Miniaturized multi-band onboard antenna and design method thereof

Abstract

The invention relates to the technical field of antennas, in particular to a miniaturized multi-band onboard antenna and a design method thereof. Through an innovative integrated structure of the central main radiator and the asymmetric peripheral parasitic unit, effective coverage of multiple frequency bands and ultra-short wave frequency bands of Beidou No.3 is realized on a single antenna body, two pairs of independent antennas required in a traditional scheme are thoroughly omitted, the equipment space is greatly saved, the weight is reduced, and the cost is reduced. The device is especially suitable for vehicle-mounted, handheld and unmanned aerial vehicle-mounted equipment sensitive to size and weight. Through accurate structural design and optimized electromagnetic coupling, the antenna provided by the invention realizes a good circular polarization characteristic with an axial ratio of less than 3dB at a Beidou B1 frequency point, and ensures stable reception of navigation signals. Meanwhile, in all Beidou working frequency bands and ultra-short wave frequency bands, the voltage standing wave ratio is smaller than 2.5, and it is indicated that the antenna has excellent impedance matching and radiation efficiency in all target frequency bands.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and more specifically, to a miniaturized multi-band onboard antenna and its design method. Background Technology

[0002] With the rapid development of fields such as the Internet of Things, emergency rescue, special communications, and unmanned platforms, increasingly stringent requirements have been placed on the integration, miniaturization, and multi-mode communication capabilities of terminal devices. The BeiDou Navigation Satellite System and VHF / UHF radios are currently the core means for achieving precise positioning and reliable communication in portable devices used in field operations, vehicles, and ships.

[0003] In traditional technical solutions, to simultaneously achieve BeiDou navigation and VHF communication functions, two independent antennas are typically required on the device. This approach not only significantly increases the size, weight, and cost of the device but also compromises the device's aesthetic integrity and internal space utilization, making it difficult to meet the high integration requirements of modern portable and embedded devices.

[0004] To address these issues, several multi-band antenna designs have emerged in the prior art, such as monopoles, inverted-F antennas (IFAs), or their planar deformable antennas (PIFAs) to achieve frequency band coverage. However, these designs often face the following prominent drawbacks when pursuing multi-band operation: First, when covering low-frequency UHF bands such as 350MHz to 400MHz, the antenna size is often too large, making true miniaturization difficult; second, the isolation between different frequency bands is poor, easily leading to mutual interference; third, the impedance bandwidth of the antenna, especially in the low-frequency band, is usually narrow, making it difficult to meet the bandwidth requirements of practical applications; furthermore, many designs struggle to simultaneously achieve the right-hand circular polarization required for the BeiDou navigation band and the linear polarization required for the UHF band within a compact structure.

[0005] Therefore, there is an urgent need in this field for a novel multifunctional antenna design that is highly compact, easy to integrate with standard PCB processes, and can simultaneously and well support BeiDou-3 multi-frequency navigation and UHF broadband communication. Summary of the Invention

[0006] The purpose of this invention is to provide a miniaturized multi-band onboard antenna and its design method to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a miniaturized multi-band onboard antenna, comprising: Dielectric substrate; A radiator assembly is disposed on one side of the dielectric substrate. The radiator assembly includes a central main radiator and peripheral parasitic radiating units. The peripheral parasitic radiating units are arranged in an asymmetrical structure around the central main radiator and form coupling gaps with the central main radiator. A power supply port is disposed on the dielectric substrate; The structural dimensions of the central main radiator are configured to resonate within the BD3-B1, BD3-B2A, BD3-B2B, and BD3-B3 frequency bands; the structural dimensions of the peripheral parasitic radiating units, and the coupling relationship between the peripheral parasitic radiating units and the central main radiator, are configured to resonate together within the 350MHz to 400MHz ultra-shortwave frequency band.

[0008] A further technical solution of this application is that the dielectric substrate is made of a high-frequency circuit board material with a dielectric constant between 2.2 and 4.0.

[0009] A further technical solution of this application is: an L-type impedance matching network is integrated at the power supply port, the L-type impedance matching network being composed of series-connected capacitor elements and parallel-connected inductor elements.

[0010] A further technical solution of this application: the peripheral parasitic radiation unit includes at least one first parasitic trace arranged parallel to and adjacent to a part of the central main radiator, and the first parasitic trace and the central main radiator form the coupling gap.

[0011] A further technical solution of this application is that the axial ratio of the onboard antenna at the BD3-B1 frequency point is less than 3dB, and the voltage standing wave ratio in each frequency band of BD3-B1, BD3-B2A, BD3-B2B, BD3-B3 and the 350MHz to 400MHz ultra-shortwave frequency band is less than 2.5.

[0012] A further technical solution of this application: the peripheral parasitic radiation element extends the impedance matching capability of the antenna in the ultra-shortwave band through electromagnetic coupling with the central main radiator.

[0013] A communication device including a miniaturized multi-band onboard antenna.

[0014] A design method for a miniaturized multi-band onboard antenna includes the following steps: S1. Establish the electromagnetic simulation model of the onboard antenna, and optimize the structural parameters by adjusting the size and coupling relationship between the central main radiator and the peripheral parasitic radiating elements, so that the antenna body can achieve the preset resonance performance in the target BD3 frequency band and the ultra-short wave frequency band. S2. Based on the optimized structural parameters, fabricate a physical prototype and measure the antenna's input impedance Za; S3. Based on the input impedance Za, perform L-type matching network debugging to make the antenna meet the impedance matching requirements in the target frequency band.

[0015] A further technical solution of this application: the L-type matching network debugging in step S3 includes the following sub-steps: S31. Normalize the measured input impedance Za; S32. Determine whether the real part ra of the normalized impedance is less than 1; S33. Select the topology of the L-type matching network based on the judgment result: if ra < 1, select the topology of parallel connection first and then series connection; if ra ≥ 1, select the topology of series connection first and then parallel connection. S34. According to the topology, adjust the values ​​of the series and parallel passive components to guide the impedance point to the matching point and complete the matching.

[0016] A further technical solution of this application: The impedance matching requirement in step S3 is to ensure that the voltage standing wave ratio of the antenna in the target frequency band reaches a preset standard.

[0017] Compared with the prior art, the technical solution provided by this invention has the following advantages: This invention achieves effective coverage of multiple frequency bands of BeiDou-3 and the VHF / UHF band simultaneously on a single antenna body through an innovative integrated structure of a central main radiator and asymmetric peripheral parasitic elements. This completely eliminates the need for two separate antennas required in traditional solutions, significantly saving equipment space and reducing weight, making it particularly suitable for size- and weight-sensitive vehicle-mounted, handheld, and UAV-borne devices. Through precise structural design and optimized electromagnetic coupling, the antenna achieves excellent circular polarization characteristics with an axial ratio of less than 3dB at the BeiDou B1 frequency, ensuring stable reception of navigation signals. Simultaneously, the voltage standing wave ratio (VSWR) is less than 2.5 across all BeiDou operating frequency bands and the VHF / UHF band, indicating excellent impedance matching and radiation efficiency in all target frequency bands. The frequency band characteristics of the antenna can be controlled by adjusting the size of the central main radiator to dominate the BeiDou band resonance, and the VHF / UHF band resonance and matching can be precisely controlled by flexibly changing the shape, size, and coupling distance between the peripheral parasitic radiating elements and the main radiator. This design provides great flexibility, allowing the antenna to adapt to different frequency band combinations.

[0018] The entire antenna structure can be etched and formed in one step using standard PCB technology, eliminating the need for complex three-dimensional structures, expensive special materials, or complicated assembly processes. This makes it extremely suitable for large-scale mass production, effectively reducing manufacturing costs. The accompanying design methodologies, particularly the L-type matching network debugging process based on input impedance normalization and real part determination, standardize and streamline the complex matching circuit design process. This method utilizes the Smith chart tool to quickly and accurately determine the matching network topology and component values, significantly shortening the antenna product development and debugging cycle and improving the design success rate. Attached Figure Description

[0019] Figure 1 This is a 2D wiring diagram of the antenna of the present invention; Figure 2 This is a plan view of the present invention; Figure 3 The standing wave test diagrams of the present invention in the BD3-B1, BD3-B2A, BD3-B2B, BD3-B3 and VHF bands are shown. Figure 4 The image shows the anechoic chamber test results at the BD3-B1 (1575.42±16.368MHz) frequency point, according to an embodiment of the present invention. Figure 5 The image shows the anechoic chamber test results at the BD3-B2A (1176.45±10.23MHz) frequency point, according to an embodiment of the present invention. Figure 6 The image shows the anechoic chamber test results at the BD3-B2B (1207.14±10.23MHz) frequency point, according to an embodiment of the present invention. Figure 7 The image shows the anechoic chamber test results at the BD3-B3 (1268.52±10.23MHz) frequency point, according to an embodiment of the present invention. Figure 8 This is a flowchart of the design method of the present invention; Figure 9 This is a flowchart of the L-shaped matching network debugging process of the present invention.

[0020] Explanation of the labels in the diagram: 1. Feed port; 2. L-shaped impedance matching network; 3. Trace; 4. Parasitic radiation element on the antenna periphery; 5. Antenna main radiating surface; 6. Parasitic radiation element on the periphery; 7. Main radiating element; 8. Dielectric substrate. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The present invention will be further described below with reference to the embodiments.

[0022] Please see Figures 1 to 7 In one embodiment of this application, a miniaturized multi-band onboard antenna includes: Dielectric substrate 8; A radiator assembly is disposed on one side of the dielectric substrate 8. The radiator assembly includes an antenna main radiating surface 5 and an antenna peripheral parasitic radiating unit 4. The antenna peripheral parasitic radiating unit 4 is arranged in an asymmetrical structure around the antenna main radiating surface 5 and forms a coupling gap with the antenna main radiating surface 5. Power supply port 1 is disposed on the dielectric substrate 8; The structural dimensions of the main radiating surface 5 of the antenna are configured to generate resonance in the BD3-B1, BD3-B2A, BD3-B2B and BD3-B3 frequency bands; the structural dimensions of the parasitic radiating element 4 on the periphery of the antenna, and the coupling relationship between the element and the main radiating surface 5 of the antenna, are configured to generate resonance together in the 350MHz to 400MHz ultra-shortwave frequency band.

[0023] Furthermore, the dielectric substrate 8 is made of a high-frequency circuit board material with a dielectric constant between 2.2 and 4.0.

[0024] Furthermore, an L-shaped impedance matching network 2 is integrated at the power supply port 1. The L-shaped impedance matching network 2 is composed of series-connected capacitor elements and parallel-connected inductor elements.

[0025] Furthermore, the peripheral parasitic radiation unit 4 of the antenna includes at least one first parasitic trace arranged parallel to and adjacent to a portion of the main radiation surface 5 of the antenna. The first parasitic trace belongs to the peripheral parasitic radiation unit 6 and forms the coupling gap between it and the main radiation surface 5 of the antenna.

[0026] Furthermore, the onboard antenna has an axial ratio of less than 3dB at the BD3-B1 frequency point, and a voltage standing wave ratio of less than 2.5 in each frequency band of BD3-B1, BD3-B2A, BD3-B2B, BD3-B3 and the 350MHz to 400MHz VHF band.

[0027] Furthermore, the parasitic radiation element 4 on the periphery of the antenna extends the impedance matching capability of the antenna in the UHF band through electromagnetic coupling with the main radiation surface 5 of the antenna.

[0028] The miniaturized multi-band onboard antenna of this invention is mainly fabricated on a high-frequency dielectric substrate 8. This dielectric substrate 8 preferably uses a dielectric constant (…). The dielectric constant is 2.65 and the thickness is 1mm. The material is rectangular with dimensions of 66mm (length) × 8mm (width) × 1mm (thickness). Those skilled in the art will understand that other high-frequency materials with a dielectric constant in the range of 2.2 to 4.0 can also be selected, and compensation can be made by adjusting the dimensions.

[0029] The radiating components of the antenna are etched onto one side (front) of the dielectric substrate 8 via metal traces 3, and mainly include the main radiating surface 5 of the antenna and the parasitic radiating elements 4 on the periphery of the antenna.

[0030] Antenna main radiating surface 5 as shown Figure 2 As shown in Figure 5, this is the main radiating part of the antenna, specifically the main radiating element 7. Its structural dimensions have been optimized through electromagnetic simulation, primarily determining the antenna's resonance in the BeiDou-3 BD3-B1 (1575.42MHz), BD3-B2A (1176.45MHz), BD3-B2B (1207.14MHz), and BD3-B3 (1268.52MHz) frequency bands. In one specific embodiment, the main radiating element 7 consists of a connected first main radiating segment (02) and a second main radiating segment (03), both with a linewidth of 2.5mm and a total length of 45mm (e.g., segment 03 is 25mm long, and segment 02 is 20mm long). The different lengths of the two segments help to excite multimode resonance.

[0031] Parasitic radiating elements 4 around the antenna Figure 2 As shown in label 4, it surrounds the main radiating surface 5 of the antenna in an asymmetrical structure. Its specific component is the peripheral parasitic radiating element 6. The first parasitic trace 01 is arranged parallel to and adjacent to the second main radiating segment 03 of the main radiating element 7, forming a coupling gap with a width of 0.6 mm between them. Furthermore, the linewidth of the peripheral parasitic radiating element 6 is designed to be 0.8 mm. This parasitic element not only participates in radiation itself, but more importantly, through strong electromagnetic coupling with the main radiating surface 5 of the antenna, it collaboratively generates resonance in the 350MHz to 400MHz ultra-shortwave band, effectively extending the impedance matching bandwidth of this low-frequency band. This mechanism allows the antenna to achieve low-frequency coverage without significantly increasing its size.

[0032] Feed port 1, located on dielectric substrate 8, is used to connect the radio frequency circuit. To achieve broadband matching, an L-shaped impedance matching network 2 is integrated at feed port 1. This network consists of a series capacitor and a parallel inductor. In a preferred, tuned embodiment, the series capacitor is 6.2 pF and the parallel inductor is 30 nH. The function of this L-shaped impedance matching network 2 is to cancel out the reactance component of the antenna itself, making its input impedance as close as possible to a 50-ohm pure resistance within the target frequency band.

[0033] refer to Figures 8 to 9 A design method for a miniaturized multi-band onboard antenna includes the following steps: S1. Establish the electromagnetic simulation model of the onboard antenna, and optimize the structural parameters by adjusting the size and coupling relationship between the central main radiator and the peripheral parasitic radiating elements, so that the antenna body can achieve the preset resonance performance in the target BD3 frequency band and the ultra-short wave frequency band. S2. Based on the optimized structural parameters, fabricate a physical prototype and measure the antenna's input impedance Za; S3. Based on the input impedance Za, perform L-type matching network debugging to make the antenna meet the impedance matching requirements in the target frequency band.

[0034] Furthermore, the L-type matching network debugging in step S3 includes the following sub-steps: S31. Normalize the measured input impedance Za; S32. Determine whether the real part ra of the normalized impedance is less than 1; S33. Select the topology of the L-type matching network based on the judgment result: if ra < 1, select the topology of parallel connection first and then series connection; if ra ≥ 1, select the topology of series connection first and then parallel connection. S34. According to the topology, adjust the values ​​of the series and parallel passive components to guide the impedance point to the matching point and complete the matching.

[0035] Furthermore, the impedance matching requirement in step S3 is to ensure that the voltage standing wave ratio (VSWR) of the antenna in the target frequency band reaches a preset standard.

[0036] Step S1: Initial Modeling and Structural Tuning Use electromagnetic simulation software (such as HFSS, CST) to create a two-dimensional antenna model. Set the material properties of the dielectric substrate ( =2.65, thickness 1mm) and initial dimensions. First, the dimensions of the central main radiator (02, 03) are optimized through parameter scanning so that its simulated S11 curve shows a resonance dip in the target BeiDou frequency band. Subsequently, the dimensions of the peripheral parasitic elements (01, 04, 05) and their coupling gaps with the main radiator (e.g., 0.6mm gap) are optimized, with the goal of enabling the simulation model to generate effective resonance in the 350-400MHz frequency band and observing bandwidth changes. The core of this stage is tuning the antenna itself to generate the required multi-band resonant points.

[0037] Step S2: Physical fabrication and impedance measurement. The optimized structural parameters are converted into PCB fabrication files to create a physical antenna prototype. To obtain accurate test data, the antenna prototype is placed in a shielded environment (e.g., in a metal shielding sleeve or microwave anechoic chamber), and its input impedance Za (a complex number: R+jX) is measured using a vector network analyzer.

[0038] Step S3: Matching network design and debugging. This step is crucial for improving antenna performance.

[0039] S31: Normalize the input impedance Za measured by the vector network analyzer (usually with 50Ω as a reference).

[0040] S32: Observe the normalized impedance point on the Smith chart and determine whether its normalized resistance value ra is less than 1.

[0041] S33: Select the topology of the L-type matching network based on the value of ra. If ra < 1, select a topology that connects components in parallel first and then in series; if ra ≥ 1, select a topology that connects components in series first and then in parallel. In this embodiment, the measured impedance point usually satisfies ra ≥ 1, so a structure of connecting capacitors in series first and then inductors in parallel is adopted.

[0042] S34: Based on the selected topology, adjust the values ​​of the series capacitor and parallel inductor in the simulation software or actual circuit. Observe the movement trajectory of the impedance point on the Smith chart, aiming to guide the impedance point to the center of the chart (1, j0), i.e., the 50Ω matching point. In this embodiment, after debugging, it was finally determined that the matching effect is best when the series capacitor is 6.2pF and the parallel inductor is 30nH. Solder this matching network to the feed port.

[0043] Step S4: Performance Verification. Final testing is performed on the antenna with the welded matching network. A vector network analyzer is used to verify its voltage standing wave ratio (VSWR), confirming that the VSWR is less than 2.5 in all target frequency bands (BD3-B1, B2A, B2B, B3, and 350-400MHz). Subsequently, its radiation pattern, gain, and axial ratio at the BeiDou B1 frequency point are measured in a microwave anechoic chamber, confirming that the axial ratio is less than 3dB, meeting the performance requirements of a circularly polarized navigation antenna.

[0044] The antenna manufactured and debugged through the above specific implementation methods successfully achieved high-performance coverage of the entire frequency band and ultra-shortwave band of BeiDou-3 in an ultra-compact size, verifying the effectiveness and superiority of the present invention.

[0045] In summary, this invention, through its innovative integrated structure of a central main radiator and asymmetric peripheral parasitic elements, achieves effective coverage of multiple frequency bands of BeiDou-3 and the UHF band simultaneously on a single antenna body. This completely eliminates the need for two separate antennas required in traditional solutions, significantly saving equipment space and reducing weight, making it particularly suitable for size- and weight-sensitive vehicle-mounted, handheld, and UAV-borne devices. Through precise structural design and optimized electromagnetic coupling, the antenna achieves excellent circular polarization characteristics with an axial ratio of less than 3dB at the BeiDou B1 frequency, ensuring stable reception of navigation signals. Simultaneously, the voltage standing wave ratio (VSWR) is less than 2.5 across all BeiDou operating frequency bands and the UHF band, indicating excellent impedance matching and radiation efficiency in all target frequency bands. The antenna's frequency band characteristics can be controlled by adjusting the size of the central main radiator to dominate BeiDou band resonance, and the UHF band resonance and matching can be precisely controlled by flexibly changing the shape, size, and coupling distance between the peripheral parasitic radiating elements and the main radiator. This design provides great flexibility, allowing the antenna to adapt to different frequency band combinations.

[0046] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

[0047] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A miniaturized multi-band onboard antenna, characterized in that, include: Dielectric substrate; A radiator assembly is disposed on one side of the dielectric substrate, the radiator assembly including a central main radiator and peripheral parasitic radiator units; The peripheral parasitic radiation units are arranged in an asymmetric structure around the central main radiator and form a coupling gap with the central main radiator. A power supply port is disposed on the dielectric substrate; The structural dimensions of the central main radiator are configured to resonate within the BD3-B1, BD3-B2A, BD3-B2B, and BD3-B3 frequency bands; the structural dimensions of the peripheral parasitic radiating units, and the coupling relationship between the peripheral parasitic radiating units and the central main radiator, are configured to resonate together within the 350MHz to 400MHz ultra-shortwave frequency band.

2. The miniaturized multi-band onboard antenna according to claim 1, characterized in that, The dielectric substrate is made of a high-frequency circuit board material with a dielectric constant between 2.2 and 4.

0.

3. The miniaturized multi-band onboard antenna according to claim 1, characterized in that, An L-shaped impedance matching network is integrated at the power supply port. The L-shaped impedance matching network consists of series-connected capacitors and parallel-connected inductors.

4. The miniaturized multi-band onboard antenna according to claim 1, characterized in that, The peripheral parasitic radiation unit includes at least one first parasitic trace arranged parallel to and adjacent to a portion of the central main radiator, and the first parasitic trace forms the coupling gap with the central main radiator.

5. The miniaturized multi-band onboard antenna according to claim 4, characterized in that, The onboard antenna has an axial ratio of less than 3dB at the BD3-B1 frequency point, and a voltage standing wave ratio of less than 2.5 in each frequency band of BD3-B1, BD3-B2A, BD3-B2B, BD3-B3 and the 350MHz to 400MHz VHF band.

6. The miniaturized multi-band onboard antenna according to claim 1 or 4, characterized in that: The peripheral parasitic radiating element extends the impedance matching capability of the antenna in the UHF band through electromagnetic coupling with the central main radiator.

7. A communication device, characterized in that, Includes a miniaturized multi-band onboard antenna as described in any one of claims 1 to 5.

8. A design method for a miniaturized multi-band onboard antenna according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Establish the electromagnetic simulation model of the onboard antenna, and optimize the structural parameters by adjusting the size and coupling relationship between the central main radiator and the peripheral parasitic radiating elements, so that the antenna body can achieve the preset resonance performance in the target BD3 frequency band and the ultra-short wave frequency band. S2. Based on the optimized structural parameters, fabricate a physical prototype and measure the antenna's input impedance Za; S3. Based on the input impedance Za, perform L-type matching network debugging to make the antenna meet the impedance matching requirements in the target frequency band.

9. The design method according to claim 7, characterized in that, The L-type matching network debugging in step S3 includes the following sub-steps: S31. Normalize the measured input impedance Za; S32. Determine whether the real part ra of the normalized impedance is less than 1; S33. Select the topology of the L-type matching network based on the judgment result: if ra < 1, select the topology of parallel connection first and then series connection; if ra ≥ 1, select the topology of series connection first and then parallel connection. S34. According to the topology, adjust the values ​​of the series and parallel passive components to guide the impedance point to the matching point and complete the matching.

10. The design method according to claim 7 or 8, characterized in that, The impedance matching requirement in step S3 is to ensure that the voltage standing wave ratio (VSWR) of the antenna in the target frequency band reaches a preset standard.

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