A broadband multi-beam end-fire antenna based on folded Butler matrix

Abstract

The application discloses a kind of broadband multi-beam end-fire antennas based on folding Butler matrix, including excitation port separator, 8*8 Butler matrix and 1*8 end-fire antenna array.Butler matrix adopts upper and lower two layers ASICL structure, and the same type coupler, cross-coupler and phase shifter corresponding to upper and lower layers are overlapped along the thickness direction arrangement, and share the ground full hole on the both sides of transmission path, to reduce the size and via density.Butler matrix realizes interlayer connection by signal transition via, and uses compensation transmission line and open-circuit stub to correct additional phase.Output stage converts branch distributed in different signal layers to the same signal layer, and is directly connected with end-fire antenna array.The application does not need blind hole, buried hole and slot coupling, has the advantages of compact structure, wideband transmission, low processing cost and easy integration, and is suitable for Ka band satellite communication multi-beam front end.

Description

Technical Field

[0001] This invention relates to the field of millimeter-wave communication and antenna technology, specifically to a broadband multi-beam end-fire antenna based on a folded Butler matrix. Background Technology

[0002] Ka-band, with its large available bandwidth and high transmission rate, has been widely used in low-Earth orbit satellite communication and satellite internet. Due to the significant propagation loss in satellite links, high-gain multi-beam antennas are required to achieve beam coverage and satellite tracking. The Butler matrix, a typical passive beamforming network, can generate multiple output signals with fixed phase differences when excited at different input ports, offering advantages such as structural stability, low cost, and ease of integration.

[0003] Existing millimeter-wave Butler matrices are mostly implemented using microstrip lines, substrate integrated waveguides (SIW), or substrate integrated coaxial lines (SICL). Substrate integrated waveguides suffer from dispersion, limiting their broadband performance; asymmetric substrate integrated coaxial lines (ASICL) support TEM mode propagation and offer advantages such as good shielding, low dispersion, and broadband transmission. As Butler matrices expand from 4×4 to 8×8, the number of couplers, phase shifters, and cross paths increases significantly, easily leading to increased network size, higher losses, and accumulated amplitude and phase errors. Some multilayer structures also require blind vias, buried vias, or slot coupling, and separate grounding vias for different signal layers, resulting in complex fabrication, high via density, and difficulties in directly connecting output ports to coplanar antenna arrays. Therefore, the miniaturization, broadbanding, and low-cost integration of 8×8 ASICL Butler matrices still require further research. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, a broadband multi-beam end-fire antenna based on a folded Butler matrix is ​​provided. This antenna employs two ASICL layers to arrange different parts of an 8×8 Butler matrix, allowing corresponding similar devices in the upper and lower layers to overlap along the thickness direction of the circuit board and share a common grounding via. This reduces the matrix planar size and the density of vias within the board while maintaining broadband amplitude and phase stability.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A broadband multi-beam end-fire antenna based on a folded Butler matrix includes an excitation port splitter, an 8×8 Butler matrix, and a 1×8 end-fire antenna array. The excitation port splitter is connected to the eight excitation ports of the 8×8 Butler matrix, and the eight output ports of the 8×8 Butler matrix are respectively connected to the eight end-fire antenna elements of the 1×8 end-fire antenna array. The excitation port splitter is used to increase the distance between adjacent excitation ports and rearrange the input transmission path. The 8×8 Butler matrix is ​​disposed in a multilayer printed circuit board, which includes a first signal metal layer, a second signal metal layer, multiple ground metal layers, and several ground vias. The several ground vias are arranged along both sides of the RF transmission path, and together with the ground metal layers on the upper and lower sides of the corresponding signal metal layers, they constitute an upper asymmetric substrate integrated coaxial transmission channel and a lower asymmetric substrate integrated coaxial transmission channel. The 8×8 Butler matrix includes a first network portion disposed on the first signal metal layer and a second network portion disposed on the second signal metal layer. The first network section and the second network section adopt a folded arrangement. The folded arrangement means that the 8×8 Butler matrix topology, which was originally unfolded in the same plane, is divided into two parts along the folding boundary line and arranged on different signal metal layers, and at least partially overlaps along the thickness direction. Corresponding RF functional devices of the same type are provided on the first network section and the second network section. The corresponding RF functional devices of the same type are overlapped along the thickness direction of the multilayer printed circuit board and share grounding vias on both sides of the RF transmission path. The RF functional devices of the same type include directional couplers, cross couplers, fixed phase shifters and phase compensators. The eight output branches of the 8×8 Butler matrix are alternately arranged on the first signal metal layer and the second signal metal layer. The four output branches located on one signal metal layer are converted to the other signal metal layer through the interlayer transition structure, so that the eight output ports are located on the same signal layer. The empty area between adjacent output branches is provided with phase compensation lines to compensate for the phase difference introduced by interlayer conversion and port rearrangement.

[0006] Furthermore, the multilayer printed circuit board comprises, from top to bottom, a first ground metal layer, a first dielectric layer, a first prepreg layer, a first signal metal layer, a second dielectric layer, a second ground metal layer, a second prepreg layer, a third ground metal layer, a third dielectric layer, a second signal metal layer, a third prepreg layer, a fourth dielectric layer, and a fourth ground metal layer. The first signal metal layer is located between the first ground metal layer and the second ground metal layer, and the equivalent dielectric thickness between the first signal metal layer and the upper and lower ground metal layers is different, forming an upper asymmetric substrate integrated coaxial transmission channel. The second signal metal layer is located between the third ground metal layer and the fourth ground metal layer, and the equivalent dielectric thickness between the second signal metal layer and the upper and lower ground metal layers is different, forming a lower asymmetric substrate integrated coaxial transmission channel.

[0007] Furthermore, the grounding via is a metallized through-hole that penetrates the multilayer printed circuit board. The grounding via is electrically connected to the first ground metal layer, the second ground metal layer, the third ground metal layer, and the fourth ground metal layer. The upper and lower layers with the same type of radio frequency functional devices that are stacked along the thickness direction share the same set of grounding vias located on both sides of their radio frequency transmission paths. This allows the same set of grounding vias to simultaneously form the lateral grounding fences for the upper substrate integrated coaxial transmission channel and the lower substrate integrated coaxial transmission channel, thereby reducing the total number of grounding vias and the via density per unit area. The multilayer printed circuit board does not use blind vias or buried vias.

[0008] Furthermore, the RF functional devices of the same type in the 8×8 Butler matrix include twelve 3dB directional couplers, four cross couplers, two first fixed phase shifters, two second fixed phase shifters, four third fixed phase shifters, four 0° phase compensators, twelve interlayer transition structures, two sets of first compensation transmission lines, and two sets of second compensation transmission lines; the input terminals of the 3dB directional couplers are connected to the input branches, and the output terminals of the 3dB directional couplers are connected to the input terminals of the first fixed phase shifters, the second fixed phase shifters, and the first compensation transmission lines, respectively; the output terminals of the first fixed phase shifters and the second fixed phase shifters are both connected to the input terminals of the first compensation transmission lines; the output terminals of the first compensation transmission lines... The input terminals of the cross-coupler and the third fixed phase shifter are connected respectively; the output terminal of the cross-coupler is connected to the input terminal of the 0° phase compensator; the output terminals of the 0° phase compensator and the third fixed phase shifter are both connected to the input terminal of the second compensation transmission line; the output terminal of the second compensation transmission line is connected to the output branch; the interlayer transition structure is set at the position where signal layer switching is required between the first signal metal layer and the second signal metal layer, one end of the interlayer transition structure is connected to the transmission path on the first signal metal layer, and the other end of the interlayer transition structure is connected to the corresponding transmission path on the second signal metal layer, so that the same type of RF functional devices set on the two signal metal layers are cascaded according to the 8×8 Butler matrix topology.

[0009] Furthermore, the first fixed phase shifter is used to provide A fixed phase shift of 67.5°; a second fixed phase shifter is used to provide... A fixed phase shift of 22.5°; a third fixed phase shifter is used to provide A fixed phase shift of 45°; the first compensation transmission line is used to compensate for the electrical length difference caused by folded wiring and interlayer conversion in different branches; the 0° phase compensator is used to compensate for the equivalent electrical length and phase frequency characteristics; the second compensation transmission line is used to extend, rearrange and compensate the phase of the subsequent transmission path so that different branches maintain a predetermined linear phase relationship at the output end.

[0010] Furthermore, the first network portion and the second network portion are arranged in a mirror image of each other about the folding boundary line, which extends along the signal transmission direction, and the corresponding radio frequency transmission paths are located in the first signal metal layer and the second signal metal layer, respectively, so as to fold the Butler matrix that was originally unfolded in the same plane to different signal layers.

[0011] Furthermore, the corresponding radio frequency functional devices of the same type in the first network section and the second network section overlap along the thickness direction of the multilayer printed circuit board, and their planar projections at least partially overlap.

[0012] Furthermore, a grounding metal layer is provided between the upper and lower layers of radio frequency functional devices of the same type. The grounding metal layer and the shared grounding through-hole together form an electromagnetic shielding structure.

[0013] Furthermore, the interlayer transition structure includes an upper layer signal line, a lower layer signal line, a signal transition via, signal pads disposed at both ends of the signal transition via, and a grounding avoidance structure disposed on the ground metal layer through which the signal transition via passes; the signal transition via directly connects the upper layer signal line and the lower layer signal line, and the signal pads and grounding avoidance structure are used to adjust the parasitic parameters and transmission impedance of the interlayer transition structure; the interlayer transition structure does not employ gap coupling.

[0014] Furthermore, the eight output branches are arranged alternately according to the first signal metal layer and the second signal metal layer, so that a wiring clearance area is formed between adjacent output branches on the first signal metal layer and the second signal metal layer; at least one of phase compensation line and open stub is set in the wiring clearance area; the four output branches located on the first signal metal layer are respectively converted to the second signal metal layer through four inter-layer structures, and the additional phase introduced by inter-layer conversion and port rearrangement is compensated by phase compensation line or open stub, so that the eight output ports are located on the same signal layer, and the spacing between adjacent output ports is adapted to the feed spacing of the 1×8 end-fire antenna array; the inter-layer structure is the same as the inter-layer transition structure.

[0015] The beneficial effects of this invention are as follows: The Butler matrix in this invention adopts a two-layer ASICL structure. Couplers, cross-couplers, and phase shifters of the same type in the upper and lower layers are overlapped along the thickness direction and share grounding vias on both sides of the transmission path to reduce planar size and via density. The Butler matrix achieves inter-layer connectivity through signal transition vias and uses compensated transmission lines and open stubs to correct additional phase. The output stage converts branches distributed across different signal layers to the same signal layer and connects directly to the end-fire antenna array. This invention eliminates the need for blind vias, buried vias, and slot coupling, offering advantages such as compact structure, broadband transmission, low manufacturing cost, and ease of integration. It is suitable for multi-beam front-ends in Ka-band satellite communication.

[0016] The antenna of this invention uses two layers of ASICL to arrange different parts of an 8×8 Butler matrix, so that corresponding similar devices in the upper and lower layers overlap along the thickness direction of the circuit board and share a common grounding via. This reduces the matrix planar size and the density of vias on the board while maintaining broadband amplitude and phase stability. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural diagram of an embodiment of the present invention; Figure 2 This is a schematic diagram of the stacked structure according to an embodiment of the present invention; Figure 3 This is the first grounding metal layer in this embodiment of the invention; Figure 4 This is the first signal metal layer in this embodiment of the invention; Figure 5 This is the second grounding metal layer in this embodiment of the invention; Figure 6 This is the third grounding metal layer in this embodiment of the invention; Figure 7 This is the second signal metal layer in this embodiment of the invention; Figure 8 This is the fourth grounding metal layer in this embodiment of the invention; Figure 9 This is a schematic diagram of the overlapping area in an embodiment of the present invention; Figure 10 This is a side view of an embodiment of the present invention; Figure 11 This is a topological diagram of an 8×8 Butler matrix according to an embodiment of the present invention; Figure 12 This is a three-dimensional structural diagram of the interlayer structure according to an embodiment of the present invention; Figure 13 This is a simulation structure diagram of the 8×8 Butler matrix according to an embodiment of the present invention; Figure 14 This is a schematic diagram of the interlayer structure and phase compensation for open-circuit branches; Figure 15 This is a simulation result diagram of the phase difference at the output port of the 8×8 Butler matrix in an embodiment of the present invention; Figure 16 The figure shows the simulation results of the return loss at the excitation port of the multi-beam antenna in this embodiment of the invention. Figure 17 This is a simulated normalized radiation pattern of the multi-beam antenna at 27 GHz in an embodiment of the present invention; Figure 18 This is a simulated normalized radiation pattern of the multi-beam antenna at 32 GHz in an embodiment of the present invention; Figure 19This is a simulated normalized radiation pattern of the multi-beam antenna at 36 GHz in an embodiment of the present invention.

[0018] The symbols for each component are as follows: 1. First grounding metal layer; 2. First dielectric layer; 3. First prepreg layer; 4. First signal metal layer; 5. Second dielectric layer; 6. Second grounding metal layer; 7. Second prepreg layer; 8. Third grounding metal layer; 9. Third dielectric layer; 10. Second signal metal layer; 11. Third prepreg layer; 12. Fourth dielectric layer; 13. Fourth grounding metal layer; 14. Grounding via; 15. Excitation port splitter; 16. 8×8 Butler matrix; 17. 1×8 end-fire antenna array; 61. Upper ASICL layer; 62. Lower ASICL layer; 63. Prepreg layer; 601. Upper layer signal line; 602. Lower layer signal line; 603. Signal transition via; 604. Signal pad; 605. Grounding avoidance structure; 701, 3dB directional coupler; 702, first fixed phase shifter; 703, second fixed phase shifter; 704, interlayer transition structure; 705, first compensation transmission line; 706, cross coupler; 707, third fixed phase shifter; 708, 0° phase compensator; 709, second compensation transmission line; 801, interlayer structure; 802, phase compensation line. Detailed Implementation

[0019] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0020] like Figure 1As shown, this embodiment provides a broadband multi-beam end-fire antenna based on a folded Butler matrix, including an excitation port splitter 15, an 8×8 Butler matrix 16, and a 1×8 end-fire antenna array 17. The excitation port splitter 15 is disposed on the input side of the 8×8 Butler matrix 16 and connected to its eight excitation ports. It is used to increase the distance between adjacent excitation ports and to separate and rearrange the input transmission paths. The 8×8 Butler matrix 16 is used to perform power distribution and phase transformation on the input RF signal, so that the eight output ports generate output signals with essentially the same amplitude and a predetermined linear phase difference. The 1×8 end-fire antenna array 17 is disposed on the output side of the 8×8 Butler matrix 16, and its eight end-fire antenna elements are respectively connected to the eight output ports to form multiple end-fire beams with different directions. In this embodiment, the 8×8 Butler matrix 16 adopts asymmetric substrate integrated coaxial line technology, i.e., ASICL technology, and forms a multi-layer folded beamforming network through upper and lower ASICL layers.

[0021] like Figure 2As shown, an 8×8 Butler matrix 16 is disposed in a multilayer printed circuit board. The circuit board, from top to bottom, includes a first ground metal layer 1, a first dielectric layer 2, a first prepreg layer 3, a first signal metal layer 4, a second dielectric layer 5, a second ground metal layer 6, a second prepreg layer 7, a third ground metal layer 8, a third dielectric layer 9, a second signal metal layer 10, a third prepreg layer 11, a fourth dielectric layer 12, and a fourth ground metal layer 13. The first signal metal layer 4 is located between the first ground metal layer 1 and the second ground metal layer 6, and its equivalent dielectric thickness is different from that of the upper and lower ground metal layers. The first ground metal layer 1, the first dielectric layer 2, the first prepreg layer 3, the first signal metal layer 4, the second dielectric layer 5, and the second ground metal layer 6 constitute the upper ASIC 61. The second signal metal layer 10 is located between the third ground metal layer 8 and the fourth ground metal layer 13, and its equivalent dielectric thickness differs from that of the upper and lower ground metal layers. The third ground metal layer 8, the third dielectric layer 9, the second signal metal layer 10, the third prepreg layer 11, the fourth dielectric layer 12, and the fourth ground metal layer 13 constitute the lower ASICL 62. A grounding via 14 penetrates the circuit board and connects to the first ground metal layer 1, the second ground metal layer 6, the third ground metal layer 8, and the fourth ground metal layer 13. Multiple grounding vias 14 are arranged along both sides of the RF transmission path, forming a grounding shielding structure for the ASICL together with the ground metal layers on the upper and lower sides of the signal layer. This confines the RF signal primarily within the corresponding transmission channel, thereby reducing radiation leakage and parasitic coupling between adjacent paths. In this embodiment, grounding vias 14 are used to achieve multi-layer grounding connections, eliminating the need for blind or buried vias. The signal conversion between the first signal metal layer 4 and the second signal metal layer 10 is achieved through a direct connection using signal transition vias, eliminating the need for a slot coupling structure. Therefore, this structure can be fabricated using conventional multilayer printed circuit board processes, which helps reduce the difficulty of drilling, lamination, and interlayer alignment. All of the aforementioned metal layers are copper layers.

[0022] like Figures 3 to 8 As shown, Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8The diagrams depict the specific patterns of the first ground metal layer 1, the first signal metal layer 4, the second ground metal layer 6, the third ground metal layer 8, the second signal metal layer 10, and the fourth ground metal layer 13. The first ground metal layer 1 and the fourth ground metal layer 13, primarily composed of large-area ground metal, form the outer ground planes of the upper and lower ASICL layers, respectively. The second ground metal layer 6 and the third ground metal layer 8 form the inner ground planes of the upper and lower ASICL layers, respectively, and together isolate the RF transmission paths on the first signal metal layer 4 and the second signal metal layer 10. Each ground metal layer has corresponding grounding avoidance structures at signal transition vias and port connection locations to prevent short circuits between the signal transition vias and the ground metal layer, and to adjust parasitic parameters at the interlayer transition points. The first signal metal layer 4 and the second signal metal layer 10 each house a portion of the transmission path of an 8×8 Butler matrix 16 and identical RF functional devices, including a 3dB directional coupler, a cross coupler, a fixed phase shifter, a 0° phase compensator, a compensation transmission line, and an output branch. Corresponding devices of the same type located on the two signal metal layers are arranged overlapping along the thickness direction of the circuit board, with their planar projections coinciding and sharing grounding vias 14 on both sides of the transmission path. The transmission paths on the first signal metal layer 4 and the second signal metal layer 10 are connected by an interlayer transition structure, enabling the RF signal to switch between the upper and lower ASICL layers. Through the coordination of the above six metal layer patterns, an upper and lower asymmetric substrate integrated coaxial transmission structure is formed inside the circuit board, achieving a multi-layer folded arrangement of an 8×8 Butler matrix.

[0023] like Figure 4 and Figure 7 As shown, Figure 4 The transmission pattern on the first signal metal layer 4 is shown. Figure 7The transmission pattern on the second signal metal layer 10 is shown. The transmission paths on the first signal metal layer 4 and the second signal metal layer 10 are connected according to an 8×8 Butler matrix topology and form a continuous multi-layer radio frequency transmission network through multiple interlayer transition structures 704. The same reference numerals in the figure indicate similar devices with the same structure and function; one or more of each similar device can be configured according to the Butler matrix topology. Ports 1 to 8 are respectively connected to the input branches of the 8×8 Butler matrix. Depending on the signal layer of each input branch, the input signal is directly transmitted to the corresponding 3dB directional coupler 701, or first converted between the first signal metal layer 4 and the second signal metal layer 10 through the interlayer transition structure 704 before being transmitted to the corresponding 3dB directional coupler 701. The 3dB directional coupler 701 distributes the input signal to two branches, so that the corresponding branches obtain radio frequency signals with basically the same amplitude and a predetermined phase relationship. The output branches of the 3dB directional coupler 701 are respectively connected to the first fixed phase shifter 702, the second fixed phase shifter 703, and the first compensation transmission line 705. The first fixed phase shifter 702 and the second fixed phase shifter 703 are respectively used to provide 67.5° and A fixed phase shift of 22.5° is applied. The signal after passing through the first fixed phase shifter 702 and the second fixed phase shifter 703 is connected to the next-stage network via the first compensated transmission line 705. The first compensated transmission line 705 connects the previous-stage 3dB directional coupler 701, the first fixed phase shifter 702, the second fixed phase shifter 703, and the cross-coupler 706 and the third fixed phase shifter 707, compensating for electrical length differences in different branches caused by folded wiring and inter-layer transitions. The cross-coupler 706 is used to implement cross-transmission of corresponding branches in the Butler matrix, and the third fixed phase shifter 707 provides... A 45° fixed phase shift is used. The corresponding output branch of the cross coupler 706 undergoes equivalent electrical length and phase frequency characteristic compensation via the 0° phase compensator 708. The branch containing the third fixed phase shifter 707 and the corresponding compensated branch are connected to the second compensated transmission line 709. The second compensated transmission line 709 is used to extend, rearrange, and compensate the phase of the subsequent transmission path, ensuring that different branches maintain a predetermined linear phase relationship at the output. An interlayer transition structure 704 is provided at the location where signal layer switching is required between the first signal metal layer 4 and the second signal metal layer 10. The interlayer transition structure 704 connects the transmission path on the first signal metal layer 4 to the corresponding transmission path on the second signal metal layer 10, so that the 3dB directional coupler 701, the first fixed phase shifter 702, the second fixed phase shifter 703, the third fixed phase shifter 707, the cross coupler 706, the 0° phase compensator 708, and the first compensated transmission line 705 and the second compensated transmission line 709, all located on the two signal metal layers, are cascaded according to a predetermined topology. Figure 7As shown, the second signal metal layer 10 is also provided with eight output feed branches corresponding to the 1×8 end-fire antenna array 17. The output signal after passing through the second compensation transmission line 709 is directly transmitted to the corresponding end-fire antenna element, or converted to the second signal metal layer 10 through the interlayer transition structure 704 on the output side, and then connected to the 1×8 end-fire antenna array 17. In this way, the eight output branches originally distributed on the first signal metal layer 4 and the second signal metal layer 10 are unified to the feed plane where the 1×8 end-fire antenna array 17 is located, realizing the direct cascading of the 8×8 Butler matrix and the 1×8 end-fire antenna array. Figure 4 and Figure 7 The upper and lower layers of the circuit board contain corresponding components of the same type arranged along the thickness direction of the circuit board. Specifically, the 3dB directional coupler 701, the first fixed phase shifter 702, the second fixed phase shifter 703, the third fixed phase shifter 707, the cross coupler 706, and the 0° phase compensator 708 on the first signal metal layer 4 at least partially overlap with their corresponding components of the same type on the second signal metal layer 10 in planar projection. The corresponding components on the upper and lower layers share grounding vias 14 arranged along both sides of the transmission path, thereby reducing the planar area occupied by the 8×8 Butler matrix and the number of grounding vias while ensuring interlayer isolation and transmission continuity.

[0024] like Figure 9 As shown, the excitation port splitter 15, the 8×8 Butler matrix 16, and the 1×8 end-fire antenna array 17 are arranged sequentially along the signal transmission direction. The transmission structures of different grayscale levels in the figure correspond to the first signal metal layer 4 and the second signal metal layer 10, respectively. The 8×8 Butler matrix 16 includes two network parts arranged in the upper ASICL 61 and the lower ASICL 62, respectively. The two network parts are arranged correspondingly about the folding boundary line; one network, after being mirrored in a plane and swapping its signal layer, forms a corresponding relationship with the other network part. Corresponding devices of the same type in the upper and lower layers are overlapped along the thickness direction of the circuit board. In this design, the upper 3dB directional coupler 701 overlaps with the corresponding lower 3dB directional coupler 701; the upper cross coupler 706 overlaps with the corresponding lower cross coupler 706; the upper first fixed phase shifter 702 overlaps with the corresponding lower first fixed phase shifter 702; the upper second fixed phase shifter 703 overlaps with the corresponding lower second fixed phase shifter 703; and the upper 0° phase compensator 708 overlaps with the corresponding lower 0° phase compensator 708. The projected portions of the corresponding devices on the circuit board surface overlap, allowing the two sets of devices to share a planar area, reducing the planar size of the miniaturized broadband Butler matrix 16. The same set of grounding vias 14 simultaneously serves as the lateral grounding structure for both the upper ASICL 61 and the lower ASICL 62, eliminating the need for separate grounding vias for the upper and lower layer devices. This reduces the total number of grounding vias and the via density per unit area, leaving more space for the phase compensation lines.

[0025] like Figure 10 As shown, the first ground metal layer 1, the first dielectric layer 2, the first prepreg layer 3, the first signal metal layer 4, the second dielectric layer 5, and the second ground metal layer 6 constitute the upper ASICL 61; the third ground metal layer 8, the third dielectric layer 9, the second signal metal layer 10, the third prepreg layer 11, the fourth dielectric layer 12, and the fourth ground metal layer 13 constitute the lower ASICL 62. The upper ASICL 61 and the lower ASICL 62 are bonded together by the prepreg layer 63 and electrically connected through the grounding via 14. The second prepreg layer 7 and the prepreg layer 63 belong to the same component, but for ease of description, they are referred to as different components in this embodiment.

[0026] like Figure 11 As shown, the 8×8 Butler matrix 16 is an 8-input, 8-output passive beamforming network, including multiple 3dB directional couplers, cross couplers, fixed phase shifters, 0° phase compensators, and interlayer transition structures. Figure 11 The solid lines represent the transmission paths on the first signal metal layer 4, and the dashed lines represent the transmission paths on the second signal metal layer 10. The circle-with-dot and circle-with-cross symbols represent the interlayer structures transitioning from the first signal metal layer 4 to the second signal metal layer 10 and from the second signal metal layer 10 to the first signal metal layer 4, respectively. The fixed phase shifter includes a first fixed phase shifter 702, a second fixed phase shifter 703, and a third fixed phase shifter 707. The first fixed phase shifter 702 is used to provide... A fixed phase shift of 67.5°, the second fixed phase shifter 703 is used to provide A fixed phase shift of 22.5°, the third fixed phase shifter 707 is used to provide A fixed phase shift of 45°. A 0° phase compensator is used to compensate for the difference in equivalent electrical length and phase slope between branches with different device cascade relationships. 67.5° phase shifter 22.5° phase shifter and A 45° phase shifter is used in conjunction with a 3dB directional coupler and a cross-coupler to create a predetermined linear phase gradient across the eight output ports. In this embodiment, the 3dB directional coupler satisfies the relationship that the phase at the through end leads the phase at the coupling end by approximately 90°; therefore, the corresponding fixed phase shifter adopts a negative phase shift configuration. Through the cascading of these devices, when the eight excitation ports operate independently, the eight output ports can form adjacent port phase differences of ±22.5°, ±67.5°, ±112.5°, and ±157.5°.

[0027] like Figure 12As shown, the interlayer transition structure is used to realize the radio frequency connection between the first signal metal layer 4 and the second signal metal layer 10, including an upper signal line 601, a lower signal line 602, a signal transition via 603, a signal pad 604, and a ground clearance structure 605. An intermediate prepreg layer 63 is disposed between the upper ASIC 61 and the lower ASIC 62. The signal transition via 603 connects the upper signal line 601 and the lower signal line 602 along the thickness direction, and signal pads 604 are provided at both ends. The signal pads 604 are used to improve the current continuity between the via and the signal line. When the signal transition via 603 passes through the ground metal layer, a ground clearance structure 605 is provided on the corresponding ground metal layer to prevent short circuit between the signal transition via 603 and the ground metal layer. By adjusting the shape and size of the signal pad 604 and the grounding avoidance structure 605, the parasitic inductance and parasitic capacitance generated by the signal transition via 603 can be adjusted, reducing impedance abrupt changes and phase changes in the interlayer transition region, and improving the broadband transmission performance of the interlayer transition structure.

[0028] like Figure 13 As shown, the 8×8 Butler matrix 16 is provided with ports 1 to 8 as excitation ports and ports 9 to 16 as output ports, and includes a 3dB directional coupler 701, a first fixed phase shifter 702, a second fixed phase shifter 703, an interlayer transition structure 704, a first compensation transmission line 705, a cross coupler 706, a third fixed phase shifter 707, a 0° phase compensator 708, and a second compensation transmission line 709. The first fixed phase shifter 702, the second fixed phase shifter 703, and the third fixed phase shifter 707 respectively provide... 67.5° 22.5° and A fixed phase shift of 45° is used. The interlayer transition structure 704 enables signal switching between the upper-layer ASICL61 and the lower-layer ASICL62 to meet the requirements of multi-layer folded wiring. The first compensation transmission line 705 is located between the preceding and following network stages, connecting the 3dB directional coupler 701, the first fixed phase shifter 702, the second fixed phase shifter 703 to the subsequent cross-coupler 706 and the third fixed phase shifter 707, while compensating for electrical length differences caused by cascading of different devices, bends, and interlayer transitions. The 0° phase compensator 708 is located in the corresponding branch, adjusting the equivalent electrical length and the slope of phase change with frequency for different branches, ensuring that each output branch maintains the required phase relationship within the operating frequency band. The second compensation transmission line 709 is located in the output stage, spatially separating the eight output branches, increasing the spacing between adjacent output ports to match the feed spacing of the 1×8 end-fire antenna array 17, and compensating for electrical length differences caused by port rearrangement. In this embodiment, 12 3dB directional couplers 701 are preferably provided, 4 cross couplers 706 are preferably provided, 2 first fixed phase shifters 702 are preferably provided, 2 second fixed phase shifters 703 are preferably provided, 4 third fixed phase shifters 707 are preferably provided, 4 0° phase compensators 708 are preferably provided, 12 interlayer transition structures 704 are preferably provided, 2 sets of first compensation transmission lines 705 are provided, and 2 sets of second compensation transmission lines 709 are preferably provided.

[0029] like Figure 13 As shown, in this embodiment, the eight output branches are arranged alternately in upper ASICL 61 and lower ASICL 62 before the output layer conversion. Therefore, in each ASICL layer, there is a spare area between two adjacent output branches, formed by the corresponding output branches of the other layer. The first compensation transmission line 705, the second compensation transmission line 709, and the corresponding open-circuit stubs are at least partially disposed in the spare area to complete electrical length and phase compensation without increasing the outer contour size of the matrix.

[0030] like Figure 14 As shown, to enable the 1×8 end-fire antenna array 17 to be fed in the same plane, four interlayer structures 801 are set in the output stage of the 8×8 Butler matrix 16 to convert the four output branches located on one ASICL layer to another ASICL layer, so that the eight output ports are uniformly located on the same signal metal layer. The interlayer structure 801 has the same structure as the interlayer transition structure 704, and the interlayer structure 801 can adopt the same... Figure 12The interlayer transition structure shown is the same as or similar to the structure shown. Since the rearrangement of the interlayer structure 801 and the output port positions introduces additional electrical length, a phase compensation line 802 is provided on the corresponding output branch. The phase compensation line 802 includes a main transmission line and an open-circuit stub connected to the main transmission line. By adjusting the length, width, and connection position of the open-circuit stub, the phase value and phase frequency response of the output branch are adjusted. The interlayer structure 801 and the phase compensation line 802 together achieve output port homogenization and broadband phase compensation, ensuring that the output branch after interlayer conversion and the output branch without interlayer conversion maintain a predetermined phase relationship within the operating frequency band.

[0031] like Figure 15 The figure shown is a simulation result of the phase difference at the output port of an 8×8 Butler matrix. Figure 15 Simulation results of the output port phase difference of an 8×8 Butler matrix 16 are presented. When different excitation ports are operating, the phase difference between adjacent output ports is basically distributed around the theoretical values ​​of ±22.5°, ±67.5°, ±112.5°, and ±157.5°. This indicates that the multilayer folded wiring, interlayer transition structure 704, 0° phase compensator 708, and first compensation transmission line 705, second compensation transmission line 709, and phase compensation line 802 can work together to achieve the required phase allocation.

[0032] like Figure 16 The figure shown is a simulation result of the return loss at the excitation port of a multi-beam antenna. Figure 16 Simulation results of return loss at ports 1 to 8 of the multi-beam antenna are presented. Within the operating frequency band, the excitation ports generally maintain good impedance matching, indicating that the excitation port splitter 15, the 8×8 Butler matrix 16, and the 1×8 end-fire antenna array 17 can be effectively cascaded.

[0033] like Figures 17 to 19 The figures show the simulated normalized radiation patterns of the multi-beam antenna at 27 GHz, 32 GHz, and 36 GHz, with the end-fire direction represented as 0°. At 27 GHz, 32 GHz, and 36 GHz, when ports 1 to 8 are excited individually, the 1×8 end-fire antenna array 17 can form eight radiation beams with different directions. The beam scanning range at 27 GHz is approximately ±67°, at 32 GHz it is approximately ±52°, and at 36 GHz it is approximately ±47°. As the operating frequency increases, the beam scanning range gradually shrinks towards the end-fire direction, but the arrangement order of the beams remains unchanged, indicating that the 8×8 Butler matrix 16 can provide an ordered output phase gradient at different frequencies, achieving broadband multi-beam scanning.

[0034] In summary, this embodiment achieves overlapping of corresponding devices of the same type along the thickness direction through the folded arrangement of the upper ASICL61 and lower ASICL62, sharing a common ground via 14. Simultaneously, phase compensation lines are arranged in the empty areas formed by the alternating layers of the output branches, and output port homogenization and broadband phase compensation are achieved through the interlayer structure 801 and open-circuit stubs. Therefore, this structure can simultaneously meet the requirements of miniaturization of the 8×8 Butler matrix, broadband transmission, low via density, and conventional multilayer printed circuit board processing, making it suitable for Ka-band satellite communication multi-beam front-ends.

[0035] In the diagram, port 1 represents the first port, port 2 represents the second port, port 3 represents the third port, port 4 represents the fourth port, port 5 represents the fifth port, port 6 represents the sixth port, port 7 represents the seventh port, port 8 represents the eighth port, port 9 represents the ninth port, port 10 represents the tenth port, port 11 represents the eleventh port, port 12 represents the twelfth port, port 13 represents the thirteenth port, port 14 represents the fourteenth port, port 15 represents the fifteenth port, and port 16 represents the sixteenth port.

[0036] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A broadband multi-beam end-fire antenna based on a folded Butler matrix, characterized in that, include: Excitation port splitter (15), 8×8 Butler matrix (16) and 1×8 end-fire antenna array (17); The excitation port splitter (15) is connected to the eight excitation ports of the 8×8 Butler matrix (16), and the eight output ports of the 8×8 Butler matrix (16) are respectively connected to the eight end-fire antenna elements of the 1×8 end-fire antenna array (17); the excitation port splitter (15) is used to increase the distance between adjacent excitation ports and rearrange the input transmission path; The 8×8 Butler matrix (16) is disposed in a multilayer printed circuit board, which includes a first signal metal layer (4), a second signal metal layer (10), multiple ground metal layers and several ground through-holes (14); the several ground through-holes (14) are arranged along both sides of the radio frequency transmission path, and together with the ground metal layers on the upper and lower sides of the corresponding signal metal layer, they form an upper asymmetric substrate integrated coaxial transmission channel and a lower asymmetric substrate integrated coaxial transmission channel. The 8×8 Butler matrix (16) includes a first network portion disposed on the first signal metal layer (4) and a second network portion disposed on the second signal metal layer (10). The first network portion and the second network portion are arranged in a folded manner, dividing the topology of the 8×8 Butler matrix (16) originally unfolded in the same plane into two parts along the folding boundary line. They are respectively arranged on different signal metal layers and overlap at least partially along the thickness direction. The first network portion and the second network portion are provided with corresponding radio frequency functional devices of the same type. The corresponding radio frequency functional devices of the same type overlap along the thickness direction of the multilayer printed circuit board and share the grounding through-hole (14) disposed on both sides of the radio frequency transmission path. The radio frequency functional devices of the same type include directional couplers, cross couplers, fixed phase shifters and phase compensators. The eight output branches of the 8×8 Butler matrix (16) are alternately arranged on the first signal metal layer (4) and the second signal metal layer (10). The four output branches located on one of the signal metal layers are converted to the other signal metal layer through the interlayer transition structure (704), so that the eight output ports are located on the same signal layer. The empty area between adjacent output branches is provided with a phase compensation line (802) to compensate for the phase difference introduced by interlayer conversion and port rearrangement.

2. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 1, characterized in that: The multilayer printed circuit board comprises, from top to bottom, a first ground metal layer (1), a first dielectric layer (2), a first prepreg layer (3), a first signal metal layer (4), a second dielectric layer (5), a second ground metal layer (6), a second prepreg layer (7), a third ground metal layer (8), a third dielectric layer (9), a second signal metal layer (10), a third prepreg layer (11), a fourth dielectric layer (12), and a fourth ground metal layer (13). The first signal metal layer (4) is located between the first ground metal layer (1) and the second ground metal layer (6), and the equivalent dielectric thickness between the first signal metal layer (4) and the upper and lower ground metal layers is different, forming an upper asymmetric substrate integrated coaxial transmission channel. The second signal metal layer (10) is located between the third ground metal layer (8) and the fourth ground metal layer (13), and the equivalent dielectric thickness between the second signal metal layer (10) and the upper and lower ground metal layers is different, forming a lower asymmetric substrate integrated coaxial transmission channel.

3. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 2, characterized in that: The grounding through-hole (14) is a metallized through-hole that penetrates the multilayer printed circuit board. The grounding through-hole (14) is electrically connected to the first grounding metal layer (1), the second grounding metal layer (6), the third grounding metal layer (8), and the fourth grounding metal layer (13). The upper and lower layers of corresponding radio frequency functional devices of the same type are stacked along the thickness direction and share the same set of grounding through holes (14) located on both sides of their radio frequency transmission path, so that the same set of grounding through holes (14) simultaneously constitutes the lateral grounding fence of the upper substrate integrated coaxial transmission channel and the lower substrate integrated coaxial transmission channel.

4. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 1, characterized in that: The RF functional devices of the same type in the 8×8 Butler matrix (16) include twelve 3dB directional couplers (701), four cross couplers (706), two first fixed phase shifters (702), two second fixed phase shifters (703), four third fixed phase shifters (707), four 0° phase compensators (708), twelve interlayer transition structures (704), two sets of first compensation transmission lines (705) and two sets of second compensation transmission lines (709); The input terminal of the 3dB directional coupler (701) is connected to the input branch, and the output terminal of the 3dB directional coupler (701) is connected to the input terminal of the first fixed phase shifter (702), the input terminal of the second fixed phase shifter (703), and the input terminal of the first compensation transmission line (705), respectively. The output terminals of the first fixed phase shifter (702) and the second fixed phase shifter (703) are both connected to the input terminal of the first compensation transmission line (705); The output of the first compensation transmission line (705) is connected to the input of the cross coupler (706) and the input of the third fixed phase shifter (707), respectively. The output of the cross coupler (706) is connected to the input of the 0° phase compensator (708); The output terminals of the 0° phase compensator (708) and the third fixed phase shifter (707) are both connected to the input terminal of the second compensation transmission line (709); The output end of the second compensation transmission line (709) is connected to the output branch; The interlayer transition structure (704) is disposed at the position where signal layer switching is required between the first signal metal layer (4) and the second signal metal layer (10). One end of the interlayer transition structure (704) is connected to the transmission path on the first signal metal layer (4), and the other end of the interlayer transition structure (704) is connected to the corresponding transmission path on the second signal metal layer (10), so that the same type of radio frequency functional devices disposed on the two signal metal layers are cascaded in an 8×8 Butler matrix topology.

5. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 4, characterized in that: The first fixed phase shifter (702) is used to provide A fixed phase shift of 67.5°; the second fixed phase shifter (703) is used to provide A fixed phase shift of 22.5°; the third fixed phase shifter (707) is used to provide A fixed phase shift of 45°; The first compensation transmission line (705) is used to compensate for the electrical length difference between different branches caused by folded wiring and inter-layer conversion; The 0° phase compensator (708) is used to compensate for the equivalent electrical length and phase frequency characteristics; the second compensation transmission line (709) is used to extend, rearrange and compensate the phase of the subsequent transmission path so that different branches maintain a predetermined linear phase relationship at the output end.

6. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 1, characterized in that: The first network portion and the second network portion are arranged in a mirror image of each other about the folding boundary line, which extends along the signal transmission direction, and the corresponding radio frequency transmission paths are located in the first signal metal layer (4) and the second signal metal layer (10) respectively, so as to fold the Butler matrix that was originally unfolded in the same plane to different signal layers.

7. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 1, characterized in that: The radio frequency functional devices of the same type corresponding to each other in the first network portion and the second network portion overlap along the thickness direction of the multilayer printed circuit board, and their planar projections at least partially overlap.

8. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 7, characterized in that: A grounding metal layer is provided between the upper and lower layers of the same type of radio frequency functional devices. The grounding metal layer and the shared grounding through hole (14) together form an electromagnetic shielding structure.

9. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 1, characterized in that: The interlayer transition structure (704) includes an upper signal line (601), a lower signal line (602), a signal transition via (603), signal pads (604) disposed at both ends of the signal transition via (603), and a grounding avoidance structure (605) disposed on the grounding metal layer through which the signal transition via (603) passes. The signal transition via (603) directly connects the upper signal line (601) and the lower signal line (602), and the signal pad (604) and the grounding avoidance structure (605) are used to adjust the parasitic parameters and transmission impedance of the interlayer transition structure.

10. The broadband multi-beam end-fire antenna based on a folded Butler matrix according to claim 1, characterized in that: The eight output branches are arranged alternately on the first signal metal layer (4) and the second signal metal layer (10), so that a wiring clearance area is formed between adjacent output branches on the first signal metal layer (4) and the second signal metal layer (10); At least one of the phase compensation line (802) and open stub is disposed in the wiring vacancy area; the four output branches located in the first signal metal layer (4) are respectively converted to the second signal metal layer (10) through four inter-layer structures (801), and the additional phase introduced by inter-layer conversion and port rearrangement is compensated by the phase compensation line (802) or open stub, so that the eight output ports are located in the same signal layer, and the spacing between adjacent output ports is adapted to the feed spacing of the 1×8 end-fire antenna array (17); the inter-layer structure (801) is the same as the inter-layer transition structure (704).

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