Low-frequency ultra-wideband ground penetrating radar miniaturized butterfly antenna and optimization method

Abstract

The application discloses a low-frequency ultra-wideband ground penetrating radar miniaturized butterfly antenna, which comprises a main plate and a side plate; the main plate comprises a positioning hole, a side plate slot, a butterfly-shaped patch, a main plate dielectric substrate and an SMA signal input end; the side plate comprises a side plate dielectric substrate and a quadrilateral patch; two side plates are inserted through the slots on the left and right sides of the main plate, the butterfly-shaped patch and the quadrilateral patch are combined into a closed complete antenna arm, and part of the antenna arm is vertically placed through ingenious design, so that the length of the antenna on the plane is greatly reduced, the antenna is more suitable for carrying and working, and the shapes of the planar antenna arm and the vertical antenna arm are reasonably optimized to obtain a suitable low-frequency point and a wide bandwidth.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of butterfly antennas, in particular to a low-frequency ultra-wideband ground penetrating radar miniaturized butterfly antenna and an optimization method. BACKGROUND

[0002] With the implementation of the 14th Five-Year Plan, China is accelerating the high-quality development driven by innovation. Ground penetrating radar (GPR) plays a crucial role in today's large-scale infrastructure era, especially as the most effective method for imaging shallow underground exploration. It is widely used to identify and solve shallow geological problems, but the key technology is still in the hands of others. Chinese enterprises have to spend a lot of money to purchase foreign version ground penetrating radar instruments. In summary, it is more valuable to manufacture a Chinese version ground penetrating radar with independent innovation.

[0003] The geological problems encountered by ground penetrating radar in engineering and environment have become the focus of attention and research. Compared with transient electromagnetic method and frequency domain electromagnetic method, ground penetrating radar has incomparable advantages in precision and accuracy in shallow geological exploration within 10m. In the process of geophysical exploration, ground penetrating radar is used to study the distribution of bedrock, soil layer, underground water and ice layer; in engineering, it is widely used in underground pipeline or pipeline detection, highway quality evaluation, bridge and tunnel crack detection and railway foundation detection.

[0004] As shown in Figure 1 A general ground penetrating radar system mainly consists of a host computer (main control unit), a transmitter and a receiver. The host computer is used to send control commands to the transmitter. After the command is issued, the transmitter gives a transmission signal to the transmission antenna to transmit radar pulse waves to the ground. The receiver converts the reflected electromagnetic wave signal obtained in the air into a voltage signal through the receiving antenna. The signal is finally obtained after AD conversion and data processing. The information of the target object in the underground space.

[0005] The antenna is the first loop for signal transmission and the last loop for signal reception, and its design parameters directly affect the quality of the detection signal, and further affect the accuracy of the instrument. In the antenna design, the corresponding antenna type is selected according to different application fields. For the pulse-type ground penetrating radar, due to the narrow effective working bandwidth of the traditional commercial radar antenna and the large antenna size, the antenna needs to be frequently replaced when detecting targets of different depths, which not only reduces the working efficiency but also is inconvenient to carry. In the process of analyzing the echo signal of the ground penetrating radar, if the signal bandwidth is wide enough, the detection accuracy of the radar can be greatly improved. At the same time, strict requirements are put forward for the design selection and parameter index of the ground penetrating radar antenna. Not only should the antenna have an ultra-wide effective working frequency band range and excellent directional radiation characteristics, but also should have a portable antenna size. Therefore, the research on the ultra-wideband antenna of the ground penetrating radar plays an important role in promoting the accurate detection of urban underground shallow pipelines.

[0006] The bandwidth of the antenna often depends on whether the impedance of the antenna changes sharply at different frequencies. According to the principle of transmission line, the antenna with good impedance matching can still have a small reflected wave at different frequencies, and a high antenna transmission efficiency; considering that the pulse signal of the ground penetrating radar has more high-frequency components, it is necessary to achieve a high bandwidth in the antenna design. At present, most of the butterfly-shaped antennas expand the bandwidth through resistance loading, structure loading and multi-resonant structure, and the antenna structure size is often large, which is not convenient to carry. SUMMARY

[0007] Therefore, the application provides a low-frequency ultra-wideband ground penetrating radar miniaturized butterfly-shaped antenna, which comprises a main plate and a side plate.

[0008] The main plate comprises a side plate slot, a butterfly-shaped patch, a main plate dielectric substrate, an SMA signal input end and a side plate.

[0009] The side plate comprises a side plate dielectric substrate and a quadrilateral patch.

[0010] The side plate slots are symmetrically distributed on the left and right sides of the main plate dielectric substrate.

[0011] The butterfly-shaped patches are symmetrically distributed on the left and right sides of the SMA signal input end.

[0012] The two side plates are connected through the side plate slots and the main plate, and are 90° in space; the edges of the butterfly-shaped patches and the quadrilateral patches at the joint of the main plate and the side plate are completely overlapped; and the butterfly-shaped patches and the quadrilateral patches form complete antenna arms.

[0013] Further, the main plate further comprises positioning holes located on the upper and lower edges of the main plate, which are used for fixing the antenna when the antenna is installed, and the number of the positioning holes is set according to requirements.

[0014] Further, the right half of the butterfly-shaped patch is shaped as a closed shape composed of two straight line segments connected with the right two top points of the SMA signal input end respectively, the right edge coinciding with the SMA signal input end, a plurality of circular arcs connected with the two straight line segments, and a line segment fully coinciding with the edge of the quadrilateral patch, the left half of the butterfly-shaped patch is shaped as a left-right symmetrical shape of the left half edge, and the butterfly-shaped patch is up-down symmetrical.

[0015] Further, the material of the main plate medium substrate and the side plate medium substrate is FR4, and the thickness is 1.6 mm.

[0016] Further, the copper thickness of the butterfly-shaped patch and the quadrilateral patch is 1 ounce.

[0017] Further, the SMA signal input end adopts a 50Ω straight insertion type SMA.

[0018] Further, the butterfly-shaped antenna works at 0.15-1.03 GHz, and the relative bandwidth is 149.2%.

[0019] The application also provides a low-frequency ultra-wideband ground penetrating radar miniaturized butterfly-shaped antenna optimization method, which is used for optimizing the low-frequency ultra-wideband ground penetrating radar miniaturized butterfly-shaped antenna.

[0020] The left half edge and the right half edge of the butterfly-shaped patch are respectively divided into two up-down symmetrical parts, the length of the line segment a connecting the right upper part of the butterfly-shaped patch with the right upper top point of the SMA signal input end is l, the included angle of the line segment a with the upper edge of the SMA signal input end is θ, and the genetic algorithm is used to optimize l and θ, so that the antenna reaches the lowest frequency point and the widest bandwidth.

[0021] A three-point circular arc method is used to design the circular arc of the butterfly-shaped patch, the right upper top point of the SMA signal input end is used as the origin, the direction of the upper edge of the SMA signal input end is used as the x axis, the direction of the right edge of the SMA signal input end is used as the y axis, the right upper part of the butterfly-shaped patch has three arc shapes, the coordinates of two end points of one of the arc shapes are (x1, y1) and (x2, y2), the third point is on the perpendicular bisector of the line segment connecting the two end points, and the two end points and the third point satisfy:

[0022]

[0023]

[0024] The genetic algorithm is used to optimize the coordinates of the three points of the arc shape to obtain the optimal antenna performance.

[0025] The parameters of the other three parts of the butterfly-shaped patch are the same as those of the right upper part of the butterfly-shaped patch.

[0026] The quadrilateral patch is a left-right symmetrical quadrilateral, the upper two corners of the quadrilateral patch are greater than 90 DEG, on the plane of the quadrilateral patch, taking the side combined with the side plate as an x axis, and the center vertical line of the side as a y axis, the upper vertex and the lower vertex of the right half of the quadrilateral patch are (m1, n1) and (m2, n2), and the two coordinate points are optimized by using a genetic algorithm.

[0027] The technical scheme provided by the application has the beneficial effects that:

[0028] The technical scheme of the application can reduce the terminal current reflection of the antenna arm, reduce the current reflection at the edge of the antenna, improve the impedance characteristics, expand the low-frequency performance, greatly reduce the length of the antenna on the plane, and be more suitable for carrying work. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a general ground penetrating radar principle block diagram;

[0030] Figure 2 It is a bottom plate shape structure diagram of the antenna embodiment of the application;

[0031] Figure 3 It is a side plate shape structure diagram of the antenna embodiment of the application;

[0032] Figure 4 It is an antenna assembly schematic diagram of the embodiment of the application;

[0033] Figure 5 It is a general butterfly-shaped antenna current distribution diagram of the embodiment of the application;

[0034] Figure 6 It is an input impedance of the general butterfly-shaped antenna of the embodiment of the application;

[0035] Figure 7 It is an antenna arm diagram near the feed point of the embodiment of the application;

[0036] Figure 8 It is a bottom plate antenna parameterization schematic diagram of the embodiment of the application;

[0037] Figure 9 It is a side plate antenna parameterization schematic diagram of the embodiment of the application;

[0038] Figure 10 It is a bottom plate slot setting diagram of the embodiment of the application;

[0039] Figure 11 It is a side plate bottom reserved distance diagram of the embodiment of the application;

[0040] Figure 12 It is a bottom plate antenna current distribution diagram of the embodiment of the application;

[0041] Figure 13 This is a current distribution diagram of the side panel antenna according to an embodiment of the present invention;

[0042] Figure 14 is the characteristic impedance of the overall antenna according to the embodiment of the present invention;

[0043] Figure 15 This is a comparison diagram of the simulated and measured return loss of the butterfly antenna according to an embodiment of the present invention;

[0044] Figure 16 The E-plane and H-plane radiation patterns of the butterfly antenna at 0.15 GHz are shown in FIG. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0046] The triangular arms of a common butterfly antenna are the radiating elements of the antenna, and the entire antenna is fed at the feeding point between the two triangular arms. First, the common antenna is simulated using Ansys HFSS software to observe the current reflection of the common butterfly antenna, such as Figure 5 As shown, and the impedance characteristics, such as Figure 6 As shown, and optimized on this basis. Figure 5 The current distribution diagram shows that the current reflection is more obvious near the antenna feed point and at the edges of the two arms. The input impedance also shows that the input impedance of the ordinary butterfly antenna has obvious jitter in both the low-frequency and high-frequency bands and is both above 100Ω. Therefore, it cannot achieve good impedance matching with the SMA, resulting in a very low bandwidth of the ordinary antenna.

[0047] Current reflection will not only cause the trailing of the emission signal, resulting in multiple reflections of the signal in the underground medium; meanwhile, the current induced at the receiving end of the antenna will also be emitted, aggravating the trailing phenomenon. Unlike the antenna used for communication, the ground penetrating radar antenna needs to identify and process the peak points of the echo data; while the current reflection will cause misjudgment of the peak points or cover the peak value of the original medium layer, thereby greatly affecting the data processing and seriously affecting the precision and detection depth of the ground penetrating radar instrument. At present, the ordinary butterfly antenna mainly adopts the lumped or distributed resistance loading or structural loading method, which improves the current reflection of the antenna to a certain extent, suppresses the trailing effect of the time domain signal, and expands the effective working bandwidth of the antenna; resistance loading is to forcibly change the impedance characteristics of the antenna by adding resistance, and the aging of the resistance will directly affect the performance of the antenna, and the resistance is an energy-consuming component, which will seriously affect the radiation efficiency of the antenna; structural loading is to change the impedance of the antenna by changing the shape of the antenna arm, and generally the shape of the antenna is not easy to change after being made, so the performance of the antenna is very stable. The low-frequency ultra-wideband antenna of the embodiment is a structural loading design of the antenna arm, which can increase the effective working bandwidth of the antenna and improve the current reflection at the end of the antenna arm, thereby obtaining a more flat impedance characteristic and a wider bandwidth.

[0048] The embodiment provides a low-frequency ultra-wideband ground penetrating radar miniaturized butterfly antenna, referring to Figure 2 、 Figure 3 and Figure 4 , comprising a main plate 9 and a side plate 8; the main plate 9 comprises a side plate slot 2, a butterfly patch 3, a main plate dielectric substrate 4 and an SMA signal input end 5; the side plate 8 comprises a side plate dielectric substrate 6 and a quadrilateral patch 7. The main plate 9 further comprises a positioning hole 1 located on the upper and lower edges of the main plate 9, which is used for fixing the antenna during installation of the antenna, and the number of the positioning hole 1 is set according to requirements.

[0049] The side plate slot 2 penetrates the main plate dielectric substrate, and the width is the length of the side plate and the depth is 1.6 mm. The substrate material and thickness can be changed as required, and generally the thicker the substrate, the wider the bandwidth of the antenna. The side plate slot 2 is symmetrically distributed on the left and right sides of the main plate dielectric substrate 4; the butterfly patch 3 is symmetrically distributed on the left and right sides of the SMA signal input end 5.

[0050] The positioning hole 1 is M3 in size, and corresponding hole distances can be used in actual application according to requirements, and the position and number of the positioning hole can also be changed, and it is required not to damage the shape of the antenna itself.

[0051] The main plate 9 is subjected to slotting treatment, the slotting depth is the thickness of the main plate 9, and the width is the length of the side plate, so that the side plate can be inserted into the bottom plate without gap. A small gap is left on the left side of the slot, and after the assembly is completed, solder can be used to further weld the gap to connect the side plate antenna and the bottom plate antenna, so that the assembly is more stable, and the use of copper foil to connect the side plate antenna and the bottom plate antenna is avoided. The use of copper foil will affect the actual length of the overall antenna arm, thereby avoiding the influence of unstable factors.

[0052] As shown in Figure 10 and Figure 11 The present application reserves a distance for the side plate antenna, and the reserved distance is 1.6 mm, which ensures that the bottom of the side plate antenna is tangent to the edge of the bottom plate antenna. At this time, the accidental error will be small after using solder to weld.

[0053] The two side plates 8 are connected through the side plate slot 2 and the main plate 9, and are 90° in space; the edges of the butterfly-shaped patch 3 and the quadrilateral patch 7 at the joint of the main plate 9 and the side plate 8 completely coincide; the butterfly-shaped patch 3 and the quadrilateral patch 7 constitute a complete antenna arm. The opening angle of the antenna arm near the SMA feed point is greater than 180°.

[0054] The right half of the butterfly-shaped patch 3 is in the shape of a closed shape composed of two straight line segments connected to the right two vertices of the SMA signal input end 5, a side coinciding with the right side of the SMA signal input end 5, a plurality of circular arcs connected to the two straight line segments, and a line segment completely coinciding with the edge of the quadrilateral patch 7. The left half of the butterfly-shaped patch 3 is symmetrical to the right half of the left half, and the butterfly-shaped patch 3 is symmetrical up and down.

[0055] In a further embodiment, the plurality of circular arcs are three arcs.

[0056] The materials of the main plate dielectric substrate 4 and the side plate dielectric substrate 6 are FR4, and the thickness is 1.6 mm.

[0057] The copper thickness of the butterfly-shaped patch 3 and the quadrilateral patch 7 is 1 ounce, which can be changed as needed. Generally speaking, the thicker the copper foil, the better the antenna radiation effect.

[0058] The embodiment of the present application is a PCB antenna, and the feeding port of the PCB antenna is usually fed by a patch-type SMA, but the stability of the patch-type SMA soldered on the PCB is weak, and it is easy to fall off during testing. After falling off, it will be very difficult to weld here, so the present application uses a straight insertion type SMA to feed the antenna. The SMA signal input end 5 uses a 50Ω straight insertion type SMA, and the characteristic impedance of the SMA needs to correspond to the pulse transmission circuit and the antenna impedance.

[0059] The butterfly antenna works at 0.15-1.03GHz, and the relative bandwidth is 149.2%.

[0060] The conventional butterfly antenna is a symmetrical structure composed of two triangles, which is a special form of biconical antenna. The working frequency of the antenna is related to the length of the triangular arm. The longer the arm, the lower the working frequency of the antenna. Therefore, the volume of the material required for assembling the low-frequency butterfly antenna will be larger. In the present design, the arm of the antenna is vertically placed by a clever design, thereby greatly reducing the length of the antenna on the plane, and it is more suitable for carrying and working. However, the vertical placement of the antenna arm will cause the deterioration of the related parameters, such as the sharp decrease of the bandwidth, and even the bandwidth cannot reach that of the conventional butterfly antenna. Therefore, the shape of the planar antenna arm and the vertical antenna arm needs to be reasonably optimized to obtain a suitable low frequency point and a wide bandwidth. Without affecting the performance of the antenna, the dielectric substrate is slotted to better fix the vertical antenna arm, so that the overall assembly structure of the antenna is more stable.

[0061] The present embodiment also provides a low-frequency ultra-wideband ground penetrating radar miniaturized butterfly antenna optimization method for optimizing the above structure of the antenna.

[0062] Antenna arm parameter optimization design

[0063] In view of the serious current reflection problem near the feed point of the ordinary butterfly antenna, the antenna arm near the feed point is first optimized to reduce the current reflection in the present design. According to the related knowledge of microwave antenna, if the antenna is classified according to the interaction between media, it is divided into air coupled antenna and dielectric coupled antenna. The butterfly antenna belongs to dielectric coupled antenna, and its characteristic impedance is related to the opening angle of the antenna. The larger the opening angle, the smaller the characteristic impedance. After consulting the relevant literature, the number of degrees of the opening angle of the antenna is basically within 180°, and there is no breakthrough of 180°. In the present embodiment, the opening angle of the antenna is broken through 180° to observe the performance change of the antenna and find the most suitable opening angle. The opening angle of the antenna is not the larger the better. When it exceeds a certain range, other characteristics of the antenna will be greatly reduced, such as the decrease of the lowest frequency and the narrowing of the bandwidth of the antenna. Therefore, the antenna arm near the feed point needs to be parameterized, and finally the genetic algorithm is used for optimization to find the most suitable opening angle to achieve the lowest frequency point and the widest bandwidth. The parameterization method of the antenna arm near the feed point is introduced as follows. Figure 7 As shown in FIG. 8, the relationship between the θ angle (θ<90°) and the opening angle of the antenna is that the opening angle of the antenna is equal to 270° minus θ. Therefore, adjusting the θ angle is equivalent to adjusting the overall opening angle of the antenna. According to the subsequent optimization, only optimizing the θ angle cannot achieve good antenna performance. The length L of the inclined arm part also has a great influence on the performance of the antenna. Therefore, the θ angle and the length parameter L of the inclined arm are normalized by using a coordinate point. This coordinate point can not only control the opening angle, but also control the length of the inclined arm. Therefore, using the genetic algorithm to optimize the coordinate point can optimize the θ angle and the length L together.

[0064] Current is similar to water flow, in the shape of the place where the sharp change will produce reflection; therefore in the antenna edge end to reduce the emergence of sharp corners, for ordinary butterfly-shaped antenna arm edge current reflection serious problem, in the corresponding place to do the arc treatment, this embodiment of the antenna arm edge part is designed to use multi-segment arc design, greatly reduces the edge current reflection. On the arc design, in order to reduce the optimization parameter and reduce the optimization difficulty, this paper adopts three-point arc method to design the arc. As shown in Figure 8 The horizontal center line and the vertical center line of the floor plane divide the floor into four symmetrical parts, and the coordinate system is established with the horizontal center line and the vertical center line of the floor plane as the x-axis and the y-axis. The 1 / 4 bottom plate antenna has three arc-shaped segments, and the arc line of the coordinate axis is one of the arc-shaped segments of the 1 / 4 bottom plate antenna. The coordinates of the two end points of the arc line are variable. In order to ensure that the third point and the two end points can form an arc line with variable angle of left lower corner protrusion, the position of the third point needs to be determined. Since the third point can be in the left lower corner plane of the line segment connected by any two end points, the parameter is extremely uncontrollable. In order to facilitate subsequent genetic algorithm optimization, the parameter of the third point needs to be controllable.

[0065] The following is an introduction to the controllability of the third point. Given two end point coordinates (x1, y1) and (x2, y2), first find the perpendicular bisector of the line segment connecting the two end points to ensure that the third point is on this perpendicular bisector. In this way, the third point only needs to be parameterized in the horizontal direction, and the vertical coordinate can be represented by the coordinates of the two end points and its horizontal coordinate. The following formula is used to find the third point:

[0066]

[0067] After sorting, we get:

[0068]

[0069] The above formula ensures that the third point is on the perpendicular bisector of the two end points. If you want to ensure that the arc protrudes to the left lower corner and the antenna arm does not exceed the range of the FR4 board, the range of the third point x and y is as follows:

[0070]

[0071] y>0

[0072] Combining all the above formulas, we get:

[0073]

[0074]

[0075] The final coordinate parameters of the third point are:

[0076]

[0077]

[0078] The method for obtaining the parameters of the other two arcs of the 1 / 4 bottom plate antenna is the same as the above method, and the Ansys HFSS software is used to perform symmetry operation on the 1 / 4 bottom plate antenna about the x axis and the y axis, so that the overall shape of the bottom plate antenna is formed, and then the genetic algorithm is used to optimize the coordinates of the three points of the arc to obtain the optimal antenna performance.

[0079] Parameterization of side plate antenna arm

[0080] According to the knowledge of microwave antenna, the length of the antenna is proportional to the wavelength and inversely proportional to the frequency. That is, the lower the frequency, the longer the wavelength, and the longer the antenna. Of course, the length of the antenna is usually not equal to a wavelength, but often 1 / 4 wavelength or 1 / 2 wavelength. When the length of the antenna is an integer multiple of 1 / 4 wavelength, the antenna resonates at the frequency of the wavelength. The antenna length is 1 / 4 wavelength for series resonance, and the antenna length is 1 / 2 wavelength for parallel resonance. In this resonant state, the antenna radiates strongly, and the transmission and reception conversion efficiency is high. Although the radiation of the oscillator exceeds 1 / 2 wavelength, the radiation of the excess part is out of phase and will be offset, so the overall radiation effect is actually discounted. However, in order to reduce the size of the antenna, a 1 / 4 wavelength antenna is usually used, and the symmetry array can be adjusted to achieve a relatively ideal standing wave ratio and use effect, while saving the erection space. The present application also uses a 1 / 4 wavelength antenna, and on this basis, it continues to strive to reduce the size of the antenna in the two-dimensional plane, and attempts to place the reduced plane size in the vertical direction, and optimizes the shape to obtain the optimal antenna performance.

[0081] As shown in Figure 9 , the design of the side plate antenna arm uses a relatively simple quadrilateral structure. This structure does not require complex mathematical calculations when parameterized, and only two end point coordinates (m1, n1) and (m2, n2) need to be set. When symmetrical about the Z axis, the overall shape of the quadrilateral is determined. Of course, in order to further reduce the reflected current, the shape of the side plate antenna also needs to reduce the place where the shape changes sharply, so the appearance of acute angles at the end points of the quadrilateral needs to be reduced. Since the right lower end point is connected to the third arc of the bottom plate in the vertical plane, the included angle between them must be greater than 90°, so only the upper right corner end point needs to be set within a range. Only when m1 < m2 will the acute angle not appear, and then the genetic algorithm is used to optimize the two coordinate points.

[0082] The antenna of the embodiment of the present invention has a novel structure, low manufacturing cost, easy assembly, and an extremely high bandwidth of about 149.2%, and is suitable for the field of pulsed ground penetrating radar. The basic antenna selected is a butterfly antenna, and the antenna arm angle near the SMA feeding point is breakthrough-widened (greater than 180°), and the overall antenna arm is designed using the three-point arc method. The antenna assembly adopts the method of inserting the side panel into the bottom panel, the purpose of which is to place part of the length of the planar antenna in the vertical direction to reduce the planar length. After determining the basic structure, a multi-objective genetic algorithm is used to optimize the parameter variables, which reduces the impedance of the high-frequency band, increases the bandwidth of the antenna, and reduces the ringing effect of the antenna, and to a certain extent achieves the optimal shape scheme that meets the optimization target within this size.

[0083] The above optimized butterfly antenna is simulated to observe the simulation effect.

[0084] (1) Antenna current distribution and impedance characteristics

[0085] The optimized butterfly antenna was simulated using Ansys HFSS software to observe the antenna current reflection ( Figure 12 、 Figure 13 ) and impedance characteristics ( Figure 13 ).from Figure 12 The bottom plate current distribution diagram shows that the current reflection near the feeding point of the bottom plate antenna and the edge of the two arms is weaker than that of the ordinary butterfly antenna. The current reflection at the edge of the bottom plate antenna is significantly lower than that of the ordinary antenna. Figure 14 The current distribution diagram of the side panel shows that there is almost no current reflection on the side panel. Figure 15 The overall antenna characteristic impedance diagram shows that although the antenna's impedance characteristics also have jitter at low frequencies, the overall impedance characteristics are around 50Ω, and the high-frequency impedance is relatively flat and also around 50Ω. Therefore, it can be well impedance matched with the 50Ω SMA and the 50Ω of the pulse transmission circuit.

[0086] (2) Return loss S11

[0087] After simulating the optimized butterfly antenna using Ansys HFSS software, the antenna was sampled and soldered to a plug-in SMA for testing. The test instrument was an Agilent Technologies network analyzer. The simulation and actual measurement comparison chart is as follows: Figure 15The simulation results show that the bandwidth of the antenna (with return loss S11 <-10dB) is from 150MHz to 1.03GHz, the absolute bandwidth is 880MHz, and the relative bandwidth is 149.2%. The actual test results are basically consistent with the simulation, and even the low frequency cutoff frequency reaches 138MHz, the high frequency cutoff frequency is greater than 1.2GHz, the absolute bandwidth is about 1.062GHz, and the relative bandwidth is about 158.7%, which fully meets the characteristics of the ultra-wideband antenna. In order to ensure the authenticity of the experimental data, the instrument simulation graph is attached.

[0088] (3) Directional diagram

[0089] The E-plane and H-plane radiation directional diagrams of the antenna of the embodiment at 0.15GHz are shown in Figure 16 , which reflects the electromagnetic wave transmitting and receiving ability in different directions. It can be seen that the E-plane directional diagram at 0.15GHz is basically in the shape of 8, and the H-plane is circular.

[0090] The above description of the disclosed embodiments enables those skilled in the art to carry out or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-frequency ultra-wideband ground penetrating radar miniaturized bowtie antenna optimization method, characterized in that, The butterfly antenna comprises a main plate (9) and a side plate (8); The main plate (9) comprises a side plate slot (2), a butterfly patch (3), a main plate dielectric substrate (4) and an SMA signal input end (5); The side plate (8) comprises a side plate dielectric substrate (6) and a quadrilateral patch (7); The side plate slot (2) is symmetrically distributed on the left and right sides of the main plate dielectric substrate (4); The butterfly patch (3) is symmetrically distributed on the left and right sides of the SMA signal input end (5); The two side plates (8) are connected by the side plate slot (2) and the main plate (9) and are 90° apart in space; the edges of the butterfly patch (3) and the quadrilateral patch (7) at the joint of the main plate (9) and the side plate (8) completely coincide; and the butterfly patch (3) and the quadrilateral patch (7) constitute a complete antenna arm; The method comprises: The right half of the butterfly patch (3) is left-right symmetrical with the left half, and the butterfly patch (3) is up-down symmetrical; the right half of the butterfly patch (3) is in a closed shape formed by two straight line segments a and b connected to the right two vertices of the SMA signal input end (5) respectively, a side coinciding with the right side of the SMA signal input end (5), three circular arcs connected to the two straight line segments a and b respectively, and a line segment completely coinciding with the edge of the quadrilateral patch (7); the lengths of the straight line segments a and b are L; the opening angle of the antenna is equal to 270° minus θ; θ is an acute angle formed by the straight line segment a or b and the upper or lower side of the SMA signal input end (5); and L and θ are optimized by using a genetic algorithm; The arc of the butterfly-shaped patch (3) is designed by three-point arc method. The right upper vertex of the SMA signal input end (5) is taken as the origin, the direction of the upper edge of the SMA signal input end (5) is taken as the x-axis, the direction of the right edge of the SMA signal input end (5) is taken as the y-axis, the right upper part of the butterfly-shaped patch (3) has three arc shapes, one end point coordinate of one arc shape is (x, y), the other end point coordinate of the arc shape is (x, y+1), the third point (x, y) is on the midline of the line segment connecting the two end points, and the two end points and the third point satisfy: , , the third point (x, y) is on the midline of the line segment connecting the two end points, and the two end points and the third point satisfy: The three coordinates of the arc are optimized by using the genetic algorithm to obtain optimal antenna performance; The other three parts of the butterfly patch (3) have the same parameters as the upper right part of the butterfly patch (3); The quadrilateral patch (7) is a left-right symmetrical quadrilateral, the upper two corners of the quadrilateral patch (7) are greater than 90°, on the plane of the quadrilateral patch (7), taking the edge combined with the side plate (8) as the X axis, the center vertical line of the edge as the Y axis, the upper vertex and the lower vertex coordinates of the right half of the quadrilateral patch (7) are , , two coordinate points are optimized by using a genetic algorithm.

2. The method of claim 1, wherein the method is characterized by: The main plate (9) further comprises positioning holes (1) located on the upper and lower edges of the main plate (9) and used for fixing the antenna when the antenna is installed; the number of the positioning holes (1) is set according to requirements.

3. The method of claim 1, wherein the method is characterized by: The materials of the main plate dielectric substrate (4) and the side plate dielectric substrate (6) are FR4, and the thicknesses are 1.6 mm.

4. The method of claim 1, wherein the method is characterized by: The copper thicknesses of the butterfly patch (3) and the quadrilateral patch (7) are 1 ounce.

5. The method of claim 1, wherein the method is characterized by: The SMA signal input end (5) adopts a 50Ω straight insertion type SMA.

6. The method of claim 1, wherein the method is used for optimizing a low-frequency ultra-wideband ground penetrating radar compacted bowtie antenna. The butterfly antenna works at 0.15-1.03 GHz, and the relative bandwidth is 149.2%.

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