An ultra-wideband four-arm dipole antenna for unmanned airborne ground penetrating radar

Abstract

The application provides an ultra-wideband four-arm dipole antenna for unmanned airborne ground penetrating radar. The ultra-wideband four-arm dipole antenna comprises: an antenna upper arm comprising a symmetrically arranged first upper arm antenna and a second upper arm antenna; and an antenna lower arm in conductive communication with the first upper arm antenna and the second upper arm antenna through a first conductive connecting piece and a second conductive connecting piece respectively and forming an equivalent parallel structure. The four-arm dipole antenna introduced by the application forms coupling with a pair of upper arms and a resistance-capacitance loaded dipole antenna as an original antenna. Under the coupling effect, the antenna can generate a new resonance point, thereby effectively expanding the bandwidth of the antenna. Meanwhile, the imaginary part of the input impedance of the original antenna is significantly improved and is close to 0 in most frequency bands, thereby effectively improving the radiation characteristics of the antenna and finally improving the antenna gain.

Description

Technical Field

[0001] This application relates to the technical field of radar antennas, and more particularly to an ultra-wideband quadrupole antenna for use as a ground-penetrating radar on an unmanned aerial vehicle. Background Technology

[0002] In recent years, the use of ground-penetrating radar (GPR) has expanded beyond the ground, with increasing integration of it into vehicle-mounted and drone-borne platforms. Compared to ground-based GPR, drone-borne GPR offers the advantage of adapting to complex terrain or large-area detection scenarios. In these cases, antenna design becomes crucial for effective radar detection.

[0003] Common UAV-borne ground-penetrating radar antennas need to meet the characteristics of ultra-wideband, high gain, and lightweight. Some ultra-wideband antennas, such as Vivaldi and log-periodic antennas, while achieving higher gain, are large in size and weight at low frequencies, posing challenges to UAV flight. In contrast, dipole antennas offer advantages in structural simplicity and lightweight design. To achieve the ultra-wideband characteristics of dipole antennas, Wu-King loading and Atschuler loading are commonly used methods, but these methods sacrifice antenna radiation efficiency. Subsequently, the hybrid loading method using inductors, capacitors, and resistors has been proven to simultaneously achieve both antenna radiation efficiency and ultra-wideband characteristics.

[0004] Furthermore, improving the gain of dipole antennas remains a pressing issue for researchers. Traditional structures such as cavity backs and metamaterials are effective methods for enhancing antenna gain. However, at frequencies of 100MHz or lower, these structures are limited by size or bandwidth. Current reported methods, such as slotting and folded double-arm techniques, effectively lower the antenna's operating frequency, but offer limited gains.

[0005] Based on this, this application proposes an ultra-wideband quadrupole antenna for UAV-borne ground-penetrating radar, aiming to solve the above-mentioned technical problems. Summary of the Invention

[0006] To address the problems existing in the prior art, this application provides an ultra-wideband quadrupole antenna for UAV-borne ground-penetrating radar.

[0007] The objective of this application is achieved through the following technical solution: This application provides an ultra-wideband quad-arm dipole antenna for UAV-borne ground-penetrating radar, comprising:

[0008] The antenna upper arm includes a first upper arm antenna and a second upper arm antenna that are symmetrically arranged.

[0009] The lower arm of the antenna is connected to the first upper arm antenna and the second upper arm antenna through the first conductive connector and the second conductive connector, respectively, and forms an equivalent parallel structure.

[0010] In some possible implementations, both the first upper arm antenna and the second upper arm antenna include an antenna upper arm substrate and an antenna upper arm metal portion disposed on a plane of the antenna upper arm substrate away from the antenna lower arm.

[0011] In some possible implementations, one end of the first conductive connector is located at the geometric center of the plane of the first upper arm antenna near the lower arm of the antenna, and one end of the second conductive connector is located at the geometric center of the plane of the second upper arm antenna near the lower arm of the antenna.

[0012] In some possible implementations, the material of the antenna upper arm substrate is FR-4.

[0013] In some possible implementations, the first conductive connector and the second conductive connector are copper pillars.

[0014] In some possible implementations, the copper pillar has a height of 50±5mm and a diameter of 12±5mm.

[0015] In some possible implementations, the thickness of the antenna upper arm substrate is 1 ± 0.1 mm.

[0016] In some possible implementations, the length of the upper arm metal portion of the antenna is 600±10mm and the width is 30±5mm.

[0017] In some possible implementations, the spacing between the two upper arm metal portions of the antenna is 40±5mm.

[0018] In some possible implementations, the lower antenna arm has a double-sided circuit board structure, and the side of the lower antenna arm facing the upper antenna arm includes, from top to bottom, a top metal part of the lower antenna arm and a substrate of the lower antenna arm; the top metal part of the lower antenna arm includes a first top metal part and a second top metal part of the lower antenna arm symmetrically arranged along the geometric center of the substrate of the lower antenna arm, and an antenna feed part for conducting the first top metal part and the second top metal part of the lower antenna arm;

[0019] The side of the lower antenna arm away from the upper antenna arm includes a bottom metal portion of the lower antenna arm. The orthographic projection of the bottom metal portion of the lower antenna arm onto the lower antenna arm substrate partially overlaps with the orthographic projections of the first top metal portion of the lower antenna arm and the second top metal portion of the lower antenna arm onto the lower antenna arm substrate, thus forming a capacitor.

[0020] In some possible implementations, the first lower arm top metal portion and the second lower arm top metal portion include a semi-elliptical metal layer connected to the antenna feed portion and a plurality of rectangular metal layers away from the antenna feed portion; the orthographic projection of the rectangular metal layer on the antenna lower arm substrate overlaps with the orthographic projection of the first lower arm top metal portion and the second lower arm top metal portion on the antenna lower arm substrate.

[0021] In some possible implementations, multiple rectangular metal layers are combined to form a sideways U-shaped configuration, with the semi-elliptical metal layer connected at the middle position of the sideways U-shaped configuration.

[0022] In some possible implementations, the length of the overlapping area between the orthographic projection of the bottom metal portion of the antenna lower arm on the antenna lower arm substrate and the orthographic projections of the first top metal portion of the lower arm and the second top metal portion of the lower arm on the antenna lower arm substrate is 20±3mm.

[0023] In some possible implementations, the material of the antenna lower arm substrate includes FR-4.

[0024] In some possible implementations, the thickness of the lower arm substrate of the antenna is 1 ± 0.1 mm.

[0025] In some possible implementations, the semi-elliptical metal layer has a semi-major axis of 647±10 mm and a minor axis of 44±5 mm.

[0026] In some possible implementations, the total length of the top metal portion of the lower arm of the antenna is 1330±10mm and the total width is 104±10mm.

[0027] In some possible implementations, the lower arm of the antenna has a resistive-capacitive loaded dipole antenna structure.

[0028] In light of the above-mentioned technical solutions and the technical problems they solve, compared with the prior art, the advantages and positive effects of the technical solution to be protected by this invention are at least as follows:

[0029] Compared to traditional lumped-element capacitive loading and slotted capacitive loading techniques, the antenna provided in this application employs a resistive-capacitive loading technique that achieves capacitive loading through coupling between the top and bottom layers of a double-sided circuit board. Compared to lumped-element loading, this method saves manufacturing costs and eliminates the need for soldering additional components, thereby improving antenna reliability. Compared to slotted capacitive loading, this method has lower precision requirements. For example, slotting typically requires millimeter-level precision in the gap, while this application only requires centimeter-level precision in the overlap area length to achieve the same capacitive loading effect.

[0030] Meanwhile, the antenna structure in the technical solution provided in this application adopts a double-layer planar design, using a dielectric substrate as the sole main material. This avoids the use of additional metal components and complex irregular structures in traditional designs, thus giving the antenna a lightweight advantage. Furthermore, the antenna structure is simple and easy to integrate with UAV platforms, significantly reducing the deployment difficulty of UAV-borne ground-penetrating radar systems. This provides a superior solution for related application fields, greatly expanding its applicability and flexibility in complex environments.

[0031] The four-arm dipole antenna proposed in this application provides an innovative approach to the design of dipole-type antennas, effectively improving their gain and expanding their bandwidth. Its core lies in the introduction of a pair of upper arms that couple with the original antenna. Under this coupling, the antenna can generate a new resonant point, thereby effectively expanding the antenna's bandwidth. Simultaneously, the imaginary part of the original antenna's input impedance is significantly improved, remaining near zero across most of the frequency band, effectively enhancing the antenna's radiation characteristics and ultimately increasing its gain. Attached Figure Description

[0032] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0033] Figure 1 This is a schematic diagram of the structure of an ultra-wideband quadrupole antenna for UAV-borne ground-penetrating radar provided in an embodiment of this application.

[0034] Figure 2 This is a side view of an ultra-wideband quadrupole antenna for UAV-borne ground-penetrating radar provided in an embodiment of this application.

[0035] Figure 3 This is a top view of an antenna upper arm provided in an embodiment of this application.

[0036] Figure 4 This is a top view of the lower arm of an antenna provided in an embodiment of this application.

[0037] Figure 5 This is a partially enlarged schematic diagram of the top metal part of the lower arm of an antenna provided in an embodiment of this application.

[0038] Figure 6 This is a schematic diagram of the bottom layer of an antenna lower arm provided in an embodiment of this application.

[0039] Figure 7 This is a cross-sectional schematic diagram of the lower arm of an antenna provided in an embodiment of this application.

[0040] Figure 8 This is a comparative schematic diagram of input impedance simulation results provided in an embodiment of this application.

[0041] Figure 9This is a comparative schematic diagram of an S11 simulation result provided in an embodiment of this application.

[0042] Figure 10 This is a comparative schematic diagram of actual gain simulation results provided in an embodiment of this application.

[0043] Diagram: xyz, coordinate system; 1, upper antenna arm; 2, lower antenna arm; 3, copper pillar; 11, upper antenna arm metal part; 12, upper antenna arm substrate; 21, top metal part of lower antenna arm; 22, antenna feed part; 23, lower antenna arm substrate; 24, bottom metal part of lower antenna arm; R21, resistor. Detailed Implementation

[0044] The present application will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. The implementation process of the present application will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation procedures, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be understood that the preferred embodiments are only for illustrating the present application and not for limiting the scope of protection of the present application.

[0045] The technical field of the embodiments of this application will be briefly described below to facilitate understanding by those skilled in the art.

[0046] Traditional UAV-borne ground-penetrating radar antennas are mostly Vivaldi antennas or log-periodic antennas, which have the advantage of high gain. However, when the radar operates in the VHF band or lower, the size, profile, and weight of these antennas increase significantly, severely impacting the deployment capability of the UAV. This contradicts the trend of UAV miniaturization. In contrast, traditional dipole antennas have the advantages of simple structure and low profile, and their lightweight and miniaturized characteristics are beneficial for the integration of low-frequency UAVs with ground-penetrating radar.

[0047] Currently, there are two main technical approaches to dipole antennas used in UAV-borne ground-penetrating radars: resistive loading and hybrid loading. While pure resistive loading can significantly broaden the antenna bandwidth, it leads to a substantial decrease in antenna gain. Hybrid loading, while balancing bandwidth and gain to some extent, suffers from a sharp drop in gain at certain frequency bands when greater bandwidth is required. Additionally, according to existing patents, some designs employ folded dipole arms. While this method can improve antenna gain at low frequencies, the problem of gain degradation at high frequencies still needs further resolution.

[0048] In other words, current technical solutions in the field of traditional UAV-borne ground-penetrating radar antennas have certain limitations. Related technologies cannot effectively optimize the performance of UAV-borne ground-penetrating radar antennas in the low-frequency band, failing to meet the high-efficiency and stable operation requirements of UAVs in complex terrain or large-area detection scenarios, thus failing to guarantee the efficient and stable operation of UAV-borne ground-penetrating radar systems. Based on this, this application provides an ultra-wideband four-arm dipole antenna for UAV-borne ground-penetrating radar. The method will be described first, followed by the apparatus, etc.

[0049] This embodiment provides an ultra-wideband quadrupole antenna for UAV-borne ground-penetrating radar, comprising:

[0050] The antenna upper arm includes a first upper arm antenna and a second upper arm antenna that are symmetrically arranged.

[0051] The lower arm of the antenna is connected to the first upper arm antenna and the second upper arm antenna through the first conductive connector and the second conductive connector, respectively, and forms an equivalent parallel structure.

[0052] The lower arm of the antenna is connected to the first and second upper arm antennas via the first and second conductive connectors, forming an equivalent parallel structure. When a signal is fed into the lower arm, part of the current flows in the lower arm, and the other part flows to the upper arm through the conductive connectors. The equivalent parallel connection makes the real part of the antenna input impedance flatter, expanding the impedance bandwidth; at the same time, the imaginary part of the input impedance remains close to 0 in most frequency bands, improving the radiation characteristics.

[0053] Therefore, the equivalent parallel structure allows the antenna to achieve impedance matching requirements over a wider frequency range, realizing ultra-wideband performance and improving detection capabilities. Maintaining a near-zero imaginary part of the input impedance allows for more efficient energy radiation from the antenna, enhancing the identification and layered detection of underground targets when applied to UAV-borne ground-penetrating radar.

[0054] In some cases, both the first upper arm antenna and the second upper arm antenna include an antenna upper arm substrate and an antenna upper arm metal portion disposed on a plane of the antenna upper arm substrate away from the antenna lower arm.

[0055] The upper arm metal portion of the antenna is disposed on the plane of the upper arm substrate away from the lower arm. When a signal is fed into the lower arm, current is transmitted to the upper arm metal portion of the upper arm, causing the upper and lower arms to work together to form a complete antenna radiation structure.

[0056] In some cases, one end of the first conductive connector is located at the geometric center of the plane of the first upper arm antenna near the lower arm of the antenna, and one end of the second conductive connector is located at the geometric center of the plane of the second upper arm antenna near the lower arm of the antenna.

[0057] In some cases, the material of the antenna upper arm substrate is FR-4.

[0058] In some cases, the first conductive connector and the second conductive connector are copper pillars.

[0059] One end of each of the first and second conductive connectors is positioned at the geometric center of the plane of the first and second upper antenna arms near the lower antenna arm. This ensures the conductive connectors are located at the geometric center, resulting in stable connections, uniform stress, and overall antenna structural stability. The FR-4 material of the antenna upper arm substrate provides excellent insulation and heat resistance, ensuring stable antenna operation in various environments.

[0060] Using copper pillars as conductive connectors provides excellent conductivity, effectively ensuring stable current conduction between the upper and lower arms and guaranteeing the antenna's normal operation and radiation performance. The upper arm of the antenna adopts a structure of substrate plus metal parts, which is easy to process and manufacture, and easy to integrate with other components such as the lower arm, facilitating the assembly of the entire antenna.

[0061] As an example, the copper pillar has a height of 50±5mm and a diameter of 12±5mm. The thickness of the antenna upper arm substrate is 1±0.1mm. The length of the metal portion of the antenna upper arm is 600±10mm and the width is 30±5mm. The spacing between the two metal portions of the antenna upper arms is 40±5mm.

[0062] In some embodiments, the lower antenna arm has a double-sided circuit board structure, and the side of the lower antenna arm facing the upper antenna arm includes, from top to bottom, a top metal part of the lower antenna arm and a substrate of the lower antenna arm; the top metal part of the lower antenna arm includes a first top metal part and a second top metal part of the lower antenna arm symmetrically arranged along the geometric center of the substrate of the lower antenna arm, and an antenna feed part for conducting the first top metal part and the second top metal part of the lower antenna arm;

[0063] The side of the lower antenna arm away from the upper antenna arm includes a bottom metal portion of the lower antenna arm. The orthographic projection of the bottom metal portion of the lower antenna arm onto the lower antenna arm substrate partially overlaps with the orthographic projections of the first top metal portion of the lower antenna arm and the second top metal portion of the lower antenna arm onto the lower antenna arm substrate, thus forming a capacitor.

[0064] The lower arm of the antenna has a double-sided circuit board structure. The side facing the upper arm includes the top metal part of the lower arm and the substrate. The top metal part consists of symmetrically arranged first and second lower arm top metal parts and the antenna feed part. The side away from the upper arm is the bottom metal part, which partially overlaps with the top metal part in the orthographic projection of the top metal part onto the substrate, forming a capacitor. During feeding, the current flows through the feed part into the top metal part of the lower arm. After reaching the end of the top part, it is capacitively coupled to the bottom metal part through the overlapping area, extending the current path and widening the low-frequency bandwidth.

[0065] It can be assumed that capacitive coupling is achieved by overlapping the top and bottom metal parts of the antenna lower arm, which eliminates the need for additional lumped components, reduces processing costs, has low precision requirements, extends the current path, widens the low-frequency bandwidth, improves antenna bandwidth and gain, and enhances low-frequency detection capabilities.

[0066] In some embodiments, the first lower arm top metal portion and the second lower arm top metal portion include a semi-elliptical metal layer connected to the antenna feed portion and a plurality of rectangular metal layers away from the antenna feed portion; the orthographic projection of the rectangular metal layer on the antenna lower arm substrate overlaps with the orthographic projection of the first lower arm top metal portion and the second lower arm top metal portion on the antenna lower arm substrate.

[0067] The top metal section of the first and second lower arms consists of a semi-elliptical metal layer connected to the feed section and multiple rectangular metal layers located away from the feed section. During feeding, current flows in from the feed section, diffuses along the semi-elliptical metal layer, and is then transmitted through the rectangular metal layers. Reflection occurs at the top end, where part of the reflected current is absorbed by the resistor, and the remaining current flows through the rectangular sections, inducing current into the bottom layer through the overlapping area. The combination of the semi-elliptical and rectangular metal layers forms a symmetrical and stable structure, which facilitates uniform current distribution and improves antenna radiation efficiency. The rectangular metal layers increase the current path length, widening the low-frequency bandwidth of the antenna.

[0068] In some embodiments, multiple rectangular metal layers are combined to form a sideways U-shaped configuration, with the semi-elliptical metal layer connected to the middle of the sideways U-shaped configuration. A resistor may be applied between the two ends to absorb reflected current and reduce the impact of reflected current on antenna impedance matching.

[0069] As an example, the length of the overlapping area between the orthographic projection of the bottom metal portion of the antenna lower arm onto the antenna lower arm substrate and the orthographic projections of the first top metal portion and the second top metal portion of the antenna lower arm onto the antenna lower arm substrate is 20±1mm. The material of the antenna lower arm substrate includes FR-4. The thickness of the antenna lower arm substrate is 1±0.1mm. The semi-elliptical metal layer has a semi-major axis of 647±5mm and a minor axis of 44±1mm. The total length of the top metal portion of the antenna lower arm is 1330±5mm and the total width is 104±1mm.

[0070] In some embodiments, the lower arm of the antenna has a resistive-capacitive loaded dipole antenna structure. The synergistic effect of the resistive and capacitive loaded elements helps to achieve good impedance matching over a wide bandwidth, enabling the antenna to operate effectively over a wider frequency range.

[0071] As an example, an ultra-wideband quadrupole antenna for UAV-borne ground-penetrating radar is provided. This antenna consists of a resistor-capacitor-loaded dipole antenna and a pair of upper arms, thus forming a quadrupole antenna. The pair of upper arms form an equivalent parallel structure with the original antenna, thereby making the real part of the antenna's input impedance flatter and thus extending the antenna's impedance bandwidth. Simultaneously, the imaginary part of the antenna's input impedance is also compensated, remaining near zero across most frequency bands, thereby improving the antenna's radiation characteristics.

[0072] The ultra-wideband quad dipole antenna includes an upper antenna arm 1 and a lower antenna arm 2. The upper antenna arm 1 includes a first upper antenna and a second upper antenna arranged symmetrically, as well as two copper pillars 3 corresponding to the first upper antenna and the second upper antenna, respectively.

[0073] A side view of an ultra-wideband quad-arm dipole antenna is shown below. Figure 2 As shown. The height h3 of copper pillar 3 is 50±1mm. The lateral distance y3 of copper pillar 3 is 350±1mm.

[0074] A partial enlarged view of the top metal part 21 of the antenna lower arm is shown below. Figure 5 As shown. Figure 5 The main focus is on the semi-elliptical end of the top metal section 21 of the antenna's lower arm. This end consists of three symmetrical rectangular regions. The first type of rectangle measures W211*W213, the second type W212*W213, and the third type L211*W214. W211 measures 58±1mm, W212 20±1mm, W213 15±1mm, L211 35±1mm, and W214 15±1mm. A resistor R21 with a resistance of 75±1Ω is applied between the second and first rectangles.

[0075] Based on the above description, the lower arm 2 of the antenna is made of a double-sided circuit board, the bottom layer of which is as follows: Figure 6 As shown, it includes a bottom metal portion 24 of the antenna lower arm. The overlap length L23 between the bottom metal portion 24 and the top metal portion 21 of the antenna lower arm is 20±1mm. The second and third adjacent rectangles partially overlap, and the non-overlapping area between the second and third adjacent rectangles is referred to as the aforementioned overlap area.

[0076] To more clearly see the overlapping relationship between the bottom metal part 24 and the top metal part 21 of the antenna lower arm, Figure 7A cross-sectional schematic diagram of the lower arm 2 of the antenna is shown, including the top layer, the bottom layer, and the substrate in between. The overlapping area constitutes the capacitive loading.

[0077] To explain its working principle, it can be understood as a four-arm dipole antenna consisting of a traditional RC-loaded dipole antenna and a pair of upper arms. After the antenna is fed, the current flows to... Figure 5 When the current reaches the end of the top metal part 21 of the lower arm of the antenna shown, reflection will occur. However, a portion of this reflected current will be... Figure 5 The resistor R21 shown absorbs the reflected current, thereby reducing the impact of the reflected current on the antenna impedance matching.

[0078] Furthermore, the residual current will continue along Figure 5 The rectangular section shown flows until the end of the third rectangle, through... Figure 6 The overlapping of the bottom metal portion 24 of the antenna lower arm, as shown, allows current to be induced to the bottom layer of the antenna lower arm. The overlapping portion acts as a capacitor. Compared to traditional multi-segment purely resistive loading, this capacitive loading method reduces antenna current loss in the resistor, while simultaneously inducing current from the top layer to the bottom layer, extending the effective current path and thus widening the antenna bandwidth in the low-frequency band. Ultimately, this achieves a balance between antenna bandwidth and gain.

[0079] Furthermore, a four-arm topology is developed based on the RC-loaded dipole antenna in related technologies, such as... Figure 1 As shown, the upper arm 1 and lower arm 2 of the antenna are connected by a copper pillar 3, forming an equivalent parallel structure. The introduction of the upper arm 1 can add an additional resonant point to the antenna, thereby expanding its bandwidth. Simultaneously, by adjusting the position and height of the copper pillar 3, different coupling effects can be created between the upper arm 1 and lower arm 2, thus controlling the antenna's input impedance. When a suitable position and height of the copper pillar 3 are selected, the antenna performance will be improved.

[0080] The effectiveness of this application can be further illustrated by the following simulation results:

[0081] Simulation settings: The antenna was simulated and its parameters optimized using CST Microwave Studio software. The simulation frequency band was set to 30MHz-170MHz.

[0082] Simulation results: such as Figure 8As shown, the horizontal axis represents the frequency range from 30MHz to 170MHz, in MHz; the vertical axis represents the input impedance (Zin), in ohms (Ω). The simulation results of the input impedance of the conventional RC-loaded dipole antenna and the four-arm dipole antenna are compared. The results show that the real part of the input impedance of the four-arm antenna is flatter than that of the conventional RC-loaded antenna, which is beneficial for achieving wider impedance matching. Simultaneously, the imaginary part of the input impedance of the four-arm antenna is closer to 0 than that of the conventional RC-loaded antenna, allowing most of the antenna's energy to be effectively radiated, thus significantly improving the antenna's radiation performance.

[0083] like Figure 9 As shown, the horizontal axis represents the frequency range from 30MHz to 170MHz in MHz; the vertical axis represents the input impedance (Zin) in ohms (Ω). The simulation results of S11 (scattering parameter S11) for the conventional RC-loaded dipole antenna and the quad-arm dipole antenna are compared. The results show that the bandwidth of the conventional RC-loaded antenna with |S11| < -10dB is 30-120MHz. The quad-arm antenna proposed in this patent generates a new resonant point around 150MHz, which effectively improves the antenna bandwidth. Ultimately, the quad-arm antenna's S11 < -10dB bandwidth is 40-165MHz, a 33% improvement over the conventional RC-loaded antenna.

[0084] like Figure 10 As shown, the horizontal axis represents the frequency range from 30MHz to 170MHz, in megahertz (MHz); the vertical axis represents the input impedance (Zin), in ohms (Ω). The simulation results of the actual gain of the conventional RC-loaded dipole antenna and the quad-arm dipole antenna are compared. The results show that in the 30-90MHz frequency band, the gain of the quad-arm antenna can be improved by up to 4dB compared to the conventional RC-loaded antenna. In the 100-170MHz range, the gain of the quad-arm antenna is improved by up to 4.2dB compared to the conventional RC-loaded antenna. Furthermore, it effectively solves the problem of gain drop in conventional RC-loaded antennas above 110MHz.

[0085] In summary, the antenna provided in this application utilizes the electrical coupling between the top and bottom layers of a double-sided circuit board to achieve a highly efficient capacitive loading mechanism. This capacitive loading method can both extend the current path and compensate for the imaginary part of the antenna input impedance, thereby improving the antenna gain while maintaining antenna bandwidth.

[0086] Meanwhile, the proposed four-arm dipole antenna consists of a pair of upper arms and a resistor-capacitor (RC) loaded dipole antenna. It should be noted that the parasitic upper arm structure proposed in this application can not only be combined with the RC loaded dipole antenna designed above, but also with other types of dipole antennas. Compared with traditional planar RC loaded dipole antennas, the bandwidth of the proposed four-arm dipole antenna can be increased by 33%, and the gain can be increased by up to 4.2 dB.

[0087] Compared to existing lumped-element capacitive loading and slotted capacitive loading techniques, the antenna provided in this application employs a resistive-capacitive loading technique that achieves capacitive loading through coupling between the top and bottom layers of a double-sided circuit board. Compared to lumped-element loading, this method saves manufacturing costs and eliminates the need for soldering additional components, thereby improving antenna reliability. Compared to slotted capacitive loading, this method has lower precision requirements. For example, slotting typically requires millimeter-level precision in the gap, while this application only requires centimeter-level precision in the overlap area length to achieve the same capacitive loading effect.

[0088] Meanwhile, the antenna structure in the technical solution provided in this application adopts a double-layer planar design, using a dielectric substrate as the sole main material. This avoids the use of additional metal components and complex irregular structures in traditional designs, thus giving the antenna a lightweight advantage. Furthermore, the antenna structure is simple and easy to integrate with UAV platforms, significantly reducing the deployment difficulty of UAV-borne ground-penetrating radar systems. This provides a superior solution for related application fields, greatly expanding its applicability and flexibility in complex environments.

[0089] The four-arm dipole antenna proposed in this application provides an innovative approach to the design of dipole-type antennas, effectively improving their gain and expanding their bandwidth. Its core lies in the introduction of a pair of upper arms that couple with the original antenna. Under this coupling, the antenna can generate a new resonant point, thereby effectively expanding the antenna's bandwidth. Simultaneously, the imaginary part of the original antenna's input impedance is significantly improved, remaining near zero across most of the frequency band, effectively enhancing the antenna's radiation characteristics and ultimately increasing its gain.

[0090] When the four-arm dipole antenna protected in this application is applied to UAV-borne ground-penetrating radar, as mentioned above, there are currently two main technical approaches to dipole antennas used in UAV-borne ground-penetrating radar: one is resistive loading, which can significantly broaden the antenna bandwidth, but introduces significant losses, leading to a substantial decrease in antenna gain and affecting the radiation intensity and detection range of the radar signal. The second is hybrid loading, which balances antenna bandwidth and gain to some extent, but when pursuing greater bandwidth, a sharp drop in gain occurs in certain frequency bands. This is mainly because hybrid loading makes it difficult to balance the contradiction between the antenna's input impedance and radiation efficiency over a wide frequency band, resulting in deterioration of the antenna's matching performance and a sharp drop in gain in specific frequency bands. The folded dipole double-arm design in related technologies can improve the antenna gain in the low-frequency band to some extent, but the problem of gain degradation in the high-frequency band of this design has not been effectively solved as the frequency increases. This is mainly because the folded structure causes more high-frequency resonance and loss in the high-frequency band, thus limiting the antenna's performance in the high-frequency band.

[0091] The antenna in this application utilizes the electrical coupling between the top and bottom layers of a double-sided circuit board to achieve a highly efficient capacitive loading mechanism. This capacitive loading method can both extend the current path and compensate for the imaginary part of the antenna's input impedance, enabling the antenna to improve gain while maintaining bandwidth. The parasitic structure on the upper arm (antenna upper arm) couples with the original antenna, generating a new resonant point, thereby effectively expanding the antenna's bandwidth. Simultaneously, the imaginary part of the original antenna's input impedance is significantly improved, remaining close to zero across most frequency bands, enhancing the antenna's radiation characteristics and ultimately increasing its gain. Because the antenna structure is simple and easily integrated with UAV platforms, it can significantly reduce the deployment difficulty of UAV-borne ground-penetrating radar systems.

[0092] It should be noted that in the embodiments of this application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple. It is worth noting that "at least one" can also be interpreted as "one or more".

[0093] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are configured to distinguish similar objects and are not necessarily configured to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0094] This application describes the invention from the perspectives of purpose, performance, progress, and novelty, and it meets the functional enhancement and use requirements emphasized by the Patent Law. The above description and drawings are merely preferred embodiments of this application and are not intended to limit this application. Therefore, all structures, devices, features, etc., that are similar to or identical to those of this application, i.e., all equivalent substitutions or modifications made in accordance with the scope of this patent application, shall fall within the scope of protection of this patent application.

Claims

1. An ultra-wideband four-arm dipole antenna for UAV-borne ground-penetrating radar, characterized in that, include: The antenna upper arm includes a first upper arm antenna and a second upper arm antenna that are symmetrically arranged. The lower antenna arm is connected to the first upper antenna and the second upper antenna through the first conductive connector and the second conductive connector, respectively, and forms an equivalent parallel structure. Both the first upper arm antenna and the second upper arm antenna include an antenna upper arm substrate and an antenna upper arm metal portion disposed on a plane of the antenna upper arm substrate away from the antenna lower arm; The lower arm of the antenna has a double-sided circuit board structure, and the side of the lower arm facing the upper arm of the antenna includes, from top to bottom, a top metal part of the lower arm and a substrate of the lower arm; the top metal part of the lower arm includes a first top metal part and a second top metal part of the lower arm symmetrically arranged along the geometric center of the substrate of the lower arm, and an antenna feed part for conducting the first top metal part and the second top metal part of the lower arm. The side of the lower antenna arm away from the upper antenna arm includes a bottom metal portion of the lower antenna arm. The orthographic projection of the bottom metal portion of the lower antenna arm onto the lower antenna arm substrate partially overlaps with the orthographic projections of the first top metal portion of the lower antenna arm and the second top metal portion of the lower antenna arm onto the lower antenna arm substrate, thus forming a capacitor.

2. The ultra-wideband four-arm dipole antenna according to claim 1, characterized in that, One end of the first conductive connector is located at the geometric center of the plane of the first upper arm antenna near the lower arm of the antenna, and one end of the second conductive connector is located at the geometric center of the plane of the second upper arm antenna near the lower arm of the antenna; and / or, the material of the upper arm substrate of the antenna is FR-4; and / or, the first conductive connector and the second conductive connector are copper pillars.

3. The ultra-wideband four-arm dipole antenna according to claim 2, characterized in that, The copper pillar has a height of 50±5mm and a diameter of 12±5mm; and / or, the thickness of the antenna upper arm substrate is 1±0.1mm; and / or, the length of the antenna upper arm metal part is 600±10mm and the width is 30±5mm; and / or, the distance between the two antenna upper arm metal parts is 40±5mm.

4. The ultra-wideband quadrupole antenna according to claim 1, characterized in that, The first lower arm top metal portion and the second lower arm top metal portion include a semi-elliptical metal layer connected to the antenna feed portion and a plurality of rectangular metal layers away from the antenna feed portion; the orthographic projection of the rectangular metal layer on the antenna lower arm substrate overlaps with the orthographic projection of the first lower arm top metal portion and the second lower arm top metal portion on the antenna lower arm substrate.

5. The ultra-wideband quadrupole antenna according to claim 4, characterized in that, Multiple rectangular metal layers are combined to form a sideways U-shaped configuration, and the semi-elliptical metal layer is connected to the middle position of the sideways U-shaped configuration.

6. The ultra-wideband four-arm dipole antenna according to claim 5, characterized in that, The length of the overlapping area between the orthographic projection of the bottom metal part of the antenna lower arm on the antenna lower arm substrate and the orthographic projections of the first top metal part of the lower arm and the second top metal part of the lower arm on the antenna lower arm substrate is 20±3mm. And / or, the material of the antenna lower arm substrate includes FR-4; and / or, the thickness of the antenna lower arm substrate is 1±0.1mm; and / or, the semi-major axis of the semi-elliptical metal layer is 647±10mm, and the minor axis is 44±5mm; and / or, the total length of the top metal part of the antenna lower arm is 1330±10mm, and the total width is 104±10mm.

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