Aperture sharing double-sided image double-frequency folding transmission array and design method

Abstract

The invention discloses an aperture sharing double-sided image double-frequency folding transmission array and a design method. The double-frequency folding transmission array comprises a first transmission and reflection metasurface, a second transmission and reflection metasurface and a horn feed source, wherein the rotation direction and the frequency of the first transmission and reflection metasurface are jointly controlled. The first transmission and reflection metasurface comprises m * m circular radiation-receiving units and (m + 1) * (m + 1) cross-shaped metal units which are arranged in a staggered mode, and phase regulation and control of efficient transmission of low-frequency electromagnetic waves and efficient reflection of high-frequency electromagnetic waves are achieved. The circular radiation-receiving unit is provided with three layers of metal and two layers of dielectric plates; the second transmission and reflection metasurface comprises n * n square radiation-receiving units which are arranged in a periodic continuation mode, and high-frequency electromagnetic wave efficient transmission phase regulation and low-frequency electromagnetic wave efficient reflection are achieved. The square radiation-receiving unit is provided with three layers of metal and two layers of dielectric plates. The aperture-sharing double-sided image double-frequency folding transmission array generates two circularly polarized wave beams with different frequency bands in opposite directions in the space under the excitation of a circularly polarized wave feed source, and has the remarkable advantages of high gain, low profile, total-space radiation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of array antenna design, and particularly to an aperture-sharing double-sided image dual-frequency folded transmissive array and a design method thereof. Background Art

[0002] In recent years, in order to achieve the design goals of high-integration and low-profile antenna arrays, the folded transmissive array antenna technology has gradually become a research hotspot. This technology is based on the path-tracing principle, and a system is composed of a top metasurface with polarization selectivity, a bottom metasurface with both reflection and polarization conversion functions, and a feed located at the center of the bottom metasurface. Its uniqueness lies in that after the electromagnetic wave emitted by the feed is reflected twice by the top and bottom metasurfaces, the antenna profile height can be reduced to 1 / 3 of the focal length. To further improve the system integration and radiation efficiency, researchers introduced the pre-modulation technology of reflected electromagnetic waves into the metasurface design, and the low-profile effect of multiple reflections can be achieved through single reflection.

[0003] However, traditional folded transmissive array antennas have problems such as limited operating frequency bands and single radiation direction, and can only radiate electromagnetic waves in a specific direction in a single band, which severely restricts their engineering application scope. Summary of the Invention

[0004] The present invention uses a dual radiation-reception structure to realize an aperture-sharing double-sided image dual-frequency folded transmissive array antenna. Combining the aperture-sharing technology and the electromagnetic wave front modulation technology, the profile in two frequency bands is reduced to 1 / 3 of that of the traditional transmissive array, and the electromagnetic waves in the two frequency bands can be radiated in two opposite directions; moreover, the double-sided image array antenna is a special form of a full-space array antenna, and different functions can occur in the forward and backward incident directions of the array, belonging to the field of two-way channel multi-functions.

[0005] The present invention provides an aperture-sharing double-sided image dual-frequency folded transmissive array, and the aperture-sharing double-sided image dual-frequency folded transmissive array includes a first transmissive-reflective metasurface, a second transmissive-reflective metasurface, and a horn feed;

[0006] The first transmissive-reflective metasurface is disposed directly above the second transmissive-reflective metasurface at a height H, the horn feed is disposed at the center of the second transmissive-reflective metasurface, and the aperture plane is in the same plane as the upper-layer receiving patch surface;

[0007] The first transmissive-reflective metasurface includes m×m circular radiation-reception units with different rotation angles arranged in a staggered manner and (m + 1)×(m + 1) cross-shaped patch units located in the receiving layer, and the circular radiation-reception unit includes a three-layer metal structure and two-layer dielectric plates;

[0008] The upper metal structure of the circular radiation-receiving unit is the radiation layer, which includes a metal patch with a C-shaped groove, and there are two arc truncations on the patch; the middle metal structure of the circular radiation-receiving unit is a metal floor with through holes; the bottom metal structure of the circular radiation-receiving unit is the receiving layer, which includes a metal patch with a C-shaped groove and there are two arc truncations on the patch; the metal patches with C-shaped grooves on the upper and lower layers are connected by metallized vias; among the two dielectric plates, the first dielectric plate is located between the upper metal patch and the middle metal floor, and the second dielectric plate is located between the middle metal floor and the bottom metal patch;

[0009] The cross-shaped patch units are located around the receiving patch of the circular radiation-receiving unit. The center points of the cross-shaped patch units around are the four corners of the circular radiation-receiving unit respectively. The cross-shaped patch unit includes a cross-shaped metal patch.

[0010] The second transmissive and reflective metasurface includes n×n square radiation-receiving units arranged in a periodic extension with equal spacing in the plane and different rotation angles. The square radiation-receiving unit includes three-layer metal structure and two dielectric plates;

[0011] The upper metal structure of the square radiation-receiving unit is a square metal patch with a C-shaped groove, and there are two triangular cutouts on the patch; the middle metal structure of the square radiation-receiving unit is a metal floor with through holes; the bottom metal structure of the square radiation-receiving unit is a square metal patch with a C-shaped groove, and there are two cutouts on the patch; the two square metal patches are connected by metallized vias; among the two dielectric plates, the first dielectric plate is located between the upper metal patch and the middle metal floor, and the second dielectric plate is located between the middle metal floor and the bottom metal patch.

[0012] Furthermore, the period P1 of the circular radiation-receiving unit is 12 mm. In the circular radiation-receiving unit, the metal patches with C-shaped grooves on the upper and bottom layers have the same size. The outer diameter of the metal patch with a C-shaped groove is r1 = 3.4 mm, the inner diameter is r3 = 2 mm, the radius of the inner circular patch is r4 = 1 mm, the angles of the two arc truncations are a = 90°, and the outer diameter of the truncated metal ring is r2 = 2.7 mm; the middle layer is a metal floor with a through hole diameter of d1 = 1 mm; the dielectric plate between the middle metal floor and the upper metal patch is h1 = 2 mm thick; the metal patches with C-shaped grooves on the upper and lower layers are connected by a metallized via with a diameter of d2 = 0.4 mm; the dielectric plate between the bottom metal patch and the middle metal floor is h1 = 2 mm thick;; the length of the bottom cross-shaped metal patch in the y direction is L1 = 5 mm, the length in the x direction is L2 = 4 mm, and the patch width is all w = 2 mm

[0013] In the square radiation-receiving unit, the side length of the square metal patch is L, the side length of the two triangular cut corners is t = 1.5 mm, the outer diameter of the C-shaped slot is r5 = 1.5 mm, and the inner diameter is r6 = 0.6 mm; the middle layer is a metal floor with a through-hole diameter of d3 = 0.6 mm; the dielectric plate between the middle layer metal floor and the upper metal patch has a thickness of h2 = 1.2 mm; the two square metal patches with C-shaped slots on the bottom layer and the upper layer are connected by a metallized via, and the diameter of the metallized via is d4 = 0.3 mm; the dielectric plate between the bottom layer metal patch and the middle layer metal floor has a thickness of h2 = 1.2 mm;

[0014] The metal material parameter is copper, with a thickness of 0.017 mm and a conductivity of 5.8×10 7 S / m; the dielectric plate material is F4B, with a dielectric constant of 2.65 and an electric tangent loss of 0.001.

[0015] Furthermore, the upper and lower radiation patches in the first transmissive-reflective metasurface respectively achieve the transmissive focusing function, so the lower radiation patch needs to achieve 360° phase coverage;

[0016] In the second transmissive-reflective metasurface, the upper receiving patch only transmits or reflects electromagnetic waves and does not require corresponding phase regulation; the lower radiation patch achieves the transmissive focusing function, so the lower radiation patch needs to achieve 360° phase coverage.

[0017] A design method for an aperture-sharing dual-sided image dual-band folded transmissive array is also provided. The design method for the aperture-sharing dual-sided image dual-band folded transmissive array includes the following steps:

[0018] Step 1, design the circular radiation-receiving unit of the first transmissive-reflective metasurface;

[0019] Step 2, design the square radiation-receiving unit of the second transmissive-reflective metasurface;

[0020] Step 3, arrange the spatial phase of the upper radiation patch of the first transmissive-reflective metasurface using the focusing phase, and arrange the spatial phase of the lower cross-shaped receiving patch of the first transmissive-reflective metasurface using the phase compensation method;

[0021] Step 4, arrange the spatial phase of the lower radiation patch of the second transmissive-reflective metasurface using the phase compensation method;

[0022] Step 5, construct the final aperture-sharing dual-sided image dual-band folded transmissive array antenna.

[0023] Further, in step 1, the upper-layer metal structure of the circular radiation-receiving unit includes a metal patch with a C-shaped slot; there are two arc truncations on the metal patch with a C-shaped slot; the middle-layer metal structure of the circular radiation-receiving unit is a metal floor with vias; the bottom-layer metal structure of the circular radiation-receiving unit is a receiving layer, including a metal patch with a C-shaped slot and there are two arc truncations on the patch; the upper and lower metal patches with C-shaped slots are connected by metallized vias; in the two dielectric plates, the first dielectric plate is located between the upper metal patch and the middle-layer metal floor, and the second dielectric plate is located between the middle-layer metal floor and the bottom-layer metal patch; the cross-shaped patch units are located around the receiving patch of the circular radiation-receiving unit, and the center points of the surrounding cross-shaped patch units are the four corners of the circular radiation-receiving unit respectively, and the cross-shaped patch units include cross-shaped metal patches.

[0024] Further, in step 2, the upper-layer metal structure of the square radiation-receiving unit is a square metal patch with a C-shaped slot, and there are two triangular cutouts on the patch; the middle-layer metal structure of the square radiation-receiving unit is a metal floor with vias; the bottom-layer metal structure of the square radiation-receiving unit is a square metal patch with a C-shaped slot, and there are two cutouts on the patch; the two square metal patches are connected by metallized vias; in the two dielectric plates, the first dielectric plate is located between the upper metal patch and the middle-layer metal floor, and the second dielectric plate is located between the middle-layer metal floor and the bottom-layer metal patch.

[0025] Further, in step 3, when the left-handed circularly polarized wave is vertically incident on the upper radiation patch of the first transmissive-reflective metasurface, the focusing phase Φ focus-1 (x1,y1):

[0026]

[0027] where k0 = 2π / λ0 is the free-space wave vector, λ0 is the wavelength at the operating frequency f0, (x1,y1) represents the relative position where the upper radiation patch of the first transmissive-reflective metasurface is located, F is the focal length, the F / D ratio is set to 0.6, D is the aperture, and F is the focal length;

[0028] The focusing phase Φ focus-1 (x1,y1) is calculated to obtain the theoretical discrete focusing phase distribution, and 360° phase coverage is achieved by rotating the metal patch with a C-shaped slot from 0° to 360°.

[0029] Further, in step 3, when the right-handed circularly polarized wave is incident on the lower cross-shaped receiving patch of the first transmissive-reflective metasurface, the compensation phase Φ(x2,y2) required at different positions:

[0030]

[0031] Among them, (x1, y2) represents the relative position of the cross-shaped receiving patch on the lower layer of the first transmissive-reflective metasurface. k0 = 2π / λ0 is the free-space wave vector, λ0 is the wavelength at the operating frequency f0. is a constant reference phase, F is the focal length, and H = F / 3 is the distance between the first transmissive-reflective metasurface and the second transmissive-reflective metasurface.

[0032] The compensation phase Φ(x2, y2) is calculated to obtain the theoretical discrete compensation phase distribution, and 360° phase coverage is achieved by rotating the cross-shaped metal patch from 0° to 180°.

[0033] Further, in step 4, when a right-handed circularly polarized wave is incident on the second transmissive-reflective metasurface, the focusing phase Φ focus-2 (x3, y3) required at different positions of the radiation patch on the lower layer of the second transmissive-reflective metasurface:

[0034]

[0035] Among them, k0 = 2π / λ0 is the free-space wave vector, λ0 is the wavelength at the operating frequency f0, (x3, y3) represents the relative position of the second transmissive-reflective metasurface unit, F is the focal length, the F / D ratio is set to 0.6, D is the aperture, and F is the focal length.

[0036] The focusing phase Φ focus-2 (x3, y3) is calculated to obtain the theoretical discrete focusing phase distribution, and 360° phase coverage is achieved by rotating the square metal patch from 0° to 360°.

[0037] Further, in step 5, the first transmissive-reflective metasurface is placed above the second transmissive-reflective metasurface, and the interval is set to H.

[0038] A right-handed circularly polarized horn feed with an aperture of 20 mm is placed at the center of the second transmissive-reflective metasurface, and the horn aperture plane and the receiving patch surface on the upper layer of the second transmissive-reflective metasurface are in the same plane. The right-handed circularly polarized wave emitted by the circularly polarized horn feed at low frequencies is reflected by the first transmissive-reflective metasurface and remains right-handed circularly polarized. Then it is reflected by the second transmissive-reflective metasurface and becomes left-handed circularly polarized. Finally, the second transmissive-reflective metasurface receives this left-handed circularly polarized wave and radiates it in the +z direction. The right-handed circularly polarized wave emitted by the circularly polarized horn feed at high frequencies is reflected by the first transmissive-reflective metasurface and becomes right-handed circularly polarized, and its phase is compensated during this process to produce a non-mirror reflection effect. Then this right-handed circularly polarized wave is received by the second transmissive-reflective metasurface and radiated as a left-handed circularly polarized beam in the -z direction.

[0039] The beneficial effects achieved by the present invention are:

[0040] Compared with the traditional folded transmission array antenna, the present invention can simultaneously realize low-profile, dual-frequency and double-sided image transmission array antenna;

[0041] Compared with the traditional folded transmission array antenna, the present invention can radiate electromagnetic waves in different directions at different frequency bands, thereby achieving a two-way communication effect.

[0042] The present invention has a very considerable antenna gain effect. The overall cross-section of the antenna is 1 / 3 of that of the traditional transmission array. The peak gain measured by the left-handed circularly polarized beam radiated in the +z direction with a low frequency of 13 GHz delay is 25.02 dBic, the side lobe level is -13.5 dB, and the corresponding aperture efficiency is 28.86%. At the same time, the peak gain measured by the left-handed circularly polarized beam radiated in the -z direction with a high frequency of 16.5 GHz delay is 24 dBic, the side lobe level is -13 dB, and the corresponding aperture efficiency is 14.16%. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of an aperture-sharing two-sided image dual-frequency folded transmission array antenna;

[0044] Figure 2 The topological structure of the circular radiation-receiving unit of the first transflective metasurface and the schematic diagram of the radiation patch, the floor and the receiving patch;

[0045] Figure 3 The numerical characteristics of the circular radiation-receiving unit simulation. (a) is the circular polarization reflection amplitude and phase when the cross-shaped receiving patch is rotated by an angle β when a right-handed circularly polarized wave is incident; (b) is the circular polarization transmission amplitude and phase when the radiation patch is rotated by an angle α when a left-handed circularly polarized wave is incident;

[0046] Figure 4 is the transmission amplitude and phase of the circular radiation-receiving unit under different incident angles of left-hand circularly polarized waves;

[0047] Figure 5 The topological structure of the square radiation-receiving unit of the second transflective metasurface and the schematic diagram of the radiation patch, the floor and the receiving patch;

[0048] Figure 6 The numerical characteristics of the square radiation-receiving unit simulation. Among them, (a) is the circular polarization transmission amplitude and phase when the radiation patch is rotated by an angle γ when a right-hand circularly polarized wave is incident; (b) is the transmission amplitude and phase of the right-hand circularly polarized wave under different angles of incidence;

[0049] Figure 7is the theoretical synthetic phase distribution of the first transmissive and reflective metasurface. Among them, (a) is the theoretical synthetic phase distribution of the radiation patch of the first transmissive and reflective metasurface at a center frequency of 13 GHz; (b) is the theoretical synthetic phase distribution of the cross-shaped receiver of the first transmissive and reflective metasurface at a center frequency of 16.5 GHz;

[0050] Figure 8 is the theoretical synthetic phase distribution of the radiation patch of the second transmissive and reflective metasurface at a center frequency of 16.5 GHz;

[0051] Figure 9 is the 3D simulated radiation pattern of the double-sided image dual-frequency folded transmissive array antenna. Among them, (a) is the 3D simulated radiation pattern of the antenna at 13 GHz; (b) is the 3D simulated radiation pattern of the antenna at 16.5 GHz;

[0052] Figure 10 is the simulated radiation direction pattern of the antenna. Among them, (a) is the radiation direction pattern of the antenna in the xoz plane at 13 GHz; (b) is the radiation direction pattern of the antenna in the yoz plane at 13 GHz; (c) is the radiation direction pattern of the antenna in the xoz plane at 16.5 GHz; (d) is the radiation direction pattern of the antenna in the yoz plane at 16.5 GHz;

[0053] Figure 11 is the gain and axial ratio curves of the simulation of the double-sided image dual-frequency folded transmissive array antenna. Specific Embodiments

[0054] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description progresses. However, these embodiments are merely exemplary and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and forms of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but these modifications and substitutions all fall within the protection scope of the present invention.

[0055] Such as Figure 1As shown in the figure, the dual-band folded transmissive array antenna with shared aperture and dual-sided images provided by the present invention is composed of a first transmissive-reflective metasurface, a second transmissive-reflective metasurface, and a horn feed. The first transmissive-reflective metasurface is disposed directly above the second transmissive-reflective metasurface at a height H. The horn feed is disposed at the center of the second transmissive-reflective metasurface, and the aperture plane is in the same plane as the upper receiving patch surface. The right-handed circularly polarized wave emitted by the circularly polarized horn feed at low frequency is reflected by the first transmissive-reflective metasurface and remains a right-handed circularly polarized wave. Then it is reflected by the second transmissive-reflective metasurface and becomes a left-handed circularly polarized wave. Finally, the second transmissive-reflective metasurface receives this left-handed circularly polarized wave and radiates it in the +z direction. The right-handed circularly polarized wave emitted by the circularly polarized horn feed at high frequency is reflected by the first transmissive-reflective metasurface and becomes a right-handed circularly polarized wave, and the phase is compensated during this process to produce a non-mirror reflection effect. Then this right-handed circularly polarized wave is received by the second transmissive-reflective metasurface and radiated as a left-handed circularly polarized beam in the -z direction. This design is based on the aperture sharing technology. In a folded transmissive array, a dual-sided image dual-band transmissive array antenna is realized, which radiates electromagnetic waves of different frequency bands in different directions and has performances such as high gain and high integration.

[0056] The first transmissive-reflective metasurface is composed of m×m circular radiation-reception units with different rotation angles and (m + 1)×(m + 1) cross-shaped patch units located in the receiving layer, which are arranged alternately; it realizes the efficient transmission, phase regulation of electromagnetic waves in a specific low-frequency band, and the efficient reflection and phase regulation of electromagnetic waves in a specific high-frequency band; the circular radiation-reception unit is composed of three layers of metal structures and two layers of dielectric plates, and the period is P1; the upper metal structure of the circular radiation-reception unit is a metal patch with a C-shaped slot, and there are two arc truncations on the patch; the middle metal structure of the circular radiation-reception unit is a metal floor with through holes; the bottom metal structure of the circular radiation-reception unit is the receiving layer, including a metal patch with a C-shaped slot and there are two arc truncations on the patch; the upper and lower metal patches with C-shaped slots are connected by metallized vias; in the two layers of dielectric plates, the first layer of dielectric plate is located between the upper metal patch and the middle metal floor, and the second layer of dielectric plate is located between the middle metal floor and the bottom metal patch; the cross-shaped patch units are located around the receiving patch of the circular radiation-reception unit, and the center points of the cross-shaped patch units around are the four corners of the circular radiation-reception unit respectively, and the cross-shaped patch unit includes a cross-shaped metal patch.

[0057] The second transmissive - reflective metasurface is composed of \(n\times n\) square radiation - receiving units with different rotation angles arranged periodically at equal intervals, realizing the efficient reflection of electromagnetic waves in the low - frequency band and the efficient transmission and phase regulation of electromagnetic waves in a specific high - frequency band; the square radiation - receiving unit is composed of three layers of metal structures and two layers of dielectric plates, with a period of \(P2\); the upper - layer metal structure of the square radiation - receiving unit is a square metal patch with a C - shaped slot, and there are two triangular cut - corners on the patch; the middle - layer metal structure of the square radiation - receiving unit is a metal floor with through - holes; the bottom - layer metal structure of the square radiation - receiving unit is a square metal patch with a C - shaped slot, and there are two cut - corners on the patch; the two layers of square metal patches are connected by metallized vias; in the two layers of dielectric plates, the first dielectric plate is located between the upper - layer metal patch and the middle - layer metal floor, and the second dielectric plate is located between the middle - layer metal floor and the bottom - layer metal patch.

[0058] The structural parameters of the two types of units are recorded as follows:

[0059] In the circular radiation - receiving unit, the upper - layer and bottom - layer metal patches with C - shaped slots have the same size. The outer diameter of the metal patch with a C - shaped slot is \(r1\), the inner diameter is \(r3\), the radius of the inner circular patch is \(r4\), the truncation angles of the two arcs are \(a\), and the outer diameter of the truncated metal ring is \(r2\); the middle layer is a metal floor with a through - hole diameter of \(d1\); the dielectric plate with a thickness of \(h1\) is located between the middle - layer metal floor and the upper - layer metal patch; the upper - layer and lower - layer metal patches with C - shaped slots are connected by a metallized via with a diameter of \(d2\); the dielectric plate with a thickness of \(h1\) is located between the bottom - layer metal patch and the middle - layer metal floor; the patch length of the bottom - layer cross - shaped metal patch along the \(y\) - direction is \(L1\), the patch length along the \(x\) - direction is \(L2\), and the patch width is \(w\).

[0060] In the square radiation - receiving unit, the side length of the square metal patch is \(L\), the side length of the two triangular cut - corners is \(t\), the outer diameter of the C - shaped slot is \(r5\), and the inner diameter is \(r6\); the middle layer is a metal floor with a through - hole diameter of \(d3\); the dielectric plate with a thickness of \(h2\) is located between the middle - layer metal floor and the upper - layer metal patch; the two square metal patches with C - shaped slots on the bottom - layer and upper - layer are connected by a metallized via with a diameter of \(d4\); the dielectric plate with a thickness of \(h2\) is located between the bottom - layer metal patch and the middle - layer metal floor.

[0061] The specific structural parameters of the aperture-sharing dual-sided image dual-frequency folded transmissive array antenna according to the described design process and method are as follows: P1 = 12 mm, r1 = 3.4 mm, r2 = 2.7 mm, r3 = 2 mm, r4 = 1 mm, a = 90°, d1 = 1 mm, d2 = 0.4 mm, h1 = 2 mm, L1 = 5 mm, L2 = 4 mm, w = 2 mm, P2 = 9 mm, L = 4.6 mm, t = 1.5 mm, r5 = 1.5 mm, r6 = 0.6 mm, d3 = 0.6 mm, d4 = 0.3 mm, h2 = 1.2 mm; the metal material parameter is copper, with a thickness of 0.017 mm and a conductivity of 5.8×10 7 S / m; the dielectric board material is F4B, with a dielectric constant of 2.65 and a dielectric tangent loss of 0.001.

[0062] According to the requirements of the dual-sided image dual-frequency folded transmissive array antenna, the present invention optimizes the design of two unit structures and the final antenna structure. The specific steps are as follows:

[0063] Step 1: Design the circular radiation-receiving unit of the first transmissive-reflective metasurface;

[0064] Compared with the traditional multi-layer stacked dielectric structure, the radiation-receiving unit can broaden the working bandwidth and flexibly control electromagnetic waves. At the same time, the aperture-sharing technology can independently control electromagnetic waves in two frequency bands. Based on this, the present invention designs a circular radiation-receiving unit that can achieve efficient transmission, phase control of electromagnetic waves in a specific low-frequency band of the antenna, and efficient reflection and phase control of electromagnetic waves in a specific high-frequency band.

[0065] The unit structure consists of three layers of metal structures and two layers of dielectric plates, with a period of P1. The upper structure of the circular radiation-receiving unit is a metal patch with a C-shaped slot, and there are two circular arc truncations on the patch. The outer diameter of the metal patch with a C-shaped slot is r1, the inner diameter is r3, the radius of the inner circular patch is r4, the angles of the two circular arc truncations are a, and the outer diameter of the metal ring after truncation is r2. The middle layer is a metal floor with a through-hole diameter of d1. The dielectric plate with a thickness of h1 is between the middle-layer metal floor and the upper-layer metal patch. The bottom layer is a metal patch with a C-shaped slot, and there are two circular arc truncations on the metal patch with a C-shaped slot. The cross-shaped patch units are located around the receiving patch of the circular radiation-receiving unit, and the center points of the surrounding cross-shaped patch units are the four corners of the circular radiation-receiving unit respectively. The cross-shaped patch unit includes a cross-shaped metal patch. The patch length of the cross-shaped metal patch in the y direction is L1, the patch length in the x direction is L2, and the patch width is w. The upper and lower metal patches with C-shaped slots are connected by a metallized via hole, and the diameter of the metallized via hole is d2. The dielectric plate with a thickness of h1 is between the bottom-layer metal patch and the middle-layer metal floor. The upper-layer radiation patch of the unit realizes the transmission focusing function; the lower-layer cross-shaped receiving patch realizes the reflection phase compensation function; the lower-layer circular receiving patch only transmits or reflects electromagnetic waves and does not require corresponding phase regulation; therefore, the upper-layer radiation patch and the lower-layer cross-shaped receiving patch need to achieve 360° phase coverage. In this design, PB (Pancharatnam-Berry) phase is used. The upper-layer radiation patch is rotated from 0° to 360° to obtain 360° transmission phase coverage, and the lower-layer cross-shaped receiving patch is rotated from 0° to 180° to obtain 360° reflection phase coverage. The unit structure parameters are simulated and optimized by using the parameter sweeping function of CST software to determine the optimal structure parameters. The optimized structure parameters are: P1 = 12mm, r1 = 3.4mm, r2 = 2.7mm, r3 = 2mm, r4 = 1mm, a = 90°, d1 = 1mm, d2 = 0.4mm, h1 = 2mm, L1 = 5mm, L2 = 4mm, w = 2mm.

[0066] To study the electromagnetic characteristics of the circular radiation-receiving unit, a series of simulations of the unit are carried out by using CST software in the present invention. During the unit simulation process, the x and y directions are set as periodic boundary conditions, the z direction is set as an open boundary condition, and the unit is excited by a wave port. Figure 3 (a) shows that when a right-handed circularly polarized wave is incident, when the rotation angle β of the cross-shaped receiving patch changes from 0° to 180°, the reflection amplitudes at low frequency (12 - 14 GHz) and high frequency (16 - 17.5 GHz) are both close to -3 dB, but the phase only achieves 360° coverage in the high-frequency band. As Figure 3As shown in (b), when a left-handed circularly polarized wave is incident, when the rotation angle α of the radiation patch changes from 0° to 360°, the transmission amplitude in the low frequency band (12 - 14 GHz) is higher than -3 dB, and the phase achieves 360° coverage, and there is no transmission in the high frequency band. Since the feed emits electromagnetic waves at different angles, the influence of the oblique incidence of these angles on the transmittance of the transmissive - reflective metasurface should be considered. From Figure 4 It can be seen that for left-handed circularly polarized waves at different incident angles, the transmission amplitude can still reach a relatively high transmittance in the low frequency band. The phase error is acceptable within the working frequency band. Therefore, the designed circular radiation - receiving unit has angle insensitivity.

[0067] Step 2: Design the square radiation - receiving unit of the second transmissive - reflective metasurface;

[0068] In the previous step, a circular radiation - receiving structural unit was designed, which can efficiently transmit electromagnetic waves at 12 - 14 GHz, and at the same time reflect electromagnetic waves at 16 - 18 GHz and perform phase regulation.

[0069] To construct a double - sided image dual - frequency folded transmissive array antenna, the present invention designs a square radiation - receiving unit. The upper - layer structure of this unit is a square metal patch with a C - shaped slot, and there are two triangular cut - corners on the patch. The side length of this square metal patch is L, the side lengths of the two triangular cut - corners are t, the outer diameter of the C - shaped slot is r5, and the inner diameter is r6; the middle layer is a metal floor with a through - hole diameter of d3; between the middle - layer metal floor and the upper - layer metal patch is a dielectric plate with a thickness of h2; the bottom layer and the two upper - layer square metal patches with C - shaped slots are connected by a metallized via hole, and the diameter of the metallized via hole is d4; between the bottom - layer metal patch and the middle - layer metal floor is a dielectric plate with a thickness of h2. The upper - layer receiving patch of this unit only transmits or reflects electromagnetic waves and does not require corresponding phase regulation; the lower - layer radiation patch realizes the transmission focusing function, so the lower - layer radiation patch needs to achieve 360° phase coverage. In this design, PB phase is used, and the full - wave simulation software CST MICROWAVE STUDIO (2020) is used for simulation calculation. The results show that this square radiation - receiving unit can radiate the right - handed circularly polarized waves incident in the high frequency band, and rotate the lower - layer radiation patch from 0° to 360° to obtain 360° transmission phase coverage.

[0070] The optimized structural parameters using the full - wave simulation software CST 2020 are: P2 = 9 mm, L = 4.6 mm, t = 1.5 mm, r5 = 1.5 mm, r6 = 0.6 mm, d3 = 0.6 mm, d4 = 0.3 mm, h2 = 1.2 mm. Finally, the unit characteristics are simulated using CST 2020. As Figure 6(a) As shown, in the frequency range of 12 - 14 GHz, the right - hand circularly polarized wave is totally reflected; while in the frequency range of 16 - 17.5 GHz, when the rotation angle γ of the unit radiation patch changes from 0° to 360°, the transmission amplitude is higher than - 3 dB, and the phase achieves 360° coverage. Since the feed emits electromagnetic waves at different angles, the influence of the oblique incidence of these angles on the transmittance of the transmissive - reflective metasurface should be considered. From Figure 6 (b), it can be seen that for the right - hand circularly polarized wave at different incident angles, the transmission amplitude can still reach a relatively high transmittance in the low - frequency band. The phase error is acceptable within the working frequency band. Therefore, the designed square radiation - receiving unit has angle insensitivity.

[0071] Step 3: Utilize the focusing phase to arrange the spatial phase of the upper - layer radiation patches of the first transmissive - reflective metasurface, and use the phase compensation method to arrange the spatial phase of the lower - layer cross - shaped receiving patches of the first transmissive - reflective metasurface;

[0072] The first transmissive - reflective metasurface consists of 17×17 circular radiation patches. When the left - hand circularly polarized wave is incident vertically, according to formula (1), calculate the required focusing phase Φ focus-1 (x1,y1):

[0073]

[0074] where, k0 = 2π / λ0 is the free - space wave vector, λ0 is the wavelength at the working frequency f0, (x1,y1) represents the relative position of the metasurface unit, F is the focal length, the F / D ratio is set to 0.6, the aperture D is 216 mm, and the focal length F is 129.6 mm. The theoretical discrete focusing phase distribution calculated by substituting formula (1) into MATLAB is as shown in Figure 7 (a). Since the circular radiation patch can rotate from 0° to 360° to achieve 360° phase coverage, rotating 1° is equivalent to achieving 1° of phase, thus arranging the upper - layer radiation patch array of the first transmissive - reflective metasurface.

[0075] The cross - shaped receiving patches and circular receiving patches of the first transmissive - reflective metasurface are arranged alternately to achieve the aperture - sharing technology. Therefore, 18×18 cross - shaped receiving patches are used during the arrangement. When the right - hand circularly polarized wave is incident, according to formula (2), calculate the required compensation phase Φ(x2,y2) at different positions of the lower - layer cross - shaped receiving patches of the first transmissive - reflective metasurface:

[0076]

[0077] where, (x2,y2) represents the relative position of the metasurface unit, k0 = 2π / λ0 is the free - space wave vector, λ0 is the wavelength at the working frequency f0, is the constant reference phase, F is the focal length, H = F / 3 is the distance between the first transmissive-reflective metasurface and the second transmissive-reflective metasurface, H = 43.2 mm. The theoretical discrete compensation phase distribution calculated by substituting formula (2) into MATLAB is as follows Figure 7 As shown in (b), since the cross-shaped receiving patch can rotate from 0° to 180° to achieve 360° phase coverage, rotating 1° is equivalent to achieving 2° of phase, so an array arrangement of the cross-shaped receiving patches in the lower layer of the first transmissive-reflective metasurface is carried out.

[0078] Step 4: Arrange the spatial phase of the radiating patches in the lower layer of the second transmissive-reflective metasurface by using the phase compensation method;

[0079] The second transmissive-reflective metasurface is composed of 24×24 square radiating patches. When a right-handed circularly polarized wave is incident, the focusing phase Φ focus-2 (x3, y3) required at different positions of the radiating patches in the lower layer of the second transmissive-reflective metasurface is calculated according to formula (3):

[0080]

[0081] where k0 = 2π / λ0 is the free-space wave vector, λ0 is the wavelength at the operating frequency f0, (x3, y3) represents the relative position of the second transmissive-reflective metasurface unit, F is the focal length, the F / D ratio is set to 0.6, D is the aperture, and F is the focal length;

[0082] The theoretical discrete focusing phase distribution calculated by substituting formula (3) into MATLAB is as follows Figure 8 As shown, since the square radiating patch can rotate from 0° to 360° to achieve 360° phase coverage, rotating 1° is equivalent to achieving 1° of phase, so an array arrangement of the radiating patches in the lower layer of the second transmissive-reflective metasurface is carried out.

[0083] Step 5: Construct the final aperture-sharing dual-sided image dual-band folded transmissive array antenna.

[0084] With the designed first transmissive-reflective metasurface and second transmissive-reflective metasurface, the final aperture-sharing dual-sided image dual-frequency folded transmissive array antenna can be constructed as follows: Place the first transmissive-reflective metasurface above the second transmissive-reflective metasurface with a spacing of H, where H = F / 3 = 43.2 mm. A right-handed circularly polarized horn feed with an aperture of 20 mm is placed at the center of the second transmissive-reflective metasurface, and the horn aperture plane and the receiving patch surface on the upper layer of the second transmissive-reflective metasurface are in the same plane. The right-handed circularly polarized wave emitted by the circularly polarized horn feed at low frequency is reflected by the first transmissive-reflective metasurface and remains right-handed circularly polarized. Then it is reflected by the second transmissive-reflective metasurface and becomes left-handed circularly polarized. Finally, the second transmissive-reflective metasurface receives this left-handed circularly polarized wave and radiates it in the +z direction; The right-handed circularly polarized wave emitted by the circularly polarized horn feed at high frequency is reflected by the first transmissive-reflective metasurface and becomes right-handed circularly polarized, and its phase is compensated during this process to produce a non-mirror reflection effect. Then this right-handed circularly polarized wave is received by the second transmissive-reflective metasurface and radiated as a left-handed circularly polarized beam in the -z direction.

[0085] Finally, the present invention designs a dual-sided image dual-frequency folded transmissive array antenna to verify this design method and conducts full-wave simulation in CST2020. As Figure 9 (a) shows, at 13 GHz, the measured gain of the left-handed circularly polarized beam radiated in the +z direction is 25.02 dBic; as Figure 9 (b), at 16.5 GHz, the measured gain of the left-handed circularly polarized beam radiated in the -z direction is 24 dBic.

[0086] Figure 10 The normalized radiation pattern of the antenna is given. It can be seen that the sidelobe level of the left-handed circularly polarized beam is -13.5 dB at 13 GHz and -13 dB at 16.5 GHz. Figure 11 The axial ratio and gain curves of the designed antenna are given. It can be seen from the figure that within the operating frequency bands of 12 - 14 GHz and 16 - 17.5 GHz, the axial ratio of the left-handed circularly polarized beam is lower than 3 dB. At 13 GHz, the measured peak gains of the left-handed circularly polarized wave at low frequency and high frequency are 25.02 dBic and 24 dBic respectively. Using the aperture efficiency formula Calculation shows that the corresponding aperture efficiencies are 28.86% and 14.16% respectively. At the same time, the 3 dB gain bandwidths of the left-handed circularly polarized beam in the two frequency bands are 8.5% and 6.7% respectively.

[0087] The above are only the specific steps of the present invention and do not constitute any limitation to the protection scope of the present invention; Any technical solutions formed by equivalent transformation or equivalent substitution fall within the scope of the protection of the present invention; The parts not elaborated in detail in the present invention belong to the well-known technologies in the art.

[0088] The above are only the specific steps of the present invention, which do not constitute any limitation to the protection scope of the present invention; all technical solutions formed by equivalent transformation or equivalent substitution fall within the scope of the rights protection of the present invention; the parts not elaborated in detail in the present invention belong to the well-known technologies of those skilled in the art.

Claims

1. A dual-frequency folded transmission array with a shared aperture, characterized in that: The aperture-sharing double-sided image dual-frequency folded transmission array comprises a first transflective metasurface, a second transflective metasurface and a horn feed source; The first transflective metasurface is arranged at a position H directly above the second transflective metasurface, the horn feed is arranged at the center of the second transflective metasurface, and the aperture surface and the upper receiving patch surface thereof are in the same plane; The first transflective metasurface includes m×m staggered circular radiation-receiving units with different rotation angles and (m+1)×(m+1) cross-shaped patch units located in the receiving layer, and the circular radiation-receiving unit includes a three-layer metal structure and two layers of dielectric plates; The upper metal structure of the circular radiation-receiving unit is a radiation layer, including a metal patch with a C-shaped groove, and the patch has two arc cuts; the middle metal structure of the circular radiation-receiving unit is a metal floor with through holes; the bottom metal structure of the circular radiation-receiving unit is a receiving layer, including a metal patch with a C-shaped groove, and the patch has two arc cuts; the upper and lower metal patches with C-shaped grooves are connected through metallized vias; in the two layers of dielectric plates, the first dielectric plate is located between the upper metal patch and the middle metal floor, and the second dielectric plate is located between the middle metal floor and the bottom metal patch; The cross-shaped patch unit is located around the receiving patch of the circular radiation-receiving unit, and the center points of the surrounding cross-shaped patch units are respectively the four corners of the circular radiation-receiving unit, and the cross-shaped patch unit includes a cross-shaped metal patch; The second transflective metasurface includes n×n square radiation-receiving units that are arranged at equal intervals and periodically extended in a plane with different rotation angles, and the square radiation-receiving units include a three-layer metal structure and two layers of dielectric plates; The upper metal structure of the square radiation-receiving unit is a square metal patch with a C-shaped groove, and there are two triangular cut corners on the patch; the middle metal structure of the square radiation-receiving unit is a metal floor with through holes; the bottom metal structure of the square radiation-receiving unit is a square metal patch with a C-shaped groove, and there are two cut corners on the patch; the two layers of square metal patches are connected by metallized vias; in the two layers of dielectric boards, the first layer of dielectric board is located between the upper metal patch and the middle layer of metal floor, and the second layer of dielectric board is located between the middle layer of metal floor and the bottom metal patch.

2. The design method of the aperture-sharing double-sided image dual-frequency folded transmission array according to claim 1 is characterized in that: The period P1 of the circular radiation-receiving unit is 12 mm. In the circular radiation-receiving unit, the metal patches with C-shaped grooves on the upper and bottom layers have the same size. The outer diameter of the metal patch with C-shaped grooves is r1=3.4 mm, the inner diameter is r3=2 mm, the radius of the circular patch inside is r4=1 mm, the truncation angle of the two arcs is a=90°, and the outer diameter of the truncation metal ring is r2=2.7 mm; the middle layer is a metal floor with a through hole with a diameter of d1=1 mm; Between the middle metal floor and the upper metal patch is a dielectric plate with a thickness of h1 = 2mm; the length of the bottom cross-shaped metal patch in the y direction is L1 = 5mm, the length of the patch in the x direction is L2 = 4mm, and the width of the patch is w = 2mm; the upper and lower metal patches with C-shaped grooves are connected by a metallized via, and the diameter of the metallized via is d2 = 0.4mm; between the bottom metal patch and the middle metal floor is a dielectric plate with a thickness of h1 = 2mm; In the square radiation-receiving unit, the side length of the square metal patch is L, the side length of the two triangular cut corners is t=1.5mm, the outer diameter of the C-shaped groove is r5=1.5mm, and the inner diameter is r6=0.6mm; the middle layer is a metal floor with a through hole diameter of d3=0.6mm; between the middle layer metal floor and the upper layer metal patch is a dielectric plate with a thickness of h2=1.2mm; the two square metal patches with C-shaped grooves on the bottom layer and the upper layer are connected by a metallized via hole, and the diameter of the metallized via hole is d4=0.3mm; between the bottom layer metal patch and the middle layer metal floor is a dielectric plate with a thickness of h2=1.2mm; The metal material parameters are copper, with a thickness of 0.017 mm and a conductivity of 5.8×10 7 S / m; the dielectric plate is made of F4B, the dielectric constant is 2.65, and the electrical tangent loss is 0.

001.

3. The design method of the aperture-sharing double-sided image dual-frequency folded transmission array according to claim 1 is characterized in that: The upper and lower radiation patches in the first transflective metasurface respectively realize the transmission focusing function, so the lower radiation patch needs to achieve 360° phase coverage; The upper receiving patch in the second transflective metasurface only transmits or reflects electromagnetic waves and does not require corresponding phase control; the lower radiating patch realizes the transmission focusing function, so the lower radiating patch needs to achieve 360° phase coverage.

4. A design method for an aperture-sharing double-sided image dual-frequency folded transmission array, characterized in that: The design method of the aperture-sharing double-sided image dual-frequency folded transmission array comprises the following steps: Step 1, designing a circular radiation-receiving unit of a first transflective metasurface; Step 2, designing a square radiation-receiving unit of the second transflective metasurface; Step 3, using the focusing phase to arrange the spatial phase of the upper radiation patch on the first transflective metasurface, and using the phase compensation method to arrange the spatial phase of the cross-shaped receiving patch on the lower layer of the first transflective metasurface; Step 4, using a phase compensation method to arrange the spatial phase of the radiation patch under the second transflective metasurface; Step 5, construct the final aperture-sharing double-sided image dual-frequency folded transmission array antenna.

5. The design method of the aperture-sharing double-sided image dual-frequency folded transmission array according to claim 4 is characterized in that: In step 1, the upper metal structure of the circular radiation-receiving unit includes a metal patch with a C-shaped groove; the metal patch with the C-shaped groove has two arc cuts; the middle metal structure of the circular radiation-receiving unit is a metal floor with through holes; the bottom metal structure of the circular radiation-receiving unit is a receiving layer, including a metal patch with a C-shaped groove, and the patch has two arc cuts; the upper and lower metal patches with C-shaped grooves are connected through metallized vias; in the two layers of dielectric plates, the first dielectric plate is located between the upper metal patch and the middle metal floor, and the second dielectric plate is located between the middle metal floor and the bottom metal patch; the cross-shaped patch unit is located around the receiving patch of the circular radiation-receiving unit, and the center points of the cross-shaped patch units around are the four corners of the circular radiation-receiving unit, and the cross-shaped patch unit includes a cross-shaped metal patch.

6. The design method of the aperture-sharing double-sided image dual-frequency folded transmission array according to claim 4 is characterized in that: In step 2, the upper metal structure of the square radiation-receiving unit is a square metal patch with a C-shaped groove, and the patch has two triangular cut corners; the middle metal structure of the square radiation-receiving unit is a metal floor with through holes; the bottom metal structure of the square radiation-receiving unit is a square metal patch with a C-shaped groove, and the patch has two cut corners; the two layers of square metal patches are connected by metallized vias; in the two layers of dielectric boards, the first layer of dielectric board is located between the upper metal patch and the middle layer of metal floor, and the second layer of dielectric board is located between the middle layer of metal floor and the bottom metal patch.

7. The design method of the aperture-sharing double-sided image dual-frequency folded transmission array according to claim 4 is characterized in that: In step 3, when the left-handed circularly polarized wave is incident vertically on the upper radiation patch of the first transflective metasurface, the focusing phase Φ required at different positions is focus (x1,y1): Where k0 = 2π / λ0 is the free space wave vector, λ0 is the wavelength at the operating frequency f0, (x1, y1) represents the relative position of the upper radiation patch on the first transflective metasurface, F is the focal length, the F / D ratio is set to 0.6, D is the aperture, and F is the focal length; The focusing phase Φ focus-1 The theoretical discrete focusing phase distribution is obtained by calculating (x1, y1), and 360° phase coverage is achieved by rotating the metal patch with a C-shaped groove from 0° to 360°.

8. The design method of the aperture-sharing double-sided image dual-frequency folded transmission array according to claim 7, characterized in that: In step 3, when the right-hand circularly polarized wave is incident on the cross-shaped receiving patch under the first transflective metasurface, the compensation phase φ(x2,y2) required at different positions is: Wherein, (x2, y2) represents the relative position of the cross-shaped receiving patch under the first transflective metasurface, k0=2π / λ0 is the free space wave vector, λ0 is the wavelength at the operating frequency f0, is a constant reference phase, F is the focal length, and H = F / 3 is the distance between the first transflective metasurface and the second transflective metasurface; The compensation phase Φ(x2, y2) is calculated to obtain a theoretical discrete compensation phase distribution, and a 360° phase coverage is achieved by rotating the cross-shaped metal patch 0° to 180°.

9. The design method of the aperture-sharing double-sided image dual-frequency folded transmission array according to claim 4, characterized in that: In step 4, when the second transflective metasurface is incident with a right-handed circularly polarized wave, the focusing phase Φ required at different positions of the lower radiation patch of the second transflective metasurface is focus-2 (x3,y3): Wherein, k0=2π / λ0 is the free space wave vector, λ0 is the wavelength at the operating frequency f0, (x3, y3) represents the relative position of the second transflective metasurface unit, F is the focal length, the F / D ratio is set to 0.6, D is the aperture, and F is the focal length; The focusing phase Φ focus-2 The theoretical discrete focusing phase distribution is obtained by calculating (x3, y3), and 360° phase coverage is achieved by rotating the square metal patch from 0° to 360°.

10. The design method of the aperture-sharing double-sided image dual-frequency folded transmission array according to claim 4, characterized in that: In step 5, the first transflective metasurface is placed above the second transflective metasurface, and the interval is set to H; A right-handed circularly polarized horn feed with an aperture of 20 mm is placed at the center of the second transflective metasurface, and the horn aperture surface and the receiving patch surface on the upper layer of the second transflective metasurface are in the same plane; the right-handed circularly polarized wave emitted by the circularly polarized horn feed at low frequency is reflected by the first transflective metasurface, and is still a right-handed circularly polarized wave at this time, and is then reflected by the second transflective metasurface to become a left-handed circularly polarized wave, and finally, the second transflective metasurface receives the left-handed circularly polarized wave and radiates it in the +z direction; the right-handed circularly polarized wave emitted by the circularly polarized horn feed at high frequency is reflected by the first transflective metasurface to become a right-handed circularly polarized wave, and its phase is compensated in the process to produce a non-mirror reflection effect, and then the right-handed circularly polarized wave is received by the second transflective metasurface and radiated in the -z direction as a left-handed circularly polarized beam.

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