A multi-band antenna for high-speed rail mobile communication system

Abstract

The application relates to the technical field of high-speed rail mobile communication equipment, in particular to a multi-band antenna for a high-speed rail mobile communication system. The multi-band antenna is arranged on an antenna floor and comprises a mounting unit including a substrate and a fixing module, a functional unit including an asymmetric microstrip dipole structure (an upper array element, a lower array element and a microstrip feed line), a multi-band low standing wave ratio structure (an open-circuit stub and a coupling ground structure) and a feed structure (a feed cable and a feed adapter block), the upper array element and the lower array element are asymmetric structures, the upper array element is provided with a low-frequency radiation stub along the length direction, and the upper array element is provided with an adjusting stub on the side; the lower array element is connected with the upper array element through the microstrip feed line; the open-circuit stub is arranged at a feed port of the microstrip feed line, and the coupling ground structure is arranged at a ground end of the lower array element. The multi-band antenna meets the requirements of multi-frequency bands, omnidirection and high gain in a very small volume through the design of structure asymmetry + electromagnetic compensation + performance recovery.

Description

Technical Field

[0001] This application relates to the field of high-speed rail mobile communication equipment technology, and in particular to a multi-band antenna for a high-speed rail mobile communication system. Background Technology

[0002] With the rapid development of high-speed rail services, the communication system of high-speed rail needs to support multiple services such as train control voice, dispatching and command, and local hotspots in carriages. Therefore, miniaturized, broadband, and high-gain antenna products are gradually becoming the research and development trend.

[0003] To meet the operational needs of high-speed rail, the communication antennas currently used mainly include multi-antenna systems, three-dimensional metal structure antennas, and microstrip antennas. Multi-antenna systems combine multiple antennas together, reducing overall size through partial structural reuse. However, due to limited installation space, interference between antennas in multi-antenna systems is severe. Among the various three-dimensional metal structure antennas, deformable monopole antennas achieve wide bandwidth, high gain, and good omnidirectional performance by loading short-circuited stubs onto a stepped monopole. Deformable planar inverted-F (PIFA) antennas use a tapered butterfly monopole with trapezoidal slots to achieve wide bandwidth and high gain performance, but their omnidirectional performance at mid-to-high frequencies is slightly worse, and the antenna width and height may cause significant wind resistance in subsequent structures. Among the many microstrip antennas, monopole microstrip antennas achieve multi-band omnidirectional radiation performance by loading bending elements, edge resonant elements, and back resonant elements, but the gain is slightly lower. Bipole microstrip antennas obtain multi-band radiation performance by slotting and loading resonant elements. At the same time, by reasonably designing the height of the antenna from the ground, image reflection is introduced to improve the omnidirectional gain, but the antenna height is relatively high, which affects the use of bipole microstrip antennas.

[0004] Therefore, traditional high-speed rail communication antennas cannot simultaneously possess the characteristics of high bandwidth, high omnidirectionality, high gain, and lightweight. Summary of the Invention

[0005] This application provides a multi-band antenna for a high-speed rail mobile communication system to solve the following technical problem: how to simultaneously improve the high bandwidth, omnidirectionality, gain, and lightweight of the communication antenna.

[0006] In a first aspect, embodiments of this application provide a multi-band antenna for a high-speed rail mobile communication system. The multi-band antenna is mounted on an antenna floor and includes: The mounting unit includes a base plate and a fixing module, wherein the bottom of the base plate is fixed to the antenna floor via the fixing module; The functional unit includes an asymmetric microstrip dipole structure, a multi-band low VSWR structure, and a feeding structure. The asymmetric microstrip dipole structure is etched onto the substrate and includes an upper dipole, a lower dipole, and a microstrip feed line. The upper and lower dipoles are asymmetric structures. The upper dipole extends along its length and is designed with low-frequency radiation stubs. Adjustment stubs are provided on the side of the upper dipole. One end of the lower dipole is connected to the microstrip feed line, and the other end of the microstrip feed line is led out to the plane where the upper dipole is located as a ground plane. The multi-band low VSWR structure includes an open-circuit stub and a coupled grounding structure. The open-circuit stub is disposed at the feed port of the microstrip feed line, and the coupled grounding structure is disposed at the grounding terminal of the lower array. The power supply structure includes a power supply cable and a power supply adapter block. The inner core of the power supply cable is fixedly connected to one side of the microstrip feed line, and the outer sheath of the power supply cable is fixedly connected to the ground and the power supply adapter block. The other side of the power supply cable serves as an RF connector and an antenna port.

[0007] Optionally, the adjustment branch is located on the side of the upper array near the low-frequency radiation branch, and the adjustment branch is an L-shaped branch.

[0008] Optionally, the coupling grounding structure and the fixing module can be an integrated structure or separate structures.

[0009] Optionally, the fixing module includes a metal clamp and / or a groove, wherein if the fixing module is a groove, the size of the groove matches the size of the junction between the substrate and the antenna ground plane.

[0010] Optionally, the asymmetric microstrip dipole structure further includes a metal via, through which the microstrip feed line is led out to the surface of the upper array.

[0011] Optionally, the thickness of the substrate is 1.2mm to 1.8mm, the height of the substrate is 80mm to 85mm, and the width of the substrate is 80mm to 85mm.

[0012] Optionally, the height of the multi-band antenna is ≤85mm.

[0013] Optionally, the resistance of the RF connector is 48Ω~52Ω.

[0014] Optionally, the voltage standing wave ratio (VSWR) of the multi-band antenna is ≤1.5 in the frequency bands of 750MHz~1116MHz, 1.7MHz~2.7GHz, and 5.7MHz~5.8GHz, the gain of the multi-band antenna is 6.3dBi~10.2dBi, and the azimuth non-circularity of the multi-band antenna is ≤6.3dB.

[0015] Optionally, the design method for the multi-band antenna includes: A half-wave dipole antenna is mounted on an antenna floor and a ground mirror current is introduced to improve the overall antenna gain, forming a pre-defined symmetrical array antenna. The symmetrical element of the preset symmetrical element antenna is designed as an asymmetrical element. The lower element of the asymmetrical element is shortened and widened. The low-frequency radiation stub in the upper element of the asymmetrical element is moved down. At the same time, an adjustment stub is introduced on the side of the upper element to adjust the high and low frequency current distribution, thus obtaining an asymmetrical microstrip dipole structure. An open-circuit stub is introduced at the feed port of the preset symmetrical array antenna. At the same time, a coupled grounding structure is introduced in the lower array to adjust the impedance matching of different frequency bands, resulting in a composite structure of multi-band low VSWR structure and asymmetric microstrip dipole structure. The power supply cable is connected to the power supply end of the microstrip power supply of the composite structure. At the same time, the power supply cable is connected to the power supply adapter block to balance the power supply and form a functional unit. The functional unit is fixed on the substrate, and then the substrate containing the functional unit is mounted on the antenna floor through the fixing module to obtain a multi-band antenna.

[0016] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a multi-band antenna for a high-speed rail mobile communication system. Through a closed-loop design combining structural asymmetry, electromagnetic compensation, and performance recovery, the antenna utilizes an asymmetric microstrip dipole structure to convert a traditional symmetrical array into an asymmetric structure. This shortens and widens the lower array and moves the low-frequency radiation stub of the upper array downwards, enabling half-wave resonance within a smaller space for the effective current path. The antenna height is reduced from 118mm to 81mm, achieving lightweight design. Simultaneously, vertical mounting above the floor introduces a ground-mirror current, effectively creating a two-element array that enhances radiation intensity and achieves high gain. Furthermore, adjusting stubs are introduced on the sides of the upper array. These stubs act as parasitic elements to adjust the distribution of high and low frequency currents, compensating for azimuth non-uniformity caused by the shortening of the lower array. This results in a horizontal radiation pattern non-circularity better than 1.8dB, simultaneously optimizing omnidirectionality and gain frequency balance. Furthermore, the feed port of the multi-band low VSWR structure incorporates an open-circuit stub, which can adjust the impedance matching from 1.7GHz to 2.7GHz. The lower array features a coupled grounding structure to improve impedance matching from 825MHz to 960MHz. These two frequency bands complement each other, resulting in a VSWR better than 1.5 across all three bands, achieving high bandwidth. Finally, the feed structure and mounting structure are introduced. The feed cable of the feed structure achieves balanced feeding via a feed adapter block, suppressing common-mode current. The mounting structure reduces the number of components required for fixing the multi-band antenna, improving its lightweight design. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of an asymmetric microstrip dipole structure in a multi-band antenna for a high-speed rail mobile communication system provided in this application embodiment; Figure 2 A schematic diagram of a multi-band low VSWR structure in a multi-band antenna for a high-speed rail mobile communication system provided in this application embodiment; Figure 3 A multi-band antenna structure diagram for a high-speed rail mobile communication system is provided in this application embodiment; Figure 4 A flowchart illustrating a design method for a multi-band antenna for a high-speed rail mobile communication system, provided in this application embodiment; Figure 5 Comparative diagrams of the design of multiband antennas provided in Embodiment 1 and Comparative Examples 1 to 3 of this application; Figure 6 A simulation diagram of the voltage standing wave ratio (VSWR) of a multi-band antenna for a high-speed rail mobile communication system is provided as an embodiment of this application. Figure 7 A gain diagram of a multi-band antenna for a high-speed rail mobile communication system is provided as an embodiment of this application; Figure 8 This application provides a normalized radiation pattern for a multi-band antenna used in a high-speed rail mobile communication system, wherein... Figure 8 A is the elevation pattern of the multi-band antenna. Figure 8 B is the azimuth pattern of the multi-band antenna; Figure 9 This is a simulation comparison chart of the voltage standing wave ratio of the multi-band antennas provided in Embodiment 1 and Comparative Examples 1 to 3 of this application; Figure 10 Gain comparison diagrams of the multi-band antennas provided in Embodiment 1 and Comparative Examples 1 to 3 of this application; Among them, 1-upper array, 2-lower array, 3-low frequency radiation stub, 4-adjustment stub, 5-open circuit stub, 6-coupled grounding structure, 7-substrate, 8-feed cable, 9-feed adapter block, 10-fixed module, 11-antenna floor, 12-metal via. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The range descriptions used in this application, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "comprising" and others used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships involved in this document, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained by purchasing from the market or by existing methods.

[0022] It should be noted that, because the communication antennas for high-speed trains need to be installed in radomes with low wind resistance structures, their structural dimensions naturally require miniaturization. In addition to high gain, these antennas should also possess good horizontal omnidirectionality to avoid communication blind spots. Figure 1 An exemplary schematic diagram of an asymmetric microstrip dipole structure in a multi-band antenna for a high-speed rail mobile communication system is shown in an embodiment of this application. Figure 2 An exemplary schematic diagram of a multi-band low VSWR structure in a multi-band antenna for a high-speed rail mobile communication system is shown in an embodiment of this application. Figure 3 An exemplary diagram of a multi-band antenna structure for a high-speed rail mobile communication system is shown in an embodiment of this application. like Figures 1 to 3 As shown in the figure, this application embodiment provides a multi-band antenna for a high-speed rail mobile communication system. The multi-band antenna is disposed on an antenna ground plane 11, and the multi-band antenna includes: The mounting unit includes a base plate 7 and a fixing module 10, wherein the bottom of the base plate 7 is fixed to the antenna ground plate 11 by the fixing module 10. The functional unit includes an asymmetric microstrip dipole structure, a multi-band low VSWR structure, and a feeding structure. The asymmetric microstrip dipole structure is etched on the substrate 7. The asymmetric microstrip dipole structure includes an upper array 1, a lower array 2, and a microstrip feed line. The upper array 1 and the lower array 2 are asymmetric structures. The upper array 1 has a low-frequency radiation stub 3 extending along its length, and an adjustment stub 4 is provided on the side of the upper array 1. The lower array 2 is connected to one end of the microstrip feed line, and the other end of the microstrip feed line is led out to the plane where the upper array 1 is located as a ground plane. The multi-band low VSWR structure includes an open-circuit stub 5 and a coupled grounding structure 6. The open-circuit stub 5 is disposed at the feed port of the microstrip feeder, and the coupled grounding structure 6 is disposed at the grounding terminal of the lower element 2. The power supply structure includes a power supply cable 8 and a power supply adapter block 9. The inner core of the power supply cable 8 is fixedly connected to one side of the microstrip feeder, and the outer sheath of the power supply cable 8 is fixedly connected to the ground and the power supply adapter block 9. The other side of the power supply cable 8 serves as an RF connector and an antenna port.

[0023] It should be noted that the power supply adapter block 9 and the ground can be fixedly connected by welding or screws.

[0024] It should be noted that the power supply cable 8 can be a semi-steel cable.

[0025] It should be noted that, theoretically, the gain of a half-wave dipole antenna and a λ / 4 monopole antenna is 2.15 dBi. In practice, the size of the antenna ground plane 11 of the monopole is easily limited, resulting in the gain of the antenna ground plane 11 of the monopole often being lower than the theoretical value. The usual methods to improve the gain are: (1) forming an array or using a directional structure to enhance the directivity; (2) reducing losses or optimizing the current distribution to improve radiation efficiency. The embodiments of this application provide a multi-band antenna for a high-speed rail mobile communication system. This multi-band antenna couples the four objectives of high bandwidth, omnidirectionality, high gain and lightweight into a unified design framework through an asymmetric microstrip dipole architecture. It is not a simple superposition of independent technologies, but a synchronous improvement achieved through electromagnetic synergy between structures. The specific mechanism is as follows: I. High bandwidth: Impedance matching of multi-band low VSWR structure.

[0026] After miniaturization, the input impedance of multi-band antennas changes drastically with frequency, making it difficult to achieve low VSWR (standby wave ratio) across multiple frequency bands simultaneously using conventional designs. This multi-band antenna employs a dual-path complementary matching mechanism: 1. Open Stub 5 (High Frequency Band): An open stub 5 is introduced at the feed port of the microstrip feeder. It is equivalent to a parallel variable reactance element. By adjusting the length and position of the open stub 5, impedance compensation is formed in the 1.7GHz~2.7GHz frequency band to offset the reactance mismatch introduced by the asymmetric structure.

[0027] 2. Coupled grounding structure 6 (low frequency band): A coupled grounding structure 6 is set at the grounding terminal of the lower element 2. By utilizing the resonance effect of the coupling capacitor and the grounding inductor, an additional impedance transformation is introduced in the 825MHz~960MHz frequency band, pulling the input impedance that originally deviated from 50Ω back to the matching center.

[0028] The spatial separation and frequency band complementarity of the two technologies ultimately enable the antenna to achieve a voltage standing wave ratio (VSWR) better than 1.5 in the three frequency bands of 825–960 MHz, 1.7–2.7 GHz, and 5.7–5.8 GHz, thus realizing broadband multi-frequency coverage.

[0029] II. Omnidirectionality: The azimuth symmetry between the microstrip dipole radiation and the ground mirror image is maintained.

[0030] High-speed rail communication requires 360° planar coverage to avoid communication blind spots: 1. Intrinsic omnidirectionality of dipoles: Microstrip dipole structures themselves have near-omnidirectional radiation characteristics in the horizontal plane. Compared with deformed PIFAs or directional arrays, there is no coverage blind zone caused by beam directivity.

[0031] 2. Vertical Mounting and Mirror Current: The functional units of the multi-band antenna are vertically mounted on the antenna floor 11 via the fixing module 10, allowing the functional units to be erected on the ground. The antenna floor 11 introduces a mirror current. This mirror current is superimposed in phase with the main current of the multi-band antenna, which not only enhances the radiation intensity but also maintains a uniform horizontal radiation field due to the rotational symmetry of the structure around the vertical axis.

[0032] 3. Azimuth compensation for asymmetric structure: Although the upper element 1 and the lower element 2 are asymmetric structures, the adjusting branch 4 compensates for the azimuth plane non-uniformity caused by the shortening of the lower element 2 by adjusting the current distribution in the horizontal direction, so that the horizontal pattern non-circularity of 825MHz~960MHz is better than 1.8dB and that of 1.7GHz~2.7GHz is better than 6.3dB.

[0033] III. High Gain: Dual Enhancement from Ground Mirror Effect and Current Distribution Optimization.

[0034] Traditional miniaturized antennas often come at the cost of gain. This multiband antenna maintains high gain while reducing size in the following ways: 1. Ground mirror gain enhancement: The functional unit is vertically mounted above the floor. Utilizing the mirror principle of an ideal conductor ground, it is equivalent to a two-element array of "antenna + mirror antenna". The electric fields are superimposed in phase in the direction perpendicular to the floor, and the theoretical gain is significantly improved compared to the free space dipole.

[0035] 2. Current balancing of adjustment stub 4: The adjustment stub 4 on the side of the upper element 1 acts as a parasitic radiation unit, changing the high-frequency current path, so that the current that was originally concentrated at low frequency due to the shortening of the lower element 2 is redistributed, realizing "uniform increase of gain in the frequency band as the frequency increases", avoiding gain dips at certain frequency points.

[0036] 3. Balanced feeding of semi-steel cable and feeder adapter block 9: Feeder adapter block 9 ensures that the outer shielding layer of the coaxial cable is tightly connected to the lead-out ground of the microstrip, suppresses common-mode current, reduces the distortion of the radiation pattern by the feeder line, and ensures that the measured gain value is close to the simulation ideal value.

[0037] IV. Lightweight: Deep miniaturization of asymmetric structure integrated with substrate 7.

[0038] 1. Asymmetric element height compression: Traditional symmetric half-wave dipoles or λ / 4 monopoles have a relatively large height (approximately 118 mm). This multi-band antenna shortens and widens the lower element 2, while the upper element 1, which includes the low-frequency radiation stub 3, is moved upwards as a whole. This allows the effective current path to achieve half-wave resonance in a smaller space, gradually reducing the antenna height from 118 mm to 81 mm, with a width of only 82 mm.

[0039] 2. Integrated etching of FR4 substrate 7: The upper array 1, the lower array 2, the microstrip feed line, and the open branch 5 are all etched in the same FR4 substrate 7. No three-dimensional metal processing or complex assembly is required, the overall weight is significantly reduced, and it can be directly integrated into a low-drag radome.

[0040] 3. Reuse of fixed module 10: The metal clamp serves as both a mechanical fastener and a coupling grounding structure 6, reducing the number of independent parts, further reducing weight and simplifying assembly.

[0041] V. Collaboration Mechanism.

[0042] The specific collaboration mechanism is shown in Table 1.

[0043] Table 1. Collaboration Mechanism

[0044] asymmetric array Introducing a mismatch (requiring compensation) Maintain horizontal symmetry Mirroring Core weight loss methods Adjusting branches 4 Indirect impedance optimization Compensation for azimuth non-uniformity Equalize the gain at each frequency point No additional volume Open-circuit stub 5+ coupled grounding Directly broaden multi-band matching The impact on the radiation pattern is controllable. Reduce mismatch loss Integrated on substrate 7 Vertical floor installation / Mirroring maintains omnidirectionality Mirroring boosts gain No additional directional structure required

[0045] In summary, the multi-band antenna for a high-speed rail mobile communication system provided in this application has the following key synergies: asymmetric design is the core of achieving lightweight multi-band antennas, but it can lead to impedance mismatch and uneven current distribution; open-circuit stub 5 and coupled grounding structure 6 are specifically designed to compensate for impedance mismatch, and adjusting stub 4 is specifically designed to repair uneven current distribution. Through a closed-loop design of "structural asymmetry → electromagnetic compensation → performance recovery", these structures can simultaneously meet the stringent requirements of multi-band, omnidirectional, and high-gain within an extremely small volume of 81mm × 82mm.

[0046] In some alternative embodiments, the adjustment branch 4 is disposed on the side of the upper array 1 near the low-frequency radiation branch 3, and the adjustment branch 4 is an L-shaped branch.

[0047] In these embodiments, the adjustment stub 4 is set on the side of the upper array 1 near the low-frequency radiation stub 3, and the adjustment stub 4 is set as an L-shaped stub. The adjustment stub 4 can compensate for the decrease in mid-low frequency gain caused by the shortening of the lower array 2.

[0048] In some alternative implementations, the coupling grounding structure 6 and the fixing module 10 are either an integral structure or separate structures.

[0049] In these embodiments, the coupling grounding structure 6 and the fixing module 10 are configured as an integrated structure or separate structures. The functional units of the multi-band antenna can be vertically mounted on the antenna floor 11 through the fixing module 10, so that the horizontal radiation field remains uniform. In addition, configuring the coupling grounding structure 6 and the fixing module 10 as an integrated structure allows the fixing module 10 to serve as both a mechanical fixing component and the coupling grounding structure 6, reducing the number of independent parts, further reducing weight, and simplifying assembly.

[0050] In some alternative embodiments, the fixing module 10 includes a metal clamp and / or a groove, wherein, if the fixing module 10 is a groove, the size of the groove matches the size of the junction between the substrate 7 and the antenna ground plane 11.

[0051] In these embodiments, using metal clamps and / or grooves as fixing modules 10 allows the functional units of the multi-band antenna to be vertically mounted on the antenna floor 11, ensuring uniformity of the horizontal radiation field. In addition, based on the use of metal clamps in fixing modules 10, the metal clamps can not only serve as mechanical fasteners but also as coupling grounding structures 6, further reducing weight and simplifying assembly.

[0052] In some alternative embodiments, the asymmetric microstrip dipole structure further includes a metal via 12 through which the microstrip feed line is led out to the surface of the upper array 1.

[0053] In these embodiments, a metal via 12 is introduced into the asymmetric microstrip dipole structure, and the microstrip feed line is led out through the metal via 12 to the surface where the upper array 1 is located, so that the microstrip feed line can be used as a lead-out ground.

[0054] In some optional embodiments, the thickness of the substrate 7 is 1.2mm to 1.8mm, the height of the substrate 7 is 80mm to 85mm, and the width of the substrate 7 is 80mm to 85mm.

[0055] In these embodiments, the substrate 7, with a thickness of 1.2mm to 1.8mm, a height of 80mm to 85mm, and a width of 80mm to 85mm, can accommodate the asymmetric microstrip dipole structure of the functional unit to the maximum extent and ensure that the height of the multi-band antenna is within a very small range, thereby achieving the lightweighting of the multi-band antenna.

[0056] The thickness of the substrate 7 can be 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm or 1.8mm.

[0057] The height of the substrate 7 can be 80mm, 81mm, 82mm, 83mm, 84mm or 85mm.

[0058] The width of the substrate 7 can be 80mm, 81mm, 82mm, 83mm, 84mm or 85mm.

[0059] In some alternative implementations, the height of the multi-band antenna is ≤85mm.

[0060] In these embodiments, the multi-band antenna with a height ≤ 85 mm illustrates that the basic functions of a communication antenna are achieved at a relatively small height through functional units such as asymmetric microstrip dipole structure, multi-band low VSWR structure and feeding structure.

[0061] In some alternative implementations, the resistance of the RF connector is 48Ω to 52Ω.

[0062] In these implementations, the RF connector with a resistance of 48Ω to 52Ω can meet the standard of a 50Ω communication antenna, enabling the multi-band antenna to meet the usage requirements of communication antennas for high-speed rail.

[0063] In some optional embodiments, the voltage standing wave ratio (VSWR) of the multi-band antenna is ≤1.5 in the frequency bands of 750MHz~1116MHz, 1.7MHz~2.7GHz, and 5.7MHz~5.8GHz, the gain of the multi-band antenna is 6.3dBi~10.2dBi, and the azimuth non-circularity of the multi-band antenna is ≤6.3dB.

[0064] In these embodiments, multi-band antennas with a voltage standing wave ratio ≤1.5, a gain of 6.3dBi~10.2dBi, and an azimuth out-of-circularity ≤6.3dB in the 750MHz~1116MHz, 1.7MHz~2.7GHz, and 5.7MHz~5.8GHz frequency bands can meet the requirements of communication antennas for high bandwidth, omnidirectional high gain performance, small size, and thin and light structure.

[0065] Figure 4 An exemplary flowchart illustrates a design method for a multi-band antenna for a high-speed rail mobile communication system provided in an embodiment of this application;

[0066] In some alternative implementations, such as Figure 4 As shown, the design method of the multi-band antenna includes: S1. The half-wave dipole antenna is mounted on the antenna floor 11 and a ground mirror current is introduced to improve the overall antenna gain and form a preset symmetrical array antenna. S2. The symmetrical element of the preset symmetrical element antenna is designed as an asymmetrical element. The lower element 2 of the asymmetrical element is shortened and widened. The low-frequency radiation stub 3 in the upper element 1 of the asymmetrical element is moved down. At the same time, an adjustment stub 4 is introduced on the side of the upper element 1 to adjust the high and low frequency current distribution, thereby obtaining an asymmetrical microstrip dipole structure. S3. An open-circuit stub 5 is introduced at the feed port of the preset symmetrical array antenna. At the same time, a coupled grounding structure 6 is introduced in the lower array 2 to adjust the impedance matching of different frequency bands, thereby obtaining a composite structure of multi-band low VSWR structure and asymmetric microstrip dipole structure. S4. Connect the power supply cable 8 to the power supply end of the microstrip power supply of the composite structure, and at the same time, connect the power supply cable 8 to the power supply adapter block 9 to balance the power supply and form a functional unit. S5. Fix the functional unit on the substrate 7, and then install the substrate 7 containing the functional unit on the antenna ground plane 11 through the fixing module 10 to obtain a multi-band antenna.

[0067] In these embodiments, a conventional half-wave dipole antenna is first mounted on the antenna floor 11, and a ground mirror current is introduced to form a pre-defined symmetrical dipole antenna. Then, the symmetrical dipoles of the pre-defined symmetrical dipole antenna are designed as asymmetrical dipoles. The lower dipole 2 is shortened and widened, the low-frequency radiation stub 3 is moved down, and an adjustment stub 4 is introduced on the side of the upper dipole 1 to adjust the high and low frequency current distribution, forming an asymmetrical microstrip dipole structure. Additionally, an open-circuit stub 5 is introduced at the feed port of the pre-defined symmetrical dipole antenna, and a coupling grounding structure 6 is introduced in the lower dipole 2. This allows for comprehensive adjustment of impedance matching across different frequency bands, forming a composite structure of a multi-band low VSWR structure and an asymmetrical microstrip dipole structure. Furthermore, a feed cable 8 is connected to the feed end of the microstrip feed line, and the feed cable 8 is connected to the feed adapter block 9 to balance the feed of the multi-band antenna, forming a functional unit. Finally, the fixing module 10 and the substrate 7 are fixedly mounted on the antenna floor 11 to complete the design of the multi-band antenna.

[0068] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0069] Example 1 A multi-band antenna for a high-speed rail mobile communication system, the multi-band antenna being mounted on an antenna floor 11, and comprising: The mounting unit includes a base plate 7 and a fixing module 10. The bottom of the base plate 7 is fixed to the antenna ground plate 11 by the fixing module 10. The functional unit includes an asymmetric microstrip dipole structure, a multi-band low VSWR structure, and a feeding structure. The asymmetric microstrip dipole structure is etched on the substrate 7. The asymmetric microstrip dipole structure includes an upper array 1, a lower array 2, and a microstrip feed line. The upper array 1 and the lower array 2 are asymmetric structures. The upper array 1 is designed with a low-frequency radiation stub 3 extending along its length direction. An adjustment stub 4 is provided on the side of the upper array 1. The lower array 2 is connected to one end of the microstrip feed line, and the other end of the microstrip feed line is led out to the plane where the upper array 1 is located to serve as a ground plane. The multi-band low VSWR structure includes an open stub 5 and a coupled grounding structure 6. The open stub 5 is located at the feed port of the microstrip feeder, and the coupled grounding structure 6 is located at the grounding terminal of the lower element 2. The power supply structure includes a power supply cable 8 and a power supply adapter block 9. The inner core of the power supply cable 8 is fixedly connected to one side of the microstrip feeder, and the outer sheath of the power supply cable 8 is fixedly connected to the ground and the power supply adapter block 9. The other side of the power supply cable 8 serves as an RF connector and an antenna port.

[0070] The adjustment branch 4 is located on the side of the upper array 1 near the low-frequency radiation branch 3, and the adjustment branch 4 is an L-shaped branch.

[0071] The coupling grounding structure 6 and the fixed module 10 can be integrated into one unit or separate units.

[0072] The fixing module 10 includes a metal clamp and / or a groove. When the fixing module 10 is a groove, the size of the groove matches the size of the contact between the substrate 7 and the antenna ground 11.

[0073] The asymmetric microstrip dipole structure also includes: a metal via 12, through which the microstrip feed line is led out to the surface of the upper array 1.

[0074] The substrate 7 is an FR4 substrate 7, with a thickness of 1.6 mm, a height of 81 mm, and a width of 82 mm.

[0075] The resistance of the RF connector is 50Ω.

[0076] The design methods for multi-band antennas include: S1. The half-wave dipole antenna is mounted on the antenna floor 11 and a ground mirror current is introduced to improve the overall antenna gain and form a preset symmetrical array antenna. S2. The symmetrical element of the preset symmetrical element antenna is designed as an asymmetrical element. The lower element 2 of the asymmetrical element is shortened and widened. The low-frequency radiation stub 3 in the upper element 1 of the asymmetrical element is moved down. At the same time, an adjustment stub 4 is introduced on the side of the upper element 1 to adjust the high and low frequency current distribution and realize the miniaturization of the multi-band antenna, thus obtaining an asymmetrical microstrip dipole structure. S3. After miniaturization design of multi-band antenna, the voltage standing wave ratio (VSWR) increases within the frequency band. Since the VSWR requirement of high-speed rail communication antenna is ≤1.5 within the operating frequency band, impedance matching design of the antenna is required. An open-circuit stub 5 is introduced at the feed port of the preset symmetrical array antenna to adjust the impedance matching of the 1.7GHz~2.7GHz frequency band. At the same time, a coupling grounding structure 6 is introduced in the lower array 2 to improve the impedance matching of the 825MHz~960MHz frequency band, resulting in a composite structure of multi-band low VSWR structure and asymmetric microstrip dipole structure. S4. After the above miniaturization and impedance matching design, simulation revealed that the feed cable 8 has a significant impact on the radiation pattern of the multiband antenna. Therefore, the feed cable 8 is fixedly connected to the microstrip feed terminal with a semi-steel cable (structural form). In order to achieve balanced feeding, a feed adapter block 9 is added and connected to the feed cable 8 to form a functional unit. S5. Fix the functional unit on the substrate 7, and then install the substrate 7 containing the functional unit on the antenna ground plane 11 through the fixing module 10 to obtain a multi-band antenna.

[0077] Comparative Example 1 Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same: A conventional half-wave dipole antenna is used, which is a symmetrical array antenna printed on a substrate 7. The substrate 7 is made of FR4 and has a thickness of 1.6 mm. The antenna height of the half-wave dipole antenna is 118 mm and the width of the half-wave dipole antenna is 50 mm.

[0078] Comparative Example 2 Compared to Comparative Example 1, the differences in this comparative example are as follows, while the rest are the same: Based on the half-wave dipole antenna of Comparative Example 1, the lower element 2 is shortened to form a multi-band antenna, and the height of the multi-band antenna is reduced to 94mm.

[0079] Comparative Example 3 Compared to Comparative Example 2, this comparative example differs as follows, while all other aspects remain the same: Based on the multiband antenna of Comparative Example 2, an adjustment stub 4 is introduced into the upper array 1, so that the height of the multiband antenna remains unchanged; an open-circuit stub 5 is introduced at the feed port of the multiband antenna.

[0080] Relevant experimental and effect data:

[0081] 1. The multi-band antenna obtained in Example 1 was vertically mounted on a 1m×1m horizontal metal surface to simulate the onboard scenario of a high-speed train. The voltage standing wave ratio, gain, and normalized radiation pattern of the multi-band antenna were statistically analyzed. The results are as follows: Figures 6 to 8 As shown. By Figures 6 to 8 It can be seen that the multi-band antenna has a voltage standing wave ratio better than 1.5 in the frequency bands of 825MHz~960MHz, 1.7GHz~2.7GHz, and 5.7GHz~5.8GHz, a gain of 6.3dBi~10.2dBi, a horizontal pattern non-circularity better than 1.8dB in the 825MHz~960MHz band, and a horizontal pattern non-circularity better than 6.3dB in the 1.7GHz~2.7GHz band.

[0082] 2. The voltage standing wave ratio and gain of the multi-band antennas of Example 1, Comparative Examples 1 to 3 were compared, and the results are as follows: Figures 9 to 10 As shown. By Figure 9 and Figure 10As can be seen, compared to the traditional half-wave dipole antenna in Comparative Example 1, the multi-band antenna in Comparative Example 2 exhibits a significantly larger voltage standing wave ratio (VSWR) in the mid-to-low frequency band, with a gain reduction of 1dB to 2dB, and a significant decrease in gain at 2.2GHz. The multi-band antenna in Comparative Example 3 shows a gain improvement of 0.5dB to 1.0dB in the mid-to-low frequency band, and compared to Comparative Example 2, the multi-band antenna in Comparative Example 3 significantly reduces the VSWR in the mid-frequency band.

[0083] In summary, the multi-band antenna for high-speed rail mobile communication systems provided in this application embodiment can simultaneously meet the stringent requirements of multi-band, omnidirectional, and high gain within an extremely small volume of 81mm×82mm through a closed-loop design of "structural asymmetry → electromagnetic compensation → performance recovery".

[0084] In addition, this application provides a multi-band antenna for a high-speed rail mobile communication system. The multi-band antenna first effectively reduces its height by using an asymmetric microstrip dipole structure. Then, it introduces an adjustment stub 4 to adjust the high and low frequency current distribution and thus adjust the frequency band gain. It introduces a coupling grounding structure 6 and an open-circuit stub 5 to achieve good impedance matching. Finally, it introduces a feeding structure including a feeding cable 8 and a feeding adapter block 9, as well as an installation unit including a substrate 7 and a fixing module 10. The feeding structure balances the feeding, and the installation unit enables the multi-band antenna to be stably fixed in the high-speed rail application scenario.

[0085] Furthermore, this application provides a multi-band antenna for a high-speed rail mobile communication system. This multi-band antenna employs a high-gain miniaturized design: a half-wave dipole antenna is mounted on the ground, introducing a ground-mirror current to improve the overall gain of the multi-band antenna. Then, the symmetrical array is designed as an asymmetrical microstrip dipole structure, shortening and widening the lower array 2, and moving the low-frequency radiation stub 3 in the upper array 1 downwards. Additionally, to adjust the current distribution at certain frequencies, ensuring a uniform increase in gain within the band as the frequency increases, an adjustment stub 4 is introduced on the side of the upper array 1. Ultimately, the height of the multi-band antenna is reduced by 30% compared to a traditional half-wave dipole antenna, while ensuring that the gain variation of the multi-band antenna remains within a reasonable range.

[0086] Furthermore, this application provides a multi-band antenna for a high-speed rail mobile communication system. This multi-band antenna is only 82mm high, with a smaller overall size and lighter weight, making it easier to integrate into a low-drag radome. Additionally, the low-frequency radiation stub 3, adjustment stub 4, and coupling grounding structure 6 of this multi-band antenna can achieve omnidirectional high-gain performance across multiple bands, thus widening the conventional impedance bandwidth (a conventional specification of voltage standing wave ratio ≤ 2) within the GSM band to 750MHz~1116MHz.

[0087] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A multi-band antenna for a high-speed rail mobile communication system, characterized in that, The multi-band antenna is mounted on the antenna floor, and the multi-band antenna includes: The mounting unit includes a base plate and a fixing module, wherein the bottom of the base plate is fixed to the antenna floor via the fixing module; The functional unit includes an asymmetric microstrip dipole structure, a multi-band low VSWR structure, and a feeding structure. The asymmetric microstrip dipole structure is etched onto the substrate and includes an upper dipole, a lower dipole, and a microstrip feed line. The upper and lower dipoles are asymmetric structures. The upper dipole extends along its length and is designed with low-frequency radiation stubs. Adjustment stubs are provided on the side of the upper dipole. One end of the lower dipole is connected to the microstrip feed line, and the other end of the microstrip feed line is led out to the plane where the upper dipole is located as a ground plane. The multi-band low VSWR structure includes an open-circuit stub and a coupled grounding structure. The open-circuit stub is disposed at the feed port of the microstrip feed line, and the coupled grounding structure is disposed at the grounding terminal of the lower array. The power supply structure includes a power supply cable and a power supply adapter block. The inner core of the power supply cable is fixedly connected to one side of the microstrip feed line, and the outer sheath of the power supply cable is fixedly connected to the ground and the power supply adapter block. The other side of the power supply cable serves as an RF connector and an antenna port.

2. The multi-band antenna according to claim 1, characterized in that, The adjustment branch is located on the side of the upper array near the low-frequency radiation branch, and the adjustment branch is an L-shaped branch.

3. The multi-band antenna according to claim 1, characterized in that, The coupling grounding structure and the fixed module can be an integrated structure or separate structures.

4. The multi-band antenna according to claim 1 or 3, characterized in that, The fixing module includes a metal clamp and / or a groove. When the fixing module is a groove, the size of the groove matches the size of the junction between the substrate and the antenna ground plane.

5. The multi-band antenna according to claim 1, characterized in that, The asymmetric microstrip dipole structure further includes a metal via, through which the microstrip feed line is led out to the surface of the upper array.

6. The multi-band antenna according to claim 1, characterized in that, The substrate has a thickness of 1.2mm to 1.8mm, a height of 80mm to 85mm, and a width of 80mm to 85mm.

7. The multi-band antenna according to claim 1, characterized in that, The height of the multi-band antenna is ≤85mm.

8. The multi-band antenna according to claim 1, characterized in that, The resistance of the radio frequency connector is 48Ω~52Ω.

9. The multi-band antenna according to claim 1, characterized in that, The voltage standing wave ratio (VSWR) of the multi-band antenna is ≤1.5 in the frequency bands of 750MHz~1116MHz, 1.7MHz~2.7GHz, and 5.7MHz~5.8GHz. The gain of the multi-band antenna is 6.3dBi~10.2dBi, and the azimuth non-circularity of the multi-band antenna is ≤6.3dB.

10. The multi-band antenna according to any one of claims 1 to 9, characterized in that, The design method for the multi-band antenna includes: A half-wave dipole antenna is mounted on an antenna floor and a ground mirror current is introduced to improve the overall antenna gain, forming a pre-defined symmetrical array antenna. The symmetrical element of the preset symmetrical element antenna is designed as an asymmetrical element. The lower element of the asymmetrical element is shortened and widened. The low-frequency radiation stub in the upper element of the asymmetrical element is moved down. At the same time, an adjustment stub is introduced on the side of the upper element to adjust the high and low frequency current distribution, thus obtaining an asymmetrical microstrip dipole structure. An open-circuit stub is introduced at the feed port of the preset symmetrical array antenna. At the same time, a coupled grounding structure is introduced in the lower array to adjust the impedance matching of different frequency bands, resulting in a composite structure of multi-band low VSWR structure and asymmetric microstrip dipole structure. The power supply cable is connected to the power supply end of the microstrip power supply of the composite structure. At the same time, the power supply cable is connected to the power supply adapter block to balance the power supply and form a functional unit. The functional unit is fixed on the substrate, and then the substrate containing the functional unit is mounted on the antenna floor through the fixing module to obtain a multi-band antenna.

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