end of the medium part of the membrane bridge is fixed on the other metal bridge pier by the folding arm; one end of each of the two high-resistance wires of the voltage bias wire is connected with the metal bridge pier and the pull-down electrode, and the other end of each of the two high-resistance wires of the voltage bias wire is connected with the bias contact; the metal contact point is positioned at the center of the metal-dielectric composite film bridge, and the signal path is conducted when the metal contact point is pulled down;

the terahertz MEMS switch array network is a radio frequency structure formed by combining six MEMS switches, and a certain route is conducted through a specific switch combination; the input end of the switch network is connected with the gradual change test balun, and the output end of the switch network is connected with the oblique beam radiation unit; the gradient test balun is positioned on one side of the antenna structure, top and bottom layers are grounded through a metallized via hole realized by a TGV process, and the gradient test balun comprises an impedance gradient section and a transition section from a grounded coplanar waveguide to a microstrip main feeder; the inclined beam radiation unit is of a quasi-yagi structure, and parameters of the balun side unit and the opposite side unit are different and are respectively tuned.

Further, the number of the radiating units is 4, each radiating unit is connected with the test balun through the MEMS switch group of the corresponding line, and only one radiating unit works at each moment.

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

The following is a more specific example:

as shown in fig. 1-3, a terahertz wide-bandwidth angular pattern reconfigurable antenna includes a graded balun 1, a microstrip main feeder 4, a mems switching network 5, voltage

bias line groups

10, 12, 14,

bias contacts

11, 13, 15, and oblique beam radiating elements 6, 7, 8, 9. The on-off of the feed line can be controlled separately by applying voltages to the voltage

bias line groups

10, 12, 14; the four radiating elements are basically identical in structure, are axisymmetric in position about the feeder line, are connected with the MEMS switch network at one end, and can be independently changed in length 16 and slot width 17.

The directional diagram reconfigurable antenna unit has a unique feed structure 1, and comprises a grounded coplanar waveguide structure 3 with the ground and line width being gradually changed at the same time and a transition structure from the grounded coplanar waveguide to a microstrip main feeder 4. The ground of the top layer is communicated with the ground of the bottom layer through a metallized via hole 2; the tail end ground of the grounded coplanar waveguide is metallized Kong Jieduan, the top ground is not extended any more and presents arc transition, and finally the microstrip main feeder 4 is output.

The MEMS switch network 5 includes three unique sets of

terahertz MEMS switches

24 and 25, 26 and 27, 28 and 29, and corresponding microstrip main feeder deformation networks. The microstrip main feeder 4 is connected with the secondary microstrip

main feeders

18 and 19 through

switches

24 and 25, respectively; the secondary microstrip main feed lines are connected to the

tertiary transmission lines

20, 21, 22, 23 by

switches

26 and 27, 28 and 29; the ends of the secondary microstrip

main feed lines

18, 19 are the same as the ends of the microstrip main feed line 4, have linearly decreasing linewidths, and the ends are divided into two parts and are linearly widened after passing through the switch contact points; the on-off of each set of MEMS switches is selected by its set of

voltage bias lines

10, 12, 14.

The six MEMS switches in the MEMS switching network 5 have the same structure and are axisymmetric with respect to the feeder line 4, and each of the six MEMS switches includes

metal bridge piers

30 and 31, an elastic metal-dielectric composite film bridge (a metal-dielectric overlap portion 32 and a dielectric portion 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-medium composite membrane bridge is of an asymmetric structure and is mainly supported by a medium, the overlapped end 32 is connected with a metal pier by a crane-shaped arm, and the medium end 33 is covered with a folding arm. The pull-down electrode 34 is located on one side of the elastic metal-dielectric bridge and the metal contact 36 is located in the center of the bridge. The voltage bias line 37 is connected with the metal bridge pier 30, the voltage bias line 38 is connected with the pull-down electrode 34, and the two line-to-line voltages generate pull-down force of the composite film bridge.

The following is another embodiment:

referring to fig. 1 to 3, a terahertz wide-bandwidth angular pattern reconfigurable antenna is composed of a graded balun 1, a MEMS switching network 5, high-resistance voltage

bias line groups

10, 12 and 14,

bias contacts

11, 13 and 15, an oblique beam radiating unit 6-9 and a fused quartz substrate 40.

The four oblique beam radiation units 6-9, the MEMS switch network 5 and the three high-resistance voltage

bias line groups

10, 12 and 14 are axisymmetric with respect to the microstrip feeder line 4; the oblique beam radiating element 6-9 of this embodiment is a segmented metal patch with a radial length 16 of about one half of the resonant frequency and the waveguide wavelength, the initial segment is a sector with a certain angle and radius, and the remaining segments are annular with the same angle and different radii; each oblique beam radiating element is connected to a microstrip feed line 4 through a MEMS switching network 5. The size 16 of the tilted beam elements 6-9 and the spacing 17 of the last segments are used to adjust the respective resonant frequencies of the antenna in each reconstruction state, as 16 increases, the antenna element first resonant frequency decreases, 16 decreases, and the first resonant frequency increases; when 17 increases, the second and third resonance frequencies of the antenna unit increase, 17 decreases, and the second and third resonance frequencies decrease; the mutual coupling between the radiating element and the feed line, the deflection angle of the maximum radiation direction in the deflected state, and the gain characteristic over this angle are also dependent on the respective resonance frequencies.

In the embodiment, the graded balun 1 is particularly optimized, the five-order chebyshev impedance transformation is utilized, the ground and the line width are graded simultaneously (as shown in a structure 3), the TGV technology is utilized at the grounded coplanar waveguide end to realize the metallized via hole on fused quartz (as shown in a structure 2), and the transition from the grounded coplanar waveguide to the microstrip main feeder 4 is further realized.

As shown in fig. 2, the details of the MEMS switch network 5 are that the microstrip main feeder 4 performs a first line selection through

switches

24 and 25, any one of the switches can be controlled to be closed through the voltage bias line 14, and a signal enters one of the secondary microstrip

main feeders

18 and 19; the tail end of the secondary microstrip main feeder is the same as the tail end of the microstrip main feeder 4, the tail ends are divided into two parts, and the linewidth is linearly widened after passing through a switch contact point; by selecting the voltage bias line set 10 or 12, the signal finally enters any one of the three-

stage transmission lines

20, 21, 22, 23.

In this embodiment, a typical MEMS switch structure is shown in fig. 3, which is driven by a dc voltage, and four high-resistance wires are respectively arranged at the positions of the three sets of

voltage bias wires

10, 12, and 14 for applying a voltage, so as to connect the metal bridge piers 30 and the pull-down electrodes 34 of the two MEMS switches respectively. When a voltage is applied to the bias line, the composite film bridge 32 formed by combining silicon dioxide or silicon nitride materials and metal is pulled down by electrostatic force, the two ends of the metal contact point 36 bridge the microstrip main feeder 39, and the switch is turned on; when the voltage is set to zero, the metal electrostatic force is released, the metal-dielectric film bridge is restored by the elastic force, and the switch is opened. The MEMS switch in this embodiment has the feature that the pull-down of the metal contacts is realized by the pull-down electrodes on the side of the bridge, and is asymmetric, whereas the metal-dielectric side 32 of the bridge is connected to the metal bridge pier 30 by the crane-shaped arm due to the imbalance of the pull-down force, and the dielectric side 33 of the bridge is covered on the metal bridge pier 31 by the hinge arm for balancing the pull-down force.

The antenna operates in the following mode: when the MEMS switch 24 is turned on and the MEMS switch 25 is turned off, half of the MEMS switch network fails, if the MEMS switch 26 is turned on and the MEMS switch 27 is turned off, 6 of the four radiation units work, and the radiation beam points to one side of an angular bisector of a sector opening angle and deviates from the normal direction vertical to the paper surface at a large angle; conversely, if 26 is off and 27 is on, the beam is directed to the angular bisector of the 9 fan-out angle. The working principle of the rest radiating elements is the same as that of the other radiating elements, current enters the secondary feeder from the primary feeder 4 of the MEMS switch network 5, then enters the tertiary feeder from the secondary feeder through selection, and finally is fed into the corresponding radiating elements to form beams covering corresponding quadrants. In the overall antenna structure shown in fig. 1, a metallic ground of the same size as the fused silica substrate 40 is used to reflect the beam toward the upper half-plane space, i.e., the main beam is deflected toward the upper half-space of the radiating structure by an angle that is related to the resonant characteristics of the radiating element and the size of the metallic ground. The smaller the ring shape of the periphery in the radiation unit is, the larger the deflection angle formed by the main beam and the plane of the microstrip main feeder line is; when the size of the metal ground is in a certain range, the main beam has the maximum deflection angle.

Two of the six MEMS switches are on, and when the rest of the six MEMS switches are off, the state is a deflection state; when all switches are open, the antenna will not operate. There are four deflection states.

To reduce the loss, a metal material having a small resistivity, such as gold, is used, and a material having a small loss, such as fused silica, is used for the dielectric substrate 40.

The structure of the MEMS feed network can have an important impact on the performance of the reconfigurable antenna, and is specifically expressed as follows:

1) The spacing between two switches in the same switch group influences the isolation of a network and directly influences the wave beam, so that the too large spacing can distort the wave beam of an antenna, and the too small spacing is difficult to process;

2) The linewidth change strategy of the microstrip in one-to-two mode influences the reflection coefficient and isolation of the network, thereby influencing the beam shape and antenna impedance matching;

3) The length of the secondary microstrip main feeder line between the switch groups influences the reflection coefficient of the network and the coupling between the radiating unit and the feed, and the antenna performance under different deflection states can be basically consistent through optimization;

when the MEMS switch network is formed, the MEMS switch structural characteristics can have an important influence on the final network performance and the final implementation of antenna beam switching, and are specifically expressed as follows:

1) The distance between the pull-down electrode and the feeder line directly influences the isolation degree of the switch, and the pull-down electrode is finally parallel to the gradual change edge of the width of the feeder line, so that the switch is integrally miniaturized and has high isolation degree, the network isolation degree is improved, and the side lobe of an antenna beam is small;

2) The length of the metal part where the contact is located influences the isolation degree of the switch when the switch is disconnected, the width influences the impedance matching when the switch is connected, and the two states need to be considered simultaneously to optimize the performance of the switch and the network, so that the reflection coefficient and the wave beam of the antenna are optimized;

3) The contact state of the contact in the pull-down state is determined by the form of the switch film bridge, the miniaturization and high isolation of the switch are realized simultaneously through the asymmetric film bridge design, and the contact needs to be fully contacted with the microstrip feeder line in the pull-down state of the direct contact switch, so that the effect of connection and disconnection is achieved.

Because the radiation unit is coupled with the feeder line, the voltage bias line and the like during specific implementation, the performances of different deflection states of the antenna are different, so that the MEMS switch form, the MEMS network structure and the radiation unit which are reasonably designed have important significance for improving the performance of the antenna with the reconfigurable directional diagram, and the final structural parameters of the antenna are the result of comprehensive optimization.

One size combination is selected below for illustration (in microns for the following data):

when the dimensions of the structure of fig. 1 are:

structure 16=653, structure 17=25, structure 3 has a graded line width=35, 34, 30, 27, 26, 23, graded pitch=5, 8, 10, 13, 20, 25;

when the dimensions of the structure of fig. 2 are:

structure 41=113, structure 42=91, structure 43=41, structure 44=46;

when the dimensions of the structure of fig. 3 are:

structure 45=25, structure 46=10;

the dielectric substrate 40 has a total thickness of 50 a and the microstrip main feed line and metal ground have a metal layer thickness of 1 a.

The electrostatic force simulation diagram of the MEMS switch in the pattern reconfigurable antenna is as follows:

the structural change of the MEMS switch at 100V potential difference in this embodiment is shown in fig. 4, which shows that the switch membrane bridge can pull down the contact by 0.8 microns, which turns on the microstrip main feed line.

At this time, the S parameters of the MEMS switch in the on and off states are as follows:

the S parameters of the MEMS-based switch in different operating states are shown in fig. 5, where the four curves are the reflection coefficient and transmission coefficient of the switch in the on and off states, respectively. The result shows that the reflection coefficient of the switch in the 320-350 GHz frequency band is smaller than-15 and dB, and the in-band insertion loss is smaller than 0.8 and dB; and the isolation of the switch is larger than 16 dB under the condition of disconnection, so that the high isolation of the terahertz frequency band is realized.

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

fig. 6 shows S-parameter characteristics of the switching network of the MEMS switch, which are divided into fig. 6 and fig. 7. FIG. 6 shows the S parameter of structure 23 when it is on, it can be seen that the reflection coefficient in 200-350 GHz frequency band is good, both are smaller than-15 dB, the insertion loss of the conduction path is smaller than 1 dB, and the isolation of the rest disconnection paths is about 20 dB; fig. 7 shows the S-parameter of the structure 20 when it is on, and the result shows that the in-band reflection coefficient of the feed line 4 is still better than-15 and dB, and the insertion loss of the conductive path is slightly larger, but also about 1 dB, and the isolation of the rest paths is larger than-17 and dB. Since the antenna is axisymmetric about the feed line, only the two states described above can be considered.

At this time, the reflection coefficient of the terahertz pattern reconfigurable antenna based on the MEMS switch network is as follows:

in fig. 8, the reflection coefficients of the radiation elements connected in the two network states are shown, and when the elements 6 and 9 are in operation, the standing wave ratio of the whole antenna at 300-370 GHz is smaller than 2, wherein the reflection coefficients of the radiation elements connected in the two network states are even smaller than 1.5 when the element 9 is in operation; and due to feeder coupling, the unit 6 has slightly poor performance in the working state, and the standing wave ratio in the 330-350 GHz frequency band is optimized to be smaller than 1.5.

At this time, the terahertz pattern reconfigurable antenna radiation pattern based on the MEMS switch network is as follows:

fig. 9 shows beam scans of the nodding and nodding surfaces at frequencies of 330 GHz, 340 GHz and 350 GHz in the two antenna states, the black curves representing the linearly polarized radiation beam curves in the operating state of the unit 9, and the gray curves representing the operation of the unit 6. Under different states, the antenna forms deflection beams respectively at horizontal azimuth angles of 45 degrees and 135 degrees, the beam deflection angle can reach 45 degrees, the beam of 3 dB can cover 80 degrees, and the beam can basically cover the upper half space.

Therefore, the reconfigurable wide-angle inclined beam of the terahertz frequency band can be realized through the directional diagram reconfigurable antenna controlled by the MEMS switch network.

The foregoing is merely an example, and if a beam reconfigurable antenna with different center frequencies is desired, different parameters may be adjusted according to the specific embodiment, for example, the working center frequency may be adjusted by adjusting the dimensions of the radiating element, the switch contact and the switch network, the beam deflection angle may be adjusted, and the impedance matching may be adjusted; the reconfigurable antenna may also be implemented by other radiating elements that may implement a deflected beam.

In the invention, the MEMS switch unit is formed into a high-isolation asymmetric structure by a metal-medium composite beam, and combines a crane-shaped arm and a folding arm to enable the switch to have a miniaturized size and a low pull-down voltage, and the MEMS switch unit is adsorbed by electrostatic force generated by potential difference between a bottom electrode and a beam metal part, and a metal contact on the beam enables a corresponding microstrip line to be conducted; when one of the MEMS switch lines on the top layer is on and the MEMS switch on the other line is off, the linearly polarized antenna beam points to the on side. The mutual coupling influence caused by a compact switching network is avoided by utilizing the tuning of the antenna unit; the reconfigurable switch unit has high isolation, the reflection coefficient is smaller than-15 dB in the frequency band of 280-360 GHz, the in-band insertion loss is smaller than 0.6 dB, and the isolation is larger than 14 dB; the switch network has broadband characteristics, the reflection coefficient is smaller than-15 dB in the 200-350 GHz frequency band, the total insertion loss is about 1 dB in different switching states, and the isolation between a disconnected line and an input end is larger than 17 dB; the final pattern reconfigurable antenna can achieve deflection angles above 45 ° from the normal direction at the center frequency, with beam widths covering up to 80 ° from the normal direction. Compared with other terahertz antenna units, the planar microstrip antenna can realize directional diagram reconstruction and wide-angle beam coverage, is convenient to manufacture, and can realize rapid manufacture.

Claims

1. The terahertz wide-bandwidth angular pattern reconfigurable antenna is characterized by comprising four oblique beam radiating units (6, 7, 8 and 9), a gradual balun (1), a feed network, a MEMS switch network (5) and three voltage bias line groups (10, 12 and 14); the feed network is composed of microstrip lines and comprises a microstrip main feed line (4), a primary bifurcation structure, two secondary bifurcation structures and four microstrip branch lines; three voltage bias line groups (10, 12, 14) and a microstrip main feeder (4) are distributed in a cross shape, the outer end of the microstrip main feeder (4) is connected with a gradual change balun (1), the inner end of the microstrip main feeder (4) is transited to four microstrip branch lines through a two-stage bifurcation structure, and the three voltage bias line groups (10, 12, 14) respectively extend to a bifurcation structure; the four inclined beam radiation units (6, 7, 8 and 9) are distributed in four 90-degree included angles formed by a cross shape formed by three voltage bias line groups (10, 12 and 14) and a microstrip main feeder line (4), and the four inclined beam radiation units (6, 7, 8 and 9) are respectively connected with a microstrip branch line; the MEMS switch network (5) comprises three groups of switch structures, the three groups of switch structures are respectively positioned at three bifurcation structures in the feed network, and the voltage bias line group at each bifurcation structure is used for controlling the switching of the switch structure at the bifurcation structure, so that the on-off of the corresponding microstrip line in the feed network is realized.

2. The terahertz wide-bandwidth angular pattern reconfigurable antenna according to claim 1, characterized in that the linewidth and spacing of the grounded coplanar waveguide part of the graded balun (1) are simultaneously changed, the terminal of the graded balun (1) is surrounded by a metallized via formed by a TGV process, and the grounded coplanar waveguide part of the graded balun (1) is finally output as a microstrip main feeder (4).

3. A terahertz wide-bandwidth angular pattern reconfigurable antenna according to claim 1, characterized in that the four oblique beam radiating elements (6, 7, 8, 9) are identical in structure and are designed with independent lengths and slot widths.

4. A terahertz wide-bandwidth angular pattern reconfigurable antenna according to claim 1, characterized in that the outer ends of the three voltage bias line sets (10, 12, 14) are respectively connected to a set of bias contacts.

5. A terahertz wide-bandwidth angular pattern reconfigurable antenna according to claim 1, characterized in that the microstrip line in the feed network is linearly narrowed in width before entering the switching structure.

6. The terahertz wide-bandwidth angular pattern reconfigurable antenna according to claim 1, characterized in that the MEMS switching network comprises 6 switching structures in total, two switching structures are arranged at each bifurcation structure, and all switching structures are axisymmetrically distributed about a microstrip main feeder (4); each voltage bias line group comprises four voltage bias lines, and each switch structure is connected with two voltage bias lines.

7. The terahertz wide-bandwidth angular pattern reconfigurable antenna according to claim 6, characterized in that the switching structure comprises an elastic metal-dielectric composite film bridge, a pull-down electrode (34), a silicon nitride isolation layer (35), a first metal bridge pier (30), a second metal bridge pier (31); the two ends of the elastic metal-medium composite film bridge are respectively provided with a crane-shaped arm, the whole elastic metal-medium composite film bridge is of an asymmetric structure, the main body of the elastic metal-medium composite film bridge is a medium part (33), the lower surface of the middle part of the medium part (33) and the lower surface of one end of the medium part to the bridge deck are respectively stuck with metal layers, so that two metal-medium overlapped parts (32) are formed, wherein the metal layers in the middle part are provided with metal contact points (36) for conducting corresponding microstrip lines, one crane-shaped arm, which is covered with the metal layers, of the elastic metal-medium composite film bridge is connected with a first metal bridge pier (30) through the metal layers, and the crane-shaped arm, which is not covered with the metal layers, of the other end of the elastic metal-medium composite film bridge covers a second metal bridge pier (31) through the folding arms; the pull-down electrode (34) is positioned below the metal layer at the bridge deck and is used for pulling down the bridge deck so as to enable the metal contact point (36) to contact the microstrip line, and the metal contact point is covered with the silicon nitride isolation layer (35); two voltage bias lines connected with the switch structure are respectively connected with the first metal bridge pier and the pull-down electrode (34) of the switch structure.

8. A terahertz wide-bandwidth angular pattern reconfigurable antenna according to claim 7, characterized in that the pull-down electrodes (34) are isosceles trapezoids with respective side waists parallel to the linearly narrowing tapering profile of adjacent microstrip lines.