A terahertz transmission array antenna based on a rotating Z-shaped unit

Abstract

The present invention discloses a terahertz transmission array antenna based on a rotating Z-shaped unit, belonging to the field of terahertz technology. The novel transmission array unit structure proposed in the present invention greatly simplifies the form of the unit structure while satisfying full phase modulation and wide-band performance, which is conducive to the processing and realization of the transmission array in the terahertz frequency band; the present solution uses the rotation angle formed by the metal structure on the upper and lower surfaces of the medium to perform phase modulation, avoids fine structures and has good anti-sensitivity to line width changes, effectively reduces the influence of processing accuracy on the performance of the transmission array, and is suitable for the terahertz frequency band; the present solution uses the spatial stacking method to achieve full phase modulation, and does not use strong resonance schemes such as polarization grids and metal vias, so it has good broadband characteristics; compared with other schemes, the terahertz transmission array antenna designed based on the novel transmission array unit structure has a simple structure, is easy to process, has stable performance and wide bandwidth.

Description

Technical Field

[0001] The invention belongs to the field of terahertz technology, and in particular relates to a terahertz transmission array antenna based on a rotating Z-shaped unit. Background Art

[0002] Due to the short wavelength and high processing precision requirements of terahertz antennas, many high-gain antenna designs such as parabolic antennas and array antennas are difficult to manufacture. Existing terahertz antennas are mainly horn antennas, with a single structure and radiation function, and there are considerable challenges in the processing and manufacturing of terahertz high-frequency bands. In order to obtain high-gain beams, multiple beams, low side lobes, beams with specific characteristics and other new energy requirements for antenna radiation in different application scenarios, reflective arrays and transmission array antennas based on metasurface design have become a good solution. Reflective array or transmission array antennas control the phase of the electromagnetic field at different positions in space based on metasurface units, thereby controlling the far-field radiation performance to meet the design requirements. The planar periodic array is printed on a dielectric plate, with the advantages of simple structure, low cost, and flexible beam control, breaking through the limitations of traditional antennas.

[0003] Compared with reflector array antennas, transmission array antennas have their own advantages and disadvantages. Reflector array units can generally achieve phase modulation capabilities covering 360° full phase based on a single layer of medium, while transmission array units have a limited modulation range and require a multi-layer structure. To achieve full phase coverage modulation capabilities, the design complexity and structural complexity are higher. However, in order to reduce feed source obstruction, the reflector array antenna feed generally uses oblique illumination. The feed inclination angle and position are fixed, which requires complex structural design, increases manufacturing costs, and is not conducive to practical applications. Transmission array antennas do not need to consider feed source obstruction issues, which greatly reduces the difficulty of overall structural design and facilitates processing.

[0004] Existing transmission array antenna solutions are relatively limited. Since most transmission array units themselves do not have the characteristics of high Q values, their phase modulation range is limited, and there are not many types of unit structures to choose from, which is far less than the wide variety of structural forms of reflective array units. On the other hand, most existing transmission array antennas are targeted at microwave frequency bands, and there are few reports on millimeter wave and terahertz frequency bands. The transmission array unit structure in the microwave frequency band is relatively complex. If it is directly converted to the terahertz frequency band, the fine structure has exceeded the limit of processing accuracy, and there is a problem of difficulty in processing and manufacturing, which cannot meet practical applications. In order to increase the phase control capability of the transmission array, it is usually adopted to increase metal vias or use narrow gap structures, which greatly increases the difficulty of processing and is difficult to achieve in the terahertz frequency band.

[0005] Reflectarray antennas and transmissionarray antennas are a good way to achieve high-gain antennas. Their gain performance, radiation pattern, etc. can be flexibly controlled, and while realizing the functions of array antennas, they do not require complex feeding networks and phase modulation modules. The phase modulation capability of the metasurface in space is used to achieve secondary control of the radiation wavefront, so as to design antennas that meet specific radiation requirements. In the terahertz frequency band, traditional antenna forms are difficult to manufacture due to limitations in processing capabilities, and reflectarray or transmissionarray antennas are a good choice. Compared with reflectarray antennas, transmissionarray antennas do not need to consider the feed source shielding effect, the structural design is simpler, and the terahertz antenna design is easier to process and realize. However, it is more difficult to obtain a unit structure with full phase modulation or close to full phase modulation. The types of transmissionarray unit structures in the available literature are relatively limited, and most of them require complex and delicate structures or the addition of metal vias. Although this is applicable in the microwave frequency band, it is difficult to extend to the terahertz frequency band.

[0006] Figure 1 The following are the structural diagrams of three transmission array units that have been reported. Figure 1 (a) For the terahertz frequency band, a single-layer dielectric double-sided metal structure is adopted, and an L-shaped metal pattern and a metal grid are printed on the upper and lower surfaces of the low-loss thin dielectric layer respectively. This structural design is simple in structure and does not require punching. It is easy to process and manufacture and is suitable for the terahertz frequency band. Its working principle is to achieve phase control by changing the side length and angle of the L-shaped pattern. Patterns of different sizes and angles are selected to form an array to form a transmission array antenna. In order to achieve full phase modulation, the structure introduces a metal grid for polarization selection. When the electromagnetic wave penetrates the unit, it has a better transmission coefficient and phase modulation capability when the polarization of the incident wave and the outgoing wave are orthogonal. The Q value of the single-layer medium is increased by polarization rotation, thereby achieving full phase control, but this method is only effective for narrowband and is not suitable for broadband design.

[0007] Figure 1 (b) with Figure 1(c) shows the design of transmission array unit structure for two microwave frequency bands. Among them, (b) uses a single-layer medium with metal patterns printed on the upper and lower surfaces of the medium, and the upper and lower surfaces are connected by four short-circuit metal vias. The introduction of metal probes increases the resonance characteristics of the transmission unit and realizes wide-range phase regulation. The introduction of metal vias is a good design method in the low-frequency band, but the related technology is still immature in the terahertz band and it is difficult to achieve processing. Figure (c) shows a transmission array unit based on a stacked structure and a phase delay line pattern design. A metal pattern is printed on one side of the medium, and a phase delay line is added on the basis of the ring to adjust the transmission phase value. The transmission phase can be regulated by changing the size of the metal pattern. Due to the limited regulation ability of a single-layer medium, a multi-layer stacking design is used to expand the range of the modulation phase. This design has been well verified in the microwave band and can be used for the design of broadband transmission arrays. However, for the terahertz band, when the size of the metal pattern is adjusted, the metal line width is too thin and the processing accuracy is limited, so it is difficult to ensure the integrity of the pattern.

[0008] By analyzing domestic and foreign published literature, patents and products, most of the existing transmission array design solutions are targeted at the microwave frequency band. Existing design solutions usually achieve full phase modulation by enhancing the resonant characteristics or introducing complex units, which requires the introduction of metal vias or increasing the complexity of metal patterns, which increases the difficulty of processing and implementation. The relevant technology is still immature in the terahertz frequency band, so many designs cannot be directly moved from the low frequency band to the terahertz frequency band.

[0009] The design of transmission arrays for the terahertz frequency band needs to meet technical requirements such as simple structure, good tolerance, and avoidance of drilling, so as to facilitate processing and implementation, and at the same time, it should meet the characteristics of broadband effectiveness and full phase modulation. For terahertz transmission array antennas, although a few reports have shown that full phase modulation can be achieved using simple structures, the effective frequency range is limited, making it impossible to design broadband antennas.

[0010] The present invention innovates on the basis of existing research and proposes a terahertz transmission array antenna based on a rotating Z-shaped unit. The rotation angle formed by the double-sided metal structure is used to achieve phase control. A wide phase modulation range is achieved by controlling the two variables of the metal pattern size and the rotation angle. On this basis, a laminated structure design is used to further achieve full phase modulation, and it is effective in wide bandwidth. The transmission array unit itself has the characteristics of simple structure, easy processing, and good tolerance. The transmission array antenna designed based on this structure has the characteristics of broadband, low side lobe, low cross polarization, and low cost, and can be used in practical engineering applications. Summary of the invention

[0011] In view of the above technical problems existing in the prior art, the present invention proposes a terahertz transmission array antenna based on a rotating Z-shaped unit, which has a reasonable design, overcomes the shortcomings of the prior art, and has good effects.

[0012] In order to achieve the above object, the present invention adopts the following technical solution:

[0013] A terahertz transmission array antenna based on a rotating Z-shaped unit comprises a standard waveguide port and four layers of identical transmission array units; the standard waveguide port is vertically irradiated along the central normal direction of the transmission array unit, and the radiation direction is vertically transmitted along the normal direction; the distance between the standard waveguide port and the transmission array unit is 5 wavelengths.

[0014] Preferably, the transmission array unit comprises an upper metal surface, a lower metal surface and a dielectric substrate; the upper metal surface and the lower metal surface are both distributed on the dielectric substrate.

[0015] Preferably, the transmission array unit adopts a double Z-shaped structure, and the Z-shaped structures are respectively located on the upper metal surface and the lower metal surface and are mirror-symmetrical; that is, the upper metal surface and the lower metal surface are respectively printed with Z-shaped structures and are mirror-symmetrical; the Z-shaped structure is a metal pattern, and the metal patterns on the upper metal surface and the lower metal surface form an X-shaped pattern but are not connected to each other.

[0016] Preferably, the middle section of the Z-shaped structure is a straight line section, and each of the two ends has an arc section.

[0017] Preferably, four layers of identical transmission array unit structures are stacked and a certain air gap is reserved between each layer, and the air gap between two adjacent layers is the same.

[0018] Preferably, the angle formed by the two Z-shaped structures is the rotation angle, and the middle section of the Z-shaped structure is the Z-shaped straight arm; the rotation angle changes synchronously with the length of the Z-shaped straight arm, which can modulate the phase change of the transmission array unit; the four-layer stacked structure design can achieve 360° full phase modulation.

[0019] Beneficial technical effects brought by the present invention:

[0020] The new transmission array unit structure proposed in the present invention greatly simplifies the form of the unit structure while meeting the full phase modulation and wide-band performance, which is conducive to the processing and realization of the transmission array in the terahertz frequency band; compared with the traditional scheme, this scheme uses the rotation angle formed by the metal structure on the upper and lower surfaces of the medium to perform phase modulation, avoiding the fine structure and having good anti-sensitivity to line width changes, effectively reducing the influence of processing accuracy on the performance of the transmission array, and is suitable for the terahertz frequency band; this scheme uses the spatial stacking method to achieve full phase modulation, and does not use strong resonance schemes such as polarization grids and metal vias, so it has good broadband characteristics. Compared with other schemes, the terahertz transmission array antenna designed based on the new transmission array unit structure has a simple structure, easy processing, stable performance and wide bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The following are the structural diagrams of three transmission array units; Figure 1 (a) is a structural diagram of a transmission array unit using the terahertz frequency band; Figure 1 (b) with Figure 1 (c) Design diagram of the transmission array unit structure for two microwave frequency bands;

[0022] Figure 2 This is a structural diagram of a transmission array unit of the present invention; Figure 2 (a) is a top view of a single-layer array element; Figure 2 (b) is a three-dimensional image of four-layer array elements.

[0023] Among them, 1-upper metal surface; 2-lower metal surface; 3-medium substrate;

[0024] Figure 3 It is a schematic diagram of the relationship between the transmission coefficient (amplitude) and the rotation angle;

[0025] Figure 4 Schematic diagram of the relationship between transmission coefficient (phase) and rotation angle;

[0026] Figure 5 Schematic diagram of the terahertz transmission array antenna structure;

[0027] Figure 6 Schematic diagram of the simulation results of the radiation pattern of the terahertz transmission array antenna (φ=0°);

[0028] Figure 7 Schematic diagram of the simulation results of the cross-polarization pattern of the terahertz transmission array antenna (φ=0°);

[0029] Figure 8 Schematic diagram of the terahertz transmission array antenna gain simulation results. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0031] The present invention proposes a terahertz transmission array antenna based on a rotating Z-shaped unit, wherein the transmission array unit structure is as follows: Figure 2 As shown. A metal pattern is printed on a quartz dielectric substrate. The quartz thickness is 30μm, the dielectric constant is 4.4, the side length of the periodic unit is P, and the thickness of the gold layer is 1μm. A Z-shaped structure is printed on the upper surface of the quartz. The middle section of the structure is a straight line section with a length of L, and there are arc lines at both ends. The Z-shaped structure is offset from the center line by an angle of θ, and all line widths are w. The metal pattern on the lower surface of the dielectric is the same as the upper surface and is mirror-symmetrical. The upper and lower metal patterns form an X-shaped pattern but are not connected to each other. Four layers of the same unit structure are stacked and a certain air gap is retained between each layer. The air gap between two adjacent layers is the same.

[0032] The operating frequency is set to 300 GHz, and the parameters obtained by optimization are as follows. P = 400 μm, w = 30 μm, the air gap between layers is 220 μm, L and θ satisfy the function transformation relationship L = f(θ), and the range of θ is -26° to 62°. There are many options for the function transformation relationship f(x), and here the exponential function relationship is selected to obtain better phase change linearity.

[0033] The working principle of the phase modulation function of the transmission array unit is as follows. When the electromagnetic wave is irradiated perpendicular to the transmission array unit and θ is 0, the electric field polarization direction is parallel to the straight line segment in the middle of the metal pattern, and an induced current is generated on the metal pattern. When the induced current is consistent with the direction of the incident field strength, it has no effect on the transmission phase, and the transmission phase is 0. When θ is not 0, the direction of the induced current is deflected, and the x-shaped structure forms a resonator, introducing equivalent capacitance and equivalent inductance. Changing the size of θ can change the value of the equivalent capacitance and equivalent inductance, thereby changing the transmission phase. The transmission phase is mainly determined by the angle formed by the two Z-shaped structures and is insensitive to the line width of the Z-shaped structure. The two Z-shaped structures are located on the upper and lower surfaces of the medium and have a good tolerance for the line width, which reduces the difficulty of processing.

[0034] Through research and analysis, it is found that although only changing θ can produce a good phase modulation effect, the phase modulation range is not wide enough to meet the requirements of full phase coverage. Two methods are introduced here to achieve 360° full phase modulation. First, the modulation phase range of the single-layer transmission array structure is expanded by changing the size of the straight line segment L in the pattern while changing the rotation angle. Secondly, a four-layer stacked structure is introduced to further broaden the phase modulation range and cover 360°. The variable L and the angle θ satisfy a functional relationship, and θ is the independent variable and L is the dependent variable. The functional relationship is selected as an exponential relationship and some parameters in the function are adjusted to obtain better phase change linearity.

[0035] The simulation results of the transmission amplitude and transmission phase change of the four-layer stacked transmission array unit are as follows: Figure 3 and Figure 4 As shown. At the design frequency of 300GHz, the transmission amplitude does not change much with the rotation angle θ and maintains good transmittance. When θ changes from -26° to 62°, the transmission coefficient amplitude is above -2dB and the transmittance is good. The relationship between the transmission coefficient phase and the rotation angle shows that at the center frequency of 300GHz, 360° full phase modulation can be achieved by changing θ between -26° and 62°. In addition, by changing the operating frequency and observing the phase change relationship, the phase curves between different frequencies maintain good parallel characteristics, which shows that the structure has good broadband working characteristics.

[0036] Based on the transmission array unit, a terahertz transmission array antenna with a center frequency of 300 GHz is designed. The antenna structure is as follows: Figure 5 As shown. According to the phase compensation principle, the compensation phase size of each unit on the array is obtained, and the rotation angle of the corresponding unit is obtained according to the change relationship of the phase curve. The standard waveguide port WR-2.8 irradiates vertically from the normal direction of the center of the array, and the main radiation direction is still vertically transmitted along the normal direction. The distance between the waveguide port and the transmission array is 5mm. The transmission array uses 21×21 units, and four layers of the same array are stacked. The array size is 10.5mm×10.5mm.

[0037] Figure 6 , Figure 7 , Figure 8 The simulation results of the radiation performance of the terahertz transmission array antenna are given when the frequency varies in the range of 280 to 340 GHz. Figure 6 for The two-dimensional radiation pattern of the surface remains stable in the broadband. Figure 7 is the simulation result of cross-polarization level. The cross-polarization level is lower than -30dB. Figure 8 The simulation results of antenna gain show that the maximum gain is higher than 26dBi when the center frequency is slightly offset, that is, 310GHz. The gain is higher than 22dBi in the range of 280-340GHz, and the 3dB gain bandwidth is about 18%. This antenna has the characteristics of wide bandwidth, stable radiation pattern, and low cross-polarization, which can meet the needs of high-performance terahertz antennas.

[0038] The key points of the present invention are as follows:

[0039] The present invention proposes a rotating Z-shaped transmission array unit structure, which realizes phase modulation of the transmitted terahertz wave by using the mirror-symmetric Z-shaped structure of the upper and lower layers of the medium. The structure is simple in form, insensitive to line width, and easy to process.

[0040] The present invention proposes a method of combining the rotation angle with the length of the Z-shaped straight arm to expand the variation range of the modulation phase, and realizes 360° full-phase modulation in combination with a four-layer stacked structure design.

[0041] Based on the novel transmission array unit structure, the present invention designs a terahertz transmission array antenna, which has the characteristics of wide bandwidth, stable radiation pattern and low cross polarization.

[0042] The protection points are as follows:

[0043] A rotating Z-shaped transmission array unit structure model is proposed, which adopts a double Z-shaped structure, which is located on the upper and lower surfaces of the medium and is mirror-symmetrical.

[0044] A method of using the rotation angle of the Z-shaped structure combined with the synchronous change of the length of the Z-shaped straight arm to achieve wide-range phase modulation is proposed.

[0045] It is pointed out that the linearity of the phase change curve is determined by the functional relationship between the rotation angle and the length of the straight arm, and it is proposed that better linearity can be obtained when the rotation angle and the length show an exponential change relationship.

[0046] A terahertz transmission array antenna design based on a rotating Z-shaped transmission array unit is proposed. The antenna has excellent performance, wide bandwidth, stable radiation pattern and low cross-polarization.

[0047] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A terahertz transmission array antenna based on a rotating Z-shaped unit, characterized in that: It includes a standard waveguide port and four identical transmission array units; the standard waveguide port is vertically irradiated along the center normal direction of the transmission array unit, and the radiation direction is vertically transmitted along the normal direction; the distance between the standard waveguide port and the transmission array unit is 5 wavelengths; The transmission array unit comprises an upper metal surface, a lower metal surface and a dielectric substrate; the upper metal surface and the lower metal surface are both distributed on the dielectric substrate; The transmission array unit adopts a double Z-shaped structure, and the Z-shaped structures are respectively located on the upper metal surface and the lower metal surface and are mirror-symmetrical; that is, the upper metal surface and the lower metal surface are respectively printed with a Z-shaped structure and are mirror-symmetrical; the Z-shaped structure is a metal pattern, and the metal patterns on the upper metal surface and the lower metal surface form an X-shaped pattern but are not connected to each other; The middle section of the Z-shaped structure is a straight line, with an arc at each end; The angle formed by the two Z-shaped structures is the rotation angle, and the middle section of the Z-shaped structure is the Z-shaped straight arm; the rotation angle changes synchronously with the length of the Z-shaped straight arm, which can modulate the phase change of the transmission array unit; the four-layer stacked structure design can achieve 360° full phase modulation; the linearity of the phase change curve is determined by the functional relationship between the rotation angle and the length of the Z-shaped straight arm, and better linearity can be obtained when the rotation angle and the length are in an exponentially changing relationship.

2. The terahertz transmission array antenna based on the rotating Z-shaped unit according to claim 1, characterized in that: Four layers of identical transmission array unit structures are stacked and a certain air gap is reserved between each layer, and the air gap between two adjacent layers is the same.

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