Dual-frequency circularly polarized folded array antenna

Abstract

The invention relates to the technical field of wireless communication, and discloses a dual-frequency circularly polarized folded array antenna, which comprises a first transmission array, a second transmission array and a feed source, and is characterized in that the feed source is arranged at the center of the second transmission array and radiates a first polarized signal of a first frequency band and a second polarized signal of a second frequency band to the first transmission array; wherein a first polarization signal of a first frequency band reaches a frequency selection layer on the first transmission array, is reflected to the second transmission array, is converted into a second polarization signal, is reflected to the frequency selection layer, and is transmitted to a first linear-circular polarization conversion unit on the first transmission array to be converted into a circular polarization signal; a second polarization signal of a second frequency band reaches the frequency selection layer, is reflected to the second transmission array, is converted into a first polarization signal, is reflected to the frequency selection layer, is transmitted to the transmission layer, and is converted into a circularly polarized signal by the second linear-circular polarization conversion unit. The antenna can realize dual-frequency communication with a small size, and has a linear-circular polarization conversion function.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a dual-frequency circularly polarized folded array antenna. Background Art

[0002] With the rapid development and widespread application of wireless communication technology, wireless spectrum resources have become increasingly scarce, and the demand for high-speed, large-capacity data transmission has continued to increase, while the millimeter wave band provides a wider spectrum resource. The millimeter wave bands currently selected by the Ministry of Industry and Information Technology are 24.25-27.5GHz and 37-42.5GHz, which can meet the needs of high-speed data transmission, large-capacity connections and low latency, and are one of the research and application focuses of 5G and future networks. For example, in high-density urban environments, this antenna technology can provide better signal coverage and capacity to meet users' needs for high-speed connectivity. In addition, as current communication equipment tends to be miniaturized, the structure of the antenna needs to be miniaturized accordingly.

[0003] Millimeter wave communication faces the challenges of high transmission loss and poor penetration. Therefore, in order to further improve the stability and large-capacity communication of millimeter wave communication, research needs to be devoted to improving the transmission efficiency and reliability of millimeter wave communication. A multi-band, high-gain, multi-function, and large-capacity millimeter wave antenna can meet application requirements. Multi-band antennas can improve spectrum efficiency and expand communication capacity. High-gain antennas can achieve longer transmission distances and enhance signal transmission and reception capabilities. Linear-circular polarization conversion technology can achieve multi-channel communication and improve anti-interference capabilities, and can adapt to complex communication environments. Summary of the invention

[0004] The purpose of the present invention is to provide a dual-frequency circularly polarized folded array antenna, which can realize dual-frequency communication in a smaller size, improve spectrum efficiency, expand communication capacity, and also has a linear-circular polarization conversion function, realize multi-channel communication and improve anti-interference ability, and can adapt to complex communication environments.

[0005] In order to achieve the above-mentioned object, the present invention provides a dual-frequency circularly polarized folded array antenna, comprising a first transmission array, comprising a first substrate and a transmission layer on its upper side and a frequency selection layer on its lower side, wherein the transmission layer has M×N first linear-circular polarization conversion units and m×n second linear-circular polarization conversion units; a second transmission array, comprising a second substrate and a plurality of linear-linear polarization conversion units thereon; a feed source, arranged at the center of the second transmission array, radiating a first polarization signal of a first frequency band and a second polarization signal of a second frequency band to the first transmission array; wherein the first polarization signal of the first frequency band is reflected to the second transmission array after reaching the frequency selection layer, is converted into a second polarization signal, is reflected to the frequency selection layer, and is then transmitted to the transmission layer and converted into a circularly polarized signal by the first linear-circular polarization conversion unit; the second polarization signal of the second frequency band is reflected to the second transmission array after reaching the frequency selection layer, is converted into the first polarization signal, is reflected to the frequency selection layer, and is then transmitted to the transmission layer and converted into a circularly polarized signal by the second linear-circular polarization conversion unit.

[0006] As an embodiment, the frequency selection layer includes a plurality of orthogonally arranged first rectangular patches and second rectangular patches, each of the first rectangular patches and the second rectangular patches being formed with an obtuse-angle groove oriented in the same direction as the polarization direction of the respectively transmitted signals; each of the first linear-circular polarization conversion units is connected to a first rectangular patch via a first metal through hole passing through the first substrate, and each of the second linear-circular polarization conversion units is connected to a second rectangular patch via a second metal through hole passing through the first substrate.

[0007] As an embodiment, the first linear-circular polarization conversion unit is a third rectangular patch having an obtuse-angle groove, and the upper end of the first metal through hole is located at a recessed side of the obtuse-angle groove.

[0008] As an implementation manner, at least two opposite corners of the third rectangular patch are cut off with preset portions; or three corners of the third rectangular patch are cut off with preset portions; or four corners of the third rectangular patch are cut off with preset portions.

[0009] As an embodiment, the second linear-circular polarization conversion unit is a circular patch having two symmetrical rectangular grooves, and the upper end of the second metal through hole deviates from the center of the circular patch.

[0010] As an implementation manner, a metal isolation layer insulated from the metal through hole is further disposed between the transmission layer and the frequency selection layer.

[0011] As an embodiment, the line-to-line polarization conversion unit includes: a cross-shaped patch; two L-shaped patches symmetrically arranged on both sides of the cross-shaped patch; wherein the cross-shaped patch and the L-shaped patch are symmetrical along the diagonal line of the line-to-line polarization conversion unit.

[0012] As an embodiment, the second transmission array further includes a metal reflective layer disposed on a side of the second substrate away from the first substrate.

[0013] As an embodiment, the third rectangular patch is rotated around the first metal through hole relative to the first initial angle. degree, forming a second polarization signal of the first frequency band The circular patch rotates around the second metal through hole relative to the second initial angle. degree, and the first polarization signal of the second frequency band is formed The phase shift value of ; ; In the formula i and j The third rectangular patch and circular patch are x axis, y The axis direction number, is the wave number in free space, is the distance from the phase center of the feed to each third rectangular patch, is the direction vector from the central third rectangular patch to other third rectangular patches, is the direction of the main beam of the first frequency band radiated by the antenna, is the distance from the phase center of the feed to each circular patch, is the direction vector from the central circular patch to other circular patches, is the direction of the second frequency band main beam radiated by the antenna, the first initial angle is the second polarization direction, and the second initial angle is the first initial angle rotated 45° counterclockwise.

[0014] As an embodiment, the feed source includes: a first transmitting structure, radiating a first polarized signal of a first frequency band to the first transmission array, including a 2×2 fourth rectangular patch array and a 2×2 first director coupled thereto; a second transmitting structure, radiating a second polarized signal of a second frequency band to the first transmission array, including a 2×2 fifth rectangular patch array and a 2×2 second director coupled thereto.

[0015] According to the above description and practice, the dual-frequency circularly polarized folded array antenna described in the present invention can realize the reflection mode for two of the three frequency bands of electromagnetic waves and the transmission mode for the other frequency band, and each frequency band has better performance. By changing the size of the transmission layer in each low-frequency radiation unit or the reflection layer structure in the high-frequency radiation unit, a wide range of phase compensation can be generated for the radiated electromagnetic waves. Therefore, the user can set the size of each transmission layer and reflection layer structure according to actual needs, and then radiate electromagnetic waves at the required angle. The setting of the two radiation units can realize independent control of the phase of the two frequency bands, namely the low-frequency band composed of the first frequency band and the second frequency band, and the high-frequency band of the third frequency band, and has a relatively simple manufacturing process. The antenna has multi-band characteristics, enhances the gain and flexibility of the overall system, and combines transmission and reflection in one, which is suitable for a variety of application scenarios.

[0016] In addition, the reflective layer in the high-frequency radiation unit of the dual-frequency circularly polarized folded array antenna adopts a double-mouthed metal sheet, which can improve the isolation between the low-frequency radiation unit and the high-frequency radiation unit, and at the same time enhance the reflection performance, making the antenna's control performance of electromagnetic waves more superior. By adjusting the value of the double-mouthed metal sheet, a good reflection coefficient and a phase shift exceeding 360° can be achieved in the third frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 and Figure 2 The figure is a schematic diagram of the three-dimensional structure of a dual-frequency circularly polarized folded array antenna involved in an embodiment of the present invention at two different viewing angles.

[0018] Figure 3 The figure is a top view of the first substrate from top to bottom in the dual-frequency circularly polarized folded array antenna involved in one embodiment of the present invention.

[0019] Figure 4 for Figure 1 Enlarged view of part A in the middle.

[0020] Figure 5 for Figure 2 Enlarged view of part B in the middle.

[0021] Figure 6 This is a partially decomposed schematic diagram of the first transmission array in the dual-frequency circularly polarized folded array antenna involved in an embodiment of the present invention, which shows the complete structure of the second linear-circular polarization conversion unit and the second rectangular patch, and shows the partial structure of the first linear-circular polarization conversion unit and the first rectangular patch.

[0022] Figure 7 The present invention is a schematic structural diagram of a line-to-line polarization conversion unit in a dual-frequency circularly polarized folded array antenna according to an embodiment of the present invention.

[0023] Figure 8 It is a schematic diagram of the decomposition of the feed source in the dual-frequency circularly polarized folded array antenna involved in one embodiment of the present invention.

[0024] Figure 9a It is a schematic diagram of the phase shift values ​​that each third rectangular patch needs to generate when the dual-frequency circularly polarized folded array antenna involved in an embodiment of the present invention forms a right-hand circularly polarized wave in the first frequency band.

[0025] Figure 9b The diagram is a schematic diagram of the phase shift values ​​that each circular patch needs to generate when the dual-frequency circularly polarized folded array antenna involved in one embodiment of the present invention forms a left-handed circularly polarized wave in the second frequency band.

[0026] Fig.10 It is a gain diagram of the feed source in the dual-frequency circularly polarized folded array antenna involved in one embodiment of the present invention.

[0027] Fig.11a and Fig.11b is a radiation pattern of a feed source in a dual-frequency circularly polarized folded array antenna according to an embodiment of the present invention, wherein Fig.11a The frequency is 26GHz. Fig.11b The frequency is 40GHz.

[0028] Fig.12a This is a radiation beam pattern of right-hand circularly polarized waves at φ=0° obtained at 26 GHz when the first port of the dual-frequency circularly polarized folded array antenna involved in one embodiment of the present invention is excited.

[0029] Figure 12b This is a radiation beam pattern of right-hand circularly polarized waves at φ=90° obtained at 26 GHz when the first port of the dual-frequency circularly polarized folded array antenna involved in one embodiment of the present invention is excited.

[0030] Fig.13a This is a radiation beam pattern of right-hand circularly polarized waves at φ=0° obtained at 40 GHz when the second port of the dual-frequency circularly polarized folded array antenna involved in one embodiment of the present invention is excited.

[0031] Fig.13b This is a radiation beam pattern of right-hand circularly polarized waves at φ=90° obtained at 40 GHz when the second port of the dual-frequency circularly polarized folded array antenna involved in one embodiment of the present invention is excited. DETAILED DESCRIPTION

[0032] The exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and fully convey the concepts of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0033] In addition, the accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated descriptions will be omitted. It should be noted that in the present disclosure, the terms "including", "configured with", and "set in" are used to express the meaning of open-ended inclusion, and mean that in addition to the listed elements / components / etc., there may be other elements / components / etc.; the terms "first", "second", etc. are only used as marks, and are not restrictions on the number or order of their objects; the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0034] Unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] This embodiment discloses a dual-frequency circularly polarized folded array antenna, please refer to Figures 1 to 8 The dual-frequency circularly polarized folded array antenna includes a first transmission array 1, a second transmission array 2 and a feed source 3. The feed source 3 is arranged at the center of the second transmission array 2 to radiate a first polarization signal of a first frequency band and a second polarization signal of a second frequency band to the first transmission array 1.

[0036] The first transmission array 1 includes a first substrate 13, a transmission layer on its upper side, and a frequency selection layer on its lower side, wherein the transmission layer has M×N first linear-circular polarization conversion units 11 and m×n second linear-circular polarization conversion units 12. The first linear-circular polarization conversion unit 11 is used to convert the second polarization signal of the first frequency band into a circular polarization signal, and the second linear-circular polarization conversion unit 12 is used to convert the first polarization signal of the second frequency band into a circular polarization signal. The frequency selection layer is used to reflect the first polarization signal of the first frequency band and transmit the second polarization signal of the first frequency band; the frequency selection layer is also used to reflect the second polarization signal of the second frequency band and transmit the first polarization signal of the second frequency band.

[0037] The second transmission array 2 includes a second substrate 22 and a plurality of line-to-line polarization conversion units 21 thereon, which are used to convert the signal of the target frequency band from the first polarization signal to the second polarization signal, or from the second polarization signal to the first polarization signal. For example, the first polarization signal of the first frequency band is converted into the second polarization signal and reflected to the first transmission array 1, and the second polarization signal of the second frequency band is converted into the first polarization signal and reflected to the first transmission array 1.

[0038] When the dual-frequency circularly polarized folded array antenna is working, the first polarization signal of the first frequency band radiated by the feed source 3 reaches the frequency selection layer and is reflected to the second transmission array 2, where it is subjected to line-to-line polarization conversion by the second transmission array 2, converted into a second polarization signal and then reflected to the frequency selection layer. At this time, it can be transmitted to the transmission layer via the frequency selection layer, where it is converted into a circularly polarized signal by the first linear-circular polarization conversion unit 11 and radiated externally; the second polarization signal of the second frequency band radiated by the feed source 3 reaches the frequency selection layer and is reflected to the second transmission array 2, where it is subjected to line-to-line polarization conversion by the second transmission array 2, converted into a first polarization signal and then reflected to the frequency selection layer. At this time, it can be transmitted to the transmission layer via the frequency selection layer, where it is converted into a circularly polarized signal by the second linear-circular polarization conversion unit 12.

[0039] The dual-frequency circularly polarized folded array antenna can realize dual-frequency communication, improve spectrum efficiency, expand communication capacity, and also has a linear-circular polarization conversion function, realizes multi-channel communication and improves anti-interference ability, and can adapt to complex communication environments. In addition, the signals in the two frequency bands are reflected twice by the frequency selection layer and the second transmission array 2 and then converted from linear to circular polarization through the transmission layer, which can produce a folding effect, reduce the cross-section of the antenna, and realize the miniaturization design of the antenna.

[0040] As an implementation method, Figure 5 and Figure 6As shown, the frequency selection layer includes a plurality of orthogonally arranged first rectangular patches 16 and second rectangular patches 17, and the first rectangular patches 16 and the second rectangular patches 17 are both formed with obtuse grooves that are consistent with the polarization direction of the respective transmitted signals, that is, the obtuse grooves on the first rectangular patch 16 are consistent with the second polarization direction, and the obtuse grooves on the second rectangular patch 17 are consistent with the first polarization direction; each first linear-circular polarization conversion unit 11 is connected to a first rectangular patch 16 via a first metal through hole 14 passing through the first substrate 13, and each second linear-circular polarization conversion unit 12 is connected to a second rectangular patch 17 via a second metal through hole 15 passing through the first substrate 13.

[0041] The frequency selective layer of this structural form, wherein the first rectangular patch 16 and the second rectangular patch 17 are orthogonally arranged, and the obtuse-angled grooves thereon are respectively oriented to various transmission polarization directions, and can receive and transmit the signal of the corresponding polarization of the corresponding frequency band, and reflect the signal of another polarization of the frequency band, and has good polarization selectivity. Each first rectangular patch 16 can reflect the first polarization signal of the first frequency band to the second transmission array 2 as much as possible, and receive and transmit the second polarization signal of the first frequency band to the first linear-circular polarization conversion unit 11 of the transmission layer. Each second rectangular patch 17 can reflect the second polarization signal of the second frequency band to the second transmission array 2 as much as possible, and receive and transmit the first polarization signal of the second frequency band to the second linear-circular polarization conversion unit 12 of the transmission layer.

[0042] As an implementation method, Figure 3 As shown, the first linear-circular polarization conversion unit 11 is a third rectangular patch with an obtuse groove, and the upper end of the first metal through hole 14 is located on the concave side of the obtuse groove, thereby guiding the current flow, forming circular polarization, and improving the polarization purity. Further, cutting off a preset portion 111 at at least two opposite corners of the third rectangular patch, such as cutting off a triangular area, can further stimulate circular polarization, and can also improve the isolation from the adjacent second linear-circular polarization conversion unit 12.

[0043] As an implementation method, Figure 3 As shown, the second linear-circular polarization conversion unit 12 is a circular patch with two symmetrical rectangular grooves, and the upper end of the second metal through hole 15 deviates from the center of the circular patch to excite a circular current, thereby having a circular polarization characteristic.

[0044] When the first linear-circular polarization conversion units 11 and the second linear-circular polarization conversion units 12 are arrayed, the first linear-circular polarization conversion units 11 rotated at different angles around the first metal through hole 14 can cause the first linear-circular polarization conversion unit 11 to produce different phase shift values ​​for electromagnetic waves in the radiated frequency band, and the second linear-circular polarization conversion units 12 rotated at different angles around the second metal through hole 15 can cause the second linear-circular polarization conversion unit 12 to produce different phase shift values ​​for electromagnetic waves in the radiated frequency band. By setting the phase shift value of each unit, an electromagnetic wave beam of a desired shape can be radiated.

[0045] As an implementation method, Figure 6 As shown, a metal isolation layer 18 insulated from the metal through hole is further provided between the transmission layer and the frequency selection layer to improve the isolation between the transmission layer and the frequency selection layer, and also to improve the reflection effect of the first polarization signal of the first frequency band and the second polarization signal of the second frequency band. For example, two first substrates 13 are provided between the transmission layer and the frequency selection layer, and the metal isolation layer 18 is provided between the two first substrates 13, so that the metal isolation layer 18 can be fixed.

[0046] As an embodiment, the third rectangular patch is rotated around the first metal through hole 14 relative to the first initial angle. degree, forming a second polarization signal of the first frequency band The circular patch rotates around the second metal through hole 15 relative to the second initial angle. degree, and the first polarization signal of the second frequency band is formed The phase shift value of ; ; In the formula i and j The third rectangular patch and circular patch are x axis, y The axis direction number, is the wave number in free space, is the distance from the phase center of feed source 3 to each third rectangular patch, is the direction vector from the central third rectangular patch to other third rectangular patches, is the direction of the main beam of the first frequency band radiated by the antenna, is the distance from the phase center of feed source 3 to each circular patch, is the direction vector from the central circular patch to other circular patches, is the direction of the second frequency band main beam radiated by the antenna, and the first initial angle is Figure 3The positive direction of the Y-axis, that is, the second polarization direction, the second initial angle is the direction of the first initial angle rotated 45° counterclockwise.

[0047] According to this formula, when designing an antenna, the phase shift value that each third rectangular patch and circular patch needs to produce for the electromagnetic waves in their respective frequency bands can be reversely calculated based on the electromagnetic wave beam shape and direction required for each frequency band, and then the rotation angle of each third rectangular patch and circular patch can be calculated.

[0048] As an embodiment, the line-to-line polarization conversion unit 21 in the second transmission array 2 includes a cross-shaped patch and two L-shaped patches, such as Figure 7 As shown, the cross-shaped patch is arranged in the center, and the two L-shaped patches are symmetrically arranged on both sides of the cross-shaped patch, and the cross-shaped patch and the L-shaped patch are symmetrical along the diagonal line of the line-to-line polarization conversion unit 21. When working, the two patch structures can excite the same direction current, obtain broadband stable linear polarization wave conversion characteristics, and have no sudden change in the reflection phase, and achieve good line-to-line polarization amplitude-phase conversion characteristics within a wide band (20-45GHz). In addition, the two patches are symmetrically arranged along the diagonal line, which can simultaneously support XY linear polarization wave conversion and YX linear polarization wave conversion, so that the linear polarization conversion has reciprocity, so that the horizontal and vertical components of the current are equal, and have reciprocal symmetry, and finally meet the needs of different linear polarization wave conversion within a wide band. Furthermore, the second transmission array 2 also includes a metal reflection layer arranged on the side of the second substrate 22 away from the first substrate 13, which can further improve the reflection effect of electromagnetic waves in the working frequency band.

[0049] As an embodiment, the feed source 3 includes a first emitting structure and a second emitting structure. Figure 8 As shown, the first transmitting structure is used to radiate the first polarized signal of the first frequency band to the first transmission array 1, including a 2×2 fourth rectangular patch array 31 and a 2×2 first director 32 coupled thereto; the second transmitting structure is used to radiate the second polarized signal of the second frequency band to the first transmission array 1, including a 2×2 fifth rectangular patch array 33 and a 2×2 second director 34 coupled thereto. The four rectangular patches of the fourth rectangular patch array 31 are connected through microstrip lines and connected to the first port 36 to feed the first polarized signal of the first frequency band, and the fourth rectangular patch array 31 radiates the signal to the coupled first director 32 to achieve stable high-gain directional radiation toward the first transmission array 1. The four rectangular patches of the fifth rectangular patch array 33 are connected through microstrip lines and connected to the second port 37 to feed the second polarized signal of the second frequency band, and the fifth rectangular patch array 33 radiates the signal to the coupled second director 34 to achieve stable high-gain directional radiation toward the first transmission array 1.

[0050] Furthermore, each director includes a main patch and a peripheral parasitic patch. In the first director 32 and the second director 34 at the top, each main patch is provided with a U-shaped groove in the same direction as the corresponding polarization direction, so as to guide the current direction and improve the cross-polarization isolation of the two transmitting structures, so as to achieve better polarization conversion performance when feeding the dual-frequency circular polarization folded array antenna. When the feed source 3 forms a MIMO array, in order to improve the port isolation and reduce the mutual interference between the two patch arrays, a C-shaped groove 35 is introduced at the center connection of the two to change the bottom current direction and offset part of the coupling current, thereby achieving the purpose of improving the port isolation.

[0051] In a specific embodiment, the first frequency band is 24.25-27.5 GHz, the second frequency band is 37-42.5 GHz, the first polarization is X polarization, and the second polarization is Y polarization. Two layers of first substrates 13 are provided in the first transmission array 1, both of which are Rogers 5880 substrates with a thickness of 0.508 mm, a dielectric constant of 2.2, and a loss tangent value of 0.0009. The upper side of the two first substrates 13 is a transmission layer, the lower side is a frequency selection layer, and the middle is a metal isolation layer 18. M×N is 19×19, and m×n is 20×20.

[0052] The first linear-circular polarization conversion unit 11 in the transmission layer operates at 24.25-27.5GHz and is a third rectangular patch with an obtuse-angle groove. At the first initial angle, the direction of the obtuse-angle groove of the rectangular patch is consistent with the Y polarization direction. The second linear-circular polarization conversion unit 12 in the transmission layer operates at 37-42.5GHz and is a circular patch with symmetrical rectangular grooves. The frequency selection layer includes a plurality of orthogonally arranged first rectangular patches 16 and second rectangular patches 17. The first rectangular patch 16 is formed with an obtuse-angle groove in the same direction as the Y polarization direction, and the second rectangular patch 17 is formed with an obtuse-angle groove in the same direction as the X polarization direction. The first metal through hole 14 is arranged in the two first substrates 13, the lower end is connected to the first rectangular patch 16, the upper end is connected to the third rectangular patch, and the middle is insulated from the metal isolation layer 18. The second metal through hole 15 is arranged through the two first substrates 13 , with the lower end connected to the second rectangular patch 17 , the upper end connected to the circular patch, and the middle is insulated from the metal isolation layer 18 .

[0053] The third rectangular patch and the circular patch in the transmission layer are rotated around the first metal through hole 14 and the second metal through hole 15 by preset angles according to the phase shift values ​​they need to generate. The first rectangular patch 16 and the second rectangular patch 17 in the frequency selection layer are orthogonally arranged and do not rotate. They are used to receive electromagnetic waves of corresponding polarization and reflect electromagnetic waves of another polarization, and have good polarization selectivity.

[0054] The line-to-line polarization conversion unit 21 involved in the second transmission array 2 in this embodiment is to realize a folded array and achieve the effect of reducing the cross section. It can convert the signals in the two frequency bands of 24.25-27.5GHz and 37-42.5GHz from X polarization to Y polarization, and convert the Y polarization signal to X polarization signal. The second transmission array 2 uses a F4B second substrate 22 with a thickness of 1mm, a dielectric constant of 2.65, and a loss tangent of 0.003. The line-to-line polarization conversion unit 21 introduces a cross-shaped patch and two L-shaped patches. When working, the two structures can excite the same direction current to obtain a wide-band stable linear polarization wave conversion characteristic, and have no sudden change in the reflection phase, achieving a good line-to-line polarization amplitude-to-phase conversion characteristic within a wide band (20-45GHz). In addition, in order to support both XY linear polarization wave conversion and YX linear polarization wave conversion and make the linear polarization conversion reciprocal, the line-to-line polarization conversion unit needs to be designed to be symmetrical along the diagonal line, so that the horizontal and vertical components of the current are equal, with reciprocal symmetry, and ultimately meet the needs of conversion of different linear polarization waves within a wide bandwidth.

[0055] In this embodiment, a 2×2 stacked patch MIMO array antenna is used as the feed source 3, and two ports are set. The first port 36 is responsible for the signal radiation in the 24.25-27.5GHz frequency band, and the second port 37 is responsible for the radiation in the 37-42.5GHz frequency band. The feed source 3 can emit X-polarized waves with high polarization purity in the 24-27.5GHz frequency band and Y-polarized waves with high polarization purity in the 37-42.5GHz frequency band. The specific implementation form is to use a 2×2 rectangular patch array antenna and a top-coupled director to achieve stable high-gain directional radiation. A U-shaped groove corresponding to the polarization direction is introduced in the top director to guide the current direction and improve the cross-polarization isolation to achieve better polarization conversion performance when feeding the millimeter wave folded array. When forming a MIMO array, in order to improve the port isolation and reduce the mutual interference between the two patch arrays, a C-shaped groove 35 is introduced at the center connection of the two to change the bottom current direction and offset part of the coupling current, thereby achieving the purpose of improving the port isolation.

[0056] Please combine Figure 1 and Figure 2, the feed source 3 is placed in the middle of the second transmission array 2 below, and the first transmission array 1 above has a good polarization selection effect on electromagnetic waves in the corresponding frequency band, that is, in the 24-27.5GHz frequency band, it has a good reflection function for X-polarized waves, only changes the path of X-polarized waves without affecting the amplitude and phase characteristics; and has good polarization conversion transmittance for Y-polarized waves, that is, it can convert Y-polarized waves into RHCP waves and has good transmission performance. In the 37-42.5GHz frequency band, the first transmission array 1 has a good reflection function for Y-polarized waves, only changes the path of Y-polarized waves without affecting the amplitude and phase characteristics; and has good polarization conversion transmittance for X-polarized waves, that is, it can convert X-polarized waves into LHCP waves and has good transmission performance. The second transmission array 2 below can perform polarization conversion on linearly polarized waves in the wide frequency band of 24-43GHz, that is, it can convert X-polarized waves into Y-polarized waves or convert Y-polarized waves into X-polarized waves.

[0057] When the antenna is working, the X-polarized wave in the 24-27.5 GHz frequency band emitted by the first port 36 is reflected by the frequency selection layer at the bottom of the first transmission array 1 to the reflection layer of the second transmission array 2 below, converted into a Y-polarized wave and radiated upward, and after passing through the frequency selection layer, reaches the transmission layer at the top, and is converted into a right-hand circularly polarized wave by the third rectangular patch. The high-frequency Y-polarized wave emitted by the second port 37 is reflected by the frequency selection layer at the bottom of the first transmission array 1 to the reflection layer of the second transmission array 2 below, converted into an X-polarized wave and radiated upward, and after passing through the frequency selection layer, reaches the transmission layer at the top, and is converted into a left-hand circularly polarized wave by the circular patch.

[0058] from Fig.10 It can be seen that the bandwidth of the feed source 3 at the first port 36 can cover 24-27.5 GHz (VSWR < 2), and the radiated X-polarized directional radiation beam gain is 10.12-10.86 dBi. The bandwidth of the feed source 3 at the second port 37 can cover 36.5-42.7 GHz (VSWR < 2), and the radiated Y-polarized directional radiation beam gain is 10.92-12.05 dBi.

[0059] from Fig.11a and Fig.11b It can be seen that at 26 GHz, when the first port 36 of the excitation feed source 3 realizes a Y-polarized wave, the cross-polarization isolation is greater than 25 dB, and the 3dB beamwidths of the E plane and the H plane are 38.3° and 43°, respectively, which can meet the index requirements of the reflector array feed source 3. At 40 GHz, when the second port 37 of the excitation feed source 3 realizes an X-polarized wave, the cross-polarization isolation is greater than 25 dB. The 3dB beamwidths of the E plane and the H plane are 42.7° and 55°, respectively, which can meet the index requirements of the reflector array feed source 3.

[0060] from Fig.12a and Figure 12b It can be seen that when the first port 36 is excited and right-hand circularly polarized radiation beams of φ=0° and φ=90° are obtained in the 26 GHz frequency band, the sidelobe level of the beam is less than -12.5 dB, the half-power beamwidth HPBW is 5°, and the cross-polarization isolation is greater than 25 dB. Fig.13a and Fig.13b It can be seen that when the left-hand circularly polarized radiation beams of φ=0° and φ=90° are obtained by exciting the second port in the 37 and 40 GHz frequency bands, the sidelobe level of the beam is less than -13 dB, the HPBW is 5.1°, and the cross-polarization isolation is greater than 25 dB. It has good beam radiation performance in both frequency bands.

[0061] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A dual-frequency circularly polarized folded array antenna, characterized in that: include: A first transmission array comprises a first substrate and a transmission layer on its upper side and a frequency selection layer on its lower side, wherein the transmission layer has M×N first linear-circular polarization conversion units and m×n second linear-circular polarization conversion units; A second transmission array includes a second substrate and a plurality of line-to-line polarization conversion units thereon; a feed source, arranged at the center of the second transmission array, radiating a first polarization signal of a first frequency band and a second polarization signal of a second frequency band to the first transmission array; in The first polarization signal of the first frequency band reaches the frequency selective layer and is reflected to the second transmission array, converted to a second polarization signal and then reflected to the frequency selective layer, and then transmitted to the transmission layer and converted into a circularly polarized signal by the first linear-circular polarization conversion unit; the second polarization signal of the second frequency band reaches the frequency selective layer and is reflected to the second transmission array, converted to the first polarization signal and then reflected to the frequency selective layer, and then transmitted to the transmission layer and converted into a circularly polarized signal by the second linear-circular polarization conversion unit.

2. The dual-frequency circularly polarized folded array antenna according to claim 1, characterized in that: The frequency selection layer includes a plurality of orthogonally arranged first rectangular patches and second rectangular patches, and each of the first rectangular patch and the second rectangular patch is formed with an obtuse angle groove which is consistent with the polarization direction of the respective transmitted signals; Each of the first linear-circular polarization conversion units is connected to one of the first rectangular patches via a first metal via through the first substrate, and each of the second linear-circular polarization conversion units is connected to one of the second rectangular patches via a second metal via through the first substrate.

3. The dual-frequency circularly polarized folded array antenna according to claim 2, characterized in that: The first linear-circular polarization conversion unit is a third rectangular patch having an obtuse-angle groove, and the upper end of the first metal through hole is located at the concave side of the obtuse-angle groove.

4. The dual-frequency circularly polarized folded array antenna according to claim 3, characterized in that: Two opposite corners of the third rectangular patch are cut off by a preset portion; or The three corners of the third rectangular patch are cut off by preset portions; or Preset portions are cut off from the four corners of the third rectangular patch.

5. The dual-frequency circularly polarized folded array antenna according to claim 3, characterized in that: The second linear-circular polarization conversion unit is a circular patch having two symmetrical rectangular grooves, and the upper end of the second metal through hole deviates from the center of the circular patch.

6. The dual-frequency circularly polarized folded array antenna according to claim 2, characterized in that: A metal isolation layer insulated from the metal through hole is also arranged between the transmission layer and the frequency selection layer.

7. The dual-frequency circularly polarized folded array antenna according to claim 1, characterized in that: The line-to-line polarization conversion unit comprises: Cross-shaped patch; Two L-shaped patches are symmetrically arranged on both sides of the cross-shaped patch; wherein The cross-shaped patch and the L-shaped patch are symmetrical along the diagonal line of the line-to-line polarization conversion unit.

8. The dual-frequency circularly polarized folded array antenna according to claim 7, characterized in that: The second transmission array further includes a metal reflection layer disposed on a side of the second substrate away from the first substrate.

9. The dual-frequency circularly polarized folded array antenna according to claim 5, characterized in that: The third rectangular patch is rotated around the first metal through hole relative to the first initial angle. degree, forming a second polarization signal of the first frequency band The circular patch rotates around the second metal through hole relative to the second initial angle. degree, and the first polarization signal of the second frequency band is formed The phase shift value of degrees; in ； ； In the formula i and j The third rectangular patch and circular patch are x axis, y The axis direction number, is the wave number in free space, is the distance from the phase center of the feed to each third rectangular patch, is the direction vector from the central third rectangular patch to other third rectangular patches, is the direction of the main beam of the first frequency band radiated by the antenna, is the distance from the phase center of the feed to each circular patch, is the direction vector from the central circular patch to other circular patches, is the direction of the second frequency band main beam radiated by the antenna, the first initial angle is the second polarization direction, and the second initial angle is the first initial angle rotated 45° counterclockwise.

10. The dual-frequency circularly polarized folded array antenna according to any one of claims 1 to 9, characterized in that: The feed source comprises: A first transmitting structure, radiating a first polarized signal of a first frequency band to the first transmission array, comprising a 2×2 fourth rectangular patch array and a 2×2 first director coupled thereto; The second transmitting structure radiates a second polarized signal of a second frequency band to the first transmission array, and includes a 2×2 fifth rectangular patch array and a 2×2 second director coupled thereto.

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