A 2-70GHz ultra-wideband, all-metal Vivaldi antenna

Abstract

A 2-70GHz ultra-wideband, all-metal Vivaldi antenna includes a metal plate with a supporting base plate at its bottom. A coaxial connector passes through the supporting base plate and connects to the metal plate. An exponentially tapered curve opening is formed on the upper inner side of the metal plate, and a matching circle is formed on the lower part of the metal plate. An inclined slot is formed on the metal plate between the exponentially tapered curve opening and the matching circle. The starting end of the exponentially tapered curve opening is connected to one end of the inclined slot, and the other end of the inclined slot is connected to the matching circle. The inner conductor of the coaxial connector contacts the upper surface of the end where the inclined slot and the matching circle are connected. Traditionally designed Vivaldi antennas rarely operate at frequencies of 40GHz and above. This Vivaldi antenna, by optimizing the thickness of the Vivaldi metal plate, allows the antenna sample to operate at frequencies greater than 70GHz with a return loss exceeding 10dB. This invention features a simple structure, low cost, ultra-wideband capability, and stable radiation pattern.

Description

Technical Field

[0001] This invention belongs to the field of ultra-wideband antenna technology, and specifically relates to an ultra-wideband, all-metal Vivaldi antenna with an operating frequency of 2-70 GHz. Background Technology

[0002] Ultra-wideband (UWB) antennas are an important research topic in antenna theory, with wide applications in many fields, such as broadband ground-penetrating radar, biomedical detection, UWB communication systems, and plasma microwave diagnostics. In recent years, UWB microwave diagnostics has become a significant development trend in plasma reflection diagnostics. UWB electromagnetic propagation can increase the diagnostic range of plasma electron density. In ultra-wideband plasma diagnostic systems, ultra-wideband antennas are indispensable components. Moreover, in high-temperature plasma diagnostic environments, antennas must be able to withstand high temperatures and maintain stable radiation performance.

[0003] Among various UWB antennas, the Vivaldi antenna is an excellent candidate due to its simple structure, light weight, ultra-wideband impedance characteristics, highly directional radiation, and stable radiation pattern. For ease of fabrication, traditional Vivaldi antennas are typically manufactured using printed circuit board (PCB) technology. Based on the exponential curve distribution on the same or opposite sides of the substrate, the antennas can be divided into two categories: coplanar Vivaldi antennas and heel-to-heel Vivaldi antennas. The coplanar Vivaldi antenna has a Vivaldi pattern printed on one side of the substrate, while the other side has a microstrip fan-shaped matching line. Because the exponential curve and feed line are separate, the bandwidth of the coplanar Vivaldi antenna is limited, typically to about 8:1. In this structure, the fan-shaped matching structure in the coplanar Vivaldi antenna also generates radiation, which may lead to a deterioration of the antenna pattern. In contrast, the heel-type Vivaldi antenna has two Vivaldi arms printed on opposite sides of the substrate. Due to the inherent ultra-wideband characteristics of the feed transition line—a smooth transition from microstrip lines to parallel stripline structures—heel-type Vivaldi antennas can achieve bandwidths exceeding 10:1. However, because the two arms of the exponential curve are printed on different sides of the substrate, the cross-polarization of the heel-type Vivaldi antenna is relatively high. To date, no Vivaldi antenna with an impedance bandwidth exceeding 35:1 has been found to meet UWB applications. Vivaldi antennas fabricated using PCB technology have poor structural strength and cannot withstand harsh environments such as high temperatures.

[0004] In recent years, all-metal Vivaldi antennas using wire cutting technology have been an important research direction. All-metal Vivaldi antennas typically use aluminum as the processing material, which offers lower material and processing costs compared to PCB technology. Furthermore, the transmission loss of metal is lower than that of high-frequency dielectric substrates, resulting in higher antenna gain. EGTianang et al. proposed an all-metal cavity-backed Vivaldi antenna, which forms a 3×4 array. The Vivaldi antenna achieved a VSWR < 2 in the frequency range of 1.5-7.5 GHz (EGTianang, MA Elmansouri, DS Filipovic, “Ultra-wideband lossless cavity-backed Vivaldi antenna,” IEEE Trans. Antennas Propag., vol. 66, (1), pp. 115-124, 2018.); Zhang Qingchun et al. proposed an improved all-metal Vivaldi element antenna, which achieved a voltage standing wave ratio (VSWR) of less than 2.0 in the range of 5-14 GHz (Q. Zhang, M. Yang, Z. Jiang, X. Liu, S. Gao, and H. Zhang, “Design and research of an ultra-wideband metal antenna with low radar cross section,” Application of Electronic Technique, Vol. 44 (6), 2018.). However, when the aforementioned all-metal Vivaldi antenna is used in a phased array, the impedance performance of a single Vivaldi element is relatively poor in some cases.

[0005] Patent application CN116613530 A discloses a lightweight ultrawideband antenna based on carbon-based material MXene and 3D printing technology. MXene is used as the antenna material, and a hollow Vivaldi antenna element and a coaxial feed structure at the bottom are arranged vertically. The Vivaldi antenna element has a specific-shaped arc-shaped opening at the top of the central axis and a connecting body at the bottom. Between the connecting body and the arc-shaped opening are a gradient groove structure and an L-shaped groove structure of specific dimensions. A rectangular matching circle is provided at the end of the horizontal part of the L-shaped groove. Although the exponential curve connects to the feed structure, the connection part has significant non-smoothness, limiting the bandwidth to a maximum of only 12:1. Furthermore, the operating frequencies of the aforementioned metal Vivaldi antennas are all below 25 GHz, and there are very few Vivaldi antennas in the prior art with operating frequencies above 30 GHz. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to propose a 2-70GHz ultra-wideband, all-metal Vivaldi antenna, which can greatly broaden the impedance performance by adding a tilted slot at the beginning of the exponential gradient curve and optimizing the thickness of the Vivaldi plate.

[0007] To achieve the above objectives, the present invention proposes the following technical solution:

[0008] A 2-70GHz ultra-wideband, all-metal Vivaldi antenna includes a metal plate 1, a supporting base plate 3 at the bottom of the metal plate 1, a coaxial connector 2 passing through the supporting base plate 3 and connecting to the metal plate 1, an exponentially tapered curve opening 4 on the upper inner side of the metal plate 1, a matching circle 6 on the lower part of the metal plate 1, and an inclined slot 5 on the metal plate 1 between the exponentially tapered curve opening 4 and the matching circle 6. The starting end of the exponentially tapered curve opening 4 is connected to one end of the inclined slot 5, and the other end of the inclined slot 5 is connected to the matching circle 6.

[0009] The metal plate 1 has comb-like structures 7 on both sides.

[0010] The width of the inclined groove 5 is consistent with the width of the starting end of the exponential gradient curve opening 4.

[0011] The tilt angle of the inclined groove 5 is between 13 and 27°.

[0012] The thickness of the metal plate 1 is less than half a wavelength of the highest operating frequency.

[0013] The inner conductor of the coaxial connector 2 is in contact with the upper surface of one end that is connected to the inclined groove 5 and the matching circle 6.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] (1) Traditional metal Vivaldi antennas are directly fed at the beginning of the exponential curve, with the feed port on one side of the metal plate. In this invention, an inclined slot 5 is added at the beginning of the exponential gradient curve 4 to extend the length of the metal plate and increase the current transmission path. Comb structures 7 are added on both sides of the metal plate 1 to improve the impedance characteristics of the low frequency band. The introduction of the inclined slot 5 also increases the adjustable parameters, namely the tilt angle and the size of the inclined slot, which can widen the impedance bandwidth of the antenna. This invention achieves an ultra-wide impedance bandwidth of 35:1, which can be better applied to ultra-wideband detection and high-temperature plasma diagnostic environments.

[0016] (2) Compared with the Vivaldi antenna processed by PCB technology, the present invention has lower material and processing costs, and the transmission loss of metal is lower than that of high frequency dielectric board, and has the characteristic of higher antenna gain.

[0017] (3) Unlike the side-feeding of the traditional Vivaldi antenna, the present invention can feed the metal plate 1 at the end after adding the tilting slot 5. The coaxial connector 2 can be directly located at the end of the metal plate 1, which makes it easier to install.

[0018] In summary, this invention significantly broadens the impedance performance by adding a tilted slot at the beginning of the exponential gradient curve, while simultaneously reducing the thickness of the metal plate, thereby greatly improving high-frequency impedance performance. The antenna of this invention features a simple structure, low cost, ultra-wideband coverage, and stable radiation pattern, offering significant advantages in ultra-wideband detection and plasma diagnostics. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention, wherein, Figure 1 (a) Front view Figure 1 (b) is an enlarged view of the power supply section.

[0020] Figure 2 This is a diagram showing the key dimensions of the present invention.

[0021] Figure 3 This is a physical sample image of Embodiment 1 of the present invention, wherein, Figure 3 (a) is the front view of Example 1. Figure 3 (b) is an enlarged view of the power supply section of Example 1.

[0022] Figure 4 This is a physical sample image of Embodiment 2 of the present invention, wherein, Figure 4 (a) is the front view of Example 2. Figure 4 (b) is an enlarged view of the power supply section of Example 2.

[0023] Figure 5 The reflection coefficient (S) of the Vivaldi antenna in Embodiments 1 and 2 of this invention is simulated and measured. 11 ).

[0024] Figure 6 This refers to the gain of the Vivaldi antenna in Embodiments 1 and 2, which were simulated and measured in this invention.

[0025] Figure 7 These are the E-plane radiation patterns of the Vivaldi antennas in Embodiments 1 and 2 of this invention, with frequencies of [missing information]. Figure 7 (a) 2GHz Figure 7 (b) 4GHz, Figure 7 (c) 10GHz, Figure 7 (d) 20GHz, Figure 7 (e)40GHz, Figure 7 (f) 70 GHz, and the H-plane radiation pattern, with frequencies of respectively... Figure 7 (g)2.0GHz, Figure 7 (h)4GHz, Figure 7 (i) 10.0GHz, Figure 7 (j)20GHz, Figure 7 (k)40GHz, Figure 7 (k)70GHz, Figure 7 (l) Radiation pattern at 70 GHz.

[0026] Among them, 1. metal plate; 2. coaxial connector; 3. supporting base plate; 4. exponential gradient curve opening; 5. inclined groove; 6. matching circle; 7. comb structure. Detailed Implementation

[0027] The structural and working principles of the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Reference Figure 1 A 2-70GHz ultra-wideband, all-metal Vivaldi antenna includes a metal plate 1 made of brass with a thickness less than half the wavelength of the highest operating frequency. A support base plate 3 is mounted at the bottom of the metal plate 1. A coaxial connector 2, a 1.85mm-K type, passes through the support base plate 3 and connects to the metal plate 1. An exponentially tapered curve opening 4 is formed on the upper inner side of the metal plate 1, radiating electromagnetic waves into space. A matching circle 6 is formed at the bottom of the metal plate 1. An inclined slot 5 is formed on the metal plate 1 between the exponentially tapered curve opening 4 and the matching circle 6. The inclined slot 5 is used to improve the ultra-wideband impedance characteristics of the antenna. The starting end of the exponentially tapered curve opening 4 is connected to one end of the inclined slot 5, and the other end of the inclined slot 5 is connected to the matching circle 6. The width of the inclined slot 5 is consistent with the width of the starting end of the exponentially tapered curve opening 4. The tilt angle of the inclined slot 5 is between 13° and 27°. The inner conductor of the coaxial connector 2 is in contact with the upper surface of the end where the inclined slot 5 and the matching circle 6 are connected.

[0029] The metal plate 1 has comb-like structures 7 on both sides to improve the antenna pattern at various frequencies and the impedance performance in the low-frequency range.

[0030] The exponential gradient curve in opening 4 should conform to the following formula:

[0031] x=±a1·exp(a2z)+a3

[0032] Where a1 and a3 are constants related to the opening of the arc, z is the independent variable, x is the dependent variable, and the arc curvature constant is a2.

[0033] To ensure the achievable integrity of the antenna, two processing types were designed:

[0034] Example 1

[0035] Reference Figure 3 A 2-70GHz ultra-wideband, all-metal Vivaldi antenna is designed with a 3mm thick metal plate 1 between the matching circle 6 and the supporting base plate 3, and the remaining plates are 1.5mm thick. The specific design requirements are as follows:

[0036] (a) Operating frequency band: 2-70GHz;

[0037] (b) Antenna size: 0.53λ L ×0.4λ L ×0.017λ L (λ L (Low frequency wavelength);

[0038] (c) Return loss: <-10dB.

[0039] Solution Analysis and Selection: To achieve a reflection coefficient (S) in the range of 2 to 70 GHz (35:1 relative bandwidth) 11 For performance less than 10dB, a Vivaldi antenna with ultra-wideband impedance characteristics must be selected. However, for the requirements of withstanding harsh environments such as high temperatures and having lower transmission loss, Vivaldi antennas manufactured using PCB technology cannot achieve this. Therefore, only all-metal Vivaldi antennas can be selected.

[0040] Reference Figure 2 The antenna was modeled and simulated in CST STUDIO SUITE 2018. The optimized parameters of the antenna were determined according to Table 1 (unit: mm).

[0041] Table 1. Antenna parameters (unit: mm)

[0042]

[0043]

[0044] Where L refers to the vertical distance from the top of metal plate 1 to the supporting base plate 3, L0 refers to the vertical distance from the top of metal plate 1 to the starting end of the exponential gradient curve opening 4, L1 refers to the vertical distance from the starting end of the inclined groove 5 to the ending end of the inclined groove 5, L2 refers to the horizontal distance from the starting end of the inclined groove 5 to the ending end of the inclined groove 5, L3 refers to the horizontal distance from the starting end of the inclined groove 5 to the center of the matching circle 6, L4 refers to the vertical distance from the center of the matching circle 6 to the supporting base plate 3, W refers to the width of metal plate 1, W0 refers to the horizontal distance at the opening of the exponential gradient curve opening 4, W1 refers to the horizontal distance at the starting end of the exponential gradient curve opening 4, W2 refers to the length of the supporting base plate 2, D0 refers to the diameter of the matching circle 6, h refers to the thickness of metal plate 1, h1 refers to the thickness of metal plate 1 between the matching circle 6 and the supporting base plate 3, X1 represents the horizontal distance from the inner conductor of the coaxial connector 2 to the matching circle 6, a1 and a3 are arc opening related constants, and a2 is the arc curvature constant.

[0045] Example 2

[0046] Reference Figure 4 A 2-70GHz ultra-wideband, all-metal Vivaldi antenna with four exponentially tapered openings. The thickness of the metal plate 1 in the curved section is 1.5mm, and the thickness of the remaining plates is 3mm. The specific design was carried out for the 2-70GHz frequency band, with the following requirements:

[0047] (a) Operating frequency band: 2-70GHz;

[0048] (b) Antenna size: 0.53λ L ×0.4λ L ×0.017λ L (λ L (Low frequency wavelength);

[0049] (c) Return loss: <-10dB.

[0050] The antenna parameters in Example 2 are the same as those in Example 1. The specific parameters are shown in Table 1.

[0051] Solution Analysis and Selection: To achieve a reflection coefficient (S) in the range of 2 to 70 GHz (35:1 relative bandwidth) 11 For performance less than 10dB, a Vivaldi antenna with ultra-wideband impedance characteristics must be selected. However, for the requirements of withstanding harsh environments such as high temperatures and having lower transmission loss, Vivaldi antennas manufactured using PCB technology cannot achieve this. Therefore, only all-metal Vivaldi antennas can be selected.

[0052] The antenna was modeled and simulated in CST STUDIO SUITE 2018. Except for the thickness of metal plate 1, the optimization parameters of the antenna were the same as those in Example 1, as shown in Table 1 (unit: mm).

[0053] Both antenna embodiments can achieve a reflection coefficient (S) in the 2-70 GHz (35:1 relative bandwidth) range. 11 The radiation performance is less than 10dB. For radiation performance, the radiation pattern of Example 1 is relatively stable throughout the entire frequency band, while the radiation pattern of Example 2 has larger sidelobes in the 30-50GHz range.

[0054] The technical effects of the present invention will be described in detail below with reference to simulation.

[0055] This invention utilizes the commercial simulation software CST 2018 to design and simulate a 2-70GHz ultra-wideband, all-metal Vivaldi antenna, and uses Anritsu's MS4647B vector network analyzer to measure the reflection coefficient of the prototype antenna.

[0056] Figure 5 The reflection coefficients (S) of the two types of antennas of this invention are 11 Simulation and measurement were performed, and the results showed that the impedance bandwidth was 35:1 (2-70GHz) and the return loss was greater than 10dB, verifying the antenna's performance.

[0057] Figure 6 The simulation and measurement gain diagrams for the two types of antennas of this invention are shown at typical frequencies. In the frequency range of 2–8 GHz, the gain of both antennas gradually increases from 4.5 dBi to 10 dBi. For the antenna of Example 1, the gain increases slightly above 8 GHz, but remains relatively stable between 8–12 dBi. However, for the antenna of Example 2, the gain is 1–4 dBi lower than that of the antenna of Example 1 in the frequency range of 30–50 GHz. The reason for the reduced gain may be that the thicker tapered plate degrades the radiation pattern within the 30–50 GHz range, such as… Figure 7 As shown in (e) and (k).

[0058] Figure 7The normalized radiation patterns of the two types of antennas of this invention are obtained from simulation and measurement at 2, 4, 10, 20, 40, and 70 GHz. As the frequency increases, the directivity of the radiation pattern becomes stronger, which is consistent with the characteristics of antenna radiation. Furthermore, at each typical frequency point, the measured and simulated radiation patterns match well. For the antenna of Example 1, the radiation pattern does not split at all frequencies, and the sidelobes are relatively low. However, for the antenna of Example 2, relatively high sidelobes exist at ±60° in the radiation pattern at 40 GHz, which affects the gain in the main radiation direction. Therefore, in the frequency range of 30-50 GHz, the gain of Example 2 is 1-4 dB lower than that of Example 1.

[0059] In summary, an ultra-wideband all-metal Vivaldi antenna underwent simulation calculations and testing verification. Adding a tilted slot at the beginning of the exponential curve significantly improves the antenna's impedance performance. The metal plate can be processed using wire cutting technology, resulting in very low cost. It can withstand a wide range of high and low temperature environments. Measurement results show that both antenna types in the two embodiments achieved an ultra-wide impedance bandwidth of 35:1 from 2 to 70 GHz, with a return loss exceeding 10 dB. This antenna has a simple structure, low cost, and ultra-wideband capability, offering significant advantages in ultra-wideband detection and plasma diagnostics.

Claims

1. A 2-70 GHz ultra-wideband, all-metal Vivaldi antenna comprising a metal plate (1), characterized in that, The bottom end of the metal plate (1) is provided with a support base plate (3), and the coaxial connector (2) passes through the support base plate (3) and connects to the metal plate (1). An exponential gradient curve opening (4) is opened on the upper inner side of the metal plate (1), and a matching circle (6) is opened on the lower part of the metal plate (1). An inclined groove (5) is opened on the metal plate (1) between the exponential gradient curve opening (4) and the matching circle (6). The starting end of the exponential gradient curve opening (4) is connected to one end of the inclined groove (5), and the other end of the inclined groove (5) is connected to the matching circle (6). The metal plate (1) has comb-like structures (7) on both sides. The width of the inclined groove (5) is consistent with the width of the starting end of the exponential gradient curve opening (4); The tilt angle of the tilted groove (5) is between 13 and 27°.

2. The 2-70GHz ultra-wideband, all-metal Vivaldi antenna according to claim 1, characterized in that, The thickness of the metal plate (1) is less than half a wavelength of the highest operating frequency.

3. The 2-70GHz ultra-wideband, all-metal Vivaldi antenna according to claim 1, characterized in that, The inner conductor of the coaxial connector (2) contacts the upper surface of one end connected to the inclined groove (5) and the mating circle (6).

4. The 2-70GHz ultra-wideband, all-metal Vivaldi antenna according to claim 1, characterized in that, The vertical distance L from the top of the metal plate (1) to the supporting base plate (3) is 80 mm; the vertical distance L0 from the top of the metal plate (1) to the starting end of the exponential gradient curve opening (4) is 68.25 mm; the vertical distance L1 from the starting end of the inclined groove (5) to the ending end of the inclined groove (5) is 3.6 mm; the horizontal distance L2 from the starting end of the inclined groove (5) to the ending end of the inclined groove (5) is 9.2 mm; the horizontal distance L3 from the starting end of the inclined groove (5) to the center of the matching circle (6) is 12.95 mm; and the width W of the metal plate (1) is... The horizontal distance W0 at the opening of the exponential gradient curve opening (4) is 38mm, the horizontal distance W1 at the starting end of the exponential gradient curve opening (4) is 0.8mm, the support base plate (3) is square with a side length W2 of 90mm, the diameter D0 of the matching circle (6) is 7.5mm, the overall thickness h of the metal plate (1) is 1.5mm, the thickness h1 of the metal plate (1) between the matching circle (6) and the support base plate (3) is 3mm, and the horizontal distance X1 from the inner conductor of the coaxial connector (2) to the matching circle (6) is 4.8mm.

5. The 2-70GHz ultra-wideband, all-metal Vivaldi antenna according to claim 1, characterized in that, The vertical distance L from the top of the metal plate (1) to the supporting base plate (3) is 80 mm; the vertical distance L0 from the top of the metal plate (1) to the starting end of the exponential gradient curve opening (4) is 68.25 mm; the vertical distance L1 from the starting end of the inclined groove (5) to the ending end of the inclined groove (5) is 3.6 mm; the horizontal distance L2 from the starting end of the inclined groove (5) to the ending end of the inclined groove (5) is 9.2 mm; the horizontal distance L3 from the starting end of the inclined groove (5) to the center of the matching circle (6) is 12.95 mm; and the width W of the metal plate (1) is... The horizontal distance W0 at the opening of the exponential gradient curve opening (4) is 38mm, the horizontal distance W1 at the starting end of the exponential gradient curve opening (4) is 0.8mm, the supporting base plate (3) is square, the side length W2 is 90mm, the diameter D0 of the matching circle (6) is 7.5mm, the overall thickness h of the metal plate (1) is 3mm, at the exponential gradient curve opening (4), the thickness of the curved part of the metal plate (1) is 1.5mm, and the horizontal distance X1 from the inner conductor of the coaxial connector (2) to the matching circle (6) is 4.8mm.

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