Ultra-wideband ground penetrating radar butterfly slot antenna optimization structure and method

Abstract

This invention discloses an optimized structure and method for an ultra-wideband ground-penetrating radar (UWPR) slotted butterfly antenna. The optimization method includes simulating a conventional butterfly antenna to analyze its impedance characteristics, reducing the high-frequency impedance by adding antenna arms, and improving the current reflection at the antenna end through antenna circularization. The optimized structure includes: a copper antenna body, an antenna signal input terminal, and a dielectric substrate. The antenna signal input terminal includes an SMA signal input terminal and antenna arms. The dielectric substrate is cuboid. The SMA signal input terminal covers the center of the copper body. The antenna arms are cuboids, numbered two, symmetrically distributed on the upper and lower sides of the SMA signal input terminal. The copper body, covered by the circularized slotted copper sheet on the dielectric substrate, constitutes the main copper body. This invention provides a novel and low-cost antenna structure that reduces high-frequency impedance, increases antenna bandwidth, reduces ringing effects, and achieves twice the gain of a conventional butterfly antenna.

Description

Technical Field

[0001] This invention relates to the field of ground penetrating radar technology, specifically to an optimized structure and method for an ultra-wideband ground penetrating radar butterfly slotted antenna. Background Technology

[0002] With the advent of the era of large-scale infrastructure construction, geological problems encountered in engineering and the environment have increasingly become a focus of attention and research. Ground Penetrating Radar (GPR), as the most effective method for imaging ultra-shallow underground layers, is widely used in identifying and solving shallow geological problems. Compared with transient electromagnetic methods and frequency domain electromagnetic methods, GPR has unparalleled advantages in accuracy and precision in shallow geological exploration within 10m. In geophysical exploration, GPR is used to study the distribution of bedrock, soil layers, groundwater, and ice layers; in engineering, it is widely used for detecting underground pipelines or conduits, assessing highway quality, detecting cracks in bridges and tunnels, and detecting railway foundations.

[0003] A typical ground-penetrating radar system mainly consists of three parts: a main unit (master control unit), a transmitter, and a receiver. The main unit sends control commands to the transmitter. After the command is issued, the transmitter transmits radar pulse waves into the ground. The receiver converts the reflected electromagnetic waves from the air into voltage signals through an antenna. This signal undergoes AD conversion and data processing to ultimately obtain information about the underground space.

[0004] In signal transmission, the antenna serves as both the final link in the chain and the first link in the chain, and its design parameters directly affect the quality of the detected signal, thus influencing the instrument's accuracy. Antenna design must select the appropriate antenna type based on the specific application. For pulse-type ground-penetrating radar, the presence of numerous frequency components necessitates high bandwidth; furthermore, to obtain deep-penetrating data, in addition to requiring a high input signal power, the antenna must also possess sufficient gain. Furthermore, in some applications where the antenna needs to be moved, high demands are placed on its size, weight, and the reliability of its physical structure. Therefore, designing a high-bandwidth, high-gain, and compact antenna is of paramount importance.

[0005] Commonly used ultra-wideband antennas in ground-penetrating radar applications include Vivaldi antennas, helical antennas, horn antennas, and butterfly antennas. Compared to other types of antennas, butterfly antennas have advantages such as light weight, ease of design and manufacturing, and compact planar structure.

[0006] Antenna bandwidth often depends on whether the antenna impedance changes drastically at different frequencies. According to the transmission line principle, an antenna that maintains good impedance matching can still have small reflected waves at different frequencies, resulting in high antenna transmission efficiency. Considering that pulse signals have many high-frequency components, high bandwidth needs to be achieved in antenna design. Currently, most butterfly antennas broaden their bandwidth through resistive loading, structural loading, and multi-resonant structures.

[0007] Resistive loading alters the antenna's bandwidth by improving the current distribution and impedance characteristics on its surface. Depending on the location of the resistor, it can be categorized as centralized or distributed loading. However, applying resistance inevitably reduces gain; therefore, when using this method for bandwidth expansion, appropriate resistance loading methods and values ​​must be chosen based on requirements. Similar to resistive loading, structural loading is primarily achieved by changing the antenna's shape. For butterfly antennas, shape changes often involve extending or slotting the base of the triangle. While typical antennas have only one or multiple resonant points that are significantly different, multi-resonant structures utilize shape and structural combinations / cutting to shift the high-frequency resonant point to the left, bringing multiple resonant frequencies closer together, thus widening the VSWR frequency range and consequently expanding the bandwidth.

[0008] Over the past few decades, there has been much research on ordinary butterfly antennas and their variants. However, to address the issue of their relatively low gain, most methods have involved adding shielding cavities, reflective materials, and dielectric lenses. The addition of reflective materials and dielectric lenses requires careful selection of appropriate materials based on the antenna's frequency and shape, making the design complex and demanding in-depth knowledge. Research on bandwidth broadening for slotted butterfly antennas with higher gain (approximately twice that of ordinary butterfly antennas) is less common, and most of the antennas designed in this area have relatively low bandwidth. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides an optimized structure and method for an ultra-wideband ground-penetrating radar butterfly slotted antenna, wherein the method includes the following steps:

[0010] S1. Simulate a common butterfly antenna using simulation software to obtain its impedance characteristics;

[0011] S2. Analyze the impedance characteristics and reduce the impedance in the high-frequency band by changing the shape of the input end of the ordinary butterfly antenna to obtain an improved butterfly antenna.

[0012] S3. Analyze the current distribution of the improved butterfly antenna to obtain the current reflection at the antenna end of the improved butterfly antenna;

[0013] S4. Based on the current reflection at the antenna end, the improved butterfly antenna is circularized, and the circularization parameters are optimized using a combination of genetic algorithm and quadratic Lagrange nonlinear programming algorithm to obtain the final butterfly antenna structure.

[0014] Further, in step S1, the dielectric substrate of the ordinary butterfly antenna is a cuboid, and copper sheets with the same length and width as the dielectric substrate are uniformly covered on the dielectric substrate. The antenna input end is covered in the center of the copper sheet. The copper sheets below the two isosceles triangles that are symmetrically distributed on the left and right sides of the antenna input end, with the vertices of the vertices located at the center of the copper sheet and the bottom edges located inside the copper sheet and parallel to the left and right sides of the dielectric substrate are slotted. The copper sheet below the antenna input end is not slotted to form an ordinary butterfly slot.

[0015] Furthermore, in step S2, changing the shape of the input end of the ordinary butterfly antenna specifically involves adding cuboid antenna arms with their long sides adjacent to the antenna signal input end on both the upper and lower sides of the ordinary butterfly antenna signal input end.

[0016] Furthermore, in step S4, the rounding process of the improved butterfly antenna specifically involves rounding the four corners of the copper sheet of the improved butterfly antenna, the bottom corner of the butterfly slot, the middle part of the two long sides of the copper sheet of the butterfly antenna, and the acute angle formed by the butterfly slot and the copper sheet below the antenna arm.

[0017] Furthermore, the circle-smoothing process specifically involves:

[0018] The specific process of rounding the four corners of the antenna copper sheet is as follows: set an auxiliary ellipse with the center of the dielectric substrate as the center of the ellipse. The major axis and minor axis of the ellipse are longer than the length and width of the dielectric substrate, respectively. The main body of the antenna center is kept inside the ellipse, and the four corners of the copper sheet are outside the ellipse. The four corner parts of the copper sheet outside the ellipse are cut off to form arcs.

[0019] The middle part of the two long sides of the copper sheet of the butterfly antenna is rounded: two auxiliary ellipses are set with their centers outside the copper sheet and located on the vertical midline of the copper sheet, and symmetrical about the horizontal midline of the copper sheet. The major axis of the ellipse is parallel to the long side of the copper sheet. The ellipse and the copper sheet have overlapping parts at the top and bottom. The overlapping parts are slotted. The overlapping parts do not include other main structures of the antenna.

[0020] The improved butterfly antenna features rounded corners at the base of the triangle and the acute angle formed by the triangle and the copper sheet below the antenna arm. After symmetrically rounding the two base corners of the triangle and the acute angle formed by the triangle and the copper sheet below the antenna arm, a slot is made in the rounded triangular copper sheet portion outside the antenna input end.

[0021] Furthermore, the circularization parameters are specifically the length of the base of the isosceles triangle, the distance from the base of the isosceles triangle to the right side of the antenna input feed, the distance from the vertex of the base of the isosceles triangle to the intersection of the arc and the base of the slotted triangle, the lengths of the major and minor axes of the auxiliary ellipse, and the length and width of the antenna arm.

[0022] An optimized structure for an ultra-wideband ground-penetrating radar (UWPR) butterfly slotted antenna, comprising the following components, optimized using the aforementioned UWPR butterfly slotted antenna optimization method:

[0023] Antenna body copper sheet, antenna signal input terminal, dielectric substrate;

[0024] The antenna signal input terminal includes an SMA signal input terminal and an antenna arm;

[0025] The dielectric substrate is a cuboid;

[0026] The SMA signal input terminal covers the center of the main copper sheet;

[0027] The antenna arms are cuboids, covering the middle of the main copper sheet. There are two of them, symmetrically distributed on the upper and lower sides of the SMA signal input terminal. The long side is adjacent to the SMA signal input terminal and parallel to the upper edge of the dielectric substrate.

[0028] The dielectric substrate is uniformly covered with copper sheets of the same length and width as the dielectric substrate. The two base angles of two isosceles triangles, whose vertices are located at the center of the copper sheet and whose bases are located inside the copper sheet and are symmetrically distributed parallel to the dielectric substrate, are symmetrically rounded. The acute angle formed by the isosceles triangles and the copper sheet below the antenna arm is rounded. The two rounded isosceles triangle copper sheets are slotted, while the copper sheet covering the antenna signal input end is not slotted, forming a butterfly-shaped slot.

[0029] Symmetrical arc-shaped notches are cut out from the upper and lower middle parts of the copper sheet to achieve rounding. The cut-out arc-shaped notches do not include other parts of the antenna. The copper sheet covering the dielectric substrate after slotting is the main copper sheet.

[0030] Furthermore, by changing the length and width of the antenna arm, the input impedance parameters of the antenna at different frequency bands can be altered, thereby increasing the antenna bandwidth.

[0031] This invention provides an optimized structure and method for an ultra-wideband ground-penetrating radar butterfly slotted antenna, which has the following beneficial effects:

[0032] The antenna structure of this invention is novel and has low manufacturing cost. It employs an arm-like design at the antenna input end and modifies the input impedance parameters of the antenna at different frequency bands by changing the length and width of the antenna arm, thereby increasing the antenna bandwidth. The circularization of the antenna reduces the ringing effect and further increases the antenna bandwidth. The optimized antenna gain is twice that of a conventional butterfly antenna, making it suitable for pulse ground-penetrating radar applications. Attached Figure Description

[0033] Figure 1 This is a flowchart of an optimization method for a butterfly slotted antenna for ultra-wideband ground-penetrating radar according to the present invention;

[0034] Figure 2 This is a structural diagram of a typical butterfly antenna;

[0035] Figure 3 This is the input impedance of a typical slotted butterfly antenna;

[0036] Figure 4 This is a current distribution diagram of the slotted antenna with an added arm according to an embodiment of the present invention;

[0037] Figure 5 This is a diagram showing the circularized position and related parameter positions in an embodiment of the present invention;

[0038] Figure 6 This is the electric field distribution diagram of the finally optimized butterfly slotted antenna in this embodiment of the invention;

[0039] Figure 7 This is a flowchart of the optimization algorithm for optimizing the parameters of the butterfly slotted antenna in an embodiment of the present invention;

[0040] Figure 8 This is a shape and structure diagram of an optimized structure for an ultra-wideband ground-penetrating radar butterfly slotted antenna according to an embodiment of the present invention;

[0041] Figure 9 This is a comparison of simulation and actual measurement of the return loss of the butterfly slotted antenna after final optimization in this embodiment of the invention;

[0042] Figure 10 This is a simulation gain diagram of the main radiation direction of the finally optimized butterfly slotted antenna in this embodiment of the invention.

[0043] Figure 11 The image shows the radiation pattern of the finally optimized butterfly slotted antenna in this embodiment of the invention. Detailed Implementation

[0044] The present invention provides a technical solution: an optimized structure and method for an ultra-wideband ground-penetrating radar butterfly slotted antenna.

[0045] Please see Figure 1 , Figure 1 This is a flowchart of an optimization method for a butterfly slotted antenna for ultra-wideband ground-penetrating radar according to the present invention. The method includes the following steps:

[0046] S1. Simulate a standard butterfly antenna using Ansys HFSS software to obtain its impedance characteristics. The standard butterfly antenna uses a cuboid dielectric substrate. A copper sheet of the same length and width as the substrate is uniformly covered on the substrate. The antenna input terminal is located in the center of the copper sheet. Slots are created below two isosceles triangles symmetrically distributed around the antenna input terminal, with their vertices centered on the copper sheet and their bases inside the copper sheet and parallel to the left and right sides of the dielectric substrate. The copper sheet below the antenna input terminal is not slotted, forming a standard butterfly-shaped slot. (Reference) Figure 2 , Figure 2 This is a structural diagram of a typical butterfly antenna.

[0047] S2, Reference Figure 3 , Figure 3 The input impedance of a standard slotted butterfly antenna is analyzed, and optimization is performed based on this analysis. Simulation results show that the high-frequency input impedance of the standard slotted butterfly antenna rapidly increases to 100 ohms, while the imaginary part is relatively smooth in this frequency band, but the overall capacitance is excessive. Therefore, to increase the bandwidth of the antenna in the high-frequency band, the impedance in the high-frequency band must be reduced. The shape of the antenna input end has the greatest impact on the antenna; based on this, horizontal cuboid antenna arms are added to the upper and lower sides of the signal input end of the standard butterfly antenna to improve the high-frequency impedance. For conductors, a larger cross-sectional area results in lower resistance; simultaneously, a larger angle at the signal input end of the standard butterfly antenna and a "fatter" overall antenna result in a wider bandwidth. Therefore, by changing the length and width of the antenna arms, the input impedance parameters of the antenna in different frequency bands can be quickly changed, thereby achieving a high bandwidth. By changing the shape of the input end of the standard butterfly antenna and reducing the high-frequency impedance, an improved butterfly antenna is obtained.

[0048] In this embodiment, the shape of the input terminal of a conventional butterfly antenna is changed by adding cuboid antenna arms with their long sides adjacent to the signal input terminal on both the top and bottom sides of the signal input terminal.

[0049] S3. Analyzing the current distribution of the improved butterfly antenna, it can be found that the reflection at the antenna end is more obvious, thus obtaining the current reflection situation at the antenna end of the improved butterfly antenna.

[0050] An infinitely long biconical antenna has impedance independent of frequency, achieving a very high bandwidth. However, practical antennas have size requirements, necessitating truncation at the end. This sudden interruption causes current reflection at the antenna tip, resulting in a ringing effect. This current reflection not only causes signal tailing, leading to multiple reflections of the signal within the underground medium, but also exacerbates the tailing phenomenon by inducing current at the antenna receiver. Unlike communication antennas, ground-penetrating radar (GPR) antennas require the identification and processing of echo data peaks; current reflection can cause misjudgments of peaks or cover peaks at existing medium layers, greatly hindering data processing and severely impacting the accuracy and detection depth of GPR instruments. Therefore, most butterfly antenna designers employ end-loading to suppress ringing; however, this resistive / capacitive loading method affects the antenna's radiation efficiency and reduces its gain.

[0051] S4. Based on the current reflection at the antenna end, the current will be reflected at places where the shape changes drastically; therefore, the sharp angle at the antenna end should be reduced and the corresponding places should be rounded.

[0052] refer to Figure 4 , Figure 4 This is a current distribution diagram of the slotted antenna with an added arm according to an embodiment of the present invention. Observing the current distribution diagram of the slotted butterfly antenna with an added arm, it can be seen that current reflection mainly occurs at the four corners of the copper sheet, the acute angle of the triangular slot, and the middle part of the long side of the antenna. Ellipticalization is applied to these areas as follows: Figure 5 As shown, Figure 5 This is a diagram showing the circularized position and related parameter positions in an embodiment of the present invention.

[0053] The rounding process for the improved butterfly antenna is as follows: rounding is performed on the four corners of the copper sheet of the improved butterfly antenna, the bottom corner of the butterfly slot, the middle part of the two long sides of the copper sheet of the butterfly antenna, and the acute angle formed by the butterfly slot and the copper sheet below the antenna arm.

[0054] The improved rounding treatment of the four corners of the copper sheet in the butterfly antenna is as follows: set an auxiliary ellipse with the center of the dielectric substrate as the center of the ellipse. The major axis and minor axis of the ellipse are longer than the length and width of the dielectric substrate, respectively. The main body of the antenna center is kept inside the ellipse, and the four corners of the copper sheet are outside the ellipse. The four corner parts of the copper sheet outside the ellipse are cut off to form arcs.

[0055] The middle part of the two long sides of the improved butterfly antenna copper sheet is rounded: two auxiliary ellipses are set with their centers outside the copper sheet and located on the vertical midline of the copper sheet, and symmetrical about the horizontal midline of the copper sheet. The major axis of the ellipse is parallel to the long side of the copper sheet. The ellipse and the copper sheet have overlapping parts at the top and bottom. The overlapping parts are slotted. The overlapping parts do not include other main structures of the antenna.

[0056] Improved rounding of the triangular base angles of the butterfly antenna: The two base angles of the triangle are symmetrically rounded. To facilitate subsequent shape optimization and reduce the number of variables, the center of the arc is located at the intersection of the angle bisectors of the base and apex angles. The radius of the arc can be varied as needed.

[0057] The specific parameters for the rounding process are: the length of the base of the isosceles triangle, the distance from the base of the isosceles triangle to the right side of the antenna input feed, the distance from the vertex of the base of the isosceles triangle to the intersection of the arc and the base of the slotted triangle, the lengths of the major and minor axes of the auxiliary ellipse, and the length and width of the antenna arm.

[0058] refer to Figure 5 The formula for calculating the distance from the center of the arc to the center of the substrate for the symmetrical rounded arc treatment of the two corners of the base of the internal slotted triangle is as follows:

[0059]

[0060] The distance from the center of the arc that symmetrically rounds the two corners of the base of the internally slotted triangle to the base of the triangle:

[0061]

[0062] The angle θ of the arc formed by symmetrically rounding the two corners of the base of the internally slotted triangle is:

[0063]

[0064] in, A L This is the distance from the bottom edge to the right side of the feeder. O W Let be the length of the base of the slotted triangle. The length and width of the SMA signal input feed are both 'a'. OW sub It is the distance from the vertex of the base angle of the slotted triangle to the intersection of the arc and the base of the slotted triangle.

[0065] Before optimizing antenna performance using optimization algorithms, the basic structure of the antenna must first be determined. Then, parameters are variably defined for this structure, such as... Figure 5 As shown. The center SMA feed has a length and width of 1cm, and the base length of the slotted triangle is... O W The distance from the bottom edge to the right side of the feeder is A L The distance from the vertex of the base of the triangle to the arc is OW sub The semi-major axis and semi-minor axis of the two cut-off ellipses are respectively E 1a ,E 1b , E 2a , E 2b The distance from the center of the ellipse 2 to the center is E 2C The length and width of the rectangular arm loaded in the middle are respectively... E aw and B al These parameters are selected within an appropriate range, with the optimization objective being a return loss of less than -20 at 0.4 GHz and a return loss of less than -10 between 0.35 GHz and 1 GHz.

[0066] After determining the antenna structure and the range of parameter values, the antenna circularization parameters are optimized using a combination of genetic algorithm and quadratic Lagrange nonlinear programming algorithm to obtain the final butterfly antenna structure.

[0067] The optimized antenna field distribution is as follows Figure 6 As shown, Figure 6 This is an electric field distribution diagram of an embodiment of the present invention. It can be seen that the current reflection around the antenna is significantly improved, and the electric field distribution around the antenna is relatively more uniform, making it suitable for application in pulse ground-penetrating radar systems.

[0068] When selecting an optimization algorithm, since antenna design variables are linear, and the influence of most variables on antenna parameters is generally linear within a small range, a combination of global optimum and local optimum algorithms can be used to improve the optimization speed. Taking the combination of Genetic Algorithm (GA) and Quadratic Lagrangian Nonlinear Programming (NLPQL) as an example, the algorithm flow is as follows: Figure 7 As shown, the initial optimization process first uses a wide range of variable values ​​with large step sizes when creating the initial population. After setting reasonable control parameters (population size, number of generations, crossover probability, mutation probability, etc.), crossover and mutation are performed on the operators to generate a new population. Finally, several parameter points with low return loss are obtained through optimization. Then, a quadratic Lagrange nonlinear programming algorithm is used to optimize the antenna parameters at those parameter points using variables with small step sizes. Finally, the antenna parameters that meet the requirements and achieve the best effect are selected.

[0069] The antenna structure optimized using the above-described optimization method for an ultra-wideband ground-penetrating radar butterfly slotted antenna is referenced. Figure 8 , Figure 8 This is a shape and structure diagram of an optimized structure for an ultra-wideband ground-penetrating radar butterfly slotted antenna according to an embodiment of the present invention.

[0070] The antenna includes a copper sheet 1 as the main body, an antenna signal input terminal 2, and a dielectric substrate 3. The antenna signal input terminal 2 includes an SMA signal input terminal 5 and an antenna arm 4. The dielectric substrate 3 is a cuboid. The SMA signal input terminal 5 covers the center of the copper sheet 1.

[0071] In this embodiment, the positioning hole size is M3, the dielectric substrate 3 is made of FR4 material with a thickness of 1.6 mm, the main copper sheet 1 has a copper thickness of 1 ounce, and to reduce damage to the dielectric substrate, the SMA signal input terminal 5 uses a 50Ω surface mount SMA.

[0072] In this embodiment, two symmetrically distributed cuboid antenna arms 4 are added on the upper and lower sides of the SMA signal input terminal 5, with their long sides adjacent to the SMA signal input terminal 5 and parallel to the upper edge of the dielectric substrate 3; the antenna arms 4 cover the middle of the main copper sheet 1. By changing the length and width of the antenna arms 4, the input impedance parameters of the antenna in different frequency bands are changed, thereby increasing the antenna bandwidth.

[0073] In this embodiment, copper sheets of the same length and width as the dielectric substrate 3 are uniformly covered on the dielectric substrate 3. The two base angles of two isosceles triangles, whose apex is located at the center of the copper sheet and whose base is located inside the copper sheet and are symmetrically distributed parallel to the dielectric substrate, are symmetrically rounded. The acute angle formed by the isosceles triangle and the copper sheet below the antenna arm is rounded. The two rounded isosceles triangle copper sheets are slotted, while the copper sheet covered by the antenna signal input terminal 2 is not slotted, forming a butterfly-shaped slot.

[0074] Symmetrical arc-shaped notches are cut out from the upper and lower middle parts of the copper sheet to achieve rounding. The cut-out arc-shaped notches do not include other parts of the antenna. The copper sheet covering the dielectric substrate 3 after slotting is the main copper sheet 1. Label 6 indicates the location of the rounding process.

[0075] The antenna simulation software used was Ansys HFSS. A prototype was fabricated and tested with an SMA (Surface Mount Equipment) mount. The testing instrument was a network analyzer from Agilent Technologies. The comparison between the simulated and measured return loss is shown in the figure below. Figure 9 As shown in the figure. Simulation results show that the antenna bandwidth (based on return loss S11 < -10dB) ranges from 0.35GHz to 1.28GHz, with an absolute bandwidth of 0.93GHz and a relative bandwidth of 114.1%. The actual test results are basically consistent with the simulation, and its low-frequency cutoff frequency even reaches 0.3GHz, while the high-frequency cutoff frequency is greater than 1.5GHz. The return loss is slightly higher in the 0.5-0.7GHz range, but the highest point is only -7.9dB, which meets the actual requirements.

[0076] The maximum gain (-15°~+15°) of the simulated antenna in the main radiation direction is as follows: Figure 10As shown, the antenna gain increases rapidly from low frequencies, and remains above 8dBi after 0.5GHz. The gain at the lowest point in the bandwidth, 0.35GHz, reaches 3.7dBi. The overall antenna gain is high and meets the actual requirements.

[0077] The radiation patterns of this antenna in the E-plane and H-plane at 0.3 GHz and 0.6 GHz are as follows: Figure 11 As shown, this reflects the electromagnetic wave transmission and reception capabilities in different directions. It can be seen that at 0.4 GHz, the E-plane radiation pattern is basically figure-eight shaped, while the H-plane is elliptical; while at 0.6 GHz, the E and H-plane radiation patterns are basically the same, both being rugby ball shaped, indicating better directivity and gain.

[0078] To constrain the directivity of the antenna, a rectangular shielding cavity can be added to one side of the antenna's radiation direction, filled with absorbing material.

[0079] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. An optimization method for a bowtie slot antenna of an ultra-wideband ground penetrating radar, characterized in that, Includes the following steps: S1. Simulate a common butterfly antenna using simulation software to obtain its impedance characteristics; S2. Analyze the impedance characteristics and reduce the impedance in the high-frequency band by changing the shape of the input end of the ordinary butterfly antenna to obtain an improved butterfly antenna. S3. Analyze the current distribution of the improved butterfly antenna to obtain the current reflection at the antenna end of the improved butterfly antenna; S4. Based on the current reflection at the antenna end, the improved butterfly antenna is circularized, and the antenna circularization parameters are optimized by combining a genetic algorithm with a second-order Lagrange nonlinear programming algorithm to obtain the final butterfly antenna structure. In step S1, the dielectric substrate of the ordinary butterfly antenna is a cuboid, and copper sheets with the same length and width as the dielectric substrate are uniformly covered on the dielectric substrate. The antenna input end is covered in the center of the copper sheet. The copper sheets below the two isosceles triangles that are symmetrically distributed on the left and right sides of the antenna input end, with the vertices of the vertices located at the center of the copper sheet and the bottom edges located inside the copper sheet and parallel to the left and right sides of the dielectric substrate are slotted. The copper sheet below the antenna input end is not slotted to form an ordinary butterfly slot. In step S2, changing the shape of the input end of the ordinary butterfly antenna specifically involves adding cuboid antenna arms with their long sides adjacent to the antenna signal input end on the upper and lower sides of the ordinary butterfly antenna signal input end. In step S4, the rounding process for the improved butterfly antenna is specifically performed as follows: the four corners of the copper sheet of the improved butterfly antenna, the middle part of the two long sides of the copper sheet, the base corner of the triangle, and the acute angle formed by the triangle and the copper sheet below the antenna arm are rounded. The rounding process is as follows: The improved rounding treatment of the four corners of the copper sheet in the butterfly antenna is as follows: set an auxiliary ellipse with the center of the dielectric substrate as the center of the ellipse. The major axis and minor axis of the ellipse are longer than the length and width of the dielectric substrate, respectively. The main body of the antenna center is kept inside the ellipse, and the four corners of the copper sheet are outside the ellipse. The four corner parts of the copper sheet outside the ellipse are cut off to form arcs. The middle part of the two long sides of the improved butterfly antenna copper sheet is rounded: two auxiliary ellipses are set with their centers outside the copper sheet and located on the vertical midline of the copper sheet, and symmetrical about the horizontal midline of the copper sheet. The major axis of the ellipse is parallel to the long side of the copper sheet. The ellipse and the copper sheet have overlapping parts at the top and bottom. The overlapping parts are slotted. The overlapping parts do not include other main structures of the antenna. The improved butterfly antenna features rounded corners at the base of the triangle and the acute angle formed by the triangle and the copper sheet below the antenna arm. After symmetrically rounding the two base corners of the triangle and the acute angle formed by the triangle and the copper sheet below the antenna arm, a slot is made in the rounded triangular copper sheet portion outside the antenna input end.

2. The method of claim 1, wherein the method is used for optimizing a bowtie slot antenna for an ultra-wideband ground penetrating radar. The specific parameters for the rounding process are: the length of the base of the isosceles triangle, the distance from the base of the isosceles triangle to the right side of the antenna input feed, the distance from the vertex of the base of the isosceles triangle to the intersection of the arc and the base of the slotted triangle, the lengths of the major and minor axes of the auxiliary ellipse, and the length and width of the antenna arm.

3. An ultra-wideband ground penetrating radar bowtie slot antenna optimized structure, characterized in that, The structure described is an optimized structure using the ultra-wideband ground-penetrating radar butterfly slotted antenna optimization method according to any one of claims 1 to 2, comprising: It includes a copper sheet for the antenna body (1), an antenna signal input terminal (2), and a dielectric substrate (3); The antenna signal input terminal (2) includes an SMA signal input terminal (5) and an antenna arm (4); The dielectric substrate (3) is a cuboid; The SMA signal input terminal (5) covers the center of the main copper sheet (1); The antenna arm (4) is a cuboid, covering the middle of the main copper sheet (1), and there are 2 of them. They are symmetrically distributed on the upper and lower sides of the SMA signal input terminal (5), with the long side close to the SMA signal input terminal (5) and the long side parallel to the upper side of the dielectric substrate (3). The dielectric substrate (3) is uniformly covered with copper sheets of the same length and width as the dielectric substrate (3). The two base angles of two isosceles triangles, whose apex is located at the center of the copper sheet and whose base is located inside the copper sheet and are symmetrically distributed parallel to the dielectric substrate, are symmetrically rounded. The acute angle formed by the isosceles triangle and the copper sheet below the antenna arm is rounded. The two rounded isosceles triangle copper sheets are slotted, and the copper sheet covered by the antenna signal input terminal (2) is not slotted, forming a butterfly-shaped slot. The upper and lower middle parts of the copper sheet are symmetrically cut out with arc-shaped notches to achieve rounding. The cut-out arc-shaped notches do not include other parts of the antenna. The copper sheet covered on the dielectric substrate (3) after slotting is the main copper sheet (1).

4. The optimized structure of a bow-tie slot antenna for ultra-wideband ground penetrating radar according to claim 3, wherein, By changing the length and width of the antenna arm (4), the input impedance parameters of the antenna in different frequency bands can be changed, thereby increasing the antenna bandwidth.

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