Geological radar antipodal Vivaldi antenna for lining deep detection

Abstract

The invention belongs to the technical field of antenna design, and provides a geological radar antipodal Vivaldi antenna for lining deep detection, which comprises a dielectric substrate, a metal radiation patch and a parasitic 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 have the same structure and are respectively composed of a radiation part and a feed part; the feed part is etched with a microstrip line, and the microstrip line is connected with the radiation part in a gradual change index curve mode. The inner edge of the radiation part is an index gradual change slot line; the side edges of the two radiation parts are symmetrically engraved with concave semi-elliptical grooves; a plurality of parallel comb-shaped open grooves which are vertical to the side edge of the dielectric substrate are formed in the semi-elliptical groove; the tail ends of the comb-shaped open grooves are attached to the contour lines of the semi-elliptical grooves at different lengths. The method can improve the accuracy and reliability of tunnel lining deep layers.

Description

Technical Field

[0001] The invention belongs to the technical field of antenna design, and in particular relates to a geological radar butt-jointed Vivaldi antenna for deep-level detection of linings. 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] As an important part of the tunnel structure, the quality of the tunnel lining is directly related to the safe operation of the tunnel. The depth of the tunnel lining is generally 0.7 meters, followed by the surrounding rock. These two indicators are crucial to the stability and safety of the tunnel. In practical applications, the tunnel lining and its deeper parts are accurately inspected to ensure the overall structural safety of the tunnel.

[0004] In order to ensure the safe operation of the tunnel, it is necessary to conduct regular in-depth inspections of the tunnel lining. As a non-destructive testing technology, geological radar has the advantages of simple operation, fast speed and high efficiency, and has become an important means of tunnel lining inspection. Geological radar transmits electromagnetic waves to penetrate the lining surface and detect the damage inside the lining. It can find some hidden diseases, such as voids and cavities. However, the existing lining inspection geological radar has certain limitations in detection depth and accuracy, and cannot meet the needs of tunnel lining and its deeper inspection. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a geological radar Vivaldi antenna for lining depth detection, which can improve the accuracy and reliability of tunnel lining depth detection.

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

[0007] A geological radar anti-heel Vivaldi antenna for deep-level detection of linings, comprising: a dielectric substrate, a metal radiation patch and a parasitic patch; a plurality of the parasitic patches are arranged at the center above the metal radiation patch and the dielectric substrate;

[0008] The two metal radiation patches are etched on the upper surface and the lower surface of the dielectric substrate; the two metal radiation patches have the same structure, and are both composed of a radiation part and a feeding part; the bottom edges of the two feeding parts are arranged flush with the bottom edge of the dielectric substrate; the two radiation parts are arranged symmetrically with respect to the dielectric substrate;

[0009] The feeding part is etched with a microstrip line, and the microstrip line is connected to the radiating part through a gradient exponential curve; the inner edge of the radiating part is an exponential gradient groove line; the side edges of the two radiating parts are symmetrically engraved with concave semi-elliptical grooves; a plurality of comb-shaped grooves parallel to and perpendicular to the side of the dielectric substrate are arranged in the semi-elliptical groove; the ends of the comb-shaped grooves fit the contour of the semi-elliptical groove with different lengths.

[0010] As an implementation manner, the two adjacent comb-shaped grooves have the same groove spacing and the same groove width.

[0011] As an implementation mode, the groove spacing and groove width of the comb-shaped grooves are in the range of 5-8 mm and 8-11 mm respectively.

[0012] As an implementation method, the parasitic patches are multi-piece, and the spacing is the maximum spacing that does not produce array reflection effect. The calculation formula of the maximum spacing is:

[0013]

[0014] Where d is the interval distance, c is the propagation speed of electromagnetic waves, f is the minimum detection frequency, ε r is the relative dielectric constant of the dielectric substrate.

[0015] As an implementation manner, the number of the parasitic patches is three.

[0016] As an implementation manner, the exponentially gradient groove line of the inner edge satisfies the equation y=e^(0.0129x).

[0017] As an implementation manner, the end opening of the exponentially tapered groove line at the inner edge corresponds to the lower limit of the working frequency band, and the end opening of the exponentially tapered groove line at the inner edge is maximized.

[0018] As an implementation manner, the end opening of the exponentially tapered groove line of the inner edge is equal to the width of the dielectric substrate.

[0019] As an embodiment, the major axis range of the contour line of the semi-elliptical groove is 180-210 mm, and the minor axis range is 90-110 mm.

[0020] As an implementation manner, the dielectric substrate is rectangular, the length of the dielectric substrate is in the range of 470-530 mm, the width is in the range of 280-320 mm, and the metal radiation patch is etched within the range of the dielectric substrate.

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention carves an inwardly concave semi-elliptical groove on the side edge of the radiation part, and provides a plurality of comb-shaped grooves in the semi-elliptical groove that are parallel and perpendicular to the side edge of the dielectric substrate, so that the ends of the comb-shaped grooves fit the contour of the semi-elliptical groove at different lengths, thereby optimizing the path of the edge current, improving the matching of the antenna, and improving the radiation efficiency.

[0023] (2) The feeding part of the present invention is etched with a microstrip line and connected to the radiation part by a gradient exponential curve, which improves the feeding and radiation efficiency, maximizes the radiation energy, and improves the detection range; a three-piece parasitic patch is provided in the center above the metal radiation patch and the dielectric substrate, which improves the unclear and unfocused main lobe caused by the metal radiation patch being divided into two pieces for the Vivaldi antenna, improves the directivity of the antenna and increases the gain, so that the Vivaldi antenna of the geological radar is suitable for deep lining detection, and finally improves the accuracy and reliability of the deep lining of the tunnel.

[0024] 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

[0025] 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.

[0026] Figure 1 1 is a schematic diagram of the structure of a geological radar butt-to-butt Vivaldi antenna for deep-level lining detection according to an embodiment of the present invention;

[0027] Figure 2 is a comparison of S11 curves formed by different exponential gradient curves in the embodiments of the present invention;

[0028] Figure 3 3 is a comparison of S11 curves formed by different semi-elliptical contour lines according to the embodiment of the present invention.

[0029] Figure 4 is a comparison of S11 curves formed by different groove widths and spacings within the semi-elliptical contour line of the embodiment of the present invention;

[0030] Figure 5 is the far-field pattern of the Vivaldi antenna of the geological radar for deep-level lining detection according to an embodiment of the present invention;

[0031] Among them: 1 is a metal radiation patch; 2 is a dielectric substrate; 3 is a radiation part; 4 is a feeding part; 5 is an exponential gradient slot line; 6 is a semi-elliptical slot; 7 is a comb-shaped slot; 8 is a microstrip line; and 9 is a parasitic patch. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Common defects of tunnel lining include cracks, water seepage, spalling, corrosion, voiding, loose concrete, insufficient lining steel protection layer, exposed steel bars, etc. These defects not only affect the appearance of the tunnel, but may also cause the bearing capacity of the lining structure to decrease, affecting the normal use of the tunnel. For example, cracks are one of the most common defects in tunnel linings. They refer to cracks formed on the surface or inside of the lining due to shrinkage and expansion caused by temperature differences inside and outside the tunnel, stress concentration of the lining caused by earthquake vibrations, unstable strata, geological tectonic activities, etc. Cracks not only affect the appearance of the tunnel, but may also lead to water seepage, leakage and further damage to the structure.

[0038] Common defects at a deeper level include voids behind the lining, loose backfill, groundwater erosion, etc. These defects will reduce the stability of the lining structure and even cause tunnel collapse accidents. For example, there are many reasons for lining voids, which can be mainly divided into insufficient rigidity, strength, and thickness of the outer formwork in the design or manufacture of the lining trolley, insufficient and uneven looseness of the waterproof board, and concrete not being poured strictly in each compartment and in layers.

[0039] In order to break through the limitations of deep-level lining detection, higher requirements are put forward for the broadband characteristics, low-frequency performance, precise directivity, etc. of geological radar antennas. The present invention provides a geological radar Vivaldi antenna for deep-level lining detection, which can improve the accuracy and reliability of deep-level tunnel lining.

[0040] Reference Figure 1 , a geological radar anti-heel Vivaldi antenna for lining deep detection according to an embodiment of the present invention is provided, comprising: a dielectric substrate 2, a metal radiation patch 1 and a parasitic patch 9; a plurality of the parasitic patches 9 are arranged at the center above the metal radiation patch 1 and the dielectric substrate 2;

[0041] The two metal radiation patches 1 are etched on the upper surface and the lower surface of the dielectric substrate 2; the two metal radiation patches 1 have the same structure, and are both composed of a radiation part 3 and a feeding part 4; the bottom edges of the two feeding parts 4 are arranged flush with the bottom edge of the dielectric substrate 2; the two radiation parts 3 are arranged symmetrically with respect to the dielectric substrate 2;

[0042] The feeding part 4 is etched with a microstrip line 8, and the microstrip line 8 is connected to the radiating part 3 through a gradient exponential curve; the inner edge of the radiating part 3 is an exponential gradient groove line 5; the side edges of the two radiating parts 3 are symmetrically engraved with concave semi-elliptical grooves 6; a plurality of comb-shaped grooves 7 parallel to and perpendicular to the side of the dielectric substrate are arranged in the semi-elliptical groove 6; the ends of the comb-shaped grooves 7 are fitted with the contour lines of the semi-elliptical grooves 6 at different lengths.

[0043] In this embodiment, a concave semi-elliptical groove is engraved on the side edge of the radiation part, and a plurality of comb-shaped grooves parallel to and perpendicular to the side edge of the dielectric substrate are arranged in the semi-elliptical groove, so that the ends of the comb-shaped grooves fit the contour of the semi-elliptical groove at different lengths, thereby optimizing the path of the edge current, improving the matching of the antenna, and improving the radiation efficiency.

[0044] The feeding part of this embodiment is etched with a microstrip line and is connected to the radiation part in a gradual exponential curve, thereby improving the feeding and radiation efficiency, maximizing the radiation energy, and increasing the detection range.

[0045] The dielectric substrate is rectangular, the length of the dielectric substrate is in the range of 470-530 mm, the width is in the range of 280-320 mm, and the metal radiation patch is etched within the range of the dielectric substrate.

[0046] In this embodiment, the length of the dielectric substrate is 500 mm and the width range is 300 mm. The exponential gradient groove line of the inner edge of this embodiment satisfies the equation y=e^(0.0129x). The size range of the end opening of the exponential gradient groove line of the inner edge is equal to the width range of the dielectric substrate, which is 280-320 mm.

[0047] The end opening of the exponentially tapered slot line at the inner edge corresponds to the lower limit of the working frequency band. In order to meet the needs of deep-level detection of the lining, the end opening of the exponentially tapered slot line at the inner edge is maximized. The length and width of the dielectric substrate are limited by the size of the actual geological radar. The geological radar used in tunnel lining detection cannot be too large. Therefore, the Vivaldi antenna composed of a series of exponential function curves passing through the end of the microstrip line and the edge point with the maximum opening is simulated and compared with the following example. Figure 2 The S11 curve shown and the analysis of the effective working frequency band and matching effect finally determined the exponential term coefficient of 0.0129, which is conducive to expanding the lower limit of the working frequency band toward the low frequency direction, thereby improving the effective depth range in actual detection.

[0048] exist Figure 2 In the figure, the S11 curve represents the radiation efficiency parameter of the antenna. The lower the S11 parameter, the better the antenna matching effect and the higher the radiation efficiency. It is generally believed that the frequency range below -10dB in the S11 curve is the working frequency band of the antenna, so the working frequency band of this antenna is 600-2500MHz. The exponential term coefficient in the figure is 0.0129, which is compared with other exponential functions passing through the beginning of the microstrip line and the edge point of the dielectric substrate (corresponding to the maximum opening). After comprehensive analysis of the frequency band range and the matching effect within it, this curve is selected as the exponential gradient slot line of the radiation part of this antenna.

[0049] The exponential slot line at the outer edge of the radiation part is the transition structure between the radiation part and the microstrip line of the feeding part, satisfying the equation y=23.7+e^(0.0355*x). The lower half of the radiation patch is the feeding part, which is connected to the feeding port at the bottom through a microstrip line.

[0050] In this embodiment, the major axis range of the contour line of the semi-elliptical groove is 180-210 mm, and the minor axis range is 90-110 mm.

[0051] In order to fully optimize the current path, the outline of the semi-elliptical slot needs to cover most of the side edges of the radiation part, but it should not be too close to the exponential gradient slot line to avoid affecting the broadband radiation characteristics of the antenna. Figure 3As shown, simulation analysis was performed for different semi-ellipse sizes, and it was ensured that the semi-ellipse contour lines did not invade the exponential gradient groove lines, and the sizes of the major axis range of 180-210mm and the minor axis range of 90-110mm were selected. The preferred major axis is 195mm and the minor axis is 100mm. This size can maintain good radiation efficiency and wide-band characteristics while optimizing the current path. The complete metal patch is not etched inside the semi-ellipse contour line. This method optimizes the current path and increases the effective aperture of the antenna. In addition, since the ellipse contour line is close to the exponential curve shape of the radiation from high frequency to low frequency, the concave ellipse contour line can improve the matching effect of the antenna in a fractal manner, improve the radiation efficiency of the antenna, and further expand the working frequency band to low frequency, thereby increasing the detection depth of the geological radar in lining detection.

[0052] In this embodiment, the two adjacent comb-shaped slots have the same slot spacing and slot width. The slot spacing and slot width of the comb-shaped slots are in the range of 5-8 mm and 8-11 mm, respectively. Preferably, the slot spacing and slot width of the comb-shaped slots are 6.5 mm and 9.5 mm, respectively. These dimensions are verified by simulation analysis to effectively reduce the reflection loss of the antenna and improve the radiation efficiency. Figure 4 As shown. The lengths of the slots are different to fit the contour of the concave semi-elliptical slot. Since the size of the semi-elliptical contour has been determined, the layout is determined according to the slot width and the size of the semi-elliptical contour. There are 12 comb-shaped slot structures inside the semi-elliptical slot, which further optimizes the path of the edge current and reduces the lower frequency limit of the antenna, so that it can work at a lower frequency, improve the matching of the antenna in a lower frequency working environment, and improve the ability of lining detection.

[0053] In this embodiment, the number of the parasitic patches is three. The structure is etched on the protruding part above the dielectric substrate, and the size range of the protruding part is 230-244mm in length and 35-45mm in width. Three metal patches are etched on the upper and lower surfaces respectively, and each piece has a length range of 35-45mm, a width of 5-10mm, and an interval of 75-85mm. Due to the particularity of the deep-level detection lining, the wavelength of the Vivaldi antenna is relatively long relative to the antenna structure itself, so the two radiating patches of the split antenna will cause the main lobe of the antenna pattern to split into two side lobes with the same amplitude and symmetrical direction. At this time, a parasitic patch is set in the middle of the opening of the radiating patch, so that the radiating pattern can form a clear main lobe. The design of the three-piece parasitic patch is based on the balance between the antenna directivity and radiation efficiency. Compared with the main frequency of 600MHz and wavelength of 0.5m for deep lining detection of antennas, the parasitic patch must reach a certain size to affect the beam, and larger single-piece parasitic patches or multi-piece parasitic patches with smaller intervals will act as reflectors or array reflectors to affect the radiation efficiency in the main radiation direction. Based on this consideration, parasitic patches are multi-piece, and the interval is the maximum interval that does not produce array reflection effect (such as 75-85mm).

[0054] In the specific implementation process, the parasitic patches are multi-piece, and the interval is the maximum interval that does not produce array reflection effect. The calculation formula of the maximum interval is:

[0055]

[0056] Where d is the interval distance, c is the propagation speed of electromagnetic waves, f is the minimum detection frequency (such as 600MHz), ε r is the relative dielectric constant of the dielectric substrate.

[0057] The length and width of a single patch are 35-45mm and 5-10mm respectively, and are designed based on the minimum size that does not affect array reflection, which is one-tenth of the wavelength. More parasitic patches will increase the design complexity. The three-piece parasitic patch can significantly improve the radiation concentration without increasing the size of the antenna, while effectively reducing the side lobes and improving the directivity of the antenna radiation.

[0058] A three-piece parasitic patch is provided in the center above the metal radiation patch and the dielectric substrate, which improves the unclear and unfocused main lobe caused by the metal radiation patch being divided into two pieces for the Vivaldi antenna, improves the directivity of the antenna and increases the gain, making the Vivaldi antenna of the geological radar suitable for deep lining detection, ultimately improving the accuracy and reliability of the deep lining of the tunnel.

[0059] In the specific implementation process, the microstrip line structure of the feeding part is etched in the middle position on both sides of the dielectric substrate, connecting the bottom feeding port and the metal patch. The microstrip line transitions to the radiation part of the metal patch through the outer edge exponential slot line, which improves the feeding efficiency and maximizes the radiation energy.

[0060] Figure 5 The far-field radiation pattern of the antenna shows the relationship between the absolute value of the far-field radiation directivity of the antenna and the angle, which shows the directional capability of the antenna. The directional gain in the main lobe direction is 10.2dBi, and the -3dB beam angle is 39.9°.

[0061] 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 geological radar heel-to-heel Vivaldi antenna for deep-level lining detection, characterized in that: include: Dielectric substrates, metal radiating patches, and parasitic patches; A plurality of the parasitic patches are arranged at the center above the metal radiation patch and the dielectric substrate; The two metal radiation patches are etched on the upper surface and the lower surface of the dielectric substrate; the two metal radiation patches have the same structure, and are both composed of a radiation part and a feeding part; the bottom edges of the two feeding parts are arranged flush with the bottom edge of the dielectric substrate; the two radiation parts are arranged symmetrically with respect to the dielectric substrate; The feeding part is etched with a microstrip line, and the microstrip line is connected to the radiating part through a gradient exponential curve; the inner edge of the radiating part is an exponential gradient groove line; the side edges of the two radiating parts are symmetrically engraved with concave semi-elliptical grooves; a plurality of comb-shaped grooves parallel to and perpendicular to the side of the dielectric substrate are arranged in the semi-elliptical groove; the ends of the comb-shaped grooves fit the contour of the semi-elliptical groove with different lengths.

2. The geological radar Vivaldi antenna for deep lining detection according to claim 1, characterized in that: The two adjacent comb-shaped slots have the same slot spacing and the same slot width.

3. The geological radar Vivaldi antenna for deep-level lining detection according to claim 1, characterized in that: The groove spacing and groove width of the comb-shaped grooves are 5-8 mm and 8-11 mm respectively.

4. The geological radar Vivaldi antenna for deep lining detection according to claim 1, characterized in that: The parasitic patches are multi-piece, and the spacing is the maximum spacing that does not produce array reflection effect. The calculation formula of the maximum spacing is: Where d is the interval distance, c is the propagation speed of electromagnetic waves, f is the minimum detection frequency, ε r is the relative dielectric constant of the dielectric substrate.

5. The geological radar Vivaldi antenna for deep-level lining detection according to claim 1 or 4, characterized in that: The number of the parasitic patches is three.

6. The geological radar Vivaldi antenna for deep-level lining detection according to claim 1, characterized in that: The exponentially gradient groove line of the inner edge satisfies the equation y=e^(0.0129x).

7. The geological radar Vivaldi antenna for deep-level lining detection according to claim 1, characterized in that: The end opening of the exponentially tapered groove line at the inner edge corresponds to the lower limit of the working frequency band, and the end opening of the exponentially tapered groove line at the inner edge is maximized.

8. The geological radar Vivaldi antenna for deep-level lining detection according to claim 1 or 7, characterized in that: The end opening of the exponentially tapered groove line of the inner edge is equal to the width of the dielectric substrate.

9. The geological radar Vivaldi antenna for deep-level lining detection according to claim 1, characterized in that: The major axis range of the outline of the semi-elliptical groove is 180-210 mm, and the minor axis range is 90-110 mm.

10. The geological radar Vivaldi antenna for deep-level lining detection according to claim 1, characterized in that: The dielectric substrate is rectangular, the length range of the dielectric substrate is 470-530 mm, the width range of the dielectric substrate is 280-320 mm, and the metal radiation patch is etched within the range of the dielectric substrate.

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