Surface wave suppression structure suitable for tight coupling phased-array antenna

Abstract

The invention discloses a surface wave suppression structure suitable for a tight coupling phased-array antenna, and belongs to the technical field of antenna engineering. The invention is based on the tightly coupled phased array antenna. In order to realize broadband scanning, an impedance matching layer is generally required to be added to a tight coupling phased-array antenna, the matching layer is used as a periodic structure to guide surface waves at the same time, and the appearance of the surface waves can cause serious directional diagram deterioration, gain reduction, standing wave uplift, isolation deterioration and the like. According to the invention, the columnar metal structure is added to the cut part of the traditional tightly-coupled phased-array antenna medium, so that the propagation condition of surface waves in a periodic environment is destroyed, the surface waves are obviously inhibited, the shape of a directional diagram is recovered to be normal, the gain is obviously improved, and the standing wave and isolation are also greatly improved. The suppression structure is made of metal, and has the characteristics of no loss, obvious surface wave suppression effect, simple structure, suitability for millimeter wave frequency bands and the like.

Description

Technical Field

[0001] The present invention belongs to the field of antenna engineering technology and relates to a surface wave suppression structure suitable for use in a tightly coupled phased array antenna. Tightly coupled phased array antennas are widely used in the fields of communication, radar, detection, etc. The surface wave suppression structure has the characteristics of no loss, obvious suppression effect, and simple structure. Background Art

[0002] With the continuous development of radar and mobile communication systems, antenna reuse to reduce equipment cost and complexity has become an inevitable result. The broadband characteristics and stable beam scanning capabilities of tightly coupled phased array antennas make them widely used in many airborne, shipborne, satellite communications and other fields. However, in order to reduce system costs, methods to increase the aperture of array units and thus reduce the number of units within a fixed aperture area are also being explored. When the unit aperture is increased, one of the urgent problems that need to be solved is the surface wave during beam scanning. The surface wave deteriorates the antenna standing wave ratio, reduces the gain, and splits the lobe, which seriously reduces the scanning performance of the tightly coupled phased array antenna. In the paper "Fully-planar ultrawideband tightly-coupled array (FPU-TCA) with integrated feed for wide-scanning millimeter-wave applications", a tightly coupled phased array antenna is proposed, but due to the presence of surface waves, its unit spacing is severely reduced to only 0.425×0.425λ. h 2 (λ his the free space wavelength corresponding to the highest frequency of the antenna), which will greatly increase the system cost; in the paper "Low-profile planar ultrawideband modular antenna array loaded with parasitic metal strips", a surface wave suppression method is proposed. By cutting off a part of the metasurface matching layer and the dielectric plate, the frequency of the TE mode surface wave during H-plane scanning is increased and moved outside the working frequency band. However, this method involves large-area cutting of the antenna dielectric plate and is suitable for lower-frequency tightly coupled antenna arrays. As the antenna operating frequency increases to the millimeter wave band, this method will be limited by the PCB process and will be difficult to implement; in the paper "Planar, ultra-wideband and dual-polarized phased array antenna for millimeter-wave vehicular communication", a surface wave suppression method is proposed. By inserting a cross metal structure at a key position of the matching layer, the TM mode surface wave during E-plane scanning is suppressed without affecting the normal radiation mode of the antenna, thereby moving the surface wave to a higher frequency outside the working band. However, this method is also limited in its effect on surface wave suppression. Summary of the invention

[0003] Based on the background technology, the present invention proposes a surface wave suppression structure suitable for tightly coupled phased array antennas. The suppression structure is made of metal and has the characteristics of no loss, obvious surface wave suppression effect, simple structure, and applicability to millimeter wave frequency bands. The structure can effectively suppress TM mode surface waves during E-plane scanning, significantly optimize the radiation pattern shape and improve antenna gain.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A surface wave suppression structure suitable for a tightly coupled phased array antenna. The surface wave suppression structure is a metal cylinder with a continuously changing axial diameter, which is arranged in the hollow part of each unit antenna in the tightly coupled phased array antenna; one end is fixed on the metal floor of the antenna, and the other end is higher than the upper surface of the tightly coupled phased array antenna.

[0006] Furthermore, the surface wave suppression structure includes N segments connected in sequence, N is greater than or equal to 3, each segment includes two parts with different diameters, and the diameter of the lower part is less than half of the diameter of the upper part.

[0007] Furthermore, the surface wave suppression structure is formed by turning a metal cylinder with uniform thickness.

[0008] A tightly coupled phased array antenna adopting a surface wave suppression structure, the antenna is composed of a plurality of unit antennas arranged in an array, each unit antenna comprises an antenna part and a surface wave suppression structure, the antenna part comprises, from bottom to top, a metal floor, a first dielectric substrate, a ground coupling sheet, a first prepreg sheet, a second dielectric substrate, a dipole, a second prepreg sheet, a third dielectric substrate, a metamaterial metal patch, a third prepreg sheet, and a fourth dielectric substrate, the antenna part is in a "cross" shape as a whole, the third dielectric substrate, the metamaterial metal patch, the third prepreg sheet, and the fourth dielectric substrate located at the center of the antenna "cross" structure are provided with a "cross" shaped cavity, the walls of the "cross" shaped cavity are all metal, the metal arms of the cavity do not contact the metamaterial metal patch, the metamaterial metal patch is a square sheet structure, and is arrayed on the upper surface of the third dielectric substrate; the ground coupling sheet is in a "cross" shape, the size of which is smaller than the projection size of the "cross" shaped cavity, and the ground coupling sheet passes through the first dielectric substrate through a grounding column to connect to the metal floor;

[0009] The surface wave suppressor structure is located in a gap between adjacent antenna parts.

[0010] Furthermore, the dipole includes four diamond-shaped metal sheets, whose vertices point to the center of the antenna's "cross" structure, and the points opposite to the vertices are connection points, wherein the connection points of two adjacent diamond structures are grounded through metal columns, and the connection points of the other two diamond structures are connected to the signal input end through metal columns.

[0011] Furthermore, each branch of the ground coupling sheet is provided with a corresponding grounding column.

[0012] The present invention is based on a tightly coupled phased array antenna. In order to achieve broadband scanning, a tightly coupled phased array antenna usually needs to add an impedance matching layer, and the matching layer, as a periodic structure, will simultaneously guide the surface wave. The appearance of the surface wave will cause serious pattern deterioration, gain reduction, standing wave rise, isolation deterioration, etc. The present invention cuts off part of the medium of the traditional tightly coupled phased array antenna and adds a columnar metal structure, so that the propagation conditions of the surface wave in the periodic environment are destroyed, so that the surface wave is significantly suppressed, the pattern shape returns to normal, the gain is significantly improved, and the standing wave and isolation are also greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 3D layered view of tightly coupled phased array antenna elements with added surface wave suppression structure for the present invention.

[0014] Figure 2 A side view of a tightly coupled phased array antenna unit to which a surface wave suppression structure is added for the present invention.

[0015] Figure 3A top view of the antenna layer of a tightly coupled phased array antenna unit to which a surface wave suppression structure is added according to the present invention.

[0016] Figure 4 A top view of a matching layer of a tightly coupled phased array antenna unit to which a surface wave suppression structure is added according to the present invention.

[0017] Figure 5 An 8×8 phased array 3D view of the surface wave suppression structure is added to the present invention.

[0018] Figure 6 This is a graph showing how the voltage standing wave ratio of the antenna unit of the present invention changes with frequency when the E plane is scanned to 30° before and after the surface wave suppression structure is added.

[0019] Figure 7 This is a graph showing how the isolation of the antenna unit of the present invention before and after adding a surface wave suppression structure varies with frequency when the E plane is scanned to 30°.

[0020] Figure 8 This is the radiation pattern of the 8×8 antenna array of the present invention before and after adding the surface wave suppression structure when the E-plane is scanned to 30° at 30 GHz.

[0021] Fig. 9 The figure is a graph showing the voltage standing wave ratio of the antenna unit of the present invention changing with frequency at various scanning angles.

[0022] Fig.10 The figure is a graph showing the variation of the orthogonal port isolation of the antenna unit of the present invention with frequency at various scanning angles.

[0023] Fig.11 Schematic diagram of the 8×8 antenna array of the present invention at various scanning angles on the E plane at 30 GHz.

[0024] Fig.12 Schematic diagram of the 8×8 antenna array of the present invention at various scanning angles in the 30 GHz H plane.

[0025] Fig.13 A 3D layered view of the surface wave suppression structure of the present invention in another tightly coupled phased array antenna unit.

[0026] Fig.14 This is the radiation pattern of another tightly coupled phased array antenna 12×13 array before and after adding the surface wave suppression structure when the E plane is scanned to 60° at 69GHz.

[0027] Figure 1 In the middle, structure 1 is the matching layer, structure 2 is the surface wave suppression structure, structure 3 is the antenna layer, and structure 4 is the floor; Figure 2The structure 5 is the first dielectric plate, the structure 6 is the second dielectric plate, the structure 7 is the third dielectric plate, the structure 8 is the fourth dielectric plate, the structure 9 is the first prepreg, the structure 10 is the second prepreg, and the structure 11 is the third prepreg; Figure 3 The middle structure 12 is a dipole arm, and the structure 13 is a ground coupling plate; Figure 4 The middle structure 14 is a super-surface metal patch, and the structure 15 is a cross metal structure. DETAILED DESCRIPTION

[0028] The surface wave suppression structure of the present invention is a metal cylinder with uneven diameter, which is formed by connecting three groups of metal cylinders with different thicknesses; from the ground upwards, there is a metal cylinder with a smaller diameter, and then upwards, there is a metal cylinder with a larger diameter, and the two are connected; further upwards, there are another two groups of metal cylinders that are the same as the above-mentioned thick and thin metal cylinders, and the three groups of metal cylinders are connected to each other; this structure can be turned from a metal cylinder with uniform thickness.

[0029] The structure is suitable for a tightly coupled phased array antenna. The tightly coupled phased array antenna in the present invention is composed of a plurality of antenna units, each of which is composed of a PCB board part and a metal floor part;

[0030] The tightly coupled phased array antenna unit PCB board is divided into two parts: an antenna multilayer board part and a matching layer multilayer board part;

[0031] The multilayer board part of the antenna is basically the same as the unit structure of the traditional tightly coupled phased array antenna, and is composed of two groups of dipoles with orthogonal feeding, feeding and short-circuit posts, and a ground coupling sheet located below the end of the dipole;

[0032] The matching layer multilayer board part is mainly composed of two parts: one part is a cross-shaped metal structure, which is located above the tail of the orthogonal dipole antenna; the other part is a metamaterial metal patch matching layer. Each antenna unit originally has 4 rows and 4 columns of square metamaterial metal patches, but on the one hand, in order to leave space for the cross-shaped metal structure, a part of the metal patch is cut off, and on the other hand, the dielectric removal of the tightly coupled antenna unit also cuts off a part of the metal patch, so that the final shape of the metamaterial matching layer is obtained;

[0033] A portion of the dielectric plate located above the metamaterial metal patch is cut away, leaving only the cross structure and some dielectric plates around it.

[0034] The PCB board part has a total of 4 layers, the PCB board close to the metal floor is named the first layer, and the rest are named the second, third and fourth layers from bottom to top, and the layers are bonded by prepregs; the dipole is located above the second dielectric board; the feeding and short-circuit columns pass through the first to second dielectric boards; the ground coupling plate is located above the first dielectric board, and its grounding column passes through the first dielectric board; the cross metal structure passes through the third to fourth dielectric boards; the metamaterial metal patch is located above the third dielectric board.

[0035] The 3D layered view of the tightly coupled phased array antenna unit in this embodiment is as follows: Figure 1 , the antenna operating frequency band is 17~31GHz, the spacing between adjacent units of this phased array is 6mm, that is, 0.62 times the high-frequency wavelength, and the maximum scanning angle of this phased array is ±30°. According to calculations, the condition for no grating lobe when the maximum scanning angle of the phased array is ±30° is that the unit spacing is less than 0.66 times the high-frequency wavelength. Therefore, this design increases the unit spacing as much as possible while meeting the condition for no grating lobe, so that the number of units can be reduced under the same caliber to significantly reduce the cost. This phased array unit consists of a matching layer 1, a surface wave suppression structure 2, an antenna layer 3 and a metal floor 4. A part of the multilayer dielectric plate of the matching layer 1 and the antenna layer 3 is cut, and the cut part is an octagonal prism, and its top view shape is a square with four corners cut off. The side length of this square is 4.4mm, and the cut corner part is an isosceles right triangle with a right angle side length of 0.9mm. The surface wave suppression structure 2 is formed by turning a metal column of uniform thickness, wherein the diameter of the thicker part is 1mm and the height is 0.3mm; the diameter of the thinner part is 0.2mm and the height is 0.7mm; the total height of the whole structure is 3mm. It is located at the center of the cut part of the dielectric plate. The surface wave suppression structure 2 exists in each phased array unit, and it has a significant suppression effect on the surface wave by changing the periodic environment required for the propagation of the surface wave, thereby optimizing the antenna radiation pattern shape, reducing the antenna standing wave, improving the isolation between orthogonal polarizations, and improving the cross polarization of the antenna.

[0036] The layered view of the tightly coupled phased array antenna unit in this embodiment is as follows: Figure 2. The thickness of the first dielectric plate 5 is 1.016mm, the thickness of the second dielectric plate 6 is 0.127mm, the thickness of the third dielectric plate 7 is 0.508mm, and the thickness of the fourth dielectric plate 8 is 0.254mm. The relative dielectric constant of the first dielectric plate 5 is 3.5, and the relative dielectric constants of the remaining dielectric plates are 3. The thickness of the first, second, and third semi-cured sheets 9, 10, and 11 are all 0.111mm, and the relative dielectric constant is 3. Among them, the first dielectric plate 5 adopts a higher dielectric constant, and its purpose is to move the common mode resonance that enters the working band due to the large unit spacing back to outside the working frequency band together with the ground coupling sheet. The fourth dielectric plate 8 and the third semi-cured sheet 11 are further cut compared to other multilayer board parts. The cutting position is the part above the dipole feeding and short-circuit column, and the length of the cut part is 3mm.

[0037] The top view of the antenna layer of the tightly coupled phased array antenna unit in this embodiment is as follows: Figure 3 . The dipole arm 12 is hollow. The ground coupling plate 13 has a total of 5 grounding posts, which are arranged in a cross shape. The center grounding post and the two thicker grounding posts on both sides have a diameter of 0.4mm, and the two thinner ones have a diameter of 0.2mm. The two thicker ones are 1mm away from the center, and the two thinner ones are 0.9mm away from the center. The antenna layer design of the tightly coupled antenna is relatively mature and is not the focus of this patent, so the remaining dimensions are not repeated.

[0038] The matching layer diagram of the tightly coupled phased array antenna unit in this embodiment is as follows: Figure 4 Each antenna unit originally has 4 rows and 4 columns of square metamaterial metal patches, with a side length of 1.4mm and a spacing of 0.1mm between two adjacent patches. However, on the one hand, in order to leave space for the cross-shaped metal structure 15, a part of the metal patch is removed, and the distance between the metal patch and the cross metal structure 15 is 0.1mm after removal. On the other hand, the dielectric removal of the tightly coupled antenna unit also cuts off a part of the metal patch, thus obtaining the final shape of the metamaterial matching layer. The cross metal structure 15 is located above the end of the dipole. From the top view, its center is aligned with the center of the ground coupling plate 13. It is composed of a metalized blind groove and pads on the upper and lower sides of the blind groove. The blind groove is in a cross shape from the top view. The cross is 2mm long and 0.7mm wide. The height is 0.92mm, which runs through the third and fourth dielectric plates 7, 8 and the third semi-cured sheet 11. The single side of the pads on the upper and lower sides of the blind groove is 0.2mm.

[0039] In this embodiment, the 3D view of the tightly coupled 8×8 phased array is as follows: Figure 5 The four sides of the antenna array were extended to facilitate assembly, and the final overall size of the array was 60mm*60mm.

[0040] Figure 6A graph showing the voltage standing wave ratio of the antenna unit of the present invention changing with frequency when the E-plane is scanned to 30° before and after the surface wave suppression structure is added is given. When the surface wave suppression structure is not added to the antenna unit, there is an obvious standing wave peak at 30 GHz, while the peak disappears after the surface wave suppression structure is added, and the standing wave as a whole has a downward trend.

[0041] Figure 7 A graph showing the variation of the isolation of the antenna unit of the present invention with frequency before and after adding the surface wave suppression structure when the E plane is scanned to 30° is given. When the surface wave suppression structure is not added to the antenna unit, there is an obvious isolation deterioration peak at 30 GHz, while the peak disappears after the surface wave suppression structure is added, and the isolation as a whole has a downward trend.

[0042] Figure 8 The directional patterns of the antenna 8×8 array of the present invention before and after adding the surface wave suppression structure when the E-plane is scanned to 30° at 30GHz are given. When the antenna 8×8 array is not added with the surface wave suppression structure, the shape of the directional pattern when the E-plane is scanned to 30° is seriously distorted, and zero depth appears near 30°. At the same time, the cross polarization is seriously deteriorated, and the amplitude is the same as the main polarization. After adding the surface wave suppression structure, the directional pattern returns to normal, and the main lobe points to the 30° direction. Finally, the gain in the 30° direction is improved by 16.14dB, and the cross polarization is improved by 36.4dB.

[0043] Fig. 9 A graph showing the voltage standing wave ratio of the antenna unit of the present invention varying with frequency at various scanning angles is given. The antenna can achieve a standing wave ratio of less than 2.2 in the range of 17 to 31 GHz (or even wider) at scanning angles of 0°, 30° on the E plane, and 30° on the H plane.

[0044] Fig.10 A graph showing the variation of the orthogonal port isolation of the antenna unit of the present invention with frequency at various scanning angles is given. The antenna can achieve an orthogonal port isolation of less than -22 dB in the range of 17 to 31 GHz at scanning angles of 0°, 30° on the E plane, and 30° on the H plane.

[0045] Fig.11 This is the radiation pattern of the 8×8 array antenna of the present invention at various scanning angles on the E-plane at 30GHz, where the beams point to 0°, 30°, and -30° respectively. It can be seen that the beam pointing of this antenna array is stable, the cross-polarization is excellent at each scanning angle, no grating lobe appears, and the gain decreases by less than 0.89dB when scanning to the maximum angle.

[0046] Fig.12This is the radiation pattern of the 8×8 array antenna of the present invention at various scanning angles in the 30GHz H plane, where the beams point to 0°, 30°, and -30° respectively. It can be seen that the beam pointing of this antenna array is stable, the cross-polarization is excellent at each scanning angle, and no grating lobe appears. When scanning to the maximum angle, the gain reduction is less than 0.99dB.

[0047] Fig.13 This is a 3D layered view of the surface wave suppression structure in the present invention in another tightly coupled phased array antenna unit. In order to prove the universality of the surface wave suppression structure in tightly coupled phased array antennas, it was applied to another tightly coupled phased array antenna in the form of a hollow dipole for verification. The highest operating frequency of the tightly coupled phased array antenna in the form of a hollow dipole is 69GHz, the antenna unit spacing is 2.1mm, and the surface wave suppression structure in the antenna unit adopts a five-segment form with a total height of 2mm.

[0048] Fig.14 This is the radiation pattern of another tightly coupled phased array antenna 12×13 array before and after adding the surface wave suppression structure, when the E-plane scans to 60° at 69GHz. When the antenna 12×13 array does not add the surface wave suppression structure, the shape of the radiation pattern is severely distorted when the E-plane scans to 60°, and zero depth appears near 60°. After adding the surface wave suppression structure, the radiation pattern shape returns to normal, and the main lobe points correctly to the 60° direction. Finally, the gain in the 60° direction is increased by 12dB, and the cross-polarization is increased by 8.5dB. After secondary verification, it can be proved that the surface wave suppression structure in the tightly coupled phased array antenna has universality and portability for the surface wave suppression capability during beam scanning.

[0049] The surface wave suppression structure can achieve the surface wave suppression effect when the tightly coupled phased array antenna is scanned on the E plane, so that when the antenna 8×8 array of the present invention is scanned to 30° on the 30GHz E plane, the gain in the 30° direction is increased by 16.14dB, and the cross polarization is increased by 36.4dB, and finally the unit spacing is 0.63 times the high-frequency wavelength, and the continuous beam scanning of -30° to 30° in the 17-31GHz band is achieved. It is characterized in that: the basic unit of the suppression structure is a metal cylinder with uneven diameter along the axial direction, and is fixed on the metal bottom plate of the antenna; that: the metal cylinder structure exists in each phased array antenna unit, and the specific position is the center of the cut-off part of the medium of each antenna unit of the tightly coupled phased array antenna; that: the metal cylinder with uneven diameter is connected by three groups of metal cylinders of different thicknesses, from the ground upwards is a metal cylinder with a smaller diameter, and then upwards is a metal cylinder with a larger diameter, the two are connected, and then upwards are two other groups of metal cylinders that are the same as the above-mentioned thick and thin metal cylinders, and the three groups of metal cylinders are connected to each other. The invention discloses a method for providing a tightly coupled phased array antenna. The method ...

Claims

1. A surface wave suppression structure suitable for a tightly coupled phased array antenna, the surface wave suppression structure being a metal cylinder with a continuously changing axial diameter, arranged in the hollow of each unit antenna in the tightly coupled phased array antenna; one end is fixed on the metal floor of the antenna, and the other end is higher than the upper surface of the tightly coupled phased array antenna.

2. A surface wave suppression structure suitable for use in a tightly coupled phased array antenna as claimed in claim 1, characterized in that: The surface wave suppression structure includes N segments connected in sequence, N is greater than or equal to 3, each segment includes two parts with different diameters, and the diameter of the lower part is less than half of the diameter of the upper part.

3. The surface wave suppression structure suitable for use in a tightly coupled phased array antenna according to claim 1, characterized in that: The surface wave suppression structure is formed by turning a metal cylinder with uniform thickness.

4. A tightly coupled phased array antenna using the surface wave suppression structure as claimed in claim 1, wherein the antenna is composed of a plurality of unit antennas arranged in an array, each unit antenna comprising an antenna part and a surface wave suppression structure, wherein the antenna part comprises, from bottom to top: A metal floor, a first dielectric substrate, a ground coupling sheet, a first layer of prepreg, a second dielectric substrate, a dipole, a second layer of prepreg, a third dielectric substrate, a metamaterial metal patch, a third layer of prepreg, and a fourth dielectric substrate. The antenna part has an overall shape of a "cross" structure. The third dielectric substrate, the metamaterial metal patch, the third layer of prepreg, and the fourth dielectric substrate located at the center of the "cross" structure of the antenna are provided with a "cross"-shaped cavity. The walls of the "cross"-shaped cavity are all made of metal. The metal arms of the cavity do not contact the metamaterial metal patch. The metamaterial metal patch is a square sheet structure and is arrayed on the upper surface of the third dielectric substrate. The ground coupling sheet is a "cross" shape, and its size is smaller than the projection size of the "cross"-shaped cavity. The ground coupling sheet passes through the first dielectric substrate through a grounding column to connect to the metal floor. The surface wave suppressor structure is located in a gap between adjacent antenna parts.

5. The tightly coupled phased array antenna according to claim 4, characterized in that: The dipole includes four diamond-shaped metal sheets, with the vertices pointing to the center of the antenna's "cross" structure, and the points opposite to the vertices are connection points, wherein the connection points of two adjacent diamond structures are grounded through metal columns, and the connection points of the other two diamond structures are connected to the signal input end through metal columns.

6. The tightly coupled phased array antenna according to claim 4, characterized in that: Each branch of the ground coupling plate is correspondingly provided with a grounding column.

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