Phased geological radar ultra-wideband antipodal Vivaldi antenna unit and array

Abstract

The invention belongs to the technical field of antenna design, and provides a phased geological radar ultra-wideband antipodal Vivaldi antenna unit and array. Wherein the antenna unit comprises a dielectric substrate and a metal radiation patch; the two metal radiation patches are etched on the upper surface and the lower surface of the dielectric substrate; the two metal radiation patches are of a butt structure; the metal radiation patch is surrounded by an inner edge and an outer edge; the inner edge is an exponential gradual change slot line and meets a frequency band distribution rule; the outer edge is an external expansion type semi-elliptical outline, an index fractal groove is formed in the side edge of the external expansion type semi-elliptical outline, and the index fractal groove is composed of an upper index curve outline and a lower index curve outline.

Description

Technical Field

[0001] The invention belongs to the technical field of antenna design, and in particular relates to an ultra-wideband anteroposterior Vivaldi antenna unit and array for a phased geological radar. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Ensuring the long-term safe and stable operation of underground projects is the focus of the current engineering community. As an efficient non-destructive testing technology, geological radar has been increasingly widely used in urban underground projects. Its main application areas include underground pipeline detection, underground cavity detection, tunnel lining defect detection, and underground structure integrity assessment. Geological radar can detect the reflected signals of underground structures by emitting and receiving electromagnetic waves, thereby judging the distribution characteristics of underground media. This technology has become one of the core means of underground engineering detection due to its advantages such as simple operation, fast detection speed, and high resolution. With the expansion of the scale and complexity of urban underground engineering construction, the technical performance of existing geological radars in terms of detection depth, detection efficiency, and resolution has been difficult to meet actual needs. For example, structures such as ventilation shafts and vertical shafts in traffic tunnels have put forward higher requirements for the detection depth of geological radars, and some large facilities such as long-distance tunnels and large dams also have higher requirements for the detection efficiency of geological radars.

[0004] Due to technical limitations, existing geological radar equipment has the following shortcomings: first, the detection depth is limited and it is difficult to cover deep underground structures; second, the detection area covered by a single survey line is limited, which limits the improvement of detection efficiency; these shortcomings have become limiting factors in the detection of urban underground projects today. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a phased array geological radar ultra-wideband Vivaldi antenna unit and array, which can improve radiation efficiency, enhance broadband characteristics, optimize current distribution and make the antenna fully miniaturized, which is more in line with the requirements of geological radar and phased array unit antenna for high radiation efficiency and small size.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides an ultra-wideband Vivaldi antenna unit for a phased geological radar.

[0008] A phased geological radar ultra-wideband anti-helical Vivaldi antenna unit, comprising a dielectric substrate and a metal radiation patch;

[0009] The two metal radiation patches are etched on the upper surface and the lower surface of the dielectric substrate; the two metal radiation patches are a butt-to-butt structure; the metal radiation patch is surrounded by an inner edge and an outer edge; the inner edge is an exponential gradient groove line that satisfies the frequency band distribution law; the outer edge is an outward-expanding semi-elliptical profile, and the side of the outward-expanding semi-elliptical profile is provided with an exponential fractal groove, and the exponential fractal groove is composed of an upper exponential curve profile and a lower exponential curve profile.

[0010] As an implementation manner, three exponential fractal grooves are respectively opened on the sides of the outwardly expanded semi-elliptical contour line of the radiation patch.

[0011] As an implementation mode, the exponential fractal slot has the antenna opening direction as the x-axis, the slot direction as the y-axis, and the slot end point as the origin. The upper exponential curve profile and the lower exponential curve profile constituting the slot structure respectively satisfy:

[0012]

[0013] Among them, a up 、a down , k up and k down are all constant coefficients; x and y are the coordinates on the x-axis and y-axis respectively.

[0014] As an implementation mode, the major axis size range of the outward-expanded semi-elliptical profile is 220mm-250mm, and the minor axis size range is 110mm-125mm. The semi-elliptical patch surrounded by the outward-expanded semi-elliptical profile is connected with both sides of the metal radiation patch and smoothly transitions.

[0015] As an implementation method, with the starting point of the exponential gradient slot line as the center, the opening direction of the long side of the antenna is the positive direction of the x-axis, and the outer side of the short side of the antenna is the positive direction of the y-axis. The edge of the exponential slot line satisfies the equation: y = e kx ; k is a constant coefficient.

[0016] As an implementation manner, the exponentially tapered slot line covers the antenna's operating frequency band range of 550 MHz to 2500 MHz.

[0017] As an implementation manner, the size range of the dielectric substrate is: a minimum of 340 mm×450 mm and a maximum of 410 mm×550 mm.

[0018] As an implementation mode, the opening width of the end of the metal radiation patch ranges from 265 mm to 335 mm, corresponding to the radiation of the lowest operating frequency.

[0019] As an implementation manner, the metal radiation patches are all connected to the feeding port at the bottom through a microstrip line transition.

[0020] A second aspect of the present invention provides an antenna array.

[0021] An antenna array is composed of the phased-control geological radar ultra-wideband butt-to-butt Vivaldi antenna units as described above arranged in a color interactive matrix, the interval range between adjacent phased-control geological radar ultra-wideband butt-to-butt Vivaldi antenna units is 0.28λ to 0.52λ, where λ is the wavelength corresponding to the antenna operating frequency; the scanning angle range is ±60°.

[0022] The beneficial effects of the present invention are:

[0023] (1) The radiation patch edge setting of the Vivaldi antenna of the present invention uses a groove composed of an exponential curve, which utilizes a self-similar structure, that is, a fractal design concept, to improve the radiation efficiency, enhance the broadband characteristics, optimize the current distribution and fully miniaturize the antenna, which is more in line with the requirements of geological radar and phased array unit antennas for high radiation efficiency and small size.

[0024] (2) The present invention increases the effective aperture of the antenna unit by setting the two sides of the radiation patch to an outward-expanding semi-ellipse, thereby increasing the overall size. Three exponential fractal slots are designed, each of which is composed of an upper exponential curve profile and a lower exponential curve profile. This can better adapt to the wide-band requirements of the geological radar, while improving the detection depth and signal stability.

[0025] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 2 is a schematic diagram of the structure of an ultra-wideband anti-cantilever Vivaldi antenna unit of a phased geological radar according to an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of a phased array antenna array according to an embodiment of the present invention;

[0029] Figure 3 is a comparison of S11 curves formed by gradient groove lines of different exponential curves in the embodiments of the present invention;

[0030] Figure 4 is a comparison of S11 curves of Vivaldi anti-heel antennas with outwardly expanded semi-elliptical profiles of different sizes according to an embodiment of the present invention;

[0031] Figure 5is a different k from the embodiment of the present invention up , k down Comparison of simulation results of exponential fractal slots with different values ​​for antenna S11;

[0032] Figure 6 The difference between the embodiments of the present invention is up , a down The simulation results of the exponential fractal slot of the value for antenna S11;

[0033] Figure 7 1 is a comparison of S11 curves of the butt-to-butt Vivaldi antenna with an outwardly expanded semi-elliptical profile having different numbers of exponential fractal grooves according to an embodiment of the present invention;

[0034] Figure 8 is a comparison of the current distribution on the side of the outward-expanded semi-elliptical profile antenna with and without the exponential fractal groove according to the embodiment of the present invention;

[0035] Fig. 9 is a directional diagram of a phased array antenna array at different scanning angles within a range of ±60° according to an embodiment of the present invention;

[0036] Fig.10 It is the S11 curve of the unit antenna of the phased array antenna array of the embodiment of the present invention at a scanning angle of 0° to 60°.

[0037] Among them: 1 is a metal radiation patch, 2 is a dielectric substrate, 3 is an exponential gradient slot line, 4 is an outward-expanding semi-elliptical profile, 5 is an exponential fractal slot, 6 is an upper exponential curve profile, 7 is a lower exponential curve profile, and 8 is a microstrip line. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] In the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention, and do not specifically refer to any part or element in the present invention and should not be understood as limitations on the present invention.

[0042] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meanings of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0043] Phased array antennas have beam focusing capabilities, which can concentrate the radiation energy from each unit in the array in a specific direction. This feature can significantly increase the detection range. Phased array antennas also have beam agility capabilities, which can change the direction of the radiation beam without rotating or moving the antenna. This feature enables radar detection on a fixed survey line to cover a larger detection area, greatly increasing detection efficiency. In view of the new requirements for geological radar equipment in terms of detection depth and detection efficiency and the unique advantages of phased array antennas, it is of great significance to develop an antenna unit and array for phased array geological radar.

[0044] Reference Figure 1 , an ultra-wideband heel-to-heel Vivaldi antenna unit of a phased geological radar according to an embodiment of the present invention is provided, comprising a dielectric substrate and a metal radiation patch;

[0045] The two metal radiation patches are etched on the upper surface and the lower surface of the dielectric substrate; the two metal radiation patches are a butt-to-butt structure; the metal radiation patch is surrounded by an inner edge and an outer edge; the inner edge is an exponential gradient groove line that satisfies the frequency band distribution law; the outer edge is an outward-expanding semi-elliptical profile, and the side of the outward-expanding semi-elliptical profile is provided with an exponential fractal groove, and the exponential fractal groove is composed of an upper exponential curve profile and a lower exponential curve profile.

[0046] In this embodiment, the size range of the dielectric substrate is: minimum 340 mm×450 mm, maximum 410 mm×550 mm. For example, the size of the dielectric substrate is 375 mm×500 mm.

[0047] The two metal radiation patches of this embodiment are of a heel-to-heel structure, which can improve the antenna directivity and gain.

[0048] Specifically, with the starting point of the exponential gradient slot line as the center, the opening direction of the long side of the antenna is the positive direction of the x-axis, and the outer side of the short side of the antenna is the positive direction of the y-axis. The edge of the exponential slot line satisfies the equation: y = e kx ; k is a constant coefficient. In this embodiment, k=0.0129.

[0049] The exponential gradient slot line covers the antenna's operating frequency band range of 550MHz to 2500MHz. The opening width of the end of the metal radiation patch ranges from 265mm to 335mm, corresponding to the radiation of the lowest operating frequency.

[0050] In order to meet the underground detection depth requirements of the ground penetrating radar, the frequency needs to be at a lower level, and there is a strong demand for the lower limit of the frequency band. Therefore, the opening size corresponding to the lowest frequency should be maximized, and the size limit of the dielectric substrate (that is, the entire ground penetrating radar) should be taken into account. Based on the above, multiple exponential curves of the exponential gradient slot are compared and simulated, such as Figure 3 As shown, by comparing the matching effects of different exponential term coefficients and combining the requirements of the phased array unit antenna and the geological radar antenna, preferably, the opening width of the end of the metal radiation patch is 300 mm, and 0.0129 is selected as the exponential term coefficient of the exponential curve of the exponential gradient slot line.

[0051] The metal radiation patches on the upper and lower surfaces are connected to the feeding port at the bottom through a microstrip line transition. The microstrip line can reduce losses, enhance matching effects, and achieve efficient feeding.

[0052] Figure 4 The S11 curve change trend of the Vivaldi antenna under different sizes of outward-expanded semi-elliptical profiles is shown. Through comparative simulation, it can be observed that under the condition of meeting the requirements of geological radar for lower frequency and higher radiation efficiency of the antenna, the outward-expanded semi-elliptical profile size with a major axis size range of 220mm to 250mm and a minor axis size range of 110mm to 125mm can significantly optimize the matching effect of the antenna, reduce the S11 value, and expand the effective frequency band range of the antenna, thereby determining the final profile size. The semi-elliptical patch surrounded by the outward-expanded semi-elliptical profile line is connected to both sides of the metal radiation patch and transitions smoothly.

[0053] The detection efficiency of the phased array antenna array is closely related to the antenna aperture. However, due to the low-frequency requirements of the ground-penetrating radar, the antenna size is large. In addition, the actual engineering operation limits the overall size of the radar. The number of antenna units is less than that of the traditional phased array radar, resulting in a smaller total antenna aperture obtained by adding the unit antenna apertures, which affects the detection efficiency. To solve this problem, the antenna unit uses the method of setting the two sides of the radiation patch as an outward-expanding semi-ellipse to increase the effective aperture of the antenna unit, thereby increasing the overall aperture. In order to determine the value of the outward-expanding semi-ellipse, multiple Vivaldi antennas with outward-expanding semi-elliptical profiles of different sizes are simulated and compared. The final size is determined based on the geological radar's requirements for lower frequencies and higher radiation efficiency of the antenna.

[0054] In this embodiment, three exponential fractal grooves are opened on each side of the outer expanded semi-elliptical contour line of the radiation patch. The exponential fractal groove takes the antenna opening direction as the x-axis, the slot direction as the y-axis, and the slot end point as the origin. The upper exponential curve contour and the lower exponential curve contour constituting the slot structure respectively satisfy:

[0055]

[0056] Among them, a up 、a down , k up and k down are all constant coefficients; x and y are the coordinates on the x-axis and y-axis respectively.

[0057] Figure 5 The S11 simulation results of the Vivaldi antenna with different exponential fractal slot curve slopes are compared. up and k down The simulation analysis of the combination shows that the final choice is k up =0.04, k down =0.055 combination achieves the best matching effect in a wider frequency band, while reducing the S11 value and optimizing the radiation performance of the antenna.

[0058] Figure 6 The different a values ​​of the antipodal Vivaldi antenna under different exponential fractal groove curves are shown. up , a down The simulation results show that a up =2.7, a down =2.9 combination can effectively improve the antenna matching performance, reduce the S11 value within the entire working frequency band, and improve the antenna radiation efficiency.

[0059] Figure 7The simulation results of the S11 curve of the Vivaldi antenna with an outward-expanded semi-elliptical profile are compared under the conditions of no exponential fractal slots, 2 exponential fractal slots, and 3 exponential fractal slots. The results show that adding exponential fractal slots can significantly optimize the matching performance of the antenna, and the fractal slot design with 3 fractal slots achieves a more efficient and larger area current distribution path optimization effect in a wider frequency band, while further improving the radiation efficiency of the antenna.

[0060] Since there is a certain gap between the current density near the edge and the current density in the opening area of ​​the exponential gradient slot, in order to affect the radiation of the antenna in a wider working frequency band, it is necessary to redefine the function and number of the exponential curve on the basis of maintaining the exponential curve shape of the slot structure. After comparing and analyzing the simulation results of different exponential curves and different numbers, the edge curve function and distribution number of a group of exponential fractal slots with the best overall optimization effect of the antenna are determined. The above design can better meet the broadband requirements of geological radar, while improving the detection depth and signal stability.

[0061] Figure 8 The scanning pattern of the ultra-wideband Vivaldi antenna array of the phased array geological radar within the range of ±60° is demonstrated, with a scanning angle step of 10°, showing the pattern characteristics from -60° to 60°. The results show that the pattern has good symmetry within the scanning range, the -3dB beamwidth in a single direction is 20.5°, and the main lobe gain reaches 12.3dBi, reflecting the excellent directivity and high gain performance of the array antenna in wide-angle scanning.

[0062] Fig. 9 The comparison of the side current distribution of the Vivaldi antenna with an outward-expanded semi-elliptical profile with and without exponential fractal slots is shown. The simulation results show that after adding the exponential fractal slots, the antenna side current path is optimized, and the current on the exponential gradient slot line in the main radiation area is more affected by the side current, further improving the matching performance and radiation efficiency of the antenna.

[0063] In one or more embodiments, Figure 2 As shown, an antenna array is also provided, which is composed of the phased-control geological radar ultra-wideband butt-to-butt Vivaldi antenna units as described above arranged in a preset matrix (4×1), and the interval range between adjacent phased-control geological radar ultra-wideband butt-to-butt Vivaldi antenna units is 0.28λ to 0.52λ, where λ is the wavelength corresponding to the antenna operating frequency; the scanning angle range is ±60°.

[0064] For example, the interval between adjacent phased-control geological radar ultra-wideband Vivaldi antenna units is 4λ, 800MHz is selected as the calculation basis of λ in the antenna array, and the range of d is 0.28λ to 0.52λ, that is, 105mm to 195mm.

[0065] Fig.10 The S11 curve changes of the unit antenna of the phased array geological radar ultra-wideband Vivaldi antenna array in the scanning angle range of 0° to 60° are shown. The results show that at each scanning angle, the overall S11 is basically lower than -10dB, indicating that the unit antenna has a good matching effect and high radiation efficiency within the working frequency band.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A phased-control geological radar ultra-wideband antipodal Vivaldi antenna unit, characterized in that: include: Dielectric substrate and metal radiating patch; The two metal radiation patches are etched on the upper surface and the lower surface of the dielectric substrate; The two metal radiation patches are butt-to-butt structures; the metal radiation patches are surrounded by an inner edge and an outer edge; the inner edge is an exponential gradient groove line that satisfies the frequency band distribution law; the outer edge is an outward-expanding semi-elliptical profile, and the outward-expanding semi-elliptical profile has an exponential fractal groove on the side, and the exponential fractal groove is composed of an upper exponential curve profile and a lower exponential curve profile.

2. The ultra-wideband anteroposterior Vivaldi antenna unit of the phased-control geological radar according to claim 1, characterized in that: The sides of the outwardly expanded semi-elliptical contour line of the radiation patch are each provided with three exponential fractal grooves.

3. The ultra-wideband anteroposterior Vivaldi antenna unit of the phased geological radar according to claim 1 or 2, characterized in that: The exponential fractal slot has the antenna opening direction as the x-axis, the slot direction as the y-axis, and the slot end point as the origin. The upper exponential curve profile and the lower exponential curve profile that constitute the slot structure satisfy the following requirements: Among them, a up 、a down , k up and k down are all constant coefficients; x and y are the coordinates on the x-axis and y-axis respectively.

4. The ultra-wideband anteroposterior Vivaldi antenna unit of the phased geological radar according to claim 1, characterized in that: The major axis size range of the outward-expanding semi-elliptical profile is 220mm-250mm, and the minor axis size range is 110mm-125mm. The semi-elliptical patch surrounded by the outward-expanding semi-elliptical profile line is connected with both sides of the metal radiation patch and smoothly transitions.

5. The ultra-wideband anteroposterior Vivaldi antenna unit of the phased geological radar according to claim 1, characterized in that: With the starting point of the exponential gradient slot as the center, the opening direction of the long side of the antenna is the positive direction of the x-axis, and the outer side of the short side of the antenna is the positive direction of the y-axis. The edge of the exponential slot satisfies the equation: y = e kx ; k is a constant coefficient.

6. The ultra-wideband anteroposterior Vivaldi antenna unit of the phased geological radar according to claim 1, characterized in that: The exponentially tapered slot line covers the antenna's operating frequency band range of 550 MHz to 2500 MHz.

7. The ultra-wideband anteroposterior Vivaldi antenna unit of the phased geological radar according to claim 1, characterized in that: The size range of the dielectric substrate is: minimum 340mm×450mm, maximum 410mm×550mm.

8. The ultra-wideband anteroposterior Vivaldi antenna unit of the phased-control geological radar according to claim 1, characterized in that: The opening width at the end of the metal radiation patch ranges from 265 mm to 335 mm, corresponding to the radiation of the lowest operating frequency.

9. The ultra-wideband anteroposterior Vivaldi antenna unit of the phased geological radar according to claim 1, characterized in that: The metal radiation patches are all connected to the feeding port through a microstrip line transition at the bottom.

10. An antenna array, characterized in that: The phased-control geological radar ultra-wideband butt-to-butt Vivaldi antenna units as described in any one of claims 1 to 9 are arranged in a set matrix, and the interval range between adjacent phased-control geological radar ultra-wideband butt-to-butt Vivaldi antenna units is 0.28λ to 0.52λ, where λ is the wavelength corresponding to the antenna operating frequency; the scanning angle range is ±60°.

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