Polarization switchable spoof surface plasmon terahertz antenna and mechanical control method

Abstract

This invention discloses a polarization-switchable pseudosurface plasmon terahertz antenna and its mechanical control method, belonging to the field of terahertz communication technology. From top to bottom, it comprises an excitation structure layer, a radiation structure layer, and a base plate. The excitation structure layer consists of a standard waveguide port and a horn gain structure. The left end of the standard waveguide port is aligned with the left end of the radiation structure layer, and the right end is attached to the horn gain structure. The radiation structure layer consists of a support plate, a pseudosurface plasmon structure, and a displacement structure inserted from the lower surface of the support plate. The displacement structure can move up and down within a central insertion hole in the support plate. This invention achieves independent mechanical control of the periodic structure, enabling the switching of electromagnetic wave signals between online polarization, elliptical polarization, and circular polarization. The antenna has a simple structure, mature manufacturing method, low cost, and independently controllable polarization, showing great potential for applications in mass production, system integration, polarization multiplexing, and encrypted communication.

Description

Technical Field

[0001] This invention belongs to the field of terahertz communication technology, specifically relating to a polarization-switchable pseudosurface plasmon terahertz antenna and its mechanical control method. Background Technology

[0002] With the development of terahertz communication technology, researchers have conducted comprehensive and in-depth explorations of terahertz communication devices (high-frequency analog discrete devices related to analog links), such as terahertz power amplifiers, terahertz frequency multipliers, terahertz mixers, and terahertz antennas. The performance indicators of these devices are directly related to the utilization of the excellent properties of the terahertz frequency band, such as its wide spectrum resources, high-speed data transmission capabilities, communication tracking and acquisition capabilities, and anti-interference / anti-interception capabilities. To further accelerate the application and industrialization of terahertz communication devices, breakthroughs in core technologies such as device adjustability, miniaturization, and integration are needed for future practical applications. Among these, the antenna, as a key component responsible for transmitting and receiving signals in a communication system, is an indispensable link in the advancement of terahertz communication technology.

[0003] Current research on terahertz antennas mainly focuses on: 1. graphene-based terahertz antennas; 2. silicon-based terahertz antennas; and 3. pseudosurface plasmon terahertz antennas. The research on these different materials and types of antennas to a certain extent meets the performance requirements of terahertz antennas in terms of frequency band and gain. More specifically, for graphene-based antennas, their radiation performance, such as operating frequency and radiation pattern, can be dynamically controlled by adjusting the conductivity through changing the electric field applied by the external gate voltage; for silicon-based lens antennas, they offer high gain and can achieve frequency-independent multi-beam control; and terahertz antennas designed using pseudosurface plasmons have the advantage of a large bandwidth.

[0004] However, the aforementioned research also has several shortcomings that limit its application value. These shortcomings include:

[0005] First, some antennas have complex original structures or their performance deficiencies can only be addressed by increasing the size of the device, resulting in large size and poor integration capabilities.

[0006] Second, for non-wideband terahertz antennas, the utilization rate of their spectrum resources is not high.

[0007] Third, some antennas have limited functionality and lack effective means to control their performance;

[0008] Fourth, the manufacturing method is complex, the process requirements are high, the cost is high, and it is difficult to achieve mass production.

[0009] Therefore, performance requirements and application value remain the focus of current research in this field. Based on the above analysis, researching and designing terahertz antennas that meet these requirements has the potential to contribute to the development of many fields such as next-generation radio communications, smart cities, and green 5G. Summary of the Invention

[0010] To overcome the shortcomings of existing technologies, this invention provides a polarization-switchable pseudosurface plasmonic terahertz antenna and its mechanical control method. This invention achieves flexible switching between online polarization, elliptical polarization, and circular polarization of electromagnetic wave signals by independently controlling the periodic structure through mechanical means. The antenna has advantages such as simple structure, mature manufacturing method, low cost, and independent control of polarization state, and therefore has great potential for applications in mass production, system integration, polarization multiplexing, and encrypted communication.

[0011] The principle of this invention is as follows:

[0012] This invention enables independent control of the periodic structure through mechanical means, allowing for flexible switching between online polarization, elliptical polarization, and circular polarization of electromagnetic wave signals.

[0013] When electrons oscillating freely on a metal surface interact with photons on a dielectric surface, a mixed excited state of electrons and photons propagating along the metal-dielectric interface is generated, known as a surface plasmon polariton (SPP). In the optical frequency band, the dielectric constant of metals is negative, allowing SPP to be excited at the metal-dielectric interface. However, as the frequency decreases to the microwave and millimeter-wave bands, the properties of metals approach those of perfect conductors, losing their negative dielectric constant. Therefore, materials that support SPP modes in the microwave and millimeter-wave bands are almost nonexistent in nature. Pseudo-surface plasmon polaritons (SpoofSPP, SSPP), as an extension and supplement to SPP, artificially construct negative dielectric constant materials in the low-frequency band through the design of periodic arrays, simulating the properties of surface plasmon polaritons and confining light waves to the subwavelength range.

[0014] The propagation of SSPP has several characteristics: First, it is a surface wave, and its energy propagates along the surface; second, SPP waves decay exponentially on both sides of the interface, and are evanescent waves. Therefore, SPP is strongly confined to a very small scale near the interface, resulting in a field enhancement effect; third, SPP waves are TM (transverse magnetic) waves, and their electric field has two components, one along the propagation direction and the other along the normal direction of the surface. The two directions are orthogonal to each other, so SPP waves have a spin electric field.

[0015] This invention utilizes the inverse spin Hall effect to cause surface plasmon waves with spin electric fields to interact with a perturbing element (cylinder or cuboid), generating mirror-image left-handed and right-handed polarized waves (including circular and elliptical polarization). According to the principle of vector superposition, two elliptical or circularly polarized waves with opposite directions of rotation can generate a linearly polarized wave.

[0016]

[0017]

[0018]

[0019] in, For a left-handed polarized electric field, Let be the right-handed circularly polarized electric field, and 'a' be the amplitude of the electric field component in the y-direction. When 'a' is 1, the electric field is circularly polarized; when 'a' is any other non-zero value, the electric field is elliptically polarized.

[0020] Because the SSPP structure supports surface waves, the radiation efficiency of polarized waves is relatively low; therefore, the perturbation element is designed as a periodic element. Guided by the leakage principle, when the waveguide structure is periodic, according to Floquet theory, this periodicity introduces a series of spatial harmonics, each of which is characterized by a phase constant β. n To represent:

[0021] β n d=β0d+2nπ

[0022] Where d is the period length of the waveguide structure, and β0 is the fundamental spatial harmonic. Fast waves will appear in these introduced spatial harmonics, generating radiation. In addition, this invention uses a mechanical device to change the position of the displacement structure, enabling the electromagnetic waves emitted by the terahertz antenna to flexibly switch between linear polarization, elliptical polarization, and circular polarization, achieving polarization multiplexing.

[0023] This invention is achieved through the following technical solution:

[0024] The polarization-switchable pseudosurface plasmon terahertz antenna comprises, from top to bottom, an excitation structure layer 1, a radiation structure layer 2, and a base plate 3. The excitation structure layer 1 consists of a standard waveguide port 4 and a horn gain structure 5. The left end of the standard waveguide port 4 is aligned with the left end of the radiation structure layer 2, and the right end is attached to the horn gain structure 5. The radiation structure layer 2 consists of a support plate 7, a pseudosurface plasmon structure 6 located on the upper surface of the support plate 7, and a displacement structure 8 inserted from the lower surface of the support plate 7. The displacement structure 8 can move up and down within the middle insertion hole of the support plate 7.

[0025] Furthermore, the excitation is introduced from the waveguide port 4, and the gradual impedance matching is achieved through the front end of the horn gain structure 5 and the pseudo-surface plasmon structure 6. Surface waves are excited at the rear end of the pseudo-surface plasmon structure 6. After being disturbed by the displacement structure 8 on the side of the pseudo-surface plasmon structure 6, the originally propagating slow wave is transformed into a radiated fast wave.

[0026] Furthermore, the bottom surface of the excitation structure layer 1 is attached to the top surface of the radiation structure layer 2. The bottom of the horn gain structure 5 of the excitation structure layer 1 is provided with multiple connecting posts, and the corresponding position of the support plate 7 of the radiation structure layer 2 is also provided with multiple connecting through holes. The multiple connecting posts are inserted into the multiple connecting through holes, thus fixing the excitation structure layer 1 onto the radiation structure layer 2. The left end of the base plate 3 is aligned with the left end of the radiation structure layer 2, and its top surface is attached to the bottom surface of the radiation structure layer 2. The upper surface of the base plate 3 is provided with multiple connecting posts, the positions and sizes of which are the same as the multiple connecting posts provided at the bottom of the horn gain structure 5. The multiple connecting posts on the upper surface of the base plate 3 are inserted into the multiple connecting through holes on the support plate 7 of the radiation structure layer 2, thus fixing the radiation structure layer 2 onto the base plate 3.

[0027] Furthermore, the pseudosurface plasmon structure 6 consists of a series of protruding metal pillars with the same period, arranged in a straight line in the middle of the support plate 7. The pseudosurface plasmon structure 6 is divided into a front end and a rear end. The front end of the pseudosurface plasmon structure 6 achieves impedance matching by varying the height of the metal pillars, with its height gradually changing from zero to the designed height. The rear end of the pseudosurface plasmon structure 6 consists of a series of metal pillars with the same height. The length of the front end of the pseudosurface plasmon structure 6 is 4-6 times the wavelength of the center frequency of the target frequency range. The length of the rear end of the pseudosurface plasmon structure 6 is 12-20 times the wavelength of the center frequency of the target frequency range.

[0028] Furthermore, the support plate 7 is a "П"-shaped cuboid, consisting of a top plate, a connecting block, and a side plate; the connecting block of the support plate 7 is located on the far left of the radiation structure layer 2, and the connecting block has a connecting through hole, which corresponds to the position of the connecting post at the bottom of the horn gain structure 5 of the excitation structure layer 1; the side plate of the support plate 7 is located on the far right of the radiation structure layer 2; the top plate of the support plate 7 has two rows of insertion holes, which are distributed parallel to each other on both sides of the pseudo-surface plasmon structure 6; the shapes of the insertion holes are circular and rectangular, with the circular insertion holes and rectangular insertion holes spaced at the same interval and staggered.

[0029] Furthermore, the distance between the vertex of the circular socket and the side of the metal pillar of the pseudo-surface plasmon structure 6 is 1 / 20 to 1 / 10 of the center frequency wavelength of the target frequency range; the top edge of the rectangular socket is in close contact with the side of the metal pillar of the pseudo-surface plasmon structure 6.

[0030] Further, the displacement structure 8 includes two periodic cylindrical structures 9 and two periodic cuboid structures 10; the periodic cylindrical structure 9 is composed of a first positioning plate 11 and a one-dimensional cylindrical array 12; the first positioning plate 11 is an "L"-shaped cuboid with one long side being comb-shaped, and the one-dimensional cylindrical array 12 stands on the upper surface of the comb-shaped long side of the first positioning plate 11; the periodic cuboid structure 10 is composed of a second positioning plate 13 and a one-dimensional cylindrical array 12; the second positioning plate 13 is generally an "L"-shaped cuboid, and a one-dimensional cuboid array 14 is distributed on one long side. The one-dimensional cylindrical array 12 and the one-dimensional cuboid array 14 have the same unit spacing and number of periods. The position of the one-dimensional cuboid array 14 corresponds to the position of the long side comb-shaped gap of the first positioning plate 11. The periodic cuboid structure 10 fits onto the lower surface of the periodic cylindrical structure 9 through the comb-shaped gap. After the periodic cylindrical structure 9 and the periodic cuboid structure 10 are fitted together, they are inserted into two rows of holes on the top plate of the support plate 7. By adjusting the depth of the one-dimensional cylindrical array 12 and the one-dimensional cuboid array 14 inserted into the holes of the support plate 7, different surface structures will appear.

[0031] Furthermore, the unit radius of the one-dimensional cylindrical array 12 is 1 / 5 to 1 / 4 of the center frequency wavelength of the target frequency range. When switching polarization states after insertion into the socket of the support plate 7, the height of the upper surface of the one-dimensional cylindrical array 12 from the top surface of the support plate 7 is 1.2 to 1.3 times the height of the metal pillar of the pseudo-surface plasmon structure 6. The width of the unit of the one-dimensional cuboid array 14 is 1 / 5 to 1 / 4 of the center frequency wavelength of the target frequency range, and the length is 1 to 1.5 times the center frequency wavelength of the target frequency range. When switching polarization states after insertion into the socket of the support plate 7, the height of the upper surface of the one-dimensional cuboid array 14 from the top surface of the support plate 7 is 1 to 1.2 times the height of the metal pillar of the pseudo-surface plasmon structure 6.

[0032] On the other hand, the present invention also provides a mechanical control method for a polarization-switchable pseudosurface plasmonic terahertz antenna, specifically including the following steps:

[0033] Step 1: After assembling the printed excitation structure layer 1, radiation structure layer 2, and base plate 3, fix them at the transmit port waveguide 18 of the vector network analyzer 17. The assembly method is that the connecting posts of the excitation structure layer 1 and the base plate 3 are inserted into the corresponding through holes of the radiation structure layer 2 to connect the three layers together; wherein, the displacement structure 8 of the radiation structure layer 2 is connected to the support plate 7 through the insertion hole in the support plate 7 to form the complete radiation structure layer 2.

[0034] Step 2: Build a control system, which includes a stepper motor control box 15 and two electric displacement stages 16. The stepper motor control box 15 and the electric displacement stages 16 are connected by cables. The electric displacement stages 16 are respectively connected to the first positioning plate 11 and the second positioning plate 13 of the displacement structure 8.

[0035] Step 3: Use the stepper motor control box 15 to control the movement of the two electric displacement stages 16 respectively, thereby adjusting the insertion depth of the periodic cylindrical structure 9 and the periodic cuboid structure 10 into the insertion hole of the support plate 7, thereby changing the distance between the top surface of the periodic cylindrical structure 9 and the periodic cuboid structure 10 and the upper surface of the support plate 7 to achieve the switching of the device surface structure, thereby generating the corresponding polarization state.

[0036] Furthermore, in step three, when the top surface of the periodic cylindrical structure 9 on one side is higher than the upper surface of the support plate 7, and the top surfaces of the periodic cuboid structures 10 on both sides are flush with the upper surface of the support plate 7, the radiated wave is a circularly polarized wave; when the top surface of the periodic cuboid structure 10 on one side is higher than the upper surface of the support plate 7, and the top surfaces of the periodic cylindrical structures 9 on both sides are flush with the top surface of the support plate 7, the radiated wave is an elliptically polarized wave; when the top surfaces of the periodic cuboid structures 10 on both sides are higher than the upper surface of the support plate 7, and the top surfaces of the periodic cylindrical structures 9 on both sides are flush with the top surface of the support plate 7, the radiated wave is a linearly polarized wave.

[0037] Compared with the prior art, the advantages of the present invention are as follows:

[0038] (1) The present invention provides a mechanically controlled polarization-switchable pseudosurface plasmonic terahertz antenna, which allows the polarization state of the terahertz antenna to be arbitrarily switched between linear polarization, elliptical polarization, and circular polarization by changing the position of the displacement structure through a mechanical device, thereby realizing polarization wave multiplexing. Polarization multiplexing increases the efficiency and freedom of terahertz band spectrum resource utilization, providing a potentially feasible solution to the increasingly scarce spectrum resources.

[0039] (2) The antenna device of the present invention operates in the terahertz band and uses a pseudo-surface plasmon structure, which has the characteristics of small size and low profile, and has great potential application value in the on-chip integration of high frequency devices.

[0040] (3) The sample device of the present invention has the advantages of small size, simple structure, and light weight. In addition, the preparation of such devices only requires the use of common metal materials or the use of magnetron sputtering, evaporation or electroplating to metallize non-metallic 3D printed devices. Therefore, the compatible processing methods (such as machining, 3D printing, etc.) have been industrialized. Therefore, the invention is not limited by specific materials and processing technologies and has broad application prospects. Attached Figure Description

[0041] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0042] Figure 1 This is a schematic diagram of the overall structure of a mechanically controlled polarization-switchable pseudosurface plasmon terahertz antenna according to the present invention.

[0043] Figure 2 This is a schematic diagram of the layered structure of the pseudosurface plasmon terahertz antenna of the present invention;

[0044] Wherein, a is a schematic diagram of excitation structure layer 1 and radiation structure layer 2, b is a schematic diagram of displacement structure, and c is a schematic diagram of base plate;

[0045] Figure 3 This is a schematic diagram of the test system for the pseudosurface plasmon terahertz antenna of the present invention;

[0046] Figure 4 This is a far-field radiation pattern of the pseudosurface plasmonic terahertz antenna of the present invention;

[0047] Where a is the top view of the antenna far field and b is the side view of the antenna far field;

[0048] Figure 5 This is a schematic diagram of the S-parameters of the pseudosurface plasmon terahertz antenna of the present invention;

[0049] Figure 6 This is a schematic diagram of the axial ratio of the pseudosurface plasmon terahertz antenna of the present invention;

[0050] In the figure: 1. Excitation structure layer; 2. Radiation structure layer; 3. Substrate; 4. Standard waveguide port; 5. Horn gain structure; 6. Pseudo-surface plasmon structure; 7. Support plate; 8. Displacement structure; 9. Periodic cylindrical structure; 10. Periodic cuboid structure; 11. First positioning plate; 12. One-dimensional cylindrical array; 13. Second positioning plate; 14. One-dimensional cuboid array; 15. Stepper motor control box; 16. Electric displacement stage; 17. Vector network analyzer; 18. Transmitting port waveguide; 19. Receiving port waveguide; 20. Horn antenna. Detailed Implementation

[0051] To clearly and completely describe the technical solution and its specific working process of the present invention, the specific embodiments of the present invention are as follows, in conjunction with the accompanying drawings:

[0052] Example 1

[0053] like Figure 1As shown, this embodiment provides a polarization-switchable pseudosurface plasmon terahertz antenna, which includes, from top to bottom, an excitation structure layer 1, a radiation structure layer 2, and a base plate 3. The excitation structure layer 1 consists of a standard waveguide port 4 and a horn gain structure 5. The left end of the standard waveguide port 4 is aligned with the left end of the radiation structure layer 2, and the right end is attached to the horn gain structure 5. The radiation structure layer 2 consists of a support plate 7, a pseudosurface plasmon structure 6 located on the upper surface of the support plate 7, and a displacement structure inserted from the lower surface of the support plate 7. The antenna consists of 8 components, and the displacement structure 8 can move up and down within the middle insertion hole of the support plate 7. The terahertz antenna based on pseudo-surface plasmon polaritons in this embodiment operates in the frequency band of 100-300GHz. The excitation is introduced from the waveguide port 4, and the gradual impedance matching is achieved through the horn gain structure 5 and the front end of the pseudo-surface plasmon polariton structure 6. Surface waves are excited at the rear end of the pseudo-surface plasmon polariton structure 6. After being disturbed by the displacement structure 8 on the side of the pseudo-surface plasmon polariton structure 6, the originally propagating slow wave is converted into a radiated fast wave.

[0054] The polarization-switchable pseudosurface plasmonic terahertz antenna of this embodiment is fabricated using 3D printing and magnetron sputtering processes. The two processes used, as well as compatible processes such as evaporation coating, have been industrialized. Therefore, this embodiment is not limited by specific materials and processing technologies, and has low cost and broad application prospects.

[0055] For 3D printing, considering the subsequent polishing and metallization processes, the entire device is divided into three layers and five parts, which are printed separately from top to bottom. Figure 2 As shown; the first layer consists of waveguide port 4 and horn gain structure 5, and six connecting posts are provided at the bottom of the first layer; the second layer consists of pseudo-surface plasmon structure 6, support plate 7, and displacement structure 8. Among them, displacement structure 8 includes two periodic cylindrical structures 9 and two periodic cuboid structures 10; the periodic cylindrical structure 9 consists of a first positioning plate 11 and a one-dimensional cylindrical array 12; the periodic cuboid structure 10 consists of a second positioning plate 13 and a one-dimensional cuboid array 14; the support plate 7 has reserved insertion holes of corresponding sizes for the one-dimensional cylindrical array 12 and the cuboid array 14; the displacement structure 8 is connected to the support plate 7 by inserting into the reserved insertion holes in the support plate 7 to complete the assembly of the second layer structure; and in the second layer, through holes of corresponding sizes are provided at the positions corresponding to the connecting posts of the first layer; the third layer is a base plate 3, which is used to assist in positioning the movement range of the displacement structure. The top of the base plate 3 is also connected to six connecting posts, the positions and sizes of which are the same as the connecting posts of the first layer.

[0056] In this embodiment, the bottom surface of the excitation structure layer 1 is attached to the top surface of the radiation structure layer 2. The bottom of the horn gain structure 5 of the excitation structure layer 1 is provided with multiple connecting posts, and the corresponding position of the support plate 7 of the radiation structure layer 2 is also provided with multiple connecting through holes. The multiple connecting posts are inserted into the multiple connecting through holes, thus fixing the excitation structure layer 1 onto the radiation structure layer 2. The left end of the base plate 3 is aligned with the left end of the radiation structure layer 2, and its top surface is attached to the bottom surface of the radiation structure layer 2. The upper surface of the base plate 3 is provided with multiple connecting posts, the positions and sizes of which are the same as the multiple connecting posts provided at the bottom of the horn gain structure 5. The multiple connecting posts on the upper surface of the base plate 3 are inserted into the multiple connecting through holes on the support plate 7 of the radiation structure layer 2, thus fixing the radiation structure layer 2 onto the base plate 3.

[0057] The pseudosurface plasmon structure 6 consists of a series of protruding, periodically identical metal pillars arranged in a straight line in the middle of the support plate 7. The pseudosurface plasmon structure 6 is divided into a front end and a rear end. The front end utilizes the varying height of the metal pillars to achieve impedance matching, with its height gradually increasing from zero to the designed height. The rear end consists of a series of metal pillars of uniform height. The length of the front end is 4-6 times the wavelength of the center frequency of the target frequency range. The length of the rear end is 12-20 times the wavelength of the center frequency of the target frequency range.

[0058] The support plate 7 is a "П"-shaped cuboid, consisting of a top plate, a connecting block, and a side plate. The connecting block of the support plate 7 is located on the far left of the radiation structure layer 2, and the connecting block has a connecting through hole, which corresponds to the position of the connecting post at the bottom of the horn gain structure 5 of the excitation structure layer 1. The side plate of the support plate 7 is located on the far right of the radiation structure layer 2. The top plate of the support plate 7 has two rows of insertion holes, which are distributed parallel to each other on both sides of the pseudo-surface plasmon structure 6. The insertion holes are circular and rectangular, with the circular and rectangular insertion holes spaced at the same interval and staggered.

[0059] The distance between the vertex of the circular socket and the side of the metal pillar of the pseudo-surface plasmon structure 6 is 1 / 20 to 1 / 10 of the center frequency wavelength of the target frequency range; the top edge of the rectangular socket is in close contact with the side of the metal pillar of the pseudo-surface plasmon structure 6.

[0060] The displacement structure 8 includes two periodic cylindrical structures 9 and two periodic cuboid structures 10; the periodic cylindrical structure 9 is composed of a first positioning plate 11 and a one-dimensional cylindrical array 12; the first positioning plate 11 is an "L"-shaped cuboid with one long side being comb-shaped, and the one-dimensional cylindrical array 12 stands on the upper surface of the comb-shaped long side of the first positioning plate 11; the periodic cuboid structure 10 is composed of a second positioning plate 13 and a one-dimensional cuboid array 14; the second positioning plate 13 is generally an "L"-shaped cuboid, with a one-dimensional cuboid array 14 distributed on one long side; The one-dimensional cylindrical array 12 and the one-dimensional cuboid array 14 have the same unit spacing and number of periods. The position of the one-dimensional cuboid array 14 corresponds to the position of the long side comb-shaped gap of the first positioning plate 11. The periodic cuboid structure 10 fits onto the lower surface of the periodic cylindrical structure 9 through the comb-shaped gap. After the periodic cylindrical structure 9 and the periodic cuboid structure 10 are fitted together, they are inserted into two rows of holes on the top plate of the support plate 7. By adjusting the depth of the one-dimensional cylindrical array 12 and the one-dimensional cuboid array 14 inserted into the holes of the support plate 7, different surface structures will appear.

[0061] The unit radius of the one-dimensional cylindrical array 12 is 1 / 5 to 1 / 4 of the center frequency wavelength of the target frequency range. When switching polarization states after insertion into the socket of the support plate 7, the height of the upper surface of the one-dimensional cylindrical array 12 from the top surface of the support plate 7 is 1.2 to 1.3 times the height of the metal pillar of the pseudo-surface plasmon structure 6. The width of the unit of the one-dimensional cuboid array 14 is 1 / 5 to 1 / 4 of the center frequency wavelength of the target frequency range, and the length is 1 to 1.5 times the center frequency wavelength of the target frequency range. When switching polarization states after insertion into the socket of the support plate 7, the height of the upper surface of the one-dimensional cuboid array 14 from the top surface of the support plate 7 is 1 to 1.2 times the height of the metal pillar of the pseudo-surface plasmon structure 6.

[0062] In this embodiment, waveguide port 4 is a standard WR8 waveguide port with a port size of 2.032mm × 1.016mm.

[0063] The connecting posts of the first and third layers fit into the through holes of the second layer to complete the connection and fixation of the three-layer structure; the connecting post has a radius of 1.2mm and a height of 7mm; the through hole has a radius of 1.3mm and a depth of 14mm.

[0064] The metal pillars of the pseudosurface plasmon structure 6 have dimensions of 1mm × 0.25mm, a height of 0.35mm, a period of 0.5mm, and a period number of 72. The front-end metal pillars of the pseudosurface plasmon structure 6 have the same dimensions and period as the rear-end metal pillars, with the height gradually changing from zero to 0.35mm and a period number of 23.

[0065] The support plate 7 measures 30.7 × 36.75 mm and has a thickness of 3.3 mm. The periodic cylindrical element 9 within the support plate 7 has a socket radius of 0.6 mm, a socket depth equal to the thickness of the support plate 7, and an element spacing of 2 mm. The periodic cuboid element 10 has a socket size of 0.76 mm × 2.6 mm and an element spacing of 2 mm.

[0066] In this embodiment, the spacing between the one-dimensional cylindrical array 12 and the cuboid array 14 is 0.5 mm, and the number of periods is 16; the radius of the one-dimensional cylindrical array 12 is 0.5 mm, and the height is 3.74 mm; the size of the one-dimensional cuboid array 14 is 0.5 × 2.4 mm, and the height is 7.45 mm.

[0067] The first positioning plate 11 of the periodic cylindrical structure 9 and the second positioning plate 13 of the periodic cuboid structure 10 are both "L"-shaped cuboids with a thickness of 3.3 mm. The long side portion has a size of 33.35 mm × 15 mm, and the side protrusion portion has a size of 12 mm × 10 mm. The long side comb-shaped gap of the positioning plate 11 has a size of 0.8 × 2.6 mm.

[0068] The dimensions of base plate 3 are 46.7mm × 30mm, and the thickness is 3.3mm.

[0069] In this embodiment, the antenna operates in the frequency band of 110-127 GHz;

[0070] All of the above structures are manufactured using photosensitive resin materials and 3D printing technology. For the magnetron sputtering process, magnetron sputtering is performed on the surface of all the above components to deposit a gold film with a thickness of 10μm, thereby achieving metallization.

[0071] Example 2

[0072] This embodiment provides a mechanical control method for a polarization-switchable pseudosurface plasmonic terahertz antenna, specifically including the following steps:

[0073] Step 1: After assembling the printed excitation structure layer 1, radiation structure layer 2, and base plate 3, fix them at the transmit port waveguide 18 of the vector network analyzer 17. The assembly method is that the connecting posts of the excitation structure layer 1 and the base plate 3 are inserted into the corresponding through holes of the radiation structure layer 2 to connect the three layers together; wherein, the displacement structure 8 of the radiation structure layer 2 is connected to the support plate 7 through the insertion hole in the support plate 7 to form the complete radiation structure layer 2.

[0074] Step 2: Build a control system, which includes a stepper motor control box 15 and two electric displacement stages 16. The stepper motor control box 15 and the electric displacement stages 16 are connected by cables. The electric displacement stages 16 are respectively connected to the first positioning plate 11 and the second positioning plate 13 of the displacement structure 8.

[0075] Step 3: Use the stepper motor control box 15 to control the movement of the two electric displacement stages 16 respectively, thereby adjusting the insertion depth of the periodic cylindrical structure 9 and the periodic cuboid structure 10 into the insertion hole of the support plate 7, thereby changing the distance between the top surface of the periodic cylindrical structure 9 and the periodic cuboid structure 10 and the upper surface of the support plate 7 to achieve the switching of the device surface structure, thereby generating the corresponding polarization state.

[0076] like Figure 3 The test system shown consists of a control section and a test section; the control section consists of a stepper motor control box 15 and an electric displacement stage 16, and the test section consists of a vector network analyzer 17, a transmitting port waveguide 18, a receiving port waveguide 19, and a horn antenna 20.

[0077] Among them, the stepper motor control box 15 is the driving device for controlling the electric displacement stage 16, and is connected to the electric displacement stage 16 through a cable; the displacement structure 8 is fixed on the electric displacement platform 16 through the first positioning plate 11 and the second positioning plate 13.

[0078] The vector network analyzer 17 is a device for generating and receiving signals. It transmits terahertz signals through the transmit port waveguide 18 and receives electromagnetic wave signals radiated from the pseudo-surface plasmon terahertz antenna through the receive port waveguide 19 and the horn antenna 20.

[0079] The pseudosurface plasmonic terahertz antenna is connected to the transmit port waveguide 18 of the vector network analyzer 17 via a flange, and radiates electromagnetic waves outward based on the scientific principles previously described in this invention.

[0080] The horn antenna 20 is fixed at the receiving waveguide port 20 of the vector network analyzer 17 as a receiving antenna to receive the electromagnetic signal radiated by the pseudosurface plasmon terahertz antenna and transmit the signal back to the vector network analyzer 17.

[0081] In this embodiment, the electric displacement stage 16 is moved by the stepper motor control box 15, thereby changing the insertion depth of the periodic cylindrical structure 9 and the periodic cuboid structure 10 into the insertion hole of the support plate 7, and switching between different surface structures. When the top surface of one side of the periodic cylindrical structure 9 is higher than the upper surface of the support plate 7, and the top surfaces of the two sides of the periodic cuboid structure 10 are flush with the upper surface of the support plate 7, the radiated wave is a circularly polarized wave; when one side of the periodic cuboid structure 10 is higher than the upper surface of the support plate 7, and the top surfaces of the two sides of the periodic cylindrical structure 9 are flush with the top surface of the support plate 7, the radiated wave is an elliptically polarized wave; when the two sides of the periodic cuboid structure 10 are higher than the upper surface of the support plate 7, and the top surfaces of the two sides of the periodic cylindrical structure 9 are flush with the top surface of the support plate 7, the radiated wave is a linearly polarized wave.

[0082] Example 3

[0083] This embodiment simulates the overall radiation performance of the polarization-switchable pseudosurface plasmonic terahertz antenna of Embodiment 1. The main performance indicators selected are S-parameters, radiation pattern and axial ratio to characterize the antenna's transmission effect, far-field radiation and polarization.

[0084] Figure 4 The diagram shows the S-parameters for a pure waveguide and three different polarization states. As can be seen from the diagram, within the operating frequency band, when the surface structure of the pseudosurface plasmon terahertz antenna of Example 1 is a pure waveguide, the S-parameter value is above -2dB, indicating that more than 63% of the energy is transmitted in the waveguide structure, and a small portion of the energy is lost. The surface structure of the pseudosurface plasmon terahertz antenna of Example 1 supports three different polarization states, and the corresponding S-parameter values ​​are all below -10dB, indicating that the impedance matching between the port and the antenna structure is relatively good. Calculations show that more than 90% of the energy can be used for radiation, indicating that with the switching of the surface structure, the pseudosurface plasmon terahertz antenna of Example 1 achieves a good transition from a pure waveguide to an antenna.

[0085] We can further understand the antenna's radiation performance by examining the far-field radiation diagram. Figure 5 The diagram shows the far-field radiation pattern when the surface structure of the device has a single cylindrical top surface higher than the upper surface of the support plate, corresponding to circular polarization. As can be seen from the figure, the main lobe direction of the antenna is perpendicular to the surface structure, and its gain can reach 17 dBi. This high gain indicates that the antenna of this invention has concentrated energy and good directivity.

[0086] Axis ratio is used to characterize the polarization state of electromagnetic waves. For ideal circular polarization, the axial ratio should be 1; for ideal linear polarization, the axial ratio approaches infinity; and for elliptical polarization, the axial ratio is between 1 and infinity. However, in practice, it is difficult to achieve the ideal situation. Therefore, in engineering, the axial ratio of circular polarization is required to be below 3 dB.

[0087] Figure 6 The figure shows the axial ratio values ​​corresponding to the three polarization states. As can be seen from the figure, in the direction of the main lobe of the radiation, the axial ratio is 2.53 when the polarization state of the radiated electromagnetic wave is circular; 9.97 when the polarization state switches to elliptical polarization; and 17.3 when the polarization state is linear polarization. All three polarization states achieve the desired effect, proving that the polarization switching function of the device of the present invention is fully realized.

[0088] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0089] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0090] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A polarization-switchable pseudosurface plasmon terahertz antenna, characterized in that, From top to bottom, it includes an excitation structure layer (1), a radiation structure layer (2), and a base plate (3); the excitation structure layer (1) consists of a standard waveguide port (4) and a horn gain structure (5), the left end of the standard waveguide port (4) is aligned with the left end of the radiation structure layer (2), and the right end is attached to the horn gain structure (5); the radiation structure layer (2) consists of a support plate (7), a pseudo-surface plasmon structure (6) located on the upper surface of the support plate (7), and a displacement structure (8) inserted from the lower surface of the support plate (7), the displacement structure (8) can move up and down in the middle insertion hole of the support plate (7); The support plate (7) is a "П" shaped cuboid, consisting of a top plate, a connecting block, and a side plate; the connecting block of the support plate (7) is located on the leftmost side of the radiation structure layer (2), and the connecting block has a connecting through hole, which corresponds to the position of the connecting post at the bottom of the horn gain structure (5) of the excitation structure layer (1); the side plate of the support plate (7) is located on the rightmost side of the radiation structure layer (2); the top plate of the support plate (7) has two rows of insertion holes, which are distributed in parallel on both sides of the pseudo-surface plasmon structure (6); the shapes of the insertion holes are circular and rectangular, with the circular insertion holes and the rectangular insertion holes spaced at the same interval and staggered. The displacement structure (8) includes two periodic cylindrical structures (9) and two periodic cuboid structures (10); the periodic cylindrical structure (9) is composed of a first positioning plate (11) and a one-dimensional cylindrical array (12); the first positioning plate (11) is an "L"-shaped cuboid with a comb-like shape on one of its long sides, and the one-dimensional cylindrical array (12) is placed on the upper surface of the comb-like long side of the first positioning plate (11); the periodic cuboid structure (10) is composed of a second positioning plate (13) and a one-dimensional cuboid array (14); the second positioning plate (13) is an "L"-shaped cuboid, and a one-dimensional cuboid array (14) is distributed on one of its long sides. The one-dimensional cylindrical array (12) and the one-dimensional cuboid array (14) have the same unit spacing and number of periods. The position of the one-dimensional cuboid array (14) corresponds to the position of the long side comb gap of the first positioning plate (11). The periodic cuboid structure (10) fits onto the lower surface of the periodic cylindrical structure (9) through the comb gap. After the periodic cylindrical structure (9) and the periodic cuboid structure (10) fit together, they are inserted into the two rows of holes on the top plate of the support plate (7). By adjusting the depth of the periodic cylindrical structure (9) and the periodic cuboid structure (10) inserted into the holes of the support plate (7), different surface structures will appear.

2. The polarization-switchable pseudosurface plasmon terahertz antenna as described in claim 1, characterized in that, The excitation is introduced from the waveguide port (4), and the gradual impedance matching is achieved through the front end of the horn gain structure (5) and the pseudo-surface plasmon structure (6). Surface waves are excited at the pseudo-surface plasmon structure (6). After the surface waves are disturbed by the displacement structure (8) on the side of the pseudo-surface plasmon structure (6), the originally propagating slow wave is converted into a radiated fast wave.

3. The polarization-switchable pseudosurface plasmon terahertz antenna as described in claim 1, characterized in that, The bottom surface of the excitation structure layer (1) is attached to the top surface of the radiation structure layer (2). The bottom of the horn gain structure (5) of the excitation structure layer (1) is provided with multiple connecting posts. The support plate (7) of the radiation structure layer (2) is also provided with multiple connecting through holes at the corresponding positions. The multiple connecting posts are inserted into the multiple connecting through holes, so that the excitation structure layer (1) is fixed on the radiation structure layer (2). The left end of the base plate (3) is aligned with the left end of the radiation structure layer (2), and the top surface is attached to the bottom surface of the radiation structure layer (2). The upper surface of the base plate (3) is provided with multiple connecting posts. The position and size of the multiple connecting posts are the same as the multiple connecting posts provided at the bottom of the horn gain structure (5). The multiple connecting posts on the upper surface of the base plate (3) are inserted into the multiple connecting through holes on the support plate (7) of the radiation structure layer (2), so that the radiation structure layer (2) is fixed on the base plate (3).

4. The polarization-switchable pseudosurface plasmon terahertz antenna as described in claim 1, characterized in that, The pseudosurface plasmon structure (6) consists of a series of protruding metal pillars with the same period, arranged in a straight line in the middle of the support plate (7). The pseudosurface plasmon structure (6) is divided into a front end and a rear end. The front end of the pseudosurface plasmon structure (6) achieves impedance matching by varying the height of the metal pillars, with its height gradually changing from zero to the designed height. The rear end of the pseudosurface plasmon structure (6) consists of a series of metal pillars with the same height. The length of the front end of the pseudosurface plasmon structure (6) is 4-6 times the wavelength of the center frequency of the target frequency range. The length of the rear end of the pseudosurface plasmon structure (6) is 12-20 times the wavelength of the center frequency of the target frequency range.

5. The polarization-switchable pseudosurface plasmon terahertz antenna as described in claim 1, characterized in that, The distance between the vertex of the circular socket and the side of the metal pillar of the pseudo-surface plasmon structure (6) is 1 / 20 to 1 / 10 of the center frequency wavelength of the target frequency range; the top edge of the rectangular socket is in close contact with the side of the metal pillar of the pseudo-surface plasmon structure (6).

6. The polarization-switchable pseudosurface plasmon terahertz antenna as described in claim 1, characterized in that, The unit radius of the one-dimensional cylindrical array (12) is 1 / 5 to 1 / 4 of the center frequency wavelength of the target frequency range. When the polarization state is switched after being inserted into the socket of the support plate (7), the height of the upper surface of the one-dimensional cylindrical array (12) from the top surface of the support plate (7) is 1.2 to 1.3 times the height of the metal pillar of the pseudo-surface plasmon structure (6). The width of the unit of the one-dimensional cuboid array (14) is 1 / 5 to 1 / 4 of the center frequency wavelength of the target frequency range, and the length is 1 to 1.5 times the center frequency wavelength of the target frequency range. When the polarization state is switched after being inserted into the socket of the support plate (7), the height of the upper surface of the one-dimensional cuboid array (14) from the top surface of the support plate (7) is 1 to 1.2 times the height of the metal pillar of the pseudo-surface plasmon structure (6).

7. The mechanical control method for the polarization-switchable pseudosurface plasmon terahertz antenna as described in claim 1, characterized in that, Specifically, the steps include the following: Step 1: After assembling the printed excitation structure layer (1), radiation structure layer (2), and base plate (3), fix them at the transmit port waveguide (18) of the vector network analyzer (17). The assembly method is to insert the connecting posts of the excitation structure layer (1) and the base plate (3) into the corresponding through holes of the radiation structure layer (2) to connect the three layers together. Among them, the displacement structure (8) of the radiation structure layer (2) is connected to the support plate (7) through the insertion hole in the support plate (7) to form a complete radiation structure layer (2). Step 2: Build a control system, which includes a stepper motor control box (15) and two electric displacement stages (16); the stepper motor control box (15) and the electric displacement stages (16) are connected by cables, and the electric displacement stages (16) are connected to the first positioning plate (11) and the second positioning plate (13) of the displacement structure (8) respectively. Step 3: Use the stepper motor control box (15) to control the movement of the two electric displacement stages (16) respectively, thereby adjusting the depth of the periodic cylindrical structure (9) and the periodic cuboid structure (10) inserted into the insertion hole of the support plate (7), thereby changing the distance between the top surface of the periodic cylindrical structure (9) and the periodic cuboid structure (10) and the upper surface of the support plate (7) to achieve the switching of the device surface structure, thereby generating the corresponding polarization state.

8. The mechanical control method for the polarization-switchable pseudosurface plasmonic terahertz antenna as described in claim 7, characterized in that, In step three, when the top surface of the periodic cylindrical structure (9) on one side is higher than the upper surface of the support plate (7), and the top surfaces of the periodic cuboid structures (10) on both sides are aligned with the upper surface of the support plate (7), the radiation wave is a circularly polarized wave; when the periodic cuboid structure (10) on one side is higher than the upper surface of the support plate (7), and the top surfaces of the periodic cylindrical structures (9) on both sides are aligned with the top surface of the support plate (7), the radiation wave is an elliptically polarized wave; when the periodic cuboid structures (10) on both sides are higher than the upper surface of the support plate (7), and the top surfaces of the periodic cylindrical structures (9) on both sides are aligned with the top surface of the support plate (7), the radiation wave is a linearly polarized wave.

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