Ultra-wideband double-slot Vivaldi antenna for air coupling radar

Abstract

The invention provides an ultra-wideband double-slot Vivaldi antenna for an air coupling radar. The ultra-wideband double-slot Vivaldi antenna comprises a dielectric substrate, a gradually-changed open slot, an elliptical open slot and a microstrip feed structure, a radiation patch is attached to the upper surface of the dielectric substrate; the gradually-changed open slot is formed in the radiation patch and has a trumpet-shaped opening; the plurality of elliptical open slots are formed in the radiation patch and are symmetrically arranged at two sides of the gradually-changed open slot, the elliptical open slots are all parts of the whole ellipse, and the centers of the plurality of elliptical open slots at the same side are gradually changed along the direction of the center line of the gradually-changed open slot; an included angle is formed between the long axis of the elliptical open slot and the center line of the gradually-changed open slot; the microstrip feed structure is arranged on the lower surface of the dielectric substrate. According to the Vivaldi antenna, the surface current distribution of the antenna is improved, the current backflow phenomenon is inhibited, the sidelobe energy is reduced, the energy is concentrated in the main radiation direction, and the gain and directivity of the antenna are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of antennas, and particularly to an ultra-wideband dual-slot Vivaldi antenna for air-coupled radar. Background Art

[0002] As a tool for receiving and transmitting signals, antennas play a huge role in fields such as wireless communication, radar applications, and microwave imaging. Especially in air-coupled radar, the quality of antenna performance directly affects the detection accuracy, imaging quality, and target recognition ability of the radar system. As a planar-structured ultra-wideband tapered slot antenna, the Vivaldi antenna has the advantages of ultra-wideband, easy integration, high gain, and good directivity, and can be used in the radio wave radar part for large-range monitoring or detection. In addition, the Vivaldi antenna can transmit the data received by the air-coupled radar system at a high rate and communicate with ground equipment.

[0003] In the prior art, there is a current reflux phenomenon on the patch surface. A part of the current will flow from the inside of the exponential tapered line to the edge of the patch, resulting in non-concentrated energy, large antenna side lobes, increased antenna loss, reduced gain, weakened beam directivity, and affecting the radiation effect and imaging effect. Summary of the Invention

[0004] In view of this, the present invention proposes an ultra-wideband dual-slot Vivaldi antenna for air-coupled radar to solve the technical problems of the current reflux phenomenon on the patch surface, large antenna side lobes, resulting in increased antenna loss, reduced gain, weakened beam directivity, and affecting the radiation effect and imaging effect as mentioned in the above background art.

[0005] The technical solution of the present invention is implemented as follows:

[0006] The present invention provides an ultra-wideband dual-slot Vivaldi antenna for air-coupled radar, including a dielectric substrate, a tapered open slot, an elliptical open slot, and a microstrip feeding structure, wherein:

[0007] A radiation patch is attached to the upper surface of the dielectric substrate;

[0008] The tapered open slot is opened on the radiation patch and has a horn-shaped opening;

[0009] A plurality of the elliptical open slots are opened on the radiation patch and are symmetrically arranged on both sides of the tapered open slot. The elliptical open slots are all parts of the whole ellipse. The centers of the plurality of elliptical open slots on the same side are gradually arranged along the center line direction of the tapered open slot, and the major axis of the elliptical open slot has an included angle with the center line of the tapered open slot;

[0010] The microstrip feeding structure is arranged on the lower surface of the dielectric substrate.

[0011] Based on the above technical solutions, preferably, the centers of multiple elliptical opening slots on the same side are arranged at intervals of a first distance in the x direction and a second distance in the y direction. The x direction is parallel to the center line of the tapered opening slot, and the y direction is perpendicular to the x direction.

[0012] Based on the above technical solutions, preferably, the included angle between the major axis of the elliptical opening slot and the y direction is 25 to 29 degrees.

[0013] Based on the above technical solutions, preferably, the major axes of each of the elliptical opening slots are equal, and the minor axes are equal.

[0014] Based on the above technical solutions, preferably, it further includes multiple gain units. The gain units are arranged on the upper surface of the dielectric substrate and are located in the area where the tapered opening slot is located. The gain units are made of sub-wavelength metamaterials.

[0015] Based on the above technical solutions, preferably, the gain unit includes multiple first rectangular blocks with gradually changing lengths and a second rectangular block. The centers of the multiple first rectangular blocks are linearly arranged along the direction parallel to the center line of the tapered opening slot. The second rectangular block is located between the two middle first rectangular blocks, and the length direction of the second rectangular block is perpendicular to the center line of the tapered opening slot.

[0016] Based on the above technical solutions, preferably, the microstrip feeding structure adopts a T-shaped power divider. The microstrip feeding structure includes a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, and a fan-shaped stub connected in sequence. The end of the first microstrip line is connected to two second microstrip lines. The second microstrip line and the fourth microstrip line are both perpendicular to the first microstrip line. The third microstrip line is parallel to the first microstrip line. The fan-shaped stub is arranged at the end of the fourth microstrip line.

[0017] Based on the above technical solutions, preferably, a V-shaped chamfer is provided at the connection between the end of the first microstrip line and the two second microstrip lines.

[0018] Based on the above technical solutions, preferably, the degree of the arc of the fan-shaped stub is 105 to 115 degrees.

[0019] Based on the above technical solutions, preferably, the material of the dielectric substrate is Rogers RT5880, the dielectric constant is 2.2, and the thickness is 0.75 to 0.8 mm.

[0020] The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar of the present invention has the following

[0021] Beneficial effects:

[0022] (1) A plurality of the elliptical open slots are formed on the radiation patch and symmetrically arranged on both sides of the tapered open slot. Each of the elliptical open slots is a part of an entire ellipse. The centers of the plurality of elliptical open slots on the same side are arranged in a tapered manner along the center line direction of the tapered open slot. The major axis of the elliptical open slot forms an angle with the center line of the tapered open slot, which improves the surface current distribution of the antenna, suppresses the current reflux phenomenon, reduces the sidelobe energy, concentrates the energy in the main radiation direction, and greatly improves the gain and directivity of the antenna.

[0023] (2) The centers of the plurality of elliptical open slots on the same side are arranged at intervals of a first distance in the x direction and a second distance in the y direction. The x direction is parallel to the center line of the tapered open slot, and the y direction is perpendicular to the x direction. While increasing the gain of the antenna, the operating bandwidth of the antenna remains basically unchanged, avoiding the reduction of the low-frequency bandwidth of the antenna and improving the reliability of the device.

[0024] (3) The angle between the major axis of the elliptical open slot and the y direction is 25 to 29 degrees. Through the setting of this angle, the gain and directivity of the antenna are further improved, making the gain effect of the antenna better.

[0025] (4) The gain unit is arranged on the upper surface of the dielectric substrate and is located in the area where the tapered open slot is located. The gain unit is made of sub-wavelength metamaterial and couples with the transmitted electromagnetic wave, so that the gain of the antenna increases within the bandwidth of 3.5 - 10.5 GHz, improving the radiation performance of the antenna in the intermediate frequency band.

[0026] (5) A V-shaped cut angle is provided at the connection between the end of the first microstrip line and the two second microstrip lines, improving the impedance matching of the antenna. Without changing the size of the antenna, the low-frequency operating point is reduced to meet the requirements of the air-coupled radar for miniaturization.

[0027] (6) The degree of the arc of the fan-shaped branch is 105 to 115 degrees, making the impedance matching of the antenna better, the return loss lower, the radiation efficiency better, and improving the performance of the antenna. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1Schematic diagram of the front of the ultra-wideband dual-slot Vivaldi antenna (before digging the elliptical opening slot) for air-coupled radar in the embodiment of the present invention;

[0030] Figure 2 Schematic diagram of the back of the ultra-wideband dual-slot Vivaldi antenna (before digging the elliptical opening slot) for air-coupled radar in Embodiment 1 of the present invention;

[0031] Figure 3 Schematic diagram of the ultra-wideband dual-slot Vivaldi antenna (after digging the elliptical opening slot) for air-coupled radar in Embodiment 1 of the present invention;

[0032] Figure 4 The (a) and (b) of this are the simulation and optimization S11 curve graphs of parameter qa and parameter qb in the Vivaldi antenna in Embodiment 1 of the present invention;

[0033] Figure 5 Comparison diagram of S11 simulation curves of the original Vivaldi, the antenna in Embodiment 1, and the antenna in Embodiment 2 in the embodiment of the present invention;

[0034] Figure 6 Comparison diagram of gain simulation curves of the original Vivaldi, the antenna in Embodiment 1, and the antenna in Embodiment 2 in the embodiment of the present invention;

[0035] Figure 7 Front view of the Vivaldi antenna in Embodiment 2 of the present invention;

[0036] Figure 8 Stereogram of the Vivaldi antenna in Embodiment 2 of the present invention;

[0037] Figure 9 Schematic diagram of the gain unit in Embodiment 2 of the present invention;

[0038] Figure 10 The (a) and (b) of this are the S parameter diagram and the equivalent dielectric parameter diagram of the gain unit of the Vivaldi antenna in Embodiment 3 of the present invention respectively;

[0039] Figure 11 The (a) and (b) of this are the front view and the back view of the physical object of the antenna in Embodiment 3 in Embodiment 3 of the present invention respectively;

[0040] Figure 12 The (a) and (b) of this are the comparison diagram of the S11 curves of the physical object of the original Vivaldi antenna and the simulation of the original Vivaldi antenna, and the comparison diagram of the S11 curves of the physical object of the Vivaldi antenna in Embodiment 2 and the simulation of the Vivaldi antenna in Embodiment 2 in the embodiment of the present invention respectively;

[0041] Figure 13 This is the comparison chart of the simulation and physical object of the original antenna in the embodiments of the present invention, and the gain of the antenna simulation and physical object in Embodiment 2;

[0042] Figure 14 In (a) and (b), they are respectively the simulation XOY plane radiation patterns of the original antenna, the antenna in Embodiment 1, and the antenna in Embodiment 2 at 4.5 GHz, and the XOY plane radiation patterns of the physical original antenna and the physical antenna in Embodiment 2 at 4.5 GHz;

[0043] Figure 15 In (a) and (b), they are respectively the simulation XOY plane radiation patterns of the original antenna, the antenna in Embodiment 1, and the antenna in Embodiment 2 at 6.5 GHz, and the XOY plane radiation patterns of the physical original antenna and the physical antenna in Embodiment 2 at 6.5 GHz;

[0044] Figure 16 In (a) and (b), they are respectively the simulation XOY plane radiation patterns of the original antenna, the antenna in Embodiment 1, and the antenna in Embodiment 2 at 8.0 GHz, and the XOY plane radiation patterns of the physical original antenna and the physical antenna in Embodiment 2 at 8.0 GHz;

[0045] Explanation of reference numerals:

[0046] 1 - dielectric substrate; 2 - tapered slot; 3 - microstrip feeding structure; 4 - rectangular slot; 5 - circular slot; 6 - elliptical slot; 7 - gain unit. Detailed implementation manners

[0047] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0048] Embodiment 1

[0049] Referring to Figure 1-16 As shown, in the embodiment of the present invention, a ultra-wideband dual-slot Vivaldi antenna for air-coupled radar is proposed, including a dielectric substrate 1, a tapered slot 2, an elliptical slot 6, and a microstrip feeding structure 3, wherein:

[0050] A radiation patch is attached to the upper surface of the dielectric substrate 1; the material of the dielectric substrate 1 is Rogers RT5880, the dielectric constant is 2.2, the thickness is 0.75 - 0.8 mm, preferably 0.787 mm, the width of the substrate wb = 86 mm, and the length of the board is 130 mm;

[0051] The tapered open slot 2 is formed on the radiating patch and has a horn-shaped opening. The tapered open slot 2 specifically includes: drawing a rectangular open slot 4 on the left side of the dielectric substrate 1, with one end of the rectangular open slot 4 connected to the starting point of the exponential taper line and the other end connected to a circular slot 5. The rectangular open slot 4 serves to couple electromagnetic waves and confine the surface current of the patch when the Vivaldi antenna is operating. Drawing a circular slot 5 on the left side of the dielectric substrate 1, and the circular slot 5 adjusts the impedance matching, increases the bandwidth, and improves the radiation characteristics when the Vivaldi antenna is operating. Draw the exponential taper line, rectangular slot, and circular slot 5 on the right side of the substrate in the same way, and the two are symmetrically structured along the center line of the substrate. In the exponential taper line, the longer exponential taper curve satisfies the following formula:

[0052] y1 = c1 * e ax -c1 + g / 2 (1);

[0053] In formula (1), c1 is the first coefficient, a is the exponential coefficient, x is the abscissa, and g is the width of the rectangular slot;

[0054] The shorter exponential taper curve satisfies the following formula:

[0055] y2 = -(c2 * e ax -c2 + g / 2) (2);

[0056] In formula (2), c2 is the second coefficient, a is the exponential coefficient, x is the abscissa, and g is the width of the rectangular slot;

[0057] c1 in formula (1) satisfies the following formula:

[0058] c1 = ((wa - g) / 2) / (e a*lb -1) (3);

[0059] In formula (3), wa is the center distance between two circular slots 5, and lb is the length of the long exponential slot line;

[0060] c2 in formula (2) satisfies the following formula:

[0061] c2 = ((wa - g) / 2) / (e a*la -1) (4);

[0062] In formula (4), la is the length of the short exponential slot line;

[0063] After simulation optimization through formulas (1)-(4), better numerical values are selected. The specific results are as follows: The lengths of the long and short exponential slot lines are lb = 100 mm and la = 50 mm respectively, the rectangular slot line lg = 5 mm, the distance from the end of the rectangular slot line to the end of the substrate l1 = 25 mm, the radius rs of the circular slot 5 is between 4.8 - 5.2 mm, preferably rs = 5 mm, the center distance wa of the two circular slots 5 is 42 mm, the width g of the rectangular slot is 0.55 - 0.65 mm, preferably g = 0.6 mm;

[0064] A plurality of the elliptical open slots 6 are formed on the radiation patch and are symmetrically arranged on both sides of the tapered open slot 2. The elliptical open slots 6 are all parts of the whole ellipse. The centers of the plurality of elliptical open slots 6 on the same side are arranged in a tapered manner along the center line direction of the tapered open slot 2. The major axis of the elliptical open slot 6 has an angle with the center line of the tapered open slot 2; The center of the first elliptical open slot 6 is at a distance ca = 18 mm from the starting point of the exponential slot line and at a distance cb = 39 mm from the center line of the dielectric substrate 1. The minor axis ta of the elliptical open slot 6 is 2.9 - 3.1 mm, preferably ta = 3 mm, and the major axis tb = 12 mm;

[0065] The microstrip feeding structure 3 is arranged on the lower surface of the dielectric substrate 1.

[0066] For the ultra-wideband dual-slot Vivaldi antenna for air-coupled radar proposed in this embodiment, a plurality of the elliptical open slots 6 are formed on the radiation patch and are symmetrically arranged on both sides of the tapered open slot 2. The elliptical open slots 6 are all parts of the whole ellipse. The centers of the plurality of elliptical open slots 6 on the same side are arranged in a tapered manner along the center line direction of the tapered open slot 2. The major axis of the elliptical open slot 6 has an angle with the center line of the tapered open slot 2, which improves the surface current distribution of the antenna, suppresses the current reflux phenomenon, reduces the sidelobe energy, and concentrates the energy in the main radiation direction, greatly improving the gain and directivity of the antenna.

[0067] In some embodiments, the centers of the plurality of elliptical open slots 6 on the same side are arranged at intervals of a first distance in the x direction and a second distance in the y direction. The x direction is parallel to the center line of the tapered open slot 2, and the y direction is perpendicular to the x direction. The centers of adjacent elliptical open slots 6 are spaced qa = 12 - 14 mm in the x direction and qb = 1.5 - 2.5 mm in the y direction. While increasing the gain of the antenna, the operating bandwidth of the antenna remains basically unchanged, avoiding the reduction of the low-frequency bandwidth of the antenna and improving the reliability of the device. In order to improve the gain of the elliptical slot 5 without affecting the antenna bandwidth, the parameters qa and qb are simulated and optimized, and the optimization results are as Figure 4 shown, preferably qa = 13 mm, qb = 2 mm.

[0068] In some embodiments, the angle between the major axis of the elliptical open slot 6 and the y-direction is 25 to 29 degrees. Through this angle setting, the gain and directivity of the antenna are further improved, making the gain effect of the antenna better. The angle is preferably 27 degrees, and its gain effect is the best.

[0069] In some embodiments, the major axes of each of the elliptical open slots 6 are equal, and the minor axes are equal. The elliptical open slot 6 of this embodiment can improve the antenna gain in the S, C, and X bands, expand the bandwidth, and increase the gain of the antenna at low frequencies, and the gain at high frequencies will not decrease.

[0070] The S11 and gain simulation results of the original Vivaldi antenna and the antenna of Embodiment 1 are as Figure 5 and Figure 6 shown. After cutting multiple pairs of gradually tapered elliptical open slots 6, the operating bandwidth of the antenna changes from 1.4 - 12 GHz to 1.3 - 12 GHz. That is to say, the operating frequency band of the antenna remains basically unchanged, while the gain of the antenna is greatly improved in the range of 2.5 - 12 GHz, with a maximum increase of 1.5 dBi. This is because the cut elliptical slots 5 improve the surface current distribution of the antenna, suppress the current reflux phenomenon, and enable more energy to be radiated from the main radiation direction. Figure 14 , 15, 16 are the simulated XOY plane radiation patterns of the antenna at 4.5, 6.5, and 8 GHz respectively. It can be clearly seen that the side lobes of the antenna become smaller, that is, the energy at the main lobe increases, and the main lobe width becomes narrower, that is, the directivity of the antenna increases and the gain increases significantly.

[0071] Embodiment 2

[0072] The difference between this embodiment and Embodiment 1 is that: on the basis of Embodiment 1, a gain unit 7 is added.

[0073] In some embodiments, the ultra-wideband dual-slot Vivaldi antenna further includes a plurality of gain units 7. The gain units 7 are arranged on the upper surface of the dielectric substrate 1 and are located in the area where the tapered open slot 2 is located. The gain units 7 are made of sub-wavelength metamaterials. The metamaterials used in this embodiment are LC-type metamaterials in electromagnetic metamaterials, which play a resonant coupling role on the transmitted electromagnetic waves. The gain units 7 couple with the transmitted electromagnetic waves, so that the gain of the antenna increases within the bandwidth of 3.5 - 10.5 GHz, and the radiation performance of the antenna in the intermediate frequency band is improved.

[0074] In some embodiments, the gain unit 7 includes a plurality of first rectangular blocks with gradually changing lengths and a second rectangular block. The centers of the plurality of first rectangular blocks are arranged linearly along a direction parallel to the center line of the gradually changing opening slot 2. The second rectangular block is located between the two middle first rectangular blocks, and the length direction of the second rectangular block is perpendicular to the center line of the gradually changing opening slot 2. The specific dimensions are as follows: x1 = 4 mm, x2 = 3 mm, x3 ranges from 1.75 to 1.85 mm, y1 = 4 mm, y2 ranges from 0.75 to 0.85 mm, y3 ranges from 0.65 to 0.75 mm, and y4 ranges from 0.18 to 0.22 mm. The simulation results of the S parameters of the gain unit 7 are as Figure 10 shown in (a). In the frequency band of 1 - 15 GHz, S11 is less than -20 dB, and the value of S21 is close to 0, indicating that the vast majority of electromagnetic waves can pass through the metamaterial structure. Figure 10 (b) shows the equivalent dielectric parameters of the gain unit 7. Its equivalent dielectric constant ε, permeability μ, and effective refractive index n are between 1 and 1.3, slightly larger than the equivalent dielectric parameters of air. According to the equivalent medium theory, the metamaterial structure can be equivalent to an artificial lens.

[0075] From Figure 5 and Figure 6 it can be seen that after adding the gain unit 7, the operating frequency band of the antenna remains basically unchanged, while the gain in the intermediate frequency band of 3.5 - 10.5 GHz increases, with a maximum increase of 0.93 dBi. This is because when electromagnetic waves pass through the metamaterial structure, they resonate with it, increasing the coupling degree of the antenna and improving the gain. From Figure 14 , 15, 16, this can be confirmed.

[0076] According to the optimized parameters obtained from the simulation, the Vivaldi antenna provided in Embodiment 3 was designed, fabricated, and tested. The physical diagram is as Figure 11 shown. The measured S11 is as Figure 12 shown, and the measured gain is as Figure 13 shown. The trend of the physical S11 curve is consistent with the simulation, with some errors in some low-frequency and high-frequency bands. The antenna gain is slightly lower than the simulation in the intermediate frequency band and lower than the simulation in the high-frequency band. This is due to the manufacturing errors of the 3D-printed physical antenna and the test environment. The working state of the test environment is poor in the high-frequency band, with large losses.

[0077] Embodiment 3

[0078] The difference between this embodiment and Embodiment 2 is that on the basis of Embodiment 2, the specific structure of the microstrip feeding structure 3 is designed.

[0079] The microstrip feeding structure 3 adopts a T-shaped power divider. The microstrip feeding structure 3 includes a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line and a fan-shaped stub connected in sequence. The end of the first microstrip line is connected to two second microstrip lines. The second microstrip line and the fourth microstrip line are both perpendicular to the first microstrip line. The third microstrip line is parallel to the first microstrip line. The fan-shaped stub is arranged at the end of the fourth microstrip line. The width w1 of the first microstrip line is 2.1 - 2.3 mm, preferably w1 = 2.2 mm, and the length l2 is 12.4 - 12.8 mm, preferably l2 = 12.6 mm; the width w2 of the second microstrip line is 0.55 - 0.65 mm, preferably w2 = 0.6 mm, and the length l4 = 20 mm; the length l5 of the third microstrip line is 13 mm, and the width is the same as that of the second microstrip line; the length l6 of the fourth microstrip line is 10 mm, and the width is the same as that of the second microstrip line.

[0080] In a further embodiment, a V-shaped chamfer is provided at the connection between the end of the first microstrip line and the two second microstrip lines. The V-shaped chamfer can improve the impedance matching of the antenna. Without changing the size of the antenna, it reduces the low-frequency operating point to meet the requirements of the air-coupled radar for miniaturization. The length l3 of the V-shaped chamfer along the length direction of the first microstrip line determines the size of the low-frequency operating point to be between 1 - 2 mm. After optimization analysis, l3 is 1.6 mm.

[0081] In some embodiments, the degree of the arc of the fan-shaped stub is 105 - 115 degrees, and its radius rp is 5.2 - 5.8 mm, preferably rp = 5.5 mm. The T-shaped power divider is used to receive the transmitted electromagnetic wave and transmit it to the radiation patch through the dielectric substrate 1 for radiation, which affects the impedance matching of the antenna. Through the above parameter settings, the impedance matching of the antenna is better, the return loss is lower, the radiation efficiency is better, and the performance of the antenna is improved. The degree of the arc is preferably 110 degrees.

[0082] In some embodiments, the material of the dielectric substrate 1 is Rogers RT5880, the dielectric constant is 2.2, and the thickness is 0.75 - 0.8 mm. Rogers RT5880 is a polytetrafluoroethylene glass fiber reinforced material. These microfibers are randomly distributed in the material, providing the maximum strength enhancement for the circuit application process and the circuit production process. This material has the lowest dielectric constant among similar materials, and its extremely low dielectric loss makes them very suitable for high-frequency and wide-band applications that require minimized dispersion and loss; it is very easy to be cut into the required shape, and at the same time it can resist the erosion of all solutions and reagents used in the etching and through-hole plating processes; the RT5880 laminate has the characteristics of the lowest dielectric loss, low moisture absorption rate, isotropy, and extremely small change in electrical performance with frequency in the reinforced polytetrafluoroethylene material.

[0083] The working principle of the ultra-wideband dual-slot Vivaldi antenna for air-coupled radar in this embodiment is as follows: A plurality of the elliptical open slots 6 are formed on the radiation patch and symmetrically arranged on both sides of the tapered open slot 2. Each of the elliptical open slots 6 is a part of an entire ellipse. The centers of the multiple elliptical open slots 6 on the same side are arranged in a tapered manner along the center line direction of the tapered open slot 2. The major axis of the elliptical open slot 6 forms an angle with the center line of the tapered open slot 2, which improves the surface current distribution of the antenna, suppresses the current reflux phenomenon, reduces the sidelobe energy, and concentrates the energy in the main radiation direction, greatly improving the gain and directivity of the antenna.

[0084] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultra-wideband dual-slot Vivaldi antenna for air-coupled radar, characterized in that: It includes a dielectric substrate, a gradient opening slot, an elliptical opening slot and a microstrip feeding structure, wherein: A radiation patch is attached to the upper surface of the dielectric substrate; The gradient opening slot is provided on the radiation patch and is a trumpet-shaped opening; A plurality of elliptical opening slots are provided on the radiation patch and are symmetrically arranged on both sides of the gradient opening slot. The elliptical opening slots are all parts of the entire ellipse. The centers of the plurality of elliptical opening slots on the same side are arranged gradiently along the direction of the center line of the gradient opening slot. The major axis of the elliptical opening slot forms an angle with the center line of the gradient opening slot. The microstrip feeding structure is arranged on the lower surface of the dielectric substrate.

2. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to claim 1, characterized in that: The centers of the multiple elliptical opening grooves on the same side are arranged at a first distance in the x direction and a second distance in the y direction, the x direction is parallel to the center line of the gradual opening groove, and the y direction is perpendicular to the x direction.

3. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to claim 2, characterized in that: The angle between the major axis of the elliptical opening groove and the y direction is 25 to 29 degrees.

4. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to claim 1, characterized in that: The major axis and minor axis of each of the elliptical opening grooves are equal.

5. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to claim 1, characterized in that: It also includes a plurality of gain units, which are arranged on the upper surface of the dielectric substrate and located in the area where the gradient opening slots are located, and are made of sub-wavelength metamaterials.

6. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to claim 5, characterized in that: The gain unit includes a plurality of first rectangular blocks with gradually varying lengths and a second rectangular block, wherein the centers of the plurality of first rectangular blocks are arranged in a straight line in a direction parallel to the center line of the gradually varying opening slot, and the second rectangular block is located between two of the first rectangular blocks in the middle, and the length direction of the second rectangular block is perpendicular to the center line of the gradually varying opening slot.

7. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to claim 1, characterized in that: The microstrip feeding structure adopts a T-type power divider, and the microstrip feeding structure includes a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line and a fan-shaped branch connected in sequence, the end of the first microstrip line is connected to two second microstrip lines, the second microstrip line and the fourth microstrip line are both perpendicular to the first microstrip line, the third microstrip line is parallel to the first microstrip line, and the fan-shaped branch is arranged at the end of the fourth microstrip line.

8. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to claim 7, characterized in that: A V-shaped cut angle is arranged at the connection between the end of the first microstrip line and the two second microstrip lines.

9. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to claim 7, characterized in that: The degree of the arc of the fan-shaped branch is 105 to 115 degrees.

10. The ultra-wideband dual-slot Vivaldi antenna for air-coupled radar according to any one of claims 1 to 9, characterized in that: The material of the dielectric substrate is Rogers RT5880, with a dielectric constant of 2.2 and a thickness of 0.75-0.8 mm.

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