Filtering antenna array based on 3*4 Butler matrix

Abstract

The invention provides a filtering antenna array based on a 3 * 4 Butler matrix. The filtering antenna array comprises a 3 * 4 Butler matrix network and a four-unit filtering antenna array. When the three input ports of the 3 * 4 Butler matrix are respectively excited, equal-amplitude output signals can be obtained at the four output ports, and the phase differences between the adjacent ports are respectively 0 degree,-90 degrees and + 90 degrees. When an antenna array arranged in a 1 * 4 form is excited through a Butler matrix network, three high-gain wave beams with different directions and filtering characteristics can be generated; when an antenna array arranged in a 2 * 2 form is excited, three orbital angular momentum wave beams with different modes and filtering characteristics can be generated. The invention realizes multifunctional beam output, has the advantages of compact structure, easy integration, good filtering performance and the like, and has important application prospects in the fields of millimeter wave communication and the like.

Description

Technical Field

[0001] This invention relates to the field of electronic devices for wireless communication systems, specifically to a filtered multi-beam or multi-mode orbital angular momentum antenna array based on a 3×4 Butler matrix. Background Technology

[0002] Filtered multi-beam antenna arrays offer advantages such as high gain and wide beam coverage, while filtered multimode orbital angular momentum antenna arrays boast perfect orthogonality of modes and high spectral efficiency. Both are planar structures, easy to fabricate, and readily integrated into RF systems, thus attracting widespread research and attention. However, current multi-beam antenna arrays based on Butler matrix feed networks still suffer from the following problems: difficulty in generating radiation beams pointing towards the side-fire direction, lack of filtering characteristics in the radiated beams, and difficulty in directly applying this structure to generate multimode orbital angular momentum beams. Therefore, designing a multi-beam antenna array or multimode orbital angular momentum antenna array capable of achieving side-fire radiation while possessing filtering characteristics is of great significance.

[0003] Existing literature shows that conventional Butler matrix networks typically employ an even number of input and output ports, preventing them from generating radiation beams oriented towards the side-fire direction. To address this issue, a 2019 study proposed a 3×4 Butler matrix network based on a microstrip coupled-line structure, using an odd number of input and even number of output ports, achieving a radiation beam in the side-fire direction. However, this approach still suffers from problems such as large size, numerous components, and the cable connection between the network and the antenna hinders system integration. In 2021, a 5×8 Butler matrix network was implemented based on a substrate-integrated waveguide structure, also capable of generating a radiation beam in the side-fire direction. However, its overall size is large, and the input and output ports are located on opposite sides of the network, forcing the radiating antenna to be concentrated on one side of the structure, posing a risk of pattern distortion. Furthermore, leveraging the characteristic that Butler matrix networks can generate specific phase differences between adjacent output ports when excited at different input ports, it could theoretically be used to generate multimode orbital angular momentum beams. However, since the orbital angular momentum beam imposes strict constraints on the feed phase distribution between array elements, it usually needs to be achieved through multi-level Butler matrix network cascading, resulting in a complex system structure and large size. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a filtered antenna array based on a 3×4 Butler matrix, which can meet the antenna array requirements of systems such as millimeter-wave communication. This antenna array, through the cascading of a novel 3×4 Butler matrix network and a filtered antenna array, can generate multi-beam or multi-mode orbital angular momentum beams with filtering characteristics. The technical solution provided by this invention is as follows:

[0005] A filtering antenna array based on a 3×4 Butler matrix includes a 3×4 Butler matrix network (1) and four filtering antenna elements (2). The 3×4 Butler matrix network (1) is connected to the input ports of the four filtering antenna elements (2). The four filtering antenna elements (2) form a 1×4 filtering antenna array (3) or a 2×2 filtering antenna array (4). A filtering multi-beam antenna array is formed by cascading the 1×4 filtering antenna array (3) through the 3×4 Butler matrix network (1), or a filtering multi-mode orbital angular momentum antenna array is formed by cascading the 2×2 filtering antenna array (4) through the 3×4 Butler matrix network (1).

[0006] The filtering antenna unit (2) includes four substrate layers and five metal layers. The four substrate layers are, from bottom to top, a first substrate layer (2a), a second substrate layer (2b), a third substrate layer (2c), and a fourth substrate layer (2d). There is a first adhesive layer (1e) between the first substrate layer (2a) and the second substrate layer (2b). The five metal layers are, from bottom to top, a first metal layer (2f), a second metal layer (2g), a third metal layer (2h), a fourth metal layer (2i), and a fifth metal layer (2j). A first slot (2k) is etched on the third metal layer (2h). The first metal layer (2f) and the third metal layer (2h) are connected by a first metal post (2m), and the third metal layer (2h) and the fourth metal layer (2i) are connected by a second metal post (2n).

[0007] Preferably, the 3×4 Butler matrix network (1) has three input ports, namely input port 1, input port 2, and input port 3, and four output ports, namely output port 1, output port 2, output port 3, and output port 4;

[0008] The three input ports of the 3×4 Butler matrix network (1) are distributed on the periphery of the network, and the four output ports are distributed at the center of the network.

[0009] Specifically, when the excitation input port is 1, the input energy is equally distributed to the four output ports, and the phase difference between adjacent output ports is 0°; when the excitation input port is 2, the input energy is equally distributed to the four output ports, and the phase difference between adjacent output ports is -90°; when the excitation input port is 3, the input energy is equally distributed to the four output ports, and the phase difference between adjacent output ports is +90°.

[0010] Preferably, the 3×4 Butler matrix network (1) includes a power divider (11), a cross coupler (12), a 90° coupler (13), and two 180° couplers (14).

[0011] Preferably, the power divider (11), cross coupler (12), 90° coupler (13), and 180° coupler (14) are one of the following structures: microstrip line, stripline, coplanar waveguide, substrate integrated waveguide, substrate integrated coaxial line, etc.

[0012] Preferably, the 3×4 Butler matrix network (1) includes two substrate layers and three metal layers. The two substrate layers are a Butler matrix first substrate layer (1a) and a Butler matrix second substrate layer (1b) arranged from bottom to top. There is a Butler matrix first adhesive layer (1c) between the Butler matrix first substrate layer (1a) and the Butler matrix second substrate layer (1b). The three metal layers are a Butler matrix first metal layer (1d), a Butler matrix second metal layer (1e), and a Butler matrix third metal layer (1f) arranged from bottom to top. The Butler matrix first metal layer (1d) and the Butler matrix third metal layer (1f) are connected by a Butler matrix first metal pillar (1g).

[0013] Preferably, the filter antenna unit (2) generates four radiation nulls by loading parasitic structures, and the frequency corresponding to each radiation null is independently adjustable. Among them, radiation null 1 is caused by the loaded second metal pillar (2n) of the filter antenna; radiation null 2 ​​is caused by the rectangular metal ring structure loaded on the fifth metal layer (2j) of the filter antenna unit; radiation null 3 is caused by the cavity structure formed by the first metal pillar (2m) of the filter antenna; and radiation null 4 is caused by the stacked structure of the fourth metal layer (2i) and the fifth metal layer (2j) of the filter antenna.

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0015] (1) The 3×4 Butler matrix network proposed in this invention consists of only five devices. By exciting the three input ports respectively, it can achieve equal amplitude output at the four output ports, and there is a phase difference of 0°, -90° and +90° between adjacent output ports. It has the advantages of simple topology and easy implementation.

[0016] (2) The 3×4 Butler matrix network proposed in this invention has its input ports located on the periphery of the network, which facilitates connection with external circuits; the output ports are concentrated in the center of the network, which facilitates direct connection with the radiating units, avoiding pattern distortion caused by the radiating units being located at the edge of the structure, and improving radiation performance and integration convenience.

[0017] (3) The filter antenna unit proposed in this invention introduces four radiation nulls by loading parasitic structures on the radiator, and the frequency corresponding to each radiation null can be adjusted independently, which has the characteristics of compact structure, flexible design and good filtering performance.

[0018] (4) The antenna array proposed in this invention, which consists of a 3×4 Butler matrix network and a filter antenna element, can flexibly generate two working modes depending on the antenna array arrangement: when the array is arranged in a 1×4 form, it can generate a filtered multi-beam with side-firing radiation capability; when the array is arranged in a 2×2 form, it can generate a multi-mode orbital angular momentum beam with filtering characteristics, which greatly improves the functional integration and application adaptability of the antenna system. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 This is a top view of the 3×4 Butler matrix network proposed in this invention;

[0021] Figure 2 This is a schematic diagram of the stacked structure of a 3×4 Butler matrix network;

[0022] Among them, 11-power divider, 12-cross coupler, 13-90° coupler, 14-180° coupler;

[0023] 1a - Butler matrix first substrate layer, 1b - Butler matrix second substrate layer, 1c - Butler matrix first adhesive layer, 1d - Butler matrix first metal layer, 1e - Butler matrix second metal layer, 1f - Butler matrix third metal layer, 1g - Butler matrix first metal pillar;

[0024] Figure 3 The S-parameters and phase characteristic curves of the 3×4 Butler matrix network are given. Figure 3 a corresponds to the reflection coefficient of input port 1, the coupling coefficient between input ports, and the transmission coefficient to each output port; Figure 3 b corresponds to the reflection coefficient of input port 2, the coupling coefficient between input ports, and the transmission coefficient to each output port; Figure 3 c corresponds to the reflection coefficient of input port 3, the coupling coefficient between input ports, and the transmission coefficient to each output port; Figure 3 d corresponds to the phase difference between adjacent output ports when the three input ports are excited respectively;

[0025] Figure 4 This is a three-dimensional schematic diagram of the filter antenna unit proposed in this invention;

[0026] Figure 5 This is a top view of each metal layer of the filter antenna element;

[0027] Among them, 2a-first substrate layer of filter antenna, 2b-second substrate layer of filter antenna, 2c-third substrate layer of filter antenna, 2d-fourth substrate layer of filter antenna, and 2e-first adhesive layer of filter antenna;

[0028] 2f - First metal layer of filter antenna, 2g - Second metal layer of filter antenna, 2h - Third metal layer of filter antenna, 2i - Fourth metal layer of filter antenna, 2j - Fifth metal layer of filter antenna, 2k - First slot of filter antenna, 2m - First metal post of filter antenna, 2n - Second metal post of filter antenna;

[0029] Figure 6 The reflection coefficient and radiation performance curves of the filtered antenna element are given. Figure 6 'a' represents the curve of the reflection coefficient of the corresponding filter antenna element as a function of frequency. Figure 6 b corresponds to the curve showing the actual gain of the filter antenna element in the side-fire direction as a function of frequency. Figure 6 c corresponds to the main polarization and cross-polarization pattern of the E-plane of the filter antenna element at the 30GHz frequency point. Figure 6 d corresponds to the main polarization and cross-polarization pattern of the H-plane of the filter antenna element at a frequency of 30 GHz;

[0030] Figure 7 This is a top view of the filtered multibeam antenna array formed by cascading the 3×4 Butler matrix network and the 1×4 filtered antenna array proposed in this invention.

[0031] Figure 8 The S-parameters and radiation performance curves of the filtered multi-beam antenna array are presented. Figure 8 a corresponds to the reflection coefficients of the three input ports of the filtered multibeam antenna array and the coupling coefficients between them. Figure 8 b corresponds to the main polarization and cross-polarization patterns of the H-plane at 30 GHz when the three input ports of the filtered multi-beam antenna array are excited respectively. Figure 8 c corresponds to the curve of the actual gain in the main radiation direction as a function of frequency when the three input ports of the filtered multibeam antenna array are excited respectively;

[0032] Figure 9 This is a top view of the filtered multimode orbital angular momentum antenna array formed by cascading the 3×4 Butler matrix network and the 2×2 filtered antenna array proposed in this invention.

[0033] Figure 10 The S-parameters and radiation performance curves of the filtered multimode orbital angular momentum beam antenna array are presented. Figure 10a corresponds to the reflection coefficients and coupling coefficients between the three input ports of the filtered multimode orbital angular momentum beam antenna array. Figure 10 b corresponds to the main polarization and cross-polarization pattern of the H-plane at the 30 GHz frequency band when the three input ports of the filtered multimode orbital angular momentum beam antenna array are excited respectively. Figure 10 c represents the curve of the actual gain in the maximum radiation direction as a function of frequency when the three input ports of the corresponding filtered multibeam antenna array are excited respectively. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To make the above-mentioned objectives, features and effects of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1: See Figure 1 , Figure 4 , Figure 7 and Figure 9 As shown, this embodiment proposes a filtered multi-beam or multi-mode orbital angular momentum antenna array based on a 3×4 Butler matrix, including a 3×4 Butler matrix network 1, filtered antenna elements 2, a 1×4 filtered antenna array 3 composed of four filtered antenna elements 2, and a 2×2 filtered antenna array 4 composed of four filtered antenna elements 2. In this example, the 3×4 Butler matrix network 1 and the 1×4 filtered antenna array 3 are cascaded to realize a filtered multi-beam antenna array, and the 3×4 Butler matrix network 1 and the 2×2 filtered antenna array 4 are cascaded to realize a filtered multi-mode orbital angular momentum antenna array.

[0037] like Figure 1 As shown, the 3×4 Butler matrix network 1 contains three input ports, namely input port 1, input port 2, and input port 3, and four output ports, namely output port 1, output port 2, output port 3, and output port 4.

[0038] The 3×4 Butler matrix network 1 also includes a power divider 11, a cross coupler 12, a 90° coupler 13, and two 180° couplers 14. The power divider 11, cross coupler 12, 90° coupler 13, and 180° coupler 14 are one of the following structures: microstrip line, stripline, coplanar waveguide, substrate integrated waveguide, substrate integrated coaxial line, etc.

[0039] like Figure 2 As shown, the 3×4 Butler matrix network 1 includes two substrate layers and three metal layers. The two substrate layers are respectively configured as a first Butler matrix substrate layer 1a and a second Butler matrix substrate layer 1b from bottom to top. There is a first Butler matrix adhesive layer 1c between the first Butler matrix substrate layer 1a and the second Butler matrix substrate layer 1b. The three metal layers are respectively configured as a first Butler matrix metal layer 1d, a second Butler matrix metal layer 1e, and a third Butler matrix metal layer 1f from bottom to top. The first Butler matrix metal layer 1d and the third Butler matrix metal layer 1f are connected by a first Butler matrix metal pillar 1g.

[0040] Figure 3 a gives the reflection coefficient (S11), the coupling coefficient between input port 1 and input port 2 (S21), the coupling coefficient between input port 1 and input port 3 (S31), and the transmission coefficients between input port 1 and the four output ports (S41, S51, S61, S71) when input port 1 of the 3×4 Butler matrix network 1 is excited. Figure 3 b gives the reflection coefficient (S22), the coupling coefficient between input port 2 and input port 1 (S12), the coupling coefficient between input port 2 and input port 3 (S32), and the transmission coefficients between input port 2 and the four output ports (S42, S52, S62, S72) when input port 2 of the 3×4 Butler matrix network 1 is excited. Figure 3 c gives the reflection coefficient (S33), the coupling coefficient between input port 3 and input port 1 (S13), the coupling coefficient between input port 2 and input port 3 (S23), and the transmission coefficients between input port 3 and the four output ports (S43, S53, S63, S73) when input port 3 of the 3×4 Butler matrix network 1 is excited. Figure 3 d gives the phase difference between adjacent output ports when input ports 1, 2, and 3 of the 3×4 Butler matrix network 1 are excited respectively.

[0041] from Figure 3 As can be seen from a, 3b, and 3c, within the 28-32GHz operating bandwidth, the reflection coefficient amplitude of all input ports is less than -10dB, the coupling coefficient amplitude between ports is less than -20dB, and the transmission coefficient amplitude between input and output ports remains around -7.5dB, indicating good output amplitude consistency. Figure 3 As can be seen from d, within the operating bandwidth, when input port 1 is excited, the phase difference between adjacent output ports is 0°; when input port 2 is excited, the phase difference between adjacent output ports is +90°; and when input port 3 is excited, the phase difference between adjacent output ports is -90°.

[0042] like Figure 4 As shown, the filter antenna unit 2 includes four substrate layers and five metal layers. The four substrate layers are respectively configured as a first substrate layer 2a, a second substrate layer 2b, a third substrate layer 2c, and a fourth substrate layer 2d from bottom to top. A first adhesive layer 2e is provided between the first substrate layer 2a and the second substrate layer 2b. The five metal layers are respectively configured as a first metal layer 2f, a second metal layer 2g, a third metal layer 2h, a fourth metal layer 2i, and a fifth metal layer 2j from bottom to top. A first slot 2k is etched on the third metal layer 2h. The first metal layer 2f and the third metal layer 2h are connected by a first metal post 2m. The third metal layer 2h and the fourth metal layer 2i are connected by a second metal post 2n.

[0043] Figure 5 A top view of the five metal layers of the filter antenna element 2 is given, wherein the top view of the first metal layer 2f of the filter antenna is shown below. Figure 5 As shown in Figure a, the top view of the second metal layer 2g of the filter antenna is as follows: Figure 5 As shown in b, the top view of the third metal layer 2h of the filter antenna is as follows. Figure 5 As shown in Figure c, the top view of the fourth metal layer 2i of the filter antenna is as follows: Figure 5 As shown in Figure d, the top view of the fifth metal layer 2j of the filter antenna is as follows: Figure 5 As shown in e.

[0044] like Figure 4 and Figure 5As shown, in this example, the filter antenna element 2 adopts a stripline slot-coupled stacked radiating patch structure, and multiple radiation nulls are introduced by loading parasitic structures on the radiator, thereby achieving filtering characteristics. The filter antenna element 2 is fed by a stripline, and its closed structure helps ensure stable operation in complex electromagnetic environments. The energy on the stripline is coupled to the stacked radiating patch through the first slot of the filter antenna etched on the third metal layer 2h, thereby exciting the radiating patch to generate radiation. The radiator of the filter antenna element 2 is selected as a rectangular stacked patch, which can generate two adjacent resonant points to extend the operating bandwidth. The parasitic structures loaded on the filter antenna element 2 generate two radiation nulls in the lower and upper sidebands of the operating frequency band, respectively, thus achieving filtering characteristics in the frequency domain. The radiation null 1 of filter antenna element 2 is located at 19 GHz, caused by the second metal pillar 2n of the filter antenna; the radiation null 2 ​​of filter antenna element 2 is located at 22.6 GHz, caused by the rectangular metal ring structure loaded on the fifth metal layer of the filter antenna element; the radiation null 3 of filter antenna element 2 is located at 35.2 GHz, caused by the cavity structure enclosed by the first metal pillar 2m of the filter antenna; the radiation null 4 of filter antenna element 2 is located at 38 GHz, caused by the stacked structure of the fourth metal layer 2i and the fifth metal layer 2j of the filter antenna. The frequencies of the four radiation nulls generated by filter antenna element 2 can be independently adjusted by adjusting the dimensions of the antenna structure.

[0045] Figure 6 The reflection coefficient and radiation performance curves of filter antenna element 2 are given. From Figure 6 Figure a shows the curve of the reflection coefficient amplitude of the filter antenna element 2 as a function of frequency. It can be seen that within the frequency range of 27.8–32.6 GHz, the reflection coefficient amplitude is below -10 dB, exhibiting a wide operating bandwidth. Figure 6 The curve showing the actual gain of the filter antenna element 2 in the side-fire direction as a function of frequency in Figure b shows that within the operating bandwidth, the actual gain in the side-fire direction remains at around 7 dBi, indicating good radiation performance. Furthermore, there are two radiation nulls in the lower sideband of the operating bandwidth, namely radiation null 1 and radiation null 2, and two radiation nulls in the upper sideband of the operating bandwidth, namely radiation null 3 and radiation null 4. Figure 6 c and 6d show the main polarization and cross-polarization patterns of the E-plane and H-plane of the filtered antenna element at 30 GHz, respectively. It can be seen that the cross-polarization level is low.

[0046] like Figure 7As shown, a 3×4 Butler matrix network 1 is cascaded with a 1×4 filter antenna array 3 to form a filtered multi-beam antenna array. During the cascading process, the four output ports of the 3×4 Butler matrix network 1 are respectively connected to the input ports of the four filter antenna elements 2 in the 1×4 filter antenna array 3.

[0047] Figure 8 The S-parameters and radiation performance curves of the filtered multi-beam antenna array are presented. From... Figure 8 As shown in Figure a, the reflection coefficients of input ports 1, 2, and 3, and the coupling coefficients between them, indicate that within the frequency range of 27.5-32.5 GHz, the amplitude of the reflection coefficients is below -10 dB, while the coupling coefficients between the ports are generally below -20 dB. Figure 8 As shown in the radiation pattern (b), when input port 1 is excited, the generated beam points towards 0°; when input port 2 is excited, the generated beam points towards 28°; and when input port 3 is excited, the generated beam points towards −28°. Figure 8 As shown in curve c, the actual gain in the maximum beam direction varies with frequency. It can be seen that within the operating bandwidth, the actual gain remains around 11.5 dBi. There are multiple radiation zeros in the lower and upper sidebands of the operating frequency band, thus achieving filtering characteristics.

[0048] like Figure 9 As shown, a 3×4 Butler matrix network 1 is cascaded with a 2×2 filter antenna array 4 to form a filtered multimode orbital angular momentum antenna array. During the cascading process, the four output ports of the 3×4 Butler matrix network 1 are respectively connected to the input ports of the four filter antenna elements 2 in the 2×2 filter antenna array 4.

[0049] Figure 10 The S-parameters and radiation performance curves of a filtered multimode orbital angular momentum antenna array are presented. From... Figure 10 As shown in Figure a, the reflection coefficients of input ports 1, 2, and 3, and the coupling coefficients between them, indicate that within the frequency range of 29-32.5 GHz, the amplitude of the reflection coefficients is below -10 dB, and the coupling coefficients between the ports are generally below -20 dB. Figure 10 As shown in the radiation pattern (b), when input port 1 is excited, a beam with an orbital angular momentum mode of 0 is generated; when input port 2 is excited, a beam with an orbital angular momentum mode of -1 is generated; and when input port 3 is excited, a beam with an orbital angular momentum mode of +1 is generated. Figure 10 As shown in curve c, the actual gain in the maximum beam direction varies with frequency. It can be seen that there are multiple radiation zeros in the lower and upper sidebands of the operating frequency band, realizing filtering characteristics in the frequency domain.

[0050] In summary, this invention provides a filtered multi-beam or multi-mode orbital angular momentum antenna array based on a 3×4 Butler matrix, which has advantages such as low profile and easy integration. It can provide multi-beam and multi-mode orbital angular momentum beam functions with filtering characteristics, and has important application prospects in millimeter-wave mobile communication and other fields.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A filtered antenna array based on a 3×4 Butler matrix, characterized in that, It includes a 3×4 Butler matrix network (1) and four filter antenna elements (2). The 3×4 Butler matrix network (1) is connected to the input ports of the four filter antenna elements (2). The four filter antenna elements (2) form a 1×4 filter antenna array (3) or a 2×2 filter antenna array (4). The 1×4 filter antenna array (3) is cascaded through the 3×4 Butler matrix network (1) to form a filter multi-beam antenna array, or the 2×2 filter antenna array (4) is cascaded through the 3×4 Butler matrix network (1) to form a filter multi-mode orbital angular momentum antenna array. The filtering antenna unit (2) includes four substrate layers and five metal layers. The four substrate layers are, from bottom to top, a first substrate layer (2a), a second substrate layer (2b), a third substrate layer (2c), and a fourth substrate layer (2d). There is a first adhesive layer (1e) between the first substrate layer (2a) and the second substrate layer (2b). The five metal layers are, from bottom to top, a first metal layer (2f), a second metal layer (2g), a third metal layer (2h), a fourth metal layer (2i), and a fifth metal layer (2j). A first slot (2k) is etched on the third metal layer (2h). The first metal layer (2f) and the third metal layer (2h) are connected by a first metal post (2m), and the third metal layer (2h) and the fourth metal layer (2i) are connected by a second metal post (2n).

2. The filtered antenna array based on a 3×4 Butler matrix according to claim 1, characterized in that, The 3×4 Butler matrix network (1) has three input ports, namely input port 1, input port 2, and input port 3, and four output ports, namely output port 1, output port 2, output port 3, and output port 4. The three input ports of the 3×4 Butler matrix network (1) are distributed on the periphery of the network, and the four output ports are distributed at the center of the network. Specifically, when the excitation input port is 1, the input energy is equally distributed to the four output ports, and the phase difference between adjacent output ports is 0°; when the excitation input port is 2, the input energy is equally distributed to the four output ports, and the phase difference between adjacent output ports is -90°; when the excitation input port is 3, the input energy is equally distributed to the four output ports, and the phase difference between adjacent output ports is +90°.

3. A filter antenna array based on a 3×4 Butler matrix according to claim 1, characterized in that, The 3×4 Butler matrix network (1) includes a power divider (11), a cross coupler (12), a 90° coupler (13), and two 180° couplers (14).

4. A filter antenna array based on a 3×4 Butler matrix according to claim 3, characterized in that, The power divider (11), cross coupler (12), 90° coupler (13), and 180° coupler (14) are one of the following structures: microstrip line, stripline, coplanar waveguide, substrate integrated waveguide, substrate integrated coaxial line, etc.

5. A filter antenna array based on a 3×4 Butler matrix according to claim 1, characterized in that, The 3×4 Butler matrix network (1) includes two substrate layers and three metal layers. The two substrate layers are Butler matrix first substrate layer (1a) and Butler matrix second substrate layer (1b) arranged from bottom to top. There is a Butler matrix first adhesive layer (1c) between Butler matrix first substrate layer (1a) and Butler matrix second substrate layer (1b). The three metal layers are Butler matrix first metal layer (1d), Butler matrix second metal layer (1e) and Butler matrix third metal layer (1f) arranged from bottom to top. Butler matrix first metal layer (1d) and Butler matrix third metal layer (1f) are connected by Butler matrix first metal pillar (1g).

6. A filtered antenna array based on a 3×4 Butler matrix according to any one of claims 1-5, characterized in that, The filter antenna unit (2) generates four radiation nulls by loading parasitic structures, and the frequency corresponding to each radiation null is independently adjustable. Among them, radiation null 1 is caused by the loaded second metal pillar (2n) of the filter antenna; radiation null 2 ​​is caused by the rectangular metal ring structure loaded on the fifth metal layer (2j) of the filter antenna unit; radiation null 3 is caused by the cavity structure formed by the first metal pillar (2m) of the filter antenna; and radiation null 4 is caused by the stacked structure of the fourth metal layer (2i) and the fifth metal layer (2j) of the filter antenna.

Images