Dual-Frequency Circularly Polarized Folded Array Antenna

Abstract

The present invention relates to the field of wireless communication technologies, and discloses a dual-band circularly polarized folded array antenna, which includes a first transmission array, a second transmission array, and a feed source. The feed source is disposed at the center of the second transmission array and radiates a first polarization signal of a first frequency band and a second polarization signal of a second frequency band to the first transmission array. Among them, the first polarization signal of the first frequency band reaches the frequency selection layer on the first transmission array and is then reflected to the second transmission array, converted into a second polarization signal and then reflected to the frequency selection layer, and transmitted to the first line-circular polarization conversion unit on the first transmission array to be converted into a circularly polarized signal. The second polarization signal of the second frequency band reaches the frequency selection layer and is then reflected to the second transmission array, converted into a first polarization signal and then reflected to the frequency selection layer, and then transmitted to the transmission layer to be converted into a circularly polarized signal by the second line-circular polarization conversion unit. This antenna can achieve dual-band communication with a smaller size and has a line-circular polarization conversion function.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and specifically, to a dual-band circularly polarized folded array antenna. Background Art

[0002] With the rapid development and wide application of wireless communication technologies, wireless spectrum resources have become increasingly scarce. The demand for high-speed and large-capacity data transmission is constantly increasing, while the millimeter-wave band provides broader spectrum resources. Currently, the millimeter-wave bands selected by the Ministry of Industry and Information Technology are 24.25 - 27.5 GHz and 37 - 42.5 GHz, which can meet the requirements of high-speed data transmission, large-capacity connection, 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 interconnection. In addition, since current communication devices tend to be miniaturized, the structure of the antenna needs to be designed accordingly for miniaturization.

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

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

[0005] To achieve the above object, the present invention provides a dual-band circularly polarized folded array antenna, which includes a first transmission array including a first substrate, a transmission layer on its upper side, and a frequency selection layer on its lower side. The transmission layer has M×N first line-to-circular polarization conversion units and m×n second line-to-circular polarization conversion units; a second transmission array including a second substrate and a plurality of line-to-line polarization conversion units thereon; a feed source disposed 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, converted into a second polarization signal, then reflected to the frequency selection layer, and then transmitted to the transmission layer to be converted into a circularly polarized signal by the first line-to-circular polarization conversion units; the second polarization signal of the second frequency band is reflected to the second transmission array after reaching the frequency selection layer, converted into a first polarization signal, then reflected to the frequency selection layer, and then transmitted to the transmission layer to be converted into a circularly polarized signal by the second line-to-circular polarization conversion units.

[0006] As an embodiment, the frequency selection layer includes a plurality of first rectangular patches and second rectangular patches arranged orthogonally, and obtuse grooves are formed on both the first rectangular patches and the second rectangular patches, with the polarization directions of the signals transmitted by them being consistent; each of the first line-to-circular polarization conversion units is connected to one of the first rectangular patches via a first metal through hole passing through the first substrate, and each of the second line-to-circular polarization conversion units is connected to one of the second rectangular patches via a second metal through hole passing through the first substrate.

[0007] As an embodiment, the first line-to-circular polarization conversion unit is a third rectangular patch with an obtuse groove, and the upper end of the first metal through hole is located on the concave side of the obtuse groove.

[0008] As an embodiment, at least two opposite corners of the third rectangular patch are cut off by a preset part; or three corners of the third rectangular patch are cut off by a preset part; or four corners of the third rectangular patch are cut off by a preset part.

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

[0010] As an embodiment, a metal isolation layer insulating from the metal through holes is further provided between the transmission layer and the frequency selection layer.

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

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

[0013] As an embodiment, the third rectangular patch rotates by degrees relative to the first initial angle about the first metal through-hole to form a degree phase shift value for the second polarization signal in the first frequency band; the circular patch rotates by degrees relative to the second initial angle about the second metal through-hole to form a degree phase shift value for the first polarization signal in the second frequency band; wherein In the formula i and j are the sequence numbers of each third rectangular patch and circular patch in the x axis and y axis directions respectively, 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 main beam of the second frequency band radiated by the antenna, the first initial angle is the second polarization direction, and the second initial angle is the first initial angle rotated counterclockwise by 45°.

[0014] As an embodiment, the feed includes: a first transmitting structure that radiates a first polarization signal in the 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 that radiates a second polarization signal in the second frequency band to the first transmission array, including a 2×2 fifth rectangular patch array and a 2×2 second director coupled thereto. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 and Figure 2 are schematic three-dimensional structural diagrams of a dual-band circularly polarized folded array antenna according to an embodiment of the present invention from two different perspectives.

[0016] Figure 3 Top view of the first substrate from top to bottom in the dual - frequency circularly polarized folded array antenna involved in an embodiment of the present invention.

[0017] Figure 4 is Figure 1 An enlarged view of part A in

[0018] Figure 5 is Figure 2 An enlarged view of part B in

[0019] Figure 6 Partial decomposition 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 structures of the second line - circular polarization conversion unit and the second rectangular patch, and shows part of the structures of the first line - circular polarization conversion unit and the first rectangular patch.

[0020] Figure 7 Structural schematic diagram of the line - linear polarization conversion unit in the dual - frequency circularly polarized folded array antenna involved in an embodiment of the present invention.

[0021] Figure 8 Decomposition schematic diagram of the feed source in the dual - frequency circularly polarized folded array antenna involved in an embodiment of the present invention.

[0022] Figure 9a 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.

[0023] Figure 9b 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 an embodiment of the present invention forms a left - hand circularly polarized wave in the second frequency band.

[0024] Figure 10 Gain diagram of the feed source in the dual - frequency circularly polarized folded array antenna involved in an embodiment of the present invention.

[0025] Figure 11a and Figure 11b are the radiation pattern of the feed source in the dual - frequency circularly polarized folded array antenna involved in an embodiment of the present invention, where Figure 11a is the 26 GHz frequency point, Figure 11b is the 40 GHz frequency point.

[0026] Figure 12a Radiation beam pattern of the right - hand circularly polarized wave obtained at 26 GHz when the dual - frequency circularly polarized folded array antenna involved in an embodiment of the present invention is excited at the first port at φ = 0°.

[0027] Figure 12b In an embodiment of the present invention, the radiation beam pattern of the right-handed circularly polarized wave obtained at 26 GHz when the dual-band circularly polarized folded array antenna excites the first port at φ = 90°.

[0028] Figure 13a In an embodiment of the present invention, the radiation beam pattern of the right-handed circularly polarized wave obtained at 40 GHz when the dual-band circularly polarized folded array antenna excites the second port at φ = 0°.

[0029] Figure 13b In an embodiment of the present invention, the radiation beam pattern of the right-handed circularly polarized wave obtained at 40 GHz when the dual-band circularly polarized folded array antenna excites the second port at φ = 90°. Detailed implementation manners

[0030] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more complete and comprehensive, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0031] In addition, the drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus repeated descriptions thereof will be omitted. It should be noted that in the present disclosure, the terms "comprising", "configured with", and "provided with" are used to mean an open inclusion, and mean that in addition to the listed elements / components / etc., there may be additional elements / components / etc.; the terms "first", "second", etc. are only used as labels and are not limitations on the number or order of their objects; the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are 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 thus cannot be construed as a limitation on the present invention.

[0032] Unless otherwise clearly defined and limited, the terms "installed", "connected", and "coupled" 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 directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In this embodiment, a dual-band circularly polarized folded array antenna is disclosed. Please refer to Figures 1 to 8 , the dual-band 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 and radiates a first polarization signal in a first frequency band and a second polarization signal in a second frequency band to the first transmission array 1.

[0034] The first transmission array 1 includes a first substrate 13, a transmission layer on its upper side and a frequency selective layer on its lower side. Among them, the transmission layer has M×N first line-to-circular polarization conversion units 11 and m×n second line-to-circular polarization conversion units 12. The first line-to-circular polarization conversion unit 11 is used to convert the second polarization signal in the first frequency band into a circular polarization signal, and the second line-to-circular polarization conversion unit 12 is used to convert the first polarization signal in the second frequency band into a circular polarization signal. The frequency selective layer is used to reflect the first polarization signal in the first frequency band and transmit the second polarization signal in the first frequency band; the frequency selective layer is also used to reflect the second polarization signal in the second frequency band and transmit the first polarization signal in the second frequency band.

[0035] 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 in 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, convert the first polarization signal in the first frequency band into the second polarization signal and reflect it onto the first transmission array 1, and convert the second polarization signal in the second frequency band into the first polarization signal and reflect it onto the first transmission array 1.

[0036] When the dual-band circularly polarized folded array antenna is working, the first polarization signal in the first frequency band radiated by the feed source 3 reaches the frequency selective layer and is reflected to the second transmission array 2. The second transmission array 2 performs line-to-line polarization conversion on it, and after being converted into the second polarization signal, it is reflected back to the frequency selective layer. At this time, it can be transmitted through the frequency selective layer to the transmission layer, and the first line-to-circular polarization conversion unit 11 converts it into a circular polarization signal and radiates it outwards; the second polarization signal in the second frequency band radiated by the feed source 3 reaches the frequency selective layer and is reflected to the second transmission array 2. The second transmission array 2 performs line-to-line polarization conversion on it, and after being converted into the first polarization signal, it is reflected back to the frequency selective layer. At this time, it can be transmitted through the frequency selective layer to the transmission layer, and the second line-to-circular polarization conversion unit 12 converts it into a circular polarization signal.

[0037] The dual - frequency circularly polarized folded array antenna can achieve dual - frequency communication, improve the spectrum efficiency, expand the communication capacity, and also has a linear - circular polarization conversion function, enabling multi - channel communication and enhancing the anti - interference ability, and can adapt to complex communication environments. Additionally, the signals in both frequency bands are reflected twice by the frequency - selective layer and the second transmission array 2 and then undergo linear - circular polarization conversion via the transmission layer, which can produce a folding effect, reduce the profile of the antenna, and achieve the miniaturized design of the antenna.

[0038] As an embodiment, as Figure 5 and Figure 6 shown, the frequency - selective layer includes a number of first rectangular patches 16 and second rectangular patches 17 arranged orthogonally. Obtuse - angled slots are formed on both the first rectangular patches 16 and the second rectangular patches 17, and the orientation of the obtuse - angled slots is consistent with the polarization direction of the signals they transmit respectively. That is, the obtuse - angled slot on the first rectangular patch 16 is consistent with the second polarization direction, and the obtuse - angled slot on the second rectangular patch 17 is 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.

[0039] For the frequency - selective layer with this structural form, the first rectangular patches 16 and the second rectangular patches 17 are arranged orthogonally, and the obtuse - angled slots on them face the polarization directions of various transmissions respectively. It can receive and transmit signals with corresponding polarizations in the corresponding frequency bands and reflect signals with the other polarization in that frequency band, having good polarization selectivity. Each of the first rectangular patches 16 can reflect the first - polarization signals in the first frequency band to the second transmission array 2 as much as possible and receive the second - polarization signals in the first frequency band for transmission to the first linear - circular polarization conversion unit 11 of the transmission layer. Each of the second rectangular patches 17 can reflect the second - polarization signals in the second frequency band to the second transmission array 2 as much as possible and receive the first - polarization signals in the second frequency band for transmission to the second linear - circular polarization conversion unit 12 of the transmission layer.

[0040] As an embodiment, as Figure 3 shown, the first linear - circular polarization conversion unit 11 is a third rectangular patch with an obtuse - angled slot. The upper end of the first metal through - hole 14 is located on the concave side of the obtuse - angled slot, thus guiding the current flow direction, forming circular polarization while improving the polarization purity. Further, a preset part 111, such as a triangular area, is cut off at at least two opposite corners of the third rectangular patch, which can further excite circular polarization and also improve the isolation degree from the adjacent second linear - circular polarization conversion unit 12.

[0041] As an embodiment, as Figure 3As shown, the second line - circular polarization conversion unit 12 is a circular patch with two symmetric rectangular grooves. The upper end of the second metal through - hole 15 deviates from the center of the circular patch to excite a circular current, thus having circular polarization characteristics.

[0042] When forming an array with each first line - circular polarization conversion unit 11 and the second line - circular polarization conversion unit 12, rotating the first line - circular polarization conversion unit 11 around the first metal through - hole 14 by different angles can make the first line - circular polarization conversion unit 11 generate different phase - shift values for the electromagnetic waves in the radiated frequency band. Rotating the second line - circular polarization conversion unit 12 around the second metal through - hole 15 by different angles can make the second line - circular polarization conversion unit 12 generate different phase - shift values for the electromagnetic waves in the radiated frequency band. By setting the phase - shift values of each unit, an electromagnetic wave beam with the required shape can be radiated.

[0043] As an embodiment, as Figure 6 shown, a metal isolation layer 18 insulated from the metal through - holes is also provided between the transmission layer and the frequency - selective layer, which improves the isolation degree between the transmission layer and the frequency - selective layer. In addition, it can also improve the reflection effect on the first - polarization signal in the first frequency band and the second - polarization signal in the second frequency band. For example, by arranging two first substrates 13 between the transmission layer and the frequency - selective layer and setting the metal isolation layer 18 between the two first substrates 13, the fixation of the metal isolation layer 18 can be achieved.

[0044] As an embodiment, the third rectangular patch rotates around the first metal through - hole 14 by degrees relative to the first initial angle, forming a - degree phase - shift value for the second - polarization signal in the first frequency band; the circular patch rotates around the second metal through - hole 15 by degrees relative to the second initial angle, forming a - degree phase - shift value for the first - polarization signal in the second frequency band; where In the formula i and j are the sequence numbers of each third rectangular patch and circular patch in the x axis and y axis directions respectively, is the wave number in free space, is the distance from the phase center of the feed 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 the feed 3 to each circular patch, is the direction vector from the central circular patch to other circular patches, is the direction of the main beam of the second frequency band of the antenna radiation, and the first initial angle is Figure 3 the positive direction of the Y-axis in Figure 3 , that is, the second polarization direction, and the second initial angle is the direction obtained by rotating the first initial angle counterclockwise by 45°.

[0045] According to this formula, when designing the antenna, for the electromagnetic wave beam shapes and directions required for each frequency band, the phase shift values that each third rectangular patch and circular patch need to generate for the electromagnetic waves of their respective frequency bands can be inversely calculated, and then the rotation angles of each third rectangular patch and circular patch can be calculated.

[0046] As an implementation manner, the line-line polarization conversion unit 21 in the second transmission array 2 includes a cross-shaped patch and two L-shaped patches. As Figure 7 shown, the cross-shaped patch is arranged in the center, 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 patches are symmetric about the diagonal of the line-line polarization conversion unit 21. When working, these two patch structures can excite co-directional currents, obtain broadband stable line polarization wave conversion characteristics, and have no sudden change effect on the reflection phase, realizing good line-line polarization amplitude-phase conversion characteristics within a broadband (20 - 45 GHz). In addition, the two patches are symmetrically arranged along the diagonal, which can support both X-Y line polarization wave conversion and Y-X line polarization wave conversion at the same time, making the line polarization conversion reciprocal, so that the horizontal and vertical components of the current are equal, with reciprocal symmetry, and finally meeting the requirements of different line polarization wave conversions within a broadband. Further, the second transmission array 2 further includes a metal reflection layer provided on the side of the second substrate 22 away from the first substrate 13, which can further improve the reflection effect on the electromagnetic waves within the working frequency band.

[0047] As an implementation manner, the feed source 3 includes a first emission structure and a second emission structure. As Figure 8 shown, the first emission structure is used to radiate the first polarization signal of the first frequency band to the first transmission array 1, and includes a 2×2 fourth rectangular patch array 31 and a 2×2 first director 32 coupled thereto; the second emission structure is used to radiate the second polarization signal of the second frequency band to the first transmission array 1, and includes 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 by microstrip lines and connected to the first port 36 to feed in the first polarization signal of the first frequency band. The fourth rectangular patch array 31 radiates this signal to the coupled first director 32 to achieve stable high-gain directional radiation towards the first transmission array 1. The four rectangular patches of the fifth rectangular patch array 33 are connected by microstrip lines and connected to the second port 37 to feed in the second polarization signal of the second frequency band. The fifth rectangular patch array 33 radiates this signal to the coupled second director 34 to achieve stable high-gain directional radiation towards the first transmission array 1.

[0048] Furthermore, each director includes a main patch and peripheral parasitic patches. In the first director 32 and the second director 34 at the top, a U-shaped slot is provided in each main patch in the same polarization direction as its corresponding polarization direction, so as to guide the current direction, improve the cross-polarization isolation of the two emission structures, and achieve better polarization conversion performance when feeding the dual-band circularly polarized folded array antenna. When the feed 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 slot 35 is introduced at the center connection line between the two, changing the bottom current direction and canceling part of the coupled current, so as to achieve the purpose of improving the port isolation.

[0049] 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. A total of two layers of first substrates 13 are provided in the first transmission array 1, both using 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 sides of the two first substrates 13 are transmission layers, the lower sides are frequency selection layers, and the middle is a metal isolation layer 18. M×N is 19×19, and m×n is 20×20.

[0050] The first line-to-circular polarization conversion unit 11 in the transmission layer operates at 24.25 - 27.5 GHz and is a third rectangular patch with an obtuse-angle slot. At the first initial angle, the direction of the obtuse-angle slot is the same as the Y polarization direction. The second line-to-circular polarization conversion unit 12 in the transmission layer operates at 37 - 42.5 GHz and is a circular patch with symmetric rectangular slots. The frequency selection layer includes a number of first rectangular patches 16 and second rectangular patches 17 arranged orthogonally. An obtuse-angle slot is formed on the first rectangular patch 16 in the same direction as the Y polarization direction, and an obtuse-angle slot is formed on the second rectangular patch 17 in the same direction as the X polarization direction. The first metal through-hole 14 penetrates through the two first substrates 13, is connected to the first rectangular patch 16 at the lower end, is connected to the third rectangular patch at the upper end, and is insulated from the metal isolation layer 18 in the middle. The second metal through-hole 15 penetrates through the two first substrates 13, is connected to the second rectangular patch 17 at the lower end, is connected to the circular patch at the upper end, and is insulated from the metal isolation layer 18 in the middle.

[0051] The third rectangular patch and the circular patch in the transmission layer are respectively rotated by a preset angle around the first metal through-hole 14 and the second metal through-hole 15 according to the phase shift values required by each. The first rectangular patches 16 and the second rectangular patches 17 in the frequency selection layer are arranged orthogonally and are not rotated, and are used to receive electromagnetic waves of the corresponding polarization and reflect electromagnetic waves of the other polarization, having good polarization selectivity.

[0052] The line-line polarization conversion unit 21 involved in the second transmission array 2 in this embodiment is to achieve a folded array, achieving the effect of reducing the profile. It can convert the signals in two frequency bands of 24.25 - 27.5 GHz and 37 - 42.5 GHz from X polarization to Y polarization, and convert Y polarization signals to X polarization signals. The second transmission array 2 selects an F4B second substrate 22 with a thickness of 1 mm, a dielectric constant of 2.65, and a loss tangent of 0.003. The line-line polarization conversion unit 21 introduces a cross-shaped patch and two L-shaped patches. When working, the two structures can excite co-directional currents, obtaining broadband and stable line polarization wave conversion characteristics, and having no sudden change effect on the reflection phase, realizing good line-line polarization amplitude-phase conversion characteristics within a broadband (20 - 45 GHz). In addition, in order to support both X-Y line polarization wave conversion and Y-X line polarization wave conversion simultaneously, making the line polarization conversion reciprocal, the line-line polarization conversion unit needs to be designed to be symmetric along the diagonal, so that the horizontal and vertical components of the current are equal, having reciprocal symmetry, and finally meeting the requirements of different line polarization wave conversions within a broadband.

[0053] In this embodiment, a 2×2 stacked patch MIMO array antenna is used as the feed source 3, with a total of two ports. The first port 36 is responsible for the signal radiation in the 24.25 - 27.5 GHz frequency band, and the second port 37 is responsible for the radiation in the 37 - 42.5 GHz frequency band. This feed source 3 can emit X polarization waves with high polarization purity in the 24 - 27.5 GHz frequency band and Y polarization waves with high polarization purity in the 37 - 42.5 GHz 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 slot in the corresponding polarization direction is introduced in the top director to guide the current direction and improve the cross-polarization isolation degree, so as to achieve better polarization conversion performance when feeding the millimeter-wave folded array. When forming the MIMO array, in order to improve the port isolation degree and reduce the mutual interference between the two patch arrays, a C-shaped slot 35 is introduced at the center connection line between the two to change the bottom current direction and cancel part of the coupled current, thereby achieving the purpose of improving the port isolation degree.

[0054] Please combine Figure 1 and Figure 2, the feed 3 is placed in the middle of the second transmission array 2 below. The upper first transmission array 1 has a good polarization selection effect on electromagnetic waves in the corresponding frequency band, that is, in the 24 - 27.5 GHz frequency band, it has a good reflection function for X - polarized waves, only changing the path of the X - polarized waves without affecting the amplitude - phase characteristics; while for Y - polarized waves, it has good polarization - conversion transmissivity, that is, it can convert Y - polarized waves into RHCP waves and has good transmission performance. In the 37 - 42.5 GHz frequency band, the first transmission array 1 has a good reflection function for Y - polarized waves, only changing the path of the Y - polarized waves without affecting the amplitude - phase characteristics; while for X - polarized waves, it has good polarization - conversion transmissivity, that is, it can convert X - polarized waves into LHCP waves and has good transmission performance. The lower second transmission array 2 can perform polarization conversion on linearly polarized waves in the wide frequency band of 24 - 43 GHz, that is, it can convert X - polarized waves into Y - polarized waves or convert Y - polarized waves into X - polarized waves.

[0055] When the antenna operates, the X - polarized waves in the 24 - 27.5 GHz frequency band emitted from the first port 36 are reflected by the frequency - selective layer at the bottom of the first transmission array 1 to the reflection layer of the second transmission array 2 below, converted into Y - polarized waves and radiated upward. After passing through the frequency - selective layer, they reach the transmission layer at the top and are converted into right - hand circularly polarized waves by the third rectangular patch. The high - frequency Y - polarized waves emitted from the second port 37 are reflected by the frequency - selective layer at the bottom of the first transmission array 1 to the reflection layer of the second transmission array 2 below, converted into X - polarized waves and radiated upward. After passing through the frequency - selective layer, they reach the transmission layer at the top and are converted into left - hand circularly polarized waves by the circular patch.

[0056] From Figure 10 It can be seen that the bandwidth of the feed 3 at the first port 36 can cover 24 - 27.5 GHz (VSWR < 2), and the gain of the X - polarized directional radiation beam radiated is 10.12 - 10.86 dBi. The bandwidth of the feed 3 at the second port 37 can cover 36.5 - 42.7 GHz (VSWR < 2), and the gain of the Y - polarized directional radiation beam radiated is 10.92 - 12.05 dBi.

[0057] From Figure 11a and Figure 11b It can be seen that at the 26 GHz frequency point, when the Y - polarized waves are realized by exciting the first port 36 of the feed 3, the cross - polarization isolation is > 25 dB, and the 3 - dB beam widths in the E - plane and H - plane are 38.3° and 43° respectively, which can meet the index requirements of the reflector array feed 3. At the 40 GHz frequency point, when the X - polarized waves are realized by exciting the second port 37 of the feed 3, the cross - polarization isolation is > 25 dB. The 3 - dB beam widths in the E - plane and H - plane are 42.7° and 55° respectively, which can meet the index requirements of the reflector array feed 3.

[0058] FromFigure 12a and Figure 12b It can be seen that when the first port 36 is excited to obtain right-handed circularly polarized radiation beams with φ = 0° and φ = 90° in the 26 GHz frequency band, the sidelobe level of the beam is < -12.5 dB, the half-power beamwidth HPBW is 5°, and the cross-polarization isolation is > 25 dB. From Figure 13a and Figure 13b It can be seen that when the second port 37 is excited to obtain left-handed circularly polarized radiation beams with φ = 0° and φ = 90° in the 40 GHz frequency band, the sidelobe level of the beam is < -13 dB, the HPBW is 5.1°, and the cross-polarization isolation is > 25 dB. Good beam radiation performance is achieved in both frequency bands.

[0059] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

Claims

1. A dual-frequency circularly polarized folded array antenna, characterized in that: include: 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; the frequency selection layer comprises 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 in the same direction as 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 through hole passing 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 through hole passing through the first substrate; 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 on the concave side of the obtuse-angle groove; 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; A second transmission array includes a second substrate and a plurality of line-to-line polarization conversion units thereon; A feed source is arranged at the center of the second transmission array, and radiates a first polarization signal of a first frequency band and a second polarization signal of a second frequency band to the first transmission array; the feed source comprises: a first transmitting structure, radiating a first polarization 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; a second transmitting structure, radiating a second polarization signal of a second frequency band to the first transmission array, comprising a 2×2 fifth rectangular patch array and a 2×2 second director coupled thereto; wherein 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: 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.

3. The dual-frequency circularly polarized folded array antenna according to claim 1, 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.

4. 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.

5. The dual-frequency circularly polarized folded array antenna according to claim 4, 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.

6. The dual-frequency circularly polarized folded array antenna according to claim 1, 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 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.

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