Radiation-receiving low-profile dual-beam array antenna and folding decoupling design method

Abstract

This invention discloses a low-profile dual-beam array antenna for radiation and reception, and a folding decoupling design method. The low-profile dual-beam array antenna consists of a transmitting metasurface, a polarization conversion metasurface, and a horn feed. The transmitting metasurface is composed of m×m radiating-receiving elements arranged periodically at equal intervals in a plane, achieving efficient transmission of electromagnetic waves in a specific frequency band and spin decoupling focusing phase modulation. The radiating-receiving elements consist of three metal layers and two dielectric layers. The polarization conversion metasurface is composed of n×n polarization conversion elements arranged periodically at equal intervals in a plane, achieving efficient reflection, polarization conversion, and non-mirror beam deflection phase modulation of electromagnetic waves in a specific frequency band. The polarization conversion elements consist of two metal layers and one dielectric layer. The low-profile dual-beam array antenna provided by this invention, under excitation by a circularly polarized wave feed, can generate two independently modulated orthogonal circularly polarized waves through spin decoupling, and has significant advantages such as high aperture efficiency and low profile.

Description

Technical Field

[0001] This invention relates to the field of array antenna design technology, and in particular to a radiating-receiving low-profile dual-beam array antenna and a folding decoupling design method. Background Technology

[0002] In recent years, folded transmission array antennas have become a research hotspot in order to achieve highly integrated transmission array antennas. Folded transmission array antennas are based on the path-tracking principle, incorporating a top metasurface with polarization selectivity, a bottom metasurface with reflectivity and polarization conversion, and a feed located at the center of the bottom metasurface. Since the electromagnetic waves emitted by the feed are reflected twice by the top and bottom metasurfaces, its profile can be reduced to 1 / 3 of the focal length. To further improve integration and radiation efficiency, reflective electromagnetic wavefront modulation technology is introduced into the metasurface, achieving a low-profile effect of multiple reflections with a single reflection. However, traditional folded transmission array antennas can only achieve single linear or circular polarization modulation within a single band, limiting engineering applications. Therefore, simultaneously achieving independent modulation of left-hand and right-hand circularly polarized waves is of great significance for improving communication system performance and has important engineering application value.

[0003] A radiating-receiving structure is a type of artificially designed metamaterial that can transmit electromagnetic waves in a specific frequency band while ensuring efficient reflection of electromagnetic waves in the frequency bands to its left and right. Furthermore, introducing spin decoupling theory into the radiating-receiving structure can break the conjugacy of circularly polarized waves, enabling two independently controllable circularly polarized beams. Traditional spin-decoupling transmission array antennas have high profiles and are difficult to integrate. At the same time, traditional folded transmission array antennas cannot achieve independent control of two orthogonal circularly polarized waves within a single frequency band. Summary of the Invention

[0004] This invention is the first to combine spin decoupling with a non-mirror reflection folding transmission array. By controlling the reflection phase of the polarization conversion metasurface, a single fold can achieve the low profile effect of a second or third fold, thereby reducing the energy loss caused by multiple reflections and achieving high efficiency while maintaining a low profile. At the same time, the spin decoupling method is used in the transmission metasurface to realize dual beams, enabling one folding transmission array to perform the functions of two traditional folding transmission arrays.

[0005] A folded transmission array antenna that simultaneously satisfies low profile, dual beam and high radiation performance and its design method are disclosed.

[0006] This invention discloses a radiating-receiving low-profile dual-beam array antenna, which comprises a three-part structure: a transmissive metasurface, a polarization-conversion metasurface, and a feed horn.

[0007] The feed horn is placed at the center of the transmissive metasurface, with its aperture surface flush with the surface of the lower receiving patch, and the polarization conversion metasurface is placed at H directly below the transmissive metasurface.

[0008] The transmissive metasurface is composed of m×m radiation-receiving units with different rotation angles arranged in a plane at equal intervals and periodically extended, realizing efficient transmission of electromagnetic waves in a specific frequency band and spin decoupling focusing phase modulation.

[0009] The radiation-receiving unit consists of a three-layer metal structure and two layers of dielectric plates, with a period of P. The upper layer is a metal patch with C-grooves; the middle layer is a metal ground plate with through holes; and the bottom layer is a metal patch with two chamfered corners along the diagonal direction. The two layers of C-grooves metal patches are connected by metallized vias. Among the two dielectric plates, the first dielectric plate is located between the upper C-grooves metal patch and the middle metal ground plate with through holes, and the second dielectric plate is located between the metal ground plate with through holes and the bottom C-grooves metal patch with two chamfered corners along the diagonal direction.

[0010] The polarization conversion metasurface is composed of n×n polarization conversion units with different opening angles arranged in a plane at equal intervals and periodically extended, realizing efficient reflection, polarization conversion and non-mirror beam deflection phase control of electromagnetic waves in a specific frequency band; the upper layer of the polarization conversion unit is an I-shaped metal ring, the lower layer is a metal back plate, and the two are separated by a dielectric plate with a period of P1.

[0011] Furthermore, the radiation-receiving unit consists of a three-layer metal structure and two layers of dielectric substrates. The upper layer of the unit is a metal patch with C-grooves, the outer diameter of which is R1, the inner diameter is R3, and the radius of the inner circular patch is R4. The middle layer is a metal base plate with a through hole diameter of D1. Between the middle layer and the upper layer is a dielectric substrate with a thickness of h1. The bottom layer is a metal patch with C-grooves and two diagonally cut corners, the two cut corner angles being α, the outer diameter of the cut metal ring being R2, and the diameter of the metallized through hole being D2. Between the bottom patch and the middle layer is a dielectric substrate with a thickness of h1.

[0012] Furthermore, the radiation-receiving unit rotates the receiving patch and the radiation patch from 0° to 360° respectively to obtain 360° phase coverage. The counterclockwise rotation angle of the receiving / transmitting patch is α / β.

[0013]

[0014] in, This represents the incident electric field after the receiving patch is rotated by an angle α. This represents the new coordinate system after the patch is rotated by an angle α. Let represent the new coordinate system after the radiating patch is rotated by an angle β, E0 represent the electric field intensity of the incident wave, and kz represent the spatial phase. T represents the transmitted electric field after the radiating patch is rotated by an angle γ. y-RCP This represents the transmission coefficient for converting a right-hand circularly polarized wave into a y-polarized wave;

[0015] The phase distributions of the left-hand circularly polarized wave and the right-hand circularly polarized wave components are obtained as follows:

[0016]

[0017] Where, Φ LCP Φ represents the phase distribution of the left-hand circularly polarized wave component. RCP This represents the phase distribution of the right-hand circularly polarized wave component;

[0018] When the phases of the bottom receiving patch and the top radiating patch of the transmissive metasurface satisfy the spin decoupling phase condition, two independently controllable orthogonally circularly polarized beams can be realized:

[0019]

[0020] in, This indicates the phase of the receiving patch after rotation by α. The phase of the radiating patch after rotation by β is represented by the phase of the receiving patch and the radiating patch, and the spin-decoupled spatial phase arrangement of the transmissive metasurface is performed based on the phase of the receiving patch and the radiating patch.

[0021] Furthermore, the polarization conversion unit has an I-shaped metal ring on the upper layer, a dielectric substrate with a thickness of h2 in the middle layer, and a metal backplate at the bottom layer to block electromagnetic wave transmission; the unit period is P1, the outer diameter of the I-shaped metal ring structure is R5, the inner diameter is R6, the opening angle of the I-shaped metal ring is γ1, the width of the middle metal strip is w, and the overall rotation angle of the I-shaped metal ring is γ2.

[0022] Furthermore, the polarization conversion unit can achieve 360° phase modulation within 11–15 GHz by changing the opening angle γ1 and rotation angle β2 of the metal ring; when a left-handed circularly polarized wave is incident perpendicularly, the required compensation phase Φ(x,y0) at different positions on the metasurface is:

[0023]

[0024] Φ(x,y) represents the compensation phase required to achieve electromagnetic wave focusing, (x,y) represents the relative position of the metasurface unit, k0=2π / λ0 is the free space wave vector, and λ0 is the wavelength at the operating frequency f0. For a constant reference phase, OM is the initial focal length, and OM′ is the focal length after the electromagnetic wave path changes.

[0025] A folding decoupling design method for a radiating-receiving low-profile dual-beam array antenna is also provided, the method comprising the following steps:

[0026] Step 1: Design the radiating-receiving unit of the radiating-receiving low-profile dual-beam array antenna;

[0027] Step 2: Design the polarization conversion unit of the radiating-receiving low-profile dual-beam array antenna;

[0028] Step 3: Arrange the spatial phase of the transmission metasurface using spin-decoupled phase arrangement;

[0029] Step 4: Arrange the spatial phase of the polarization conversion metasurface using the phase compensation method;

[0030] Step 5: Based on the designed transmissive metasurface and polarization conversion metasurface, construct the final radiating-receiving low-profile dual-beam array antenna.

[0031] Furthermore, in step 1, the radiation-receiving unit consists of a three-layer metal structure and two layers of dielectric substrates. The upper layer of the unit is a metal patch with C-grooves, the outer diameter of which is R1, the inner diameter is R3, and the radius of the inner circular patch is R4. The middle layer is a metal base plate with a through-hole diameter of D1. Between the middle layer and the upper layer is a dielectric substrate with a thickness of h1. The bottom layer is a metal patch with C-grooves and two diagonally shaped bevels, the two bevel angles being α, the outer diameter of the metal ring after beveling being R2, and the diameter of the metallized via being D2. Between the bottom layer patch and the middle layer is a dielectric substrate with a thickness of h1.

[0032] In step 2, the upper layer of the polarization conversion unit is an I-shaped metal ring, the middle layer dielectric plate has a thickness of h2, and the bottom layer is a metal backplate to block electromagnetic wave transmission; the unit period is P1, the outer diameter of the I-shaped metal ring structure is R5, the inner diameter is R6, the opening angle of the I-shaped metal ring is γ1, the width of the middle metal strip is w, and the overall rotation angle of the I-shaped metal structure is γ2.

[0033] Furthermore, in step 3, the receiving patch and the radiating patch of the radiating-receiving unit are rotated from 0° to 360° respectively to obtain 360° phase coverage. When the receiving / transmitting patch is rotated counterclockwise by an angle α / β, we have:

[0034]

[0035] in, This represents the incident electric field after the receiving patch is rotated by an angle α. This represents the new coordinate system after the patch is rotated by an angle α. Let represent the new coordinate system after the radiating patch is rotated by an angle β, E0 represent the electric field intensity of the incident wave, and kz represent the spatial phase. T represents the transmitted electric field after the radiating patch is rotated by an angle β. y-RCP This represents the transmission coefficient for converting a right-hand circularly polarized wave into a y-polarized wave;

[0036] The phase distributions of the left-hand circularly polarized wave and the right-hand circularly polarized wave components are obtained as follows:

[0037]

[0038] Where, Φ LCP Φ represents the phase distribution of the left-hand circularly polarized wave component. RCP This represents the phase distribution of the right-hand circularly polarized wave component;

[0039] When the phase of the bottom receiving patch and the phase of the top radiating patch of the transmissive metasurface satisfy the spin decoupling phase condition, two independently controllable orthogonally circularly polarized beams can be realized:

[0040]

[0041] in, This indicates the phase of the receiving patch after rotation by α. The phase of the radiating patch after rotation by β is represented by the phase of the receiving patch and the radiating patch, and the spin-decoupled spatial phase arrangement of the transmissive metasurface is performed based on the phase of the receiving patch and the radiating patch.

[0042] Furthermore, in step 4, the polarization conversion unit can totally reflect the incident left-handed circularly polarized wave into a right-handed circularly polarized wave, and by changing the opening angle γ1 and rotation angle γ2 of the metal ring, 360° phase modulation can be achieved within 11–15 GHz. When the left-handed circularly polarized wave is incident perpendicularly, the compensation phase Φ(x,y) required at different positions of the polarization conversion metasurface is:

[0043]

[0044] Φ(x,y) represents the compensation phase required to achieve electromagnetic wave focusing, (x,y) represents the relative position of the metasurface unit, k0=2π / λ0 is the free space wave vector, and λ0 is the wavelength at the operating frequency f0. For a constant reference phase, OM is the initial focal length, and OM′ is the focal length after the electromagnetic wave path changes.

[0045] The above formula is used to arrange the polarization conversion metasurfaces in a spatial phase compensation manner.

[0046] Furthermore, in step 5, the transmissive metasurface is placed above the polarization conversion metasurface, and the interval is set to H; the circularly polarized horn feed is placed at the center of the transmissive metasurface, and the horn aperture surface is flush with the receiving patch surface of the bottom layer of the transmissive metasurface.

[0047] In the two cases where H equals F / 3 or F / 4, F is the focal length after the electromagnetic wave path is changed. The left-hand circularly polarized wave emitted by the circularly polarized horn feed is reflected into a right-hand circularly polarized wave through the polarization conversion metasurface. Then, it is received by the transmission metasurface and generated independently controllable left-hand and right-hand circularly polarized beams radiating along the +z direction through spin decoupling.

[0048] The beneficial effects achieved by this invention are:

[0049] Compared to traditional folded transmission array antennas, this invention can simultaneously achieve low profile, high aperture efficiency, and independent control of dual circularly polarized beams.

[0050] This invention proposes an effective design method that can design a low-profile dual-beam array antenna with a lower profile according to requirements and design flow.

[0051] This invention exhibits remarkable antenna gain. When the overall antenna profile is 1 / 3 that of a conventional transmission array, the measured peak gains of the left-hand circularly polarized and right-hand circularly polarized beams are 24.53 dBic and 24.12 dBic, respectively, with corresponding aperture efficiencies of 37.12% and 33.78%. Simultaneously, when the overall antenna profile is 1 / 4 that of a conventional transmission array, the measured peak gains of the left-hand circularly polarized and right-hand circularly polarized beams are 22.56 dBic and 22.42 dBic, respectively, with corresponding aperture efficiencies of 23.6% and 22.8%. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of a low-profile dual-beam array antenna.

[0053] Figure 2 The topology of the transmissive metasurface radiation-receiving unit, as well as the radiation patch and the receiving patch.

[0054] Figure 3 This is a side view of the current distribution of the receiver-transmitter structure under the action of different electromagnetic waves.

[0055] (a) Left-handed circularly polarized wave; (b) Right-handed circularly polarized wave.

[0056] Figure 4 Numerical characteristics of the radiator-receiver unit as simulated.

[0057] (a) Cross-circular polarization transmission amplitude and phase when the receiving patch is rotated at angle α;

[0058] (b) Common-circular polarization transmission amplitude and phase when the receiving patch is rotated by angle α;

[0059] (c) Cross-circular polarization transmission amplitude and phase when the radiating patch is rotated at an angle β;

[0060] (d) Common-circular polarization transmission amplitude and phase when the radiating patch is rotated at an angle β.

[0061] Figure 5 The transmission amplitude and phase of the radiation-receiving unit under right-hand circularly polarized wave incident at different angles.

[0062] (a) Cross-circular polarization; (b) Common-circular polarization.

[0063] Figure 6 The design and simulation results are for polarization conversion metasurfaces.

[0064] (a) Top view of the polarization conversion metasurface and cross-circular polarization reflection amplitudes of left-handed circularly polarized waves at different incident angles when γ1 and γ2 are 20° and 45°, respectively;

[0065] (b) Cross-circular polarization reflection amplitude and phase at 13 GHz when γ2 is 45° and -45°, and γ1 varies from 7° to 132°.

[0066] Figure 7 This represents the theoretically synthesized phase distribution of the transmission metasurface at a center frequency of 13 GHz.

[0067] (a) Phase distribution of a left-hand circularly polarized beam at (10°, 0°); (b) Phase distribution of a right-hand circularly polarized beam at (-25°, 0°);

[0068] (c) Phase distribution of the receiving patch; (d) Phase distribution of the transmitting patch.

[0069] Figure 8 The theoretically synthesized phase distribution of the polarization-conversion metasurface at a center frequency of 13 GHz.

[0070] (a) Phase distribution with H1 = F / 3; (b) Phase distribution with H2 = F / 4.

[0071] Figure 9 This is a 3D simulated radiation diagram of a left-hand circularly polarized feed excited at a frequency of 13 GHz.

[0072] (a) H1 = F / 3; (b) H2 = F / 4.

[0073] Figure 10 (a) Antenna model for fabrication; (b) Experimental setup.

[0074] Figure 11 The simulated and measured radiation patterns of the array antenna with H1 = F / 3 at 13 GHz are shown. (a) Left-hand circularly polarized and (b) Right-hand circularly polarized beams in the xz plane; (c) yz... L Left-hand circularly polarized beam on a plane; (d)yz R A right-hand circularly polarized beam on a plane.

[0075] Figure 12 The gain and axial ratio curves for the H1=F / 3 array antenna are shown in the simulation and experimental results. (a) Left-hand circularly polarized beam; (b) Right-hand circularly polarized beam.

[0076] Figure 13 Simulated and measured radiation patterns of an array antenna with H2 = F / 4 at 13 GHz. (a) Left-hand circularly polarized and (b) Right-hand circularly polarized beams in the xz plane; (c) yz L Left-hand circularly polarized beam on a plane; (d)yz R A right-hand circularly polarized beam on a plane.

[0077] Figure 14 The gain and axial ratio curves for the H2=F / 4 array antenna are from simulation and experiment.

[0078] (a) Left-hand circularly polarized beam; (b) Right-hand circularly polarized beam. Detailed Implementation

[0079] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0080] like Figure 1 As shown, the low-profile dual-beam array antenna provided by this invention consists of a transmissive metasurface, a polarization-conversion metasurface, and a horn feed. The polarization-conversion metasurface is placed at position H directly below the transmissive metasurface, and the horn feed is placed at the center of the transmissive metasurface, with its aperture surface parallel to its underlying receiving patch. Under the excitation of the horn feed, the polarization-conversion metasurface performs a non-mirror reflection of the electromagnetic wave, which is then received by the transmissive metasurface and transmitted and converted into two independently modulated orthogonal circularly polarized waves through spin decoupling theory. This design achieves the effect of three folds in a traditional folded transmissive array antenna through a single reflection, greatly reducing energy loss during the reflection process and improving the overall radiation efficiency and integration of the antenna.

[0081] The transmissive metasurface is composed of m×m radiation-receiving units with different rotation angles, periodically extended at equal intervals in a plane, achieving efficient transmission of electromagnetic waves in a specific frequency band and spin decoupling focusing phase modulation. Each radiation-receiving unit consists of a three-layer metal structure and two dielectric substrates, with a period of P. The upper layer is a metal patch with C-grooves; the middle layer is a metal ground plate with through-holes; the bottom layer is a metal patch with two C-grooves cut diagonally. The two C-grooved metal patches are connected by metal vias. Of the two dielectric substrates, the first dielectric substrate is located on the upper layer. Between the C-groove metal patch and the intermediate metal ground plane with through holes, the second dielectric plate is located between the metal ground plane with through holes and the bottom C-groove metal patch with two chamfered corners in the diagonal direction; the polarization conversion metasurface is composed of n×n polarization conversion units with different opening angles arranged in a plane at equal intervals and periodically extended, realizing efficient reflection, polarization conversion and non-mirror beam deflection phase control of electromagnetic waves in a specific frequency band; the upper layer of the polarization conversion unit is an I-shaped metal patch, and the bottom layer is a metal backplate, which are separated by a dielectric plate with a period of P1;

[0082] The structural parameters of the two units are as follows: First part: The outer diameter of the metal patch with C-grooves is R1, the inner diameter is R3, and the radius of the inner circular patch is R4; the diameter of the through-hole in the metal ground plane is D1; ​​the chamfer angle of the metal patch with C-grooves with two diagonal chamfers is α, and the outer diameter of the metal ring after chamfering is R2; the diameter of the metallized via is D2; the thickness of both the first and second dielectric substrates is h1; Second part: The outer diameter of the I-shaped metal ring structure is R5, the inner diameter is R6, the opening angle of the I-shaped metal ring is γ1, the width of the middle metal strip is w, and the overall rotation angle of the I-shaped metal structure is γ2; the dielectric substrate thickness is h2, and the distance between the polarization conversion metasurface and the transmission metasurface is H.

[0083] The specific structural parameters of the low-profile dual-beam array antenna according to the design process and method are as follows: P = 10mm, H1 = 36mm, H2 = 27mm, R1 = 3.2mm, R2 = 2.6mm, R3 = 2.3mm, R4 = 1mm, a = 90°, D1 = 1mm, D2 = 0.4mm, P1 = 6mm, R5 = 2.5mm, R6 = 1.6mm, w = 0.9mm, γ1 = 20°, γ2 = 45°, h1 = 2mm, h2 = 2.5mm; the metal material parameters are copper with a thickness of 0.017mm and an electrical conductivity of 5.8 × 10⁻⁶. 7 S / m; The dielectric substrate material is F4B, the dielectric constant is 2.65, and the electrical tangent loss is 0.001.

[0084] Based on the requirements of low-profile dual-beam array antennas, this invention optimizes the design of two unit structures and the final antenna structure. The specific steps are as follows:

[0085] Step 1: Design the radiating-receiving unit;

[0086] Compared to traditional multilayer stacked dielectric structures, radiating-receiving units can broaden the operating bandwidth and flexibly control electromagnetic waves. Based on this, the present invention designs a radiating-receiving unit that features efficient transmission and spin-channel spin decoupling focusing phase control in the antenna operating frequency band, and can perform polarization conversion through upper and lower metal patches.

[0087] This structural unit consists of three metal layers and two dielectric substrates, with a period of P. The upper layer is a metal patch with C-grooves. The outer diameter of the C-grooved metal patch is R1, the inner diameter is R3, and the radius of the inner circular patch is R4. The middle layer is a metal base plate with a through-hole diameter of D1. Between the middle layer and the upper layer is a dielectric substrate with a thickness of h1. The bottom layer is a metal patch with C-grooves and two diagonally cleaved corners, with the two corner angles being α. The outer diameter of the cleaved metal ring is R2, and the diameter of the metallized through-hole is D2. Between the bottom layer and the middle layer is a dielectric substrate with a thickness of h1. Rotating the lower receiving patch and the upper radiating patch from 0° to 360° respectively, 360° phase coverage can be obtained. The structural parameters of the unit are simulated and optimized using the parameter scanning function of CST software to determine the optimal structural parameters. The optimized structural parameters are: P = 10mm, R1 = 3.2mm, R2 = 2.6mm, R3 = 2.3mm, R4 = 1mm, a = 90°, D1 = 1mm, D2 = 0.4mm.

[0088] To study the electromagnetic characteristics of the radiating-receiving unit, this invention used CST software to perform a series of simulations on the unit. During the unit simulation, the x and y directions were set as periodic boundary conditions, the z direction as an open boundary condition, and the unit was excited by a waveport. Figure 3 The current distribution diagram of the cell is shown when a circularly polarized electromagnetic wave is incident along the +z direction. The current induced by the left-hand circularly polarized wave is mainly concentrated on the receiving patch, while there is no current on the radiating patch. This phenomenon indicates that most of the left-hand circularly polarized wave is reflected by the receiving patch and the metal ground plane. On the other hand, the current induced by the right-hand circularly polarized wave can reach the radiating patch through the metallized vias. Therefore, the cell operates in transmission mode when a right-hand circularly polarized wave is incident. Figure 4 The transmission coefficient and phase of the element are given when a right-hand circularly polarized wave is incident along the +z direction. Here, the present invention uses the cross-circular polarization transmission coefficient T. LR and cocircular polarization transmission coefficient T RR The left-hand and right-hand circularly polarized wave components of the transmitted field are studied independently. Since the linearly polarized transmitted wave is equally divided into left-hand and right-hand circularly polarized waves, the maximum transmitted amplitude is close to -3 dB. Figure 4As shown in (a) and (b), when the rotation angle α of the receiving patch changes from 0° to 360°, the transmission amplitude approaches -3dB, and the phase can achieve 360° coverage in the range of 11.5–14.5 GHz. Similarly, changing the rotation angle β of the radiating patch will produce similar results, such as... Figure 4 As shown in (c) and (d), since the feed emits electromagnetic waves at different angles, the effect of oblique incidence at these angles on the transmittance of the transmissive metasurface should be considered. From Figure 5 As can be seen from (a) and (b), the right-hand circularly polarized wave can still achieve a high transmittance at different incident angles. The phase error is acceptable within the operating frequency band, therefore the designed radiator-receiver unit is angle-insensitive.

[0089] Step 2, design the polarization conversion unit;

[0090] The previous step designed a radiating-receiving structural unit that can efficiently transmit electromagnetic waves in the 11.5–14.5 GHz range. To construct a low-profile dual-beam array antenna, this invention designs an I-shaped polarization conversion structure. The upper layer of this polarization conversion unit is an I-shaped metal patch, the middle layer is a dielectric substrate with a thickness of h2, and the bottom layer is a metal backplate to block electromagnetic wave transmission. The unit period is P1, the outer diameter of the I-shaped metal ring structure is R5, the inner diameter is R6, the opening angle of the I-shaped metal ring is γ1, the width of the middle metal strip is w, and the overall rotation angle of the I-shaped metal structure is γ2. Simulation calculations using the full-wave simulation software CSTMICROWAVE STUDIO (2020) show that the polarization conversion unit can totally reflect the incident left-handed circularly polarized wave into a right-handed circularly polarized wave, and that changing the opening angle γ1 and the rotation angle γ2 of the metal ring can achieve 360° phase modulation within the 11–15 GHz range.

[0091] The optimized structural parameters using the full-wave simulation software CST 2020 are: P1 = 6mm, R5 = 2.5mm, R6 = 1.6mm, w = 0.9mm, γ1 = 20°, γ2 = 45°, h2 = 2.5mm. Finally, the element characteristics are simulated using CST 2020. Here, R... RL This indicates the amplitude of the cross-circular polarization reflection when a left-handed circularly polarized wave is incident. For example... Figure 6 As shown in (a), within the frequency range of 11.5–14.5 GHz, left-handed circularly polarized waves are efficiently converted into right-handed circularly polarized waves, and the reflection amplitude remains stable under different incident angles. Meanwhile, Figure 6 (b) shows that at 13 GHz, a phase coverage of 180° can be achieved by fixing γ2 = 45° and changing the aperture angle γ1 from 7° to 132°; and an additional 180° of reflection phase coverage can be achieved by changing γ2 from 45° to -45° and adjusting γ1 from 7° to 132°.

[0092] Step 3: Arrange the spatial phase of the transmission metasurface using spin-decoupled phase arrangement;

[0093] Combination Figure 2 This invention provides a corresponding derivation of the spin decoupling theory.

[0094] Assuming the non-rotating receiving patch is irradiated by a right-handed circularly polarized plane wave propagating along the +z direction, the incident electric field can be written as follows:

[0095]

[0096] Where E0 is the electric field intensity of the incident wave, and kz represents the spatial phase.

[0097] After transmission, the right-hand circularly polarized wave is converted into a y-polarized wave, and the transmission electric field can be expressed as:

[0098]

[0099] Among them, T y-RCP It is the transmission coefficient for converting a right-hand circularly polarized wave into a y-polarized wave.

[0100] When the receive / transmit patch rotates counterclockwise by an angle α / β, the coordinate system will change from... Transferred to The new coordinate system can be written as:

[0101]

[0102] According to equation (3), the incident electric field and the transmission electric field can be written as:

[0103]

[0104] in, Let E0 represent the incident electric field after the receiving patch is rotated by an angle α, and E0 represent the electric field intensity of the incident wave. T represents the transmitted electric field after the radiating patch is rotated by an angle β. y-RCP This represents the transmission coefficient for converting a right-hand circularly polarized wave into a y-polarized wave;

[0105] The phase distributions of the left-hand circularly polarized wave and the right-hand circularly polarized wave components are obtained as follows:

[0106]

[0107] Where, Φ LCP Φ represents the phase distribution of the left-hand circularly polarized wave component. RCPThis represents the phase distribution of the right-hand circularly polarized wave component; therefore, when the phase of the bottom receiving patch and the phase of the top radiating patch of the transmissive metasurface satisfy the spin decoupling phase condition shown in equation (7), two independently modulated orthogonal circularly polarized beams can be realized.

[0108]

[0109] in This indicates the phase of the receiving patch after rotation by α. This indicates the phase of the radiating patch after rotation by β.

[0110] The required phase at different positions of the transmissive metasurface is calculated according to formula (7). The present invention arranges corresponding radiation-receiving units at the corresponding positions, ultimately designing an 18×18 transmissive metasurface. The transmissive metasurface can undergo spin decoupling when a right-hand circularly polarized wave is incident, thereby generating two independently modulated orthogonal circularly polarized waves. The phase calculations for the left-hand and right-hand circularly polarized waves are shown in formula (8):

[0111]

[0112] Where k0 is the wave vector in free space, F is the focal length, the F / D ratio is set to 0.6, the aperture D is 180mm, and the focal length F is 108mm. The direction of the left-hand circularly polarized / right-hand circularly polarized beam is given by θ, where θ is the elevation angle. Here, the azimuth angle is used, and the directions of the left-hand circularly polarized and right-hand circularly polarized beams are selected as (10°, 0°) and (-25°, 0°), respectively. Based on the calculated phase distribution at different locations, Figure 7 (a) and (b) give the required phase distributions for two separate left-handed and right-handed circularly polarized beams. Furthermore, substituting equation (8) into equation (7) yields the required phase distributions for the receiving and radiating layers, as shown below. Figure 7 As shown in (c) and (d).

[0113] Step 4: Arrange the spatial phase of the polarization conversion metasurface using the phase compensation method;

[0114] When a left-handed circularly polarized wave is incident perpendicularly, the required compensation phase φ(x,y) at different positions on the polarization-converted metasurface is calculated according to formula (9):

[0115]

[0116] Where Φ(x,y) represents the compensation phase required to achieve electromagnetic wave focusing, (x,y) represents the relative position of the metasurface unit, k0=2π / λ0 is the free space wave vector, and λ0 is the wavelength at the operating frequency f0. Assuming a constant reference phase, OM is the initial focal length, and OM′ is the focal length after the electromagnetic wave path has changed. From Figure 1 It can be seen that OM′=F, OM=2H, and H is the distance between the transmission metasurface and the polarization conversion metasurface.

[0117] Based on formula (9), the required compensation phase at different positions is calculated. The present invention arranges metasurface units with corresponding reflection functions at the corresponding positions, and finally designs a 30×30 polarization conversion metasurface. The polarization conversion metasurface can perform phase compensation when a left-handed circularly polarized wave is incident, thereby realizing the non-mirror reflection function, and at the same time, it can realize the rotation direction change of the circularly polarized wave.

[0118] Step 5: Design of low-profile dual-beam array antenna.

[0119] With the designed transmissive metasurface and polarization conversion metasurface, the final radiating-receiving low-profile dual-beam array antenna can be constructed. Specifically: The transmissive metasurface is placed above the polarization conversion metasurface, with a spacing of H. The value of H depends on the phase compensation distance of the polarization conversion metasurface; here, this invention sets H1 = F / 3 and H2 = F / 4. A 20mm diameter circularly polarized horn feed is placed at the center of the transmissive metasurface, with the horn aperture surface flush with the receiving patch surface of the bottom layer of the transmissive metasurface. The left-hand circularly polarized wave emitted by the circularly polarized horn feed is reflected as a right-hand circularly polarized wave by the polarization conversion metasurface, and then received by the transmissive metasurface. Through spin decoupling, independently controllable left-hand and right-hand circularly polarized beams radiating along the +z direction are generated.

[0120] Finally, this invention designed two low-profile dual-beam array antennas to verify this design method, and performed full-wave simulation at CST2020. Figure 9 As shown, in both cases H1 = F / 3 and H2 = F / 4, left-hand circularly polarized and right-hand circularly polarized beams can be generated in the set direction.

[0121] To further verify the correctness of the low-profile dual-beam array antenna design method, this invention, based on the designed simulation model, used PCB technology to fabricate and manufacture a physical sample of the design, such as... Figure 10 As shown in (a), four 50mm high nylon struts are used to ensure the distance H between the transmission metasurface and the polarization conversion metasurface. In the actual testing of the antenna characteristics of the fabricated samples, this invention was carried out in a microwave anechoic chamber, which effectively avoids interference from the surrounding complex electromagnetic environment, such as... Figure 10 As shown in (b), the antenna sample was placed at the center of a cylindrical foam that could rotate around its central axis, while a standard gain receiving horn operating at 8-18 GHz was placed on another cylindrical foam 10 m away from the sample. A laser level was used to ensure that the centers of both were on the same straight line.

[0122] Figure 11 The radiation mode with H1 = F / 3 is given, and it can be seen that the directions of the left-hand and right-hand circularly polarized beams are completely consistent with the previously designed directions. In the measurement, the sidelobe levels of the left-hand and right-hand circularly polarized beams obtained by this invention are -15dB and -14.8dB, respectively. Figure 12 The axial ratio and gain curves of the designed antenna are presented. As can be seen from the figures, within the operating frequency band of 11-15 GHz, the axial ratios of both left-hand and right-hand circularly polarized beams are below 3 dB. At 13 GHz, the measured peak gains of the left-hand and right-hand circularly polarized beams are 24.53 dBic and 24.12 dBic, respectively. Using the aperture efficiency formula... Calculations show that the corresponding aperture efficiencies are 37.12% and 33.78%, respectively. Meanwhile, the 3dB gain bandwidths for left-hand and right-hand circularly polarized beams are 23.1% and 23.1%, respectively. Figure 13 The radiation mode with H2 = F / 4 is given, and it can be seen that the directions of the left-hand and right-hand circularly polarized beams are completely consistent with the previously designed directions. The measured sidelobe levels of the left-hand and right-hand circularly polarized beams are -15.5 dB and -15.1 dB, respectively. Figure 14 (a) and (b) show the simulated and measured performance of gain and axial ratio curves achieved in the 11–15 GHz frequency range. At 13 GHz, the measured peak gains of the left-hand and right-hand circularly polarized beams are 22.56 dBic and 22.42 dBic, respectively, with corresponding aperture efficiencies of 23.6% and 22.8%. Simultaneously, the measurements show that the 3 dB gain bandwidths of the left-hand and right-hand circularly polarized beams are 23.1% and 23%, respectively. Throughout the operating frequency band, the axial ratios of both the left-hand and right-hand circularly polarized beams are below 3 dB. The slight difference between the simulated and measured results is primarily due to distance errors between the transmission metasurface and the polarization conversion metasurface when using nylon struts for mounting; alignment errors between the feed horn and the sample during measurement are also a contributing factor.

[0123] The above are merely specific steps of the present invention and do not constitute any limitation on the scope of protection of the present invention; all technical solutions formed by equivalent transformation or equivalent substitution fall within the scope of protection of the present invention; the parts of the present invention not described in detail are common knowledge to those skilled in the art.

Claims

1. A radiating-receiving low-profile dual-beam array antenna, characterized in that, The radiation-receiver low-profile dual-beam array antenna comprises three structural parts: a transmissive metasurface, a polarization-conversion metasurface, and a feed horn. The feed horn is placed at the center of the transmissive metasurface, with its aperture surface flush with the surface of the lower receiving patch. The polarization conversion metasurface is placed directly below the transmissive metasurface at a distance from... Place; The transmission metasurface is made of The radiation-receiving units with different rotation angles are arranged in a periodic extension at equal intervals in the plane to achieve efficient transmission of electromagnetic waves in a specific frequency band and spin decoupling focusing phase modulation. The radiation-receiving unit consists of a three-layer metal structure and two layers of dielectric plates, with a period of [missing information]. The upper layer is a circular metal patch with C-grooves; the middle layer is a metal floor with through holes; the bottom layer is a circular metal patch with C-grooves and two annular chamfers along the diagonal direction; the two layers of circular metal patches with C-grooves are connected by metallized vias; in the two dielectric boards, the first dielectric board is located between the upper circular metal patch with C-grooves and the middle metal floor with through holes, and the second dielectric board is located between the metal floor with through holes and the bottom circular metal patch with C-grooves and two annular chamfers along the diagonal direction. The polarization conversion metasurface is composed of A series of polarization conversion units with different opening angles and rotation angles are arranged in a plane at equal intervals and periodically to achieve efficient reflection, polarization conversion, and non-mirror beam deflection phase control of electromagnetic waves in a specific frequency band. The upper layer of each polarization conversion unit is an I-shaped metal ring, and the lower layer is a metal backplate, separated by a dielectric substrate. The period is... ; The radiation-receiving unit rotates the receiving patch and the radiation patch from 0° to 360° respectively to obtain 360° phase coverage. When the counterclockwise rotation angle of the receiving patch is α and the counterclockwise rotation angle of the radiation patch is β: ； in, Indicates the rotation angle of the receiving patch. The incident electric field after that, Indicates the rotation angle of the receiving patch. The new coordinate system after Indicates the rotation angle of the radiating patch The new coordinate system after This represents the electric field strength of the incident wave. Indicates spatial phase, Indicates the rotation angle of the radiating patch The transmitted electric field afterward, This indicates that a right-hand circularly polarized wave is converted into a circularly polarized wave. The transmission coefficient of polarized waves; The phase distributions of the left-hand circularly polarized wave and the right-hand circularly polarized wave components are obtained as follows: ； in, This represents the phase distribution of the left-hand circularly polarized wave component. This represents the phase distribution of the right-hand circularly polarized wave component; When the phase of the bottom receiving patch and the phase of the top radiating patch of the transmissive metasurface satisfy the spin decoupling phase condition, two independently controllable orthogonally circularly polarized beams can be realized: ； in, Indicates receiving patch rotation The subsequent phase, Indicates the rotation of the radiating patch The phase after that is used to perform spin-decoupled spatial phase arrangement of the transmissive metasurface based on the phase of the receiving patch and the radiating patch.

2. The radiating-receiving low-profile dual-beam array antenna according to claim 1, characterized in that, The first and second dielectric substrates have the same thickness.

3. The radiating-receiving low-profile dual-beam array antenna according to claim 1, characterized in that, The polarization conversion unit can change the opening angle of the metal ring. and rotation angle exist Internally, 360° phase modulation is achieved; when a left-handed circularly polarized wave is incident perpendicularly, the required compensation phase at different positions on the metasurface is adjusted. for: ； This represents the compensation phase required to achieve electromagnetic wave focusing. Indicates the relative position of the metasurface unit. For free space wave vectors, Operating frequency wavelength at that location, For constant reference phase, The initial focal length, The focal length is the result of the change in the electromagnetic wave path.

4. A folding decoupling design method for a radiating-receiving low-profile dual-beam array antenna as described in claim 1, characterized in that, The folding decoupling design method for the radiation-receiver low-profile dual-beam array antenna includes the following steps: Step 1: Design the radiating-receiving unit of the radiating-receiving low-profile dual-beam array antenna; Step 2: Design the polarization conversion unit of the radiating-receiving low-profile dual-beam array antenna; Step 3: Arrange the spatial phase of the transmission metasurface using spin-decoupled phase arrangement; Step 4: Arrange the spatial phase of the polarization conversion metasurface using the phase compensation method; Step 5: Based on the designed transmissive metasurface and polarization conversion metasurface, construct the final radiating-receiving low-profile dual-beam array antenna.

5. The folding decoupling design method for a radiating-receiving low-profile dual-beam array antenna according to claim 4, characterized in that, In step 1, the first dielectric plate and the second dielectric plate of the radiation-receiving unit have the same thickness.

6. The folding decoupling design method for a radiating-receiving low-profile dual-beam array antenna according to claim 4, characterized in that, In step 4, the polarization conversion unit can totally reflect the incident left-handed circularly polarized wave into a right-handed circularly polarized wave and change the opening angle of the metal ring. and rotation angle It is possible The internal structure achieves 360° phase modulation, adjusting the required compensation phase at different locations on the polarization-converting metasurface when a left-handed circularly polarized wave is incident perpendicularly. for: ； This represents the compensation phase required to achieve electromagnetic wave focusing. Indicates the relative position of the metasurface unit. For free space wave vectors, Operating frequency wavelength at that location, For constant reference phase, The initial focal length, The focal length after the electromagnetic wave path changes; The above formula is used to arrange the polarization conversion metasurfaces in a spatial phase compensation manner.

7. The folding decoupling design method for a radiating-receiving low-profile dual-beam array antenna according to claim 4, characterized in that, In step 5, the transmission metasurface is placed above the polarization conversion metasurface, and the interval is set to... The circularly polarized horn feed is placed at the center of the transmissive metasurface, with the horn aperture surface and the receiving patch surface of the bottom layer of the transmissive metasurface flush. exist equal or In both cases, The focal length after the electromagnetic wave path change is determined by the left-hand circularly polarized wave emitted by the circularly polarized horn feed. This left-hand circularly polarized wave is reflected as a right-hand circularly polarized wave by the polarization-conversion metasurface, and then received by the transmission metasurface. Through spin decoupling, a right-hand circularly polarized wave is generated along the path of the electromagnetic wave. Independently adjustable left-hand circularly polarized beams and right-hand circularly polarized beams for directional radiation.

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