Ultra-wideband differential feed monopole antenna for ground penetrating radar

Abstract

The invention belongs to the technical field of antennas, and particularly discloses an ultra-wideband differential feed monopole antenna for a ground penetrating radar. Comprising a reflection cavity box body with an opening in the top end, a third wave-absorbing material, a second wave-absorbing material, a first wave-absorbing material, a second 3D printing medium block, a medium substrate, a first 3D printing medium block, a first half-cut monopole metal patch, a second half-cut monopole metal patch, a first differential feeding point and a second differential feeding point. Aiming at the problems of large size, poor directivity, limited bandwidth, complicated manufacturing and the like of the existing ground penetrating radar antenna, the invention provides a double-patch differential feed bisected monopole antenna structure which is compact in structure, excellent in performance and controllable in process.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and in particular to an ultra-wideband differentially fed monopole antenna for ground penetrating radar. Background Technology

[0002] Ground penetrating radar (GPR) is a non-destructive detection tool that uses electromagnetic waves to detect underground targets or geological structures. It is widely used in geological exploration, engineering inspection, archaeology, and national defense. As one of the core components of GPR, the antenna's performance directly affects the radar system's detection depth, resolution, and target identification capabilities.

[0003] Currently, there are many types of antennas used for ground-penetrating radar, among which dipole antennas, horn antennas, and monopole antennas are the most common. Dipole antennas have a simple structure and broadband characteristics, but their large size, especially in low-frequency applications, poses significant design challenges for portable radar systems. Horn antennas, on the other hand, are suitable for some high-frequency ground-penetrating applications due to their high gain and good directivity, but their bulky size, complex manufacturing process, and limited performance in the low-frequency band all make them difficult to meet portability requirements.

[0004] In contrast, monopole antennas, with their relatively small size, moderate gain, and good broadband performance, have become a commonly used antenna in ground-penetrating radars (GPRs). Especially in portable GPRs, monopole antennas offer significant advantages due to their ease of installation and manufacturing. However, the radiation pattern of monopole antennas has certain limitations. Their radiation pattern typically exhibits enhanced vertical radiation and omnidirectional horizontal radiation, causing the main lobe direction to deviate from the forward detection direction required by the radar system, forming an oblique beam. This makes it difficult to effectively concentrate radiated energy towards the target, resulting in decreased energy utilization and difficulty meeting performance requirements such as high gain and directional detection. Furthermore, monopole antennas are still relatively large in the low-frequency band, and the current distribution is prone to inconsistency when operating at high frequencies, further affecting their impedance matching and radiation stability.

[0005] In existing technologies, methods such as capacitive loading, inductive loading, dielectric loading, and folded structures are commonly used to achieve antenna miniaturization. However, these methods often bring a series of problems in practical applications. For example, loading structures may lead to narrowing of the antenna bandwidth and reduction of radiation efficiency, while folded designs may increase manufacturing complexity and cost. On the other hand, to address the problem of main lobe skew in monopole antennas, some studies have attempted to correct the radiation pattern by adding parasitic elements or loading electromagnetic modulation structures. However, such methods often rely on additional structures or complex adjustments, which not only increase the antenna size and design difficulty but also make it difficult to achieve dipole-like forward radiation characteristics without lengthening the antenna. Summary of the Invention

[0006] To address the problems of large size, poor directivity, limited bandwidth, and complex manufacturing of existing ground-penetrating radar antennas, this invention proposes an ultra-wideband differentially fed monopole antenna for ground-penetrating radar that is compact in structure, has excellent performance, and is manufactured with controllable processes.

[0007] To achieve the above objectives, the present invention is implemented according to the following technical solution: An ultra-wideband differential-fed monopole antenna for ground-penetrating radar includes a reflective cavity housing with an open top. Inside the reflective cavity housing, from bottom to top, are arranged a third absorbing material, a second absorbing material, a first absorbing material, a second 3D-printed dielectric block, a dielectric substrate, and a first 3D-printed dielectric block, all in close contact. The upper surface of the second 3D-printed dielectric block has a flat-bottomed V-groove structure. The dielectric substrate is a flat-bottomed V-shaped block. The lower end of the first 3D-printed dielectric block mates with the dielectric substrate. The upper surface of the first 3D-printed dielectric block is on the same plane as the upper surface of the reflective cavity housing. The end faces of the two sidewalls of the flat-bottomed V-shaped block... The upper part is asymmetrically bonded with a first half-cut monopole metal patch and a second half-cut monopole metal patch. The first half-cut monopole metal patch and the second half-cut monopole metal patch are two identical half-structure monopoles cut from a monopole metal patch along the central axis of symmetry. The remaining cavity inside the reflective cavity box is filled with 3D printed medium material. A first differential feed point and a second differential feed point are symmetrically arranged on two opposite surfaces of the reflective cavity box. One end of the first half-cut monopole metal patch is connected to the first differential feed point, and one end of the second half-cut monopole metal patch is connected to the second differential feed point.

[0008] Furthermore, the reflective cavity housing includes a U-shaped metal reflective cavity substrate, and a first side substrate and a second side substrate fixed to the open ends on both sides of the U-shaped metal reflective cavity substrate; the first differential feed point and the second differential feed point are symmetrically arranged on the two side walls of the U-shaped metal reflective cavity substrate.

[0009] Furthermore, the material of the dielectric substrate is FR-4.

[0010] Furthermore, the first and second side substrates are made of FR-4 material, and the U-shaped metal reflective cavity substrate is made of copper plate with a thickness of 2mm.

[0011] Furthermore, the first 3D printing media block and the second 3D printing media block are made of photosensitive resin.

[0012] Furthermore, the distance between the upper surface of the dielectric substrate and the upper surface of the first absorbing material is 5 mm.

[0013] Furthermore, the first absorbing material is made of Laird Eccosorb LS-24; the second absorbing material is made of Laird Eccosorb LS-26; and the third absorbing material is made of Laird Eccosorb LS-30.

[0014] Furthermore, the included angle between the two sidewalls and the bottom of the flat-bottomed V-shaped block is 156°.

[0015] Furthermore, the edges of the first half-cut monopole metal patch and the second half-cut monopole metal patch are formed by two curves connected end to end, forming an asymmetric patch structure with a gradually changing width. The interval between the first half-cut monopole metal patch and the second half-cut monopole metal patch on the dielectric substrate is 7 mm.

[0016] Furthermore, a first circular through hole is formed on the first half-cut monopole metal patch near the first differential feed point, and a second circular through hole is formed on the second half-cut monopole metal patch near the second differential feed point.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Achieve antenna miniaturization and compact structure This invention reduces the structural area by half without significantly altering the current path, creating a "cut-to-cut monopole patch" by symmetrically cutting a traditional monopole patch structure. This significantly reduces the antenna size, making it particularly suitable for size-sensitive portable ground-penetrating radar devices. Compared to traditional dipole or horn antennas, this structure also achieves size compression in the low-frequency band, facilitating integrated deployment.

[0018] 2. Improve directionality and forward gain This invention enhances forward radiation capability by arranging two patch units at an inward rotation angle, concentrating their main radiation direction. Furthermore, a differential feeding method is employed, applying equal-amplitude, opposite-phase excitation currents to the two patches, resulting in higher current symmetry and radiation consistency for the overall antenna. This differential structure achieves a symmetrical forward radiation direction similar to a dipole antenna without increasing antenna length, significantly improving the beam tilt problem of traditional monopole antennas. Simultaneously, an integrated metal reflector cavity is incorporated beneath the patches, and a three-layer absorbing material structure is further arranged within the cavity to effectively absorb backscattered and multipath reflected signals, significantly suppressing backscattering and improving the target response quality of the radar system.

[0019] 3. Excellent broadband response and impedance matching performance The patch edge employs a hyperbolic contour design, forming a gradual boundary transition structure. This effectively reduces edge current reflection and standing wave formation, improves current termination smoothness, thereby enhancing impedance continuity and expanding the effective operating bandwidth. Simultaneously, circular slot structures are incorporated in high-frequency current abrupt change regions to further adjust the current path and optimize impedance distribution.

[0020] 4. Simple to manufacture and highly integrated structure This invention adopts an integrated structural design for the reflective cavity and the ground plane, while filling the interior of the reflective cavity with 3D-printed media material for electromagnetic transition and structural support, simplifying the assembly process and improving the accuracy of repeated manufacturing. The overall structure has a clear hierarchy and a small number of parts, making it suitable for modular assembly and mass production, and possessing good engineering feasibility. Attached Figure Description

[0021] Figure 1 This is a perspective view of one angle of the ultra-wideband differentially fed monopole antenna for ground-penetrating radar of the present invention. Figure 2 This is a perspective view of the ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to the present invention. Figure 3 This is a three-dimensional assembly diagram of the ultra-wideband differentially fed monopole antenna for ground-penetrating radar of the present invention. Figure 4 This is a three-dimensional view of the patch and dielectric substrate structure of the ultra-wideband differentially fed monopole antenna for ground penetrating radar of the present invention. Figure 5 This is a schematic diagram of a monopole antenna being cut. Figure 6 This is a planar unfolded view of the patch and dielectric substrate structure of the ultra-wideband differentially fed monopole antenna for ground penetrating radar of the present invention. Figure 7 The following are the S-parameter simulation results of the ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to the present invention.

[0022] In the figure, the reference numerals are as follows: 1. First half-cut monopole metal patch; 2. Second half-cut monopole metal patch; 3. Dielectric substrate; 4. First 3D printed dielectric block; 5. Second 3D printed dielectric block; 6. First absorbing material; 7. Second absorbing material; 8. Third absorbing material; 9. U-shaped metal reflector substrate; 10. First differential feed point; 11. Second differential feed point; 12. First side substrate; 13. Second side substrate; 14. First circular through hole; 15. Second circular through hole. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0024] The purpose of this embodiment is to design an ultra-wideband differentially fed monopole antenna for ground penetrating radar. The specific design method is as follows; 1) Determine the required operating frequency band and physical size limitations of the antenna based on the application scenario of the target ground penetrating radar system; 2) Based on conventional monopole patches, the dimensions of the first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2 are initially determined; 3) Simulate the entire antenna in a background with a dielectric constant of 6 to reduce the amount of simulation computation.

[0025] 4) Based on the simulation of the working frequency band, determine the specific dimensions of the first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2; 5) Based on impedance simulation, determine the edge curve parameters of the first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2; determine the positions of the first differential feed point 10 and the second differential feed point 11 on the U-shaped metal reflective cavity substrate 9; determine the material of the dielectric substrate 3; and determine the dimensions of the U-shaped metal reflective cavity substrate 9. 6) Determine the size and position of the first circular through hole 14 and the second circular through hole 15 based on the reverse current appearing in the antenna in the current distribution.

[0026] Using the above method, an ultra-wideband differentially fed monopole antenna for ground-penetrating radar was designed as an example, such as... Figures 1-6As shown, the device includes a reflective cavity housing with an open top. Inside the reflective cavity housing, from bottom to top, are arranged a third absorbing material 8, a second absorbing material 7, a first absorbing material 6, a second 3D printed medium block 5, a medium substrate 3, and a first 3D printed medium block 4, all closely attached to each other. The upper surface of the second 3D printed medium block 5 has a flat-bottomed V-groove structure. The medium substrate 3 is a flat-bottomed V-shaped block. The lower end of the first 3D printed medium block 4 mates with the medium substrate 3. The reflective cavity housing contains three layers of first absorbing material 6, second absorbing material 7, and third absorbing material 8 with different performance parameters, forming a progressive energy absorption structure to absorb reflected signals of different frequencies and angles, thereby significantly reducing time-domain trailing. The upper surface of the first 3D printed medium block 4 is on the same plane as the upper surface of the reflective cavity housing. The distance between the upper surface of the medium substrate 3 and the upper surface of the first absorbing material 6 is 5. mm, to improve matching and increase radiation efficiency; the two sidewalls of the flat-bottomed V-shaped block are asymmetrically attached with a first half-cut monopole metal patch 1 and a second half-cut monopole metal patch 2. The angle between the two sidewalls of the flat-bottomed V-shaped block and the bottom is 156°. The first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2 are arranged with an inward rotation angle relative to the antenna centerline, that is, each patch is tilted inward at a certain angle relative to the vertical direction, thereby achieving focusing in the main radiation direction and improving directivity and forward gain; the first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2 are two structurally identical half-structure monopoles cut from a monopole metal patch along the central axis of symmetry. The remaining cavity inside the reflector cavity is filled with 3D printed medium material (photosensitive resin) to improve the uniformity of the field distribution inside the cavity and the overall mechanical strength, and enhance the coupling stability between the antenna and the ground. The reflector cavity has a first differential feed point 10 and a second differential feed point 11 symmetrically arranged on two opposite surfaces. One end of the first half-cut monopole metal patch 1 is connected to the first differential feed point 10, and one end of the second half-cut monopole metal patch 2 is connected to the second differential feed point 11. This is used to excite the first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2. The first differential feed point 10 and the second differential feed point 11 are driven by differential feeding, that is, they are respectively connected to a pair of equal amplitude and opposite signal sources.

[0027] Specifically, such as Figure 3 As shown, the reflective cavity housing includes a U-shaped metal reflective cavity substrate 9, and a first side substrate 12 and a second side substrate 13 fixed to the open ends on both sides of the U-shaped metal reflective cavity substrate 9; a first differential feed point 10 and a second differential feed point 11 are symmetrically arranged on the two side walls of the U-shaped metal reflective cavity substrate 9. For ease of demonstration, as shown... Figure 3 As shown, the U-shaped metal reflective cavity substrate 9 is split into two parts.

[0028] like Figure 4 , Figure 5and Figure 6 As shown, the edges of the first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2 are formed by two curves connected end to end, creating an asymmetric patch structure with a gradually changing width. The curve contours transition through the gradually changing edges, reducing the concentration of the electric field at the edges and allowing the current to terminate smoothly at the edges, thereby effectively suppressing reflection and edge standing wave formation. Simultaneously, it can provide a more uniform input impedance response at different frequencies, reducing reflection losses caused by impedance abrupt changes and improving the matching bandwidth of the feed port. The spacing between the first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2 on the dielectric substrate 3 is 7 mm. A first circular through-hole 14 is formed on the first half-cut monopole metal patch 1 near the first differential feed point 10, and a second circular through-hole 15 is formed on the second half-cut monopole metal patch 2 near the second differential feed point 11. These are used to locally guide the current flow, alleviate impedance abrupt changes caused by the superposition of high-frequency reverse currents, and further improve high-frequency matching and radiation efficiency.

[0029] During simulation testing, the dielectric substrate 3 is made of FR-4 material with a thickness of 1.6 mm and a relative permittivity of 4.4; the first side substrate 12 and the second side substrate 13 are made of FR-4 material with a thickness of 1.6 mm and a relative permittivity of 4.4; the U-shaped metal reflective cavity substrate 9 is made of copper with a thickness of 2 mm and an overall size of 30 mm * 30 mm * 30 mm; the first absorbing material 6 is made of Laird Eccosorb LS-24 material with a thickness of 3.2 mm; the second absorbing material 7 is made of Laird Eccosorb LS-26 material with a thickness of 3.2 mm; the third absorbing material 8 is made of Laird Eccosorb LS-30 material with a thickness of 12.7 mm; the length of the first half-cut monopole metal patch 1 and the second half-cut monopole metal patch 2 is 20 mm and the maximum width is 10 mm; the radius of the first circular through hole 14 and the second circular through hole 15 is 3 mm.

[0030] Based on the above parameter settings, the corresponding S-parameter simulation results are as follows: Figure 7 As shown, the antenna operates at frequencies of 0.91 GHz to 4.82 GHz, with a frequency range of less than -10 dB across the entire frequency band (relative bandwidth of 136%, and a relative bandwidth >20% is considered an ultra-wideband antenna).

[0031] In summary, this invention, through multi-dimensional design methods such as structural optimization, current control, reflection adjustment, and functional material integration, effectively improves the temporal performance and manufacturing feasibility of the antenna while achieving enhanced directivity, miniaturization, and broadband performance. It is particularly suitable for portable ground-penetrating radar systems with high requirements for electrical performance and size.

[0032] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. An ultra-wideband differentially fed monopole antenna for ground-penetrating radar, characterized in that, The device includes a reflective cavity housing with an open top. Inside the reflective cavity housing, from bottom to top, are arranged a third absorbing material (8), a second absorbing material (7), a first absorbing material (6), a second 3D printing medium block (5), a medium substrate (3), and a first 3D printing medium block (4) that are closely attached to each other. The upper surface of the second 3D printing medium block (5) has a flat-bottomed V-groove structure. The medium substrate (3) is a flat-bottomed V-shaped block. The lower end of the first 3D printing medium block (4) mates with the medium substrate (3), and the upper surface of the first 3D printing medium block (4) is on the same plane as the upper surface of the reflective cavity housing. A first half-cut single-layer material is asymmetrically attached to the end faces of the two side walls of the flat-bottomed V-shaped block. The first half-cut monopole metal patch (1) and the second half-cut monopole metal patch (2) are two identical half-structure monopoles cut from a monopole metal patch along the central axis of symmetry. The remaining cavity inside the reflective cavity box is filled with 3D printing medium material. The reflective cavity box has a first differential feed point (10) and a second differential feed point (11) symmetrically arranged on two opposite surfaces. One end of the first half-cut monopole metal patch (1) is connected to the first differential feed point (10), and one end of the second half-cut monopole metal patch (2) is connected to the second differential feed point (11).

2. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 1, characterized in that: The reflective cavity housing includes a U-shaped metal reflective cavity substrate (9), and a first side substrate (12) and a second side substrate (13) fixed at the open ends on both sides of the U-shaped metal reflective cavity substrate (9); the first differential feed point (10) and the second differential feed point (11) are symmetrically arranged on the two side walls of the U-shaped metal reflective cavity substrate (9).

3. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 1, characterized in that: The dielectric substrate (3) is made of FR-4.

4. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 2, characterized in that: The first side substrate (12) and the second side substrate (13) are made of FR-4 material, and the U-shaped metal reflective cavity substrate (9) is made of copper plate with a thickness of 2mm.

5. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 1, characterized in that: The first 3D printing media block (4) and the second 3D printing media block (5) are made of photosensitive resin.

6. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 1, characterized in that: The distance between the upper surface of the dielectric substrate (3) and the upper surface of the first absorbing material (6) is 5 mm.

7. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 1, characterized in that: The first absorbing material (6) is made of Laird Eccosorb LS-24; the second absorbing material (7) is made of Laird Eccosorb LS-26; and the third absorbing material (8) is made of Laird Eccosorb LS-30.

8. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 1, characterized in that: The angle between the two side walls and the bottom of the flat-bottomed V-shaped block is 156°.

9. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 1 or 8, characterized in that: The edges of the first half-cut monopole metal patch (1) and the second half-cut monopole metal patch (2) are formed by two curves connected end to end, forming an asymmetric patch structure with a gradually changing width. The interval between the first half-cut monopole metal patch (1) and the second half-cut monopole metal patch (2) on the dielectric substrate (3) is 7 mm.

10. The ultra-wideband differentially fed monopole antenna for ground-penetrating radar according to claim 1 or 9, characterized in that: A first circular through hole (14) is provided on the first half-cut monopole metal patch (1) near the first differential feed point (10), and a second circular through hole (15) is provided on the second half-cut monopole metal patch (2) near the second differential feed point (11).

Images