A leaky-wave antenna array based on a multi-mode substrate integrated waveguide coupler

Abstract

The application provides a leaky-wave antenna array based on a multimode substrate integrated waveguide coupler, relates to the technical fields of wireless communication and radar, and comprises a dielectric substrate, a multimode substrate integrated waveguide coupler and two leaky-wave antenna units. The multimode substrate integrated waveguide coupler is integrated on the dielectric substrate and is configured to excite modes and modes of the substrate integrated waveguide respectively in the same frequency range, generate even-mode signals with equal amplitude and in-phase and odd-mode signals with equal amplitude and opposite phase. The two leaky-wave antenna units are symmetrically arranged on the two sides of the upper surface metal layer of the dielectric substrate and are connected with two output ports of the multimode substrate integrated waveguide coupler respectively. The two leaky-wave antenna units are configured to radiate a wave beam and a difference wave beam in response to the even-mode signals and the odd-mode signals. The application solves the problem of low measurement accuracy of a traditional single-pulse antenna, has the technical effects of simplifying the design of a feed network, improving radiation performance and thus improving measurement accuracy.

Description

Technical Field

[0001] This invention relates to the fields of wireless communication and radar technology, and in particular to a leaky antenna array based on a multi-mode substrate integrated waveguide coupler. Background Technology

[0002] Millimeter-wave monopulse antenna systems, based on the principle of sum and difference beamforming, have been widely used in key defense and aerospace fields such as radar detection, missile guidance, and space monitoring. As the requirements for target tracking accuracy and detection range continue to increase, the limitations of traditional sequential beam scanning and conical scanning technologies are becoming increasingly apparent. As a typical multi-beam radiation system, the monopulse antenna can simultaneously form sum and difference beam patterns, effectively suppressing signal fluctuations and angle measurement errors. Therefore, it has become the core means for achieving sub-milliradian level high-precision direction finding in modern radar systems.

[0003] In a monopulse system, the sum-difference network is a crucial component. It generates mutually orthogonal sum and difference beams through the superposition of coherent signals. The sum channel enhances the detection range, while the difference channel suppresses multipath interference and environmental noise. Regarding antenna architecture selection for monopulse functionality, in addition to traditional reflectors, lenses, and waveguide slot arrays, leaky-wave antennas with high directional radiation characteristics exhibit advantages in long-range detection. Their unique frequency-tuned beam scanning capability enables flexible spatial coverage. In recent years, the introduction of multimode excitation technology has further simplified the feeding structure, providing a new technical path for independent control of the sum and difference beams.

[0004] However, traditional leaky wave antennas have low structural integration, and their large profile height makes it difficult to meet the stringent compactness requirements of modern millimeter wave systems. In terms of electrical performance, they are limited by defects such as discontinuous beam scanning and easy elevation of open stopbands, which makes it difficult for sum and difference beams to achieve high gain and low sidelobe coordination, resulting in low measurement accuracy. Summary of the Invention

[0005] To address the low measurement accuracy of traditional monopulse antennas, this invention provides a leaky wave antenna array based on a multi-mode substrate integrated waveguide coupler. By integrating multiple components onto a dielectric substrate, selectively exciting modes within the same operating frequency band and independently generating sum and difference beams, it not only simplifies the feed network design but also improves radiation performance, thereby enhancing measurement accuracy.

[0006] The above-mentioned objective of this invention is achieved through the following technical solutions:

[0007] A leaky antenna array based on a multimode substrate integrated waveguide coupler, comprising:

[0008] Dielectric substrate, multimode substrate integrated waveguide coupler and two leaky antenna elements;

[0009] The multimode substrate integrated waveguide coupler, integrated on the dielectric substrate, is configured to excite the substrate integrated waveguide within the same frequency range. Model and The mode generates equal-amplitude, in-phase even-mode signals and equal-amplitude, out-of-phase odd-mode signals;

[0010] Two leaky antenna elements are symmetrically arranged on both sides of the metal layer on the upper surface of the dielectric substrate and are respectively connected to the two output ports of the multimode substrate integrated waveguide coupler. The two leaky antenna elements are configured to respond to the even-mode signal radiation and beam and the odd-mode signal radiation difference beam.

[0011] By adopting the above technical solution, the multimode substrate integrated waveguide coupler can be excited separately within the same frequency range. Model and The system generates equal-amplitude, in-phase even-mode signals and equal-amplitude, out-of-phase odd-mode signals, which are then fed into two symmetrically arranged leaky antenna elements. This allows the antenna array to simultaneously radiate sum and difference beams, achieving the sum and difference beam functionality required by monopulse radar. This structure is highly integrated on a dielectric substrate, offering advantages such as low profile and ease of fabrication. Furthermore, it achieves high isolation and wide bandwidth characteristics through a multi-mode coupling mechanism, supporting continuous beam scanning in complex electromagnetic environments and effectively improving the detection reliability and angle measurement accuracy of the radar system.

[0012] Preferably, the multimode substrate integrated waveguide coupler includes:

[0013] The gradient microstrip line disposed on the lower surface of the dielectric substrate is used for excitation. The gradient microstrip line is configured to achieve impedance matching in a frequency range of 24 GHz to 30 GHz.

[0014] A dielectric layer is disposed above the dielectric substrate, and a microstrip line is disposed on the dielectric layer. A slot is formed in the metal layer on the upper surface of the dielectric substrate, and the microstrip line is perpendicularly coupled to the slot for excitation. mold.

[0015] By adopting the above technical solution, by... Model and The excitation structures for the modes are respectively set on the top and bottom sides and the surface of the dielectric substrate, achieving effective isolation and independent control of the two modes; among them, the gradient microstrip line is located at the bottom of the substrate for efficient excitation. The mode achieves broadband impedance matching, while the dielectric layer and its microstrip lines located above the substrate are specifically used for excitation through vertical cross-coupling with the surface slots. The model not only enhances the isolation between models, but also makes... The excitation intensity and phase of the mode can be flexibly controlled by adjusting the dielectric layer, thereby optimizing the generation quality of odd mode signals and further improving the differential beam performance and the overall tuning capability of the antenna.

[0016] Preferably, the multimode substrate integrated waveguide coupler further includes: an isolation structure;

[0017] The isolation structure is composed of an array of metallized isolation vias disposed on the dielectric substrate, and the array of isolation vias connects the upper and lower surface metal layers of the dielectric substrate.

[0018] By employing the above technical solution, a metallized isolation via array is formed in the dielectric substrate, effectively creating waveguide sidewalls that restrict the electromagnetic field distribution, enhancing the structural integrity of the substrate-integrated waveguide, and thus suppressing... Model and Energy leakage and parasitic coupling between modes are eliminated, ensuring the independence and stability of the two operating modes during transmission. This guarantees the amplitude and phase consistency of even-mode and odd-mode signals, which not only reduces mode interference and improves the isolation and operating bandwidth of the multi-mode substrate integrated waveguide coupler, but also helps to achieve cleaner sum and difference beam radiation, ultimately improving the antenna's radiation pattern performance and angle measurement accuracy in complex application scenarios.

[0019] Preferably, each of the leaky antenna elements comprises a plurality of periodically arranged asymmetric elements, each of the asymmetric elements comprising:

[0020] A longitudinal slot is provided in the metal layer on the upper surface of the dielectric substrate, wherein the longitudinal slot has a length of 3.5 mm and a width of 0.2 mm, and the offset between the longitudinal slot and the inductor post is 2.9 mm;

[0021] An inductor post that penetrates the dielectric substrate and connects the upper and lower surface metal layers of the dielectric substrate;

[0022] The longitudinal slot and the inductor post are alternately offset in opposite directions relative to the central axis of the leaky antenna element.

[0023] By adopting the above technical solution, a periodic arrangement of asymmetric units with alternating reverse offsets of longitudinal slots and inductor pillars is used to introduce a specific phase constant gradient into the leaky wave antenna unit. This effectively controls the propagation constant and leakage rate of electromagnetic waves, enabling the antenna to achieve continuous forward beam scanning in the millimeter-wave band. Furthermore, the asymmetric structure breaks the field distribution symmetry of traditional symmetric units, improving the energy radiation efficiency of electromagnetic waves. At the same time, it effectively suppresses the open stopband phenomenon, ensuring the continuity and stability of beam scanning and improving the scanning performance and radiation efficiency of the antenna in a wide-angle range.

[0024] Preferably, the longitudinal gaps within each asymmetric unit and the inductor pillars constitute an asymmetric hybrid reactance structure;

[0025] The asymmetric hybrid reactance structure is used to adjust the ratio of the phase constant to the free space wave number so that the beam pointing angle of the leaky wave antenna array meets the preset requirements under the preset fast wave condition, thereby suppressing the open stopband effect.

[0026] By adopting the above technical solution, the asymmetric hybrid reactance structure formed by the alternating reverse offset of longitudinal slots and inductor pillars changes the periodic boundary conditions of the traditional symmetric structure, thereby achieving continuous and designable modulation of the phase propagation constant in the waveguide. This structure can precisely control the ratio of the phase constant to the free space wavenumber by adjusting its geometric parameters, so as to meet the preset fast wave conditions, convert the electromagnetic wave energy from the bound state to the radiable leakage state, and directionally couple it into free space to form a controllable beam pointing. At the same time, it effectively destroys the conditions for forming an open stopband resonance, suppresses energy reflection and radiation interruption, and ensures the continuity of beam scanning and high radiation efficiency of the antenna throughout the entire operating frequency band.

[0027] Preferably, the preset fast wave conditions are as follows:

[0028] ;

[0029] In the formula, To adjust the phase constant, is the free space wavenumber.

[0030] By adopting the above technical solution, it is clearly stipulated that the fast wave condition is that the absolute value of the adjustment phase constant is less than the free space wave number. In principle, the threshold for the leaky wave antenna to enter the fast wave radiation mode from the slow wave transmission mode is defined. When this inequality holds, the space harmonics can be synchronized with the free space wave, the energy can be effectively radiated outward, and the beam can be pointed in a specific direction, ensuring that the designed physical structure can produce the required radiation characteristics.

[0031] Preferably, the preset requirements are as follows:

[0032] ;

[0033] In the formula, The direction of radiation is n, the spatial harmonic order is n, and the period of the asymmetric unit is p.

[0034] By adopting the above technical solution, an accurate mathematical model between the physical parameters of the antenna structure and its radiation performance was established. By adjusting the periodic structural parameters of the asymmetric unit to change the phase constant, the pointing angle of the antenna's main beam in free space was accurately predicted and controlled.

[0035] Preferably, each of the leaky antenna elements has a metal slot short-circuit boundary at the end away from the multimode substrate integrated waveguide coupler, and the metal slot short-circuit boundary includes a metallized through-hole penetrating the metal layers on the upper and lower surfaces of the dielectric substrate.

[0036] By adopting the above technical solution, a metal slot short-circuit boundary is set at the end of the leaky wave antenna element, forming an effective waveguide terminal reflection structure. This structure is composed of metallized through-holes that penetrate the metal layers on the upper and lower surfaces of the dielectric substrate. It can achieve near-ideal electric wall boundary conditions in the millimeter-wave band, suppressing the energy leakage of electromagnetic waves at the transmission terminal. This not only effectively reduces the return loss of the antenna and improves the radiation efficiency, but also optimizes the amplitude distribution of the antenna aperture field by controlling the terminal reflection phase, thereby improving the far-field radiation pattern characteristics of the antenna, enhancing the beam pointing accuracy and sidelobe suppression capability, and strengthening the overall performance of the antenna in monopulse direction finding applications.

[0037] Preferably, the dielectric substrate is further provided with a coupling slot located between the two leaky antenna elements for coupling. Modulus energy and adjust phase constant.

[0038] By adopting the above technical solution, a coupling slot is set between the two leaky wave antenna elements, thus constructing an effective coupling channel. The mode energy coupling path, this slot can precisely control a portion of it. The directional coupling of mode energy between the two antenna elements enables flexible control of the phase relationship between the two channels. This not only optimizes the amplitude consistency with beamforming but also compensates for phase deviations caused by structural asymmetry or manufacturing errors by adjusting the coupling strength. This effectively improves the symmetry and stability of the differential beam null depth and ultimately enhances the antenna's angle resolution accuracy and anti-interference capability in single-pulse amplitude comparison direction finding.

[0039] Preferably, the dielectric material of the dielectric substrate is RO4350.

[0040] By adopting the above technical solution and selecting RO4350 as the dielectric substrate material, its excellent dielectric properties in the millimeter-wave band are fully utilized to ensure the integrity of high-frequency signal transmission.

[0041] In summary, the present invention has at least one of the following beneficial technical effects:

[0042] This invention utilizes a multimode substrate integrated waveguide coupler for synchronous excitation within the same frequency band. Model and The system generates equal-amplitude, in-phase even-mode signals and equal-amplitude, out-of-phase odd-mode signals, which are then fed into two symmetrically arranged leaky antenna elements. This allows the antenna array to simultaneously radiate sum and difference beams, thus achieving the sum and difference beam functionality required by monopulse radar. This structure is highly integrated on a dielectric substrate, offering advantages such as low profile and ease of fabrication. Furthermore, it utilizes a multi-mode coupling mechanism to achieve high isolation and wide bandwidth characteristics, enabling continuous beam scanning in complex electromagnetic environments and effectively improving the detection reliability and angle measurement accuracy of the radar system.

[0043] This invention employs an asymmetric periodic structure with alternating reverse offsets of longitudinal slots and inductor pillars to form a controllable phase gradient in the leaky wave antenna. This allows for precise control of the propagation and leakage characteristics of electromagnetic waves, breaking the traditional symmetrical field distribution, improving radiation efficiency, effectively suppressing open stopbands, ensuring continuous and stable beam scanning in the millimeter-wave band, and enhancing the wide-angle scanning performance and overall radiation efficiency of the antenna. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall structure of a leaky antenna array based on a multi-mode substrate integrated waveguide coupler provided in an embodiment of the present invention.

[0045] Figure 2 This is an embodiment of the present invention. Figure 1 Schematic diagram of the groove-microstrip transition structure at point A.

[0046] Figure 3 This is an embodiment of the present invention. Figure 1 A schematic diagram of the gradient microstrip line structure at point B.

[0047] Figure 4 This is a schematic diagram of the layered structure of a leaky antenna array based on a multimode substrate integrated waveguide coupler provided in an embodiment of the present invention.

[0048] Figure 5 (a) is a diagram showing the test and simulation results of S-parameters of a leaky antenna array based on a multimode substrate integrated waveguide coupler when excited by even mode, according to an embodiment of the present invention.

[0049] Figure 5 (b) is a diagram showing the phase difference test and simulation results between adjacent output ports of a leaky antenna array based on a multimode substrate integrated waveguide coupler provided in an embodiment of the present invention when the multimode substrate integrated waveguide coupler is excited in even mode.

[0050] Figure 5 (c) is a figure showing the test and simulation results of S-parameters of a leaky antenna array based on a multimode substrate integrated waveguide coupler under odd-mode excitation, according to an embodiment of the present invention.

[0051] Figure 5 (d) is a diagram showing the phase difference test and simulation results between adjacent output ports of a leaky antenna array based on a multimode substrate integrated waveguide coupler provided in an embodiment of the present invention when the multimode substrate integrated waveguide coupler is excited in odd mode.

[0052] Figure 6 (a) The S-parameter test and simulation results of a SIWLWA array based on a multi-mode substrate integrated waveguide coupler provided in an embodiment of the present invention.

[0053] Figure 6 (b) A diagram showing the radiation direction test and simulation results of a SIWLWA array based on a multi-mode substrate integrated waveguide coupler and a beam scanning of a leaky wave antenna array provided in an embodiment of the present invention.

[0054] Figure 6 (c) is a test and simulation result of the three-dimensional radiation direction of the SIWLWA array at 27GHz, which is based on a multi-mode substrate integrated waveguide coupler and is provided in an embodiment of the present invention.

[0055] Figure 6 (d) is a figure showing the three-dimensional radiation direction test and simulation results of a 27GHz time difference beam of a SIWLWA array based on a multi-mode substrate integrated waveguide coupler provided in an embodiment of the present invention.

[0056] In the figure, 1. Metal layer on the upper surface of the dielectric substrate; 2. Dielectric substrate; 3. Multimode substrate integrated waveguide coupler; 4. First leaky antenna element; 5. Second leaky antenna element; 6. Asymmetric element; 7-1. First feed network; 7-2. Second feed network; 8. Metal slot short-circuit boundary; 9. Isolation structure; 10. Dielectric layer; 11. Coupled slot; 12. Microstrip line; 13. Slot; 14. Tapered microstrip line; 4-1. First longitudinal slot; 4-2. First inductor post; 5-1. Second longitudinal slot; 5-2. Second inductor post. Detailed Implementation

[0057] This invention provides a leaky antenna array and system based on a multimode substrate integrated waveguide coupler. It addresses the shortcomings of traditional leaky antennas, such as low structural integration, large profile height making them unsuitable for the stringent compactness requirements of modern millimeter-wave systems, and electrical performance limitations due to beam scanning discontinuities and easily elevated sidelobe levels (OSBs), hindering the coordinated operation of the sum and difference beams to achieve high gain and low sidelobes, thus resulting in low measurement accuracy. This invention integrates multiple components onto a dielectric substrate 2, enabling selective excitation within the same operating frequency band. Model and The mode can independently generate sum and difference beams, which not only simplifies the design of the feed network but also improves radiation performance, thereby improving measurement accuracy.

[0058] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0059] In the description of this invention, it should be noted that the terms "front", "rear", "upper", "lower", "both ends", "center", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0060] Unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; or they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example

[0061] Please see Figures 1 to 4 The present invention provides a leaky antenna array based on a multimode substrate integrated waveguide coupler, comprising: a dielectric substrate 2, a multimode substrate integrated waveguide coupler 3, and two leaky antenna elements; the multimode substrate integrated waveguide coupler 3 is integrated on the dielectric substrate 2 and is configured to excite the modes of the substrate integrated waveguide respectively within the same frequency range. and The two leaky antenna elements are symmetrically arranged on both sides of the metal layer on the upper surface of the dielectric substrate 2 and connected to the two output ports of the multimode substrate integrated waveguide coupler 3, respectively. The two leaky antenna elements are configured to respond to the radiation beam of the even mode signal and the radiation difference beam of the odd mode signal.

[0062] Understandably, the dielectric substrate 2, which serves as the support and transmission carrier for the entire antenna structure, has metal layers on both its upper and lower surfaces.

[0063] The multimode substrate integrated waveguide coupler 3 adopts a layered integrated structure. The top dielectric layer 10 is in close contact with the lower dielectric substrate 2 through physical bonding. Signal transmission between the two is achieved through electromagnetic coupling. The multimode substrate integrated waveguide coupler 3 contains two independent feeding networks for exciting different modes respectively.

[0064] The first feed network 7-1 includes a dielectric layer 10, a microstrip line 12, and a slot 13. The dielectric layer 10 is tightly bonded to the upper surface metal layer 1 of the underlying dielectric substrate 2 by means of adhesive sheet or low-temperature welding. The microstrip line 12 disposed on the upper surface of the dielectric layer 10 is fabricated on the upper surface metal layer 1 of the dielectric substrate 2 by photolithography. The microstrip line 12 and the slot 13 fabricated on the upper surface metal layer 1 of the dielectric substrate 2 are perpendicular to each other in the vertical direction, forming a slot-microstrip transition structure, which is used to excite the mode of the substrate integrated waveguide to generate an odd-mode signal with equal amplitude and inverse phase.

[0065] The second feed network 7-2 includes a gradient microstrip line 14 formed by etching on the lower surface of the dielectric substrate 2. The gradient microstrip line 14 structure is used to excite the integrated waveguide on the substrate. The mode generates an even-mode signal with equal amplitude and in phase.

[0066] It is worth mentioning that the tapered microstrip line 14 structure, as an even-mode excitation port, can continuously and efficiently feed signal energy into the antenna structure with low reflection over a wide frequency range of 24 GHz to 30 GHz, and excite the required signal. In electromagnetic wave mode, the effective operating bandwidth reaches 22.22% of the center frequency, while the slot line-microstrip transition structure, as the odd mode excitation port, can continuously feed signal energy into the antenna structure efficiently and with low reflection in a wide frequency range of 24.87GHz to 28.17GHz, with an effective operating bandwidth of 12.4% of the center frequency.

[0067] Preferably, the dimensions of the slot 13 are Wslot=0.3mm and Lslot=2.802mm.

[0068] It is worth mentioning that the dielectric layer 10 is a dielectric substrate and is a detachable structure. This allows for fine-tuning of the phase and coupling strength of the odd-mode excitation by replacing the dielectric layer 10 with different dielectric constants or thicknesses during the assembly or debugging phase. This enables independent and flexible optimization of the impedance matching characteristics of the first feed network 7-1 without changing the core circuit, ensuring that the differential beam performance reaches its optimal level.

[0069] Preferably, the thickness of the dielectric layer 10 is 0.254 mm.

[0070] The first leaky wave antenna element 4 and the second leaky wave antenna element 5 are distributed on both sides of the upper surface of the dielectric substrate 2 with the center line of the multimode substrate integrated waveguide coupler 3 as the axis of symmetry, and are respectively connected to the two output ports of the multimode substrate integrated waveguide coupler 3.

[0071] It should be noted that the first leaky wave antenna unit 4, the second leaky wave antenna unit 5 and the multimode substrate integrated waveguide coupler 3 are formed by photolithography, etching and drilling in one step using the same dielectric substrate 2, using standard printed circuit board process or low temperature co-fired ceramic process, and share the same dielectric material and upper and lower surface metal layers.

[0072] When the multimode substrate integrated waveguide coupler 3 is excited In even mode, it outputs equal-amplitude and in-phase electromagnetic energy to the first leaky antenna element 4 and the second leaky antenna element 5. After receiving the signal, the first leaky antenna element 4 and the second leaky antenna element 5 begin to radiate in the same direction. The electromagnetic waves superimpose in phase in the far field, forming a directional beam. When the multimode substrate integrated waveguide coupler 3 is excited... In the odd mode, electromagnetic energy with equal amplitude but 180-degree phase difference (opposite phase) will be output to two antenna elements. After receiving the signal, the first leaky antenna element 4 and the second leaky antenna element 5 will radiate in a positive and negative manner. The electromagnetic waves cancel each other out of phase in front (axial direction) to form a difference beam with zero depth in the middle of the radiation pattern.

[0073] It is worth mentioning that both the first leaky antenna element 4 and the second leaky antenna element 5 are composed of 19 periodically arranged asymmetric elements 6, with the center-to-center spacing between adjacent elements, i.e., the period p, being 3.9 mm. Each asymmetric element 6 includes a longitudinal slot and an inductor post. Specifically, the first leaky antenna element 4 includes a first longitudinal slot 4-1 and a first inductor post 4-2, and the second leaky antenna element 5 includes a second longitudinal slot 5-1 and a second inductor post 5-2.

[0074] The longitudinal slit is a non-closed opening formed on the metal layer 1 on the upper surface of the dielectric substrate 2 by an etching process. Its two ends are connected to the metal layer 1 on the upper surface of the dielectric substrate 2. The length Ls of the longitudinal slit is 3.5 mm and the width Ws is 0.2 mm. It is used to interrupt the lateral current distribution on the upper surface metal layer, forcing the current to bypass, thereby exciting the electromagnetic field and radiating energy into free space.

[0075] The inductor post is a metallized through-hole that penetrates the dielectric substrate 2, and its two ends are connected to the upper surface metal layer 1 and the lower surface metal layer of the dielectric substrate 2, respectively.

[0076] The longitudinal slots and inductor posts are offset alternately in opposite directions relative to the geometric center axis of the leaky antenna element in which they are located. That is, if the slot in an element is offset to the left, then the inductor post paired with it is offset to the right. In the next adjacent periodic element, this offset pattern is reversed. The offset ds is 2.9 mm. The total length L3 of the inductor posts arranged along the waveguide direction is 100 mm. The longitudinal slot 8 and the inductor post 9 together constitute an asymmetric hybrid reactance structure, which is used to suppress the open stopband effect.

[0077] Preferably, the asymmetric hybrid reactance structure adjusts the phase constant. With free space wavenumber The ratio satisfies the fast wave condition. Beam pointing angle Determined by the following formula:

[0078]

[0079] In the formula, p is the unit period and n is the spatial harmonic order.

[0080] It is worth mentioning that the alternating offset direction of the longitudinal slots and inductor pillars in the periodic unit structure is designed to adjust the phase difference of the feed network, thereby enabling left-hand or right-hand beam scanning and enhancing the flexibility of antenna applications.

[0081] The multimode substrate integrated waveguide coupler 3 and two leaky antenna units are all integrated on the dielectric substrate 2, forming a complete planar structure with dimensions of 100.1mm × 13mm × 0.578mm. Compared with the prior art, the printed circuit process of this embodiment effectively reduces the profile height by at least less than 1.5mm, which is especially suitable for millimeter-wave wireless communication and satellite communication systems.

[0082] In a preferred embodiment, to achieve electromagnetic isolation, the multimode substrate integrated waveguide coupler 3 further includes an isolation structure 9.

[0083] It is understandable that the isolation structure 9 is composed of a metallized via array arranged periodically on the dielectric substrate 2. The via array penetrates and connects the upper and lower surface metal layers of the dielectric substrate 2 to form a complete waveguide cavity sidewall, constituting an electromagnetic shielding boundary.

[0084] Preferably, the metallized via array can be 0.2mm-0.4mm.

[0085] During installation, this metallized via array physically separates the transmission paths of even and odd modes, forming a complete electromagnetic shielding boundary. Through precise control of the via spacing and diameter ratio, it effectively suppresses... Model and Energy crosstalk between modes is eliminated, ensuring an isolation of over 40dB between the two operating modes, and providing a reliable electromagnetic environment for independent control of the sum and difference beams.

[0086] In a preferred embodiment, to improve the sum and difference beam quality, the dielectric substrate 2 is further provided with a coupling slot 11 located between the two leaky antenna elements for coupling. Modulus energy and adjust phase constant.

[0087] Preferably, the width of the coupling slot 11 can be 0.4 mm, and the length can be between 1 / 4 and 1 / 3 of the wavelength.

[0088] It is understandable that the coupling slot 11 is a circular slot, which is made on the upper surface metal layer 1 of the dielectric substrate 2 by etching process. Its length direction is parallel to the electromagnetic wave propagation direction, and a controllable energy coupling path is established between the two leaky antenna elements.

[0089] The center point of the coupling slot 11 is precisely located on the physical center symmetry axis of the entire antenna array, and extends from near the output port of the multimode substrate integrated waveguide coupler 3 toward the end of the leaky antenna element, passing through the common upper surface metal layer between the two leaky antenna elements.

[0090] It is worth mentioning that the coupling slot 11 enables the propagation of a portion of the material in the SIW to pass through. The mode energy no longer simply propagates forward along its respective waveguide channel, but instead couples from one channel to another through this slot, thereby enabling modulation. The mode energy is directionally coupled between the first leaky antenna element 4 and the second leaky antenna element 5 to compensate for the phase deviation caused by structural asymmetry or manufacturing error.

[0091] In a preferred embodiment, to suppress reflection and improve radiation efficiency, each leaky antenna element is provided with a metal slot short-circuit boundary 8 at the end away from the multimode substrate integrated waveguide coupler 3. The metal slot short-circuit boundary 8 includes metallized through holes that penetrate the upper and lower surface metal layers of the dielectric substrate 2.

[0092] It is understandable that the metal slot short-circuit boundary 8 is composed of two rows of parallel metallized through-hole arrays, respectively setting the end of the first leaky antenna unit 4 and the second leaky antenna unit 5 away from the feed end of the multimode substrate integrated waveguide coupler 3, that is, the end point of electromagnetic wave propagation in the leaky antenna.

[0093] It should be noted that the short-circuit boundary 8 of the metal slot serves as the terminal reflection structure of the leaky wave antenna element. It is connected to the metal layers on the upper and lower surfaces of the dielectric substrate 2, which can effectively suppress the energy leakage of electromagnetic waves at the transmission terminal and reduce the port reflection coefficient in the working frequency band to below -15dB. At the same time, by controlling the terminal reflection phase, the amplitude distribution of the antenna aperture field is optimized, and the antenna radiation efficiency is increased to over 85%.

[0094] It is worth mentioning that the setting of the short-circuit boundary 8 of the metal slot also effectively improves the impedance matching characteristics of the antenna throughout the entire operating frequency band by suppressing the standing wave effect generated by the end reflection, ensuring that the gain fluctuation is less than 1.5dB during beam scanning, and providing a stable radiation performance basis for continuous beam scanning.

[0095] In a preferred embodiment, to ensure efficient signal transmission and radiation performance in the millimeter-wave band, the dielectric substrate 2 is made of RO4350 high-frequency circuit board material.

[0096] The RO4350 high-frequency circuit board material has the characteristics of relative permittivity ε_r=3.66 and loss tangent tanδ=0.004, which can effectively suppress energy loss in the medium, thereby improving the radiation efficiency of the antenna in the millimeter wave band.

[0097] The working principle of this invention is as follows: Independent excitation within the same frequency range is achieved through a multimode substrate integrated waveguide coupler. Model and The modulus generates equal-amplitude, in-phase even-mode signals and equal-amplitude, out-of-phase odd-mode signals, respectively. The mode is used for generating beams. The mode is used to generate the difference beam. Electromagnetic isolation of more than 40dB is achieved between the two modes through a metallized through-hole array. These signals are fed into two symmetrically distributed leaky wave antenna elements. Through an asymmetric hybrid reactance structure composed of periodically arranged longitudinal slots and inductive pillars, broadband impedance matching and efficient radiation are achieved. At the same time, its alternating offset design effectively suppresses the open stopband effect. Finally, by optimizing the dispersion characteristics of the asymmetric elements, the antenna meets the fast wave condition in the frequency band, achieving continuous beam scanning from -30° to 7.5°, while maintaining a peak gain of 14.7dBi and a gain fluctuation of less than 1.5dB. This completes the sum and difference beam coordination required by monopulse radar. It has wide bandwidth, high isolation, low profile and continuous beam scanning capability, and is especially suitable for 5G millimeter wave communication and future 6G communication systems.

[0098] To illustrate the effectiveness of this patented technical solution, the following explanation focuses on electromagnetic simulation and physical testing:

[0099] 1. Experimental environment setup:

[0100] Simulation platform: Using industry-standard high-frequency electromagnetic simulation software, a three-dimensional model that is completely consistent with the design drawings has been established, including accurate material properties, metal conductivity and all structural dimensions.

[0101] Test platform: An actual antenna (100.1mm×13mm×0.578mm) was fabricated. The test was conducted in a microwave anechoic chamber. The S-parameters were measured using a vector network analyzer, and the radiation pattern was measured using a near-field scanning system or a far-field test system.

[0102] 2. Performance verification of multimode substrate integrated waveguide coupler:

[0103] Experimental method: In simulation and testing, signals were fed into the even-mode port (gradient microstrip line) and the odd-mode port (slot line-microstrip transition structure), respectively, and a matched load was connected to the other port. The reflection coefficient and transmission coefficient of the port, as well as the transmission phase difference between the two output ports, were measured.

[0104] Please see Figure 5 (a): Even-mode excitation S-parameters. The curves show that within the 24-30 GHz band, both the simulation and test results of the reflection coefficient of the even-mode port are below -10 dB, indicating good impedance matching. The simulation and test results of the transmission coefficient are flat and close to -3 dB in the passband, indicating that the energy is evenly distributed to the two output ports.

[0105] Please see Figure 5 (b): Phase difference at the output ports of the even-mode excitation. The curve shows that the phase difference measured at the two output ports is stable at around 0° (within ±5°) throughout the 24-30GHz frequency band, as demonstrated by both simulation and test results, proving the successful excitation of the equal-amplitude and in-phase (even-mode) signal.

[0106] Please see Figure 5 (c): S-parameters of odd-mode excitation. The curves show that, within the 24.87-28.17 GHz frequency band, the simulation and test results of the reflection coefficient of the odd-mode port are both below -10 dB; the simulation and test results of the transmission coefficient are flat and close to -3 dB in the passband.

[0107] Please see Figure 5 (d): Phase difference at the output port of the odd-mode excitation. The curve shows that the phase difference measured at the two output ports is within the 24.87-28.17 GHz frequency band, and the simulation and test results are stable at around 180° (e.g., 175°-185°), which proves the successful excitation of the equal-amplitude inverted (odd-mode) signal.

[0108] 3. Overall performance verification of the antenna array:

[0109] Experimental method: The multimode substrate integrated waveguide coupler was integrated with the leaky wave antenna unit and then simulated and tested. The S-parameters of the antenna port were measured to determine the operating bandwidth. The scanning characteristics of the sum and difference beams were measured by changing the frequency of the input signal. At a fixed frequency point (e.g., 27 GHz), the three-dimensional radiation patterns of the sum and difference beams were measured.

[0110] Please see Figure 6 (a): S-parameters of the SIWLWA array. The curves show that under even-mode excitation, the -10dB impedance bandwidth at the antenna port covers 24-31GHz; under odd-mode excitation, the impedance bandwidth covers 24.87-28.17GHz, which corresponds to the performance of the multi-mode substrate integrated waveguide coupler, proving that the antenna array has broadband matching characteristics.

[0111] Please see Figure 6 (b): Radiation pattern of beam scanning. A set of beam patterns measured at different frequencies (e.g., 25, 26, 27, 28, 29 GHz) are superimposed. The main lobe of the beam scans continuously from approximately -30° to +7.5° as the frequency increases, visually demonstrating the frequency scanning capability of the antenna.

[0112] Please see Figure 6 (c): Three-dimensional radiation pattern of the sonic beam at 27 GHz. The three-dimensional graphic shows that the sonic beam is a pencil beam pointing at a specific angle (e.g., -10°), with a sharp main lobe, low sidelobe levels, and a peak gain of up to 14.7 dBi according to simulation and testing.

[0113] Please see Figure 6 (d): Three-dimensional radiation pattern of the 27GHz time difference beam. The three-dimensional graphic shows that the difference beam presents a very deep and sharp null in front (0°), with a main lobe on each side. The simulation and test results of the null depth are better than -35dB, which fully meets the requirements of monopulse radar for high-precision angle tracking.

[0114] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A leaky wave antenna array based on a multimode substrate integrated waveguide coupler, characterized in that, include: Dielectric substrate, multimode substrate integrated waveguide coupler and two leaky antenna elements; The multimode substrate integrated waveguide coupler is integrated on the dielectric substrate and is configured to excite the modes and modes of the substrate integrated waveguide respectively within the same frequency range, generating an equal-amplitude and in-phase even-mode signal and an equal-amplitude and out-of-phase odd-mode signal. Two leaky antenna elements are symmetrically arranged on both sides of the metal layer on the upper surface of the dielectric substrate, and are respectively connected to the two output ports of the multimode substrate integrated waveguide coupler. The two leaky antenna elements are configured to respond to the even-mode signal radiation and beam and the odd-mode signal radiation difference beam. The multimode substrate integrated waveguide coupler includes: The gradient microstrip line disposed on the lower surface of the dielectric substrate is used for excitation. The gradient microstrip line is configured to achieve impedance matching in a frequency range of 24 GHz to 30 GHz. A dielectric layer is disposed above the dielectric substrate, and a microstrip line is disposed on the dielectric layer. A slot is formed in the metal layer on the upper surface of the dielectric substrate, and the microstrip line is perpendicularly coupled to the slot for excitation. mold; Each of the leaky antenna elements comprises a plurality of periodically arranged asymmetric elements, each of the asymmetric elements comprising: A longitudinal slot is provided in the metal layer on the upper surface of the dielectric substrate, wherein the longitudinal slot has a length of 3.5 mm and a width of 0.2 mm, and the offset between the longitudinal slot and the inductor post is 2.9 mm; An inductor post that penetrates the dielectric substrate and connects the upper and lower surface metal layers of the dielectric substrate; The longitudinal slot and the inductor post are alternately offset in opposite directions relative to the central axis of the leaky antenna element.

2. The leaky antenna array based on a multi-mode substrate integrated waveguide coupler according to claim 1, characterized in that, The multimode substrate integrated waveguide coupler also includes: an isolation structure; The isolation structure is composed of an array of metallized isolation vias disposed on the dielectric substrate, and the array of isolation vias connects the upper and lower surface metal layers of the dielectric substrate.

3. The leaky antenna array based on a multi-mode substrate integrated waveguide coupler according to claim 1, characterized in that, include: The longitudinal gaps within each of the asymmetric units and the inductor pillars constitute an asymmetric hybrid reactance structure; The asymmetric hybrid reactance structure is used to adjust the ratio of the phase constant to the free space wave number so that the beam pointing angle of the leaky wave antenna array meets the preset requirements under the preset fast wave condition, thereby suppressing the open stopband effect.

4. A leaky antenna array based on a multi-mode substrate integrated waveguide coupler according to claim 3, characterized in that, The preset fast wave conditions are as follows: ； In the formula, To adjust the phase constant, is the free space wavenumber.

5. A leaky antenna array based on a multi-mode substrate integrated waveguide coupler according to claim 3, characterized in that, The specific preset requirements are as follows: ； In the formula, The direction of radiation is n, the spatial harmonic order is n, and the period of the asymmetric unit is p.

6. A leaky antenna array based on a multi-mode substrate integrated waveguide coupler according to claim 1, characterized in that, Each of the leaky antenna elements has a metal slot short-circuit boundary at the end away from the multimode substrate integrated waveguide coupler. The metal slot short-circuit boundary includes a metallized through-hole that penetrates the upper and lower surface metal layers of the dielectric substrate.

7. A leaky antenna array based on a multi-mode substrate integrated waveguide coupler according to claim 1, characterized in that, The dielectric substrate also has a coupling slot located between the two leaky antenna elements for coupling. Modulus energy and adjust phase constant.

8. A leaky antenna array based on a multi-mode substrate integrated waveguide coupler according to claim 1, characterized in that, The dielectric material of the dielectric substrate is RO4350.

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