Ultra-wideband low-profile monopole antenna with composite structure

Abstract

The invention discloses an ultra-wideband low-profile monopole antenna with a composite structure. The ultra-wideband low-profile monopole antenna comprises an antenna radiator, a metal short circuit column, a lumped loading module, a metal floor and a coaxial connector, a coaxial connector is arranged in the center of the metal floor; the coaxial connector is connected with the bottom of the antenna radiator; the antenna radiator is located above the center of the metal floor, a certain distance exists between the bottom of the antenna radiator and the metal floor, the metal short-circuit columns are arranged around the antenna radiator at equal intervals, the bottoms of the metal short-circuit columns are installed on the lumped loading module, and the lumped loading module is located on the metal floor. The antenna has the characteristics of ultra wide band, low profile and omnidirectional radiation.

Description

Technical Field

[0001] The invention belongs to the technical field of antennas, and in particular relates to an ultra-wideband low-profile composite structure monopole antenna. Background Art

[0002] In recent years, with the rapid development of information and communication technology, more and more wireless communication modes have emerged, which require antennas to work simultaneously in multiple frequency bands. However, simply expanding the working frequency band by increasing the number of antennas will not only increase the size of the antenna and complicate the layout, but may also cause coupling effects between multiple antennas, affecting the antenna performance. In this context, ultra-wideband technology has been widely used and has become an effective solution to meet the needs of multi-band operation. Traditional monopole antennas are large in size in low frequency bands (such as 0.1GHz), and their theoretical length can reach 750mm, which limits their application in compact devices. However, the low-profile ultra-wideband monopole antenna has been optimized to significantly reduce its size while maintaining excellent performance. Compared with traditional monopole antennas, low-profile ultra-wideband monopole antennas can significantly shorten the antenna length and meet the requirements of modern communication equipment for miniaturization, high integration and high performance.

[0003] Low-profile monopole antennas need to meet the technical challenges of ultra-wideband impedance matching and stable radiation pattern while meeting the compact size. Common design methods include using gradient radiators, loading matching networks or parasitic elements, etc.

[0004] Among them, the gradient radiator design optimizes the frequency response and impedance matching of the antenna by gradually changing the shape of the antenna's radiator. This design improves the bandwidth, efficiency and directional pattern stability of the antenna by optimizing the current distribution and electromagnetic wave radiation pattern of the antenna structure at different frequencies. Common gradient radiator shapes include linear or nonlinear width changes, such as a tapered structure from narrow to wide, or a V-shaped radiator. This transition design helps to reduce the impedance discontinuity of the antenna at different frequencies, thereby improving the matching performance of the wideband. However, this improvement has certain limitations. For some application scenarios with very high requirements for ultra-wideband, relying solely on gradient radiators may not be able to meet the requirements of sufficiently wide bandwidth, and other design methods need to be combined to further expand the bandwidth.

[0005] Loading technology is a commonly used antenna design method and is widely used in the process of antenna miniaturization. By loading specific structures on the antenna, such as top loading and short-circuit loading, the electrical characteristics of the antenna can be effectively adjusted to achieve size reduction and optimize low-frequency resonance performance. Lumped element loading introduces lumped elements such as inductance, capacitance or resistance into the antenna to optimize its performance by adjusting the electrical characteristics of the antenna. However, whether it is top loading, short-circuit loading or lumped element loading, it will increase the complexity of the antenna structure and may also introduce more parasitic effects and losses, affecting the overall performance of the antenna. Therefore, various factors need to be considered comprehensively.

[0006] The literature Zhao J, Peng T, Chen CC, et al. Low-profile ultra-wideband inverted-hat monopole antenna for 50MHz–2GHz operation [J]. Electronics letters, 2009, 45 (3): 142-144. introduces a new low-profile ultra-wideband (UWB) monopole antenna for the frequency range of 50MHz to 2GHz. The antenna consists of two elliptical segments, a larger ellipse at the top and a smaller ellipse at the bottom. The entire structure is similar to an inverted hat. This design effectively reduces the electrical size of the antenna. The antenna profile height is only λ / 39, the relative bandwidth reaches 190%, and the antenna gain ranges from -25 to 5dBi. However, the highest frequency of the antenna can only reach 2GHz and cannot cover a higher frequency range.

[0007] Reference B.-l.Jia, Y.-j.Zhao and L.Xing,"Ultra-wideband monopole antenna with lumped elements,"2017Sixth Asia-Pacific Conference on Antennas and Propagation (APCAP), Xi'an, China, 2017, pp.1-3, doi:10.1109 / APCAP.2017.8420572. introduces an ultra-wideband monopole antenna, which realizes broadband impedance characteristics by loading lumped resistance and inductance elements at appropriate positions of the antenna and loading a disk on the top. The lumped element loading and top loading structure enable it to operate in the ultra-wideband range of 20MHz to 4GHz, with a relative bandwidth of 198%. The maximum gain of the antenna ranges from -20 to 15dBi, but the profile height is λ / 15, which is still relatively high.

[0008] Reference K.Keum and J.Choi,"An Electrically Small Top-Loaded Mono-Cone Antenna with Ring Slot,"2020 International Symposium on Antennas and Propagation (ISAP), Osaka, Japan, 2021, pp. 555-556, doi: 10.23919 / ISAP47053.2021.9391470. This paper introduces an electrically small top-loaded mono-cone antenna with a height of 49.53 mm. The main radiator is a mono-cone structure with a circular ring structure introduced on the top, and grounded short-circuit pins and cylinders are introduced on the mono-cone and circular ring structures, respectively. The antenna is miniaturized by the grounded short-circuit pin cylinder. The antenna has a cross-sectional height of λ / 11 and operates in the frequency range of 0.52 GHz to 1.74 GHz with a relative bandwidth of 107%. However, the antenna has a narrow bandwidth and cannot cover more frequency bands.

[0009] In summary, when traditional monopole antennas are used to achieve ultra-wideband coverage, they are large in size, have poor directional pattern stability, and have limited bandwidth expansion, making it difficult to meet the needs of modern communication equipment for miniaturization, high performance, and multi-band coverage. Antenna miniaturization, ultra-wideband, and high gain affect and restrict each other, and it is difficult to meet all three requirements at the same time. How to make the antenna ultra-wideband and miniaturized while ensuring the antenna gain is the main research direction and breakthrough point. Summary of the invention

[0010] In order to overcome the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a composite structure monopole antenna, which has the characteristics of ultra-wideband, low profile and omnidirectional radiation.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] An ultra-wideband low-profile composite structure monopole antenna, comprising an antenna radiator, a metal short-circuit post, a lumped loading module, a metal floor and a coaxial connector;

[0013] The lumped loading module includes a plurality of microstrip lines connected in series with resistors and inductors, a microstrip line at one end of the series structure is connected to the antenna radiator through the metal short-circuit post, and a microstrip line at the other end of the series structure is connected to the metal floor;

[0014] The outer shaft of the coaxial connector is connected to the metal floor, and the inner shaft is connected to the antenna radiator.

[0015] The antenna radiator is located directly above the metal floor, and the outline of the vertical cross section of the antenna radiator is a combined curve, including a cone structure formed by a linear curve and a disk structure formed by an elliptical curve, and the top edge of the cone structure and the bottom edge of the disk structure are spliced ​​and connected.

[0016] A circular ring structure is provided at the top of the antenna radiator extending outward by 7 mm to 8 mm, connected to the antenna radiator, and the top of the metal short-circuit post is in contact with the outer side of the circular ring structure;

[0017] The antenna radiator is a hollow structure, and the antenna radiator and the ring structure are made of the same material.

[0018] The antenna radiator is coaxially arranged with the metal floor.

[0019] The metal short-circuit posts are evenly distributed in four groups in a centrally symmetrical distribution, and the metal short-circuit posts are arranged in a vertical rotation around the center of the antenna radiator.

[0020] The lumped loading module includes a dielectric plate, a rectangular microstrip line, a circular cross-section metallized through hole, a resistor and an inductor;

[0021] The dielectric board is arranged with rectangular microstrip lines and circular cross-section metallized through holes, the circular cross-section metallized through holes are located on the rectangular microstrip lines, presenting an N-row periodic arrangement structure to ensure the grounding of the lumped loading module; N is greater than or equal to 1;

[0022] The resistor and the inductor are in a series circuit structure, and the microstrip lines are in three groups of rectangular horizontal arrangements with intervals less than 2 mm.

[0023] A coaxial connector located at the center of the metal floor is fed, and the inner conductor of the coaxial connector passes through the metal floor and is connected to the antenna radiator;

[0024] The metal floor has a central hole through which the inner conductor of the coaxial connector can pass.

[0025] The coaxial connector is located at the center of the metal floor, and the inner conductor of the coaxial connector is connected to the antenna radiator through the aperture position of the metal floor.

[0026] The ultra-wideband low-profile composite structure monopole antenna is used in radar detection, Sub-6GHz communication and industrial Internet of Things.

[0027] The ultra-wideband low-profile composite structure monopole antenna is used in a 0.1G to 6GHz operating frequency band.

[0028] Beneficial effects of the present invention:

[0029] The present invention can effectively broaden the antenna bandwidth, and through short-circuit post loading and top loading, the current distribution is changed without changing the physical height of the antenna, and the equivalent impedance of the antenna is indirectly adjusted, so that it can cover a wider communication frequency band and maintain a lower profile height. The present invention is suitable for scenarios requiring miniaturized equipment, high-frequency coverage, and wide-bandwidth.

[0030] Through the structure of the present invention, miniaturization is ensured by a low-profile monopole structure design, and loading is used to compensate for impedance changes caused by antenna miniaturization, thereby ensuring good signal transmission between the antenna and the transmission line, providing better gain and lower standing wave ratio.

[0031] The present invention is applied to low-profile monopole antennas in the 0.1G to 6GHz operating frequency band, and has significant performance improvements, especially in the low-frequency bandwidth. The antenna structure adopts a special profile structure combination, and through the short-circuit column loading and lumped loading design, it is equivalent to adding a specific impedance element to the antenna circuit, which can adjust the input impedance of the antenna to match the impedance of the coaxial feeder, reduce signal reflection, and improve the impedance matching of the antenna in different frequency bands, so that the working performance of the antenna within the frequency band is effectively optimized, especially in the matching effect and radiation directivity within the 0.1G to 6GHz frequency band, and maintain a relatively uniform omnidirectional radiation mode within a wider frequency band.

[0032] The antenna structure of the present invention is relatively simple, easy to manufacture, and has a low cost. Compared with the traditional monopole antenna design, the low-profile monopole antenna of the present invention improves performance while reducing space occupation, making it very suitable for compact, high-performance small wireless devices and systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the present invention.

[0034] Figure 2 It is a side view of the antenna radiator of the present invention.

[0035] Figure 3 It is a schematic diagram of the lumped loading module of the present invention.

[0036] Figure 4 It is the 0.1-2 GHz standing wave ratio of the present invention.

[0037] Figure 5 It is the 2-6 GHz standing wave ratio of the present invention.

[0038] Figure 6 This is the maximum gain diagram of the horizontal plane in the range of 0.1 to 2 GHz of the present invention.

[0039] Figure 7This is the maximum gain diagram of the horizontal plane from 2 to 6 GHz of the present invention.

[0040] Figure 8 This is the 0.1 GHz radiation pattern of the present invention.

[0041] Fig. 9 This is the 0.6 GHz radiation pattern of the present invention.

[0042] Fig.10 This is the 1 GHz radiation pattern of the present invention.

[0043] Fig.11 This is the 2 GHz radiation pattern of the present invention.

[0044] Fig.12 This is the 4 GHz radiation pattern of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0046] The present invention can be applied in fields such as radar detection, Sub-6GHz communication and industrial Internet of Things.

[0047] The present invention designs a composite structure low-profile antenna with omnidirectional radiation characteristics that needs to cover an ultra-wide frequency band of 0.1 GHz to 6 GHz in a compact space of 300 mm in diameter and 150 mm in height, which can take into account both miniaturization and stable performance. By changing the contour shape of the monopole, top loading, short-circuit column loading, and lumped loading,

[0048] The present invention proposes an ultra-wideband composite structure low-profile monopole antenna. The antenna size is small, and its profile height is only 142mm (λ / 21). The bandwidth coverage ratio can reach more than 1:60, the relative bandwidth reaches 193%, and the radiation pattern presents omnidirectional radiation characteristics. The present invention is very suitable for small communication and detection equipment, and Internet of Things terminals. It meets the design requirements of miniaturization and high performance while achieving ultra-wideband coverage, and provides a solution for wireless communication systems.

[0049] Example

[0050] like Figure 1-Figure 3 As shown, a low-profile ultra-wideband monopole antenna is mainly composed of five parts, which are, from top to bottom, an antenna radiator 1, a metal short-circuit post 2, a lumped loading module 3, a metal floor 4 and a coaxial connector 5.

[0051] The overall size is 304.8mm*304.8mm*142mm, and the antenna frequency band is 0.1~6GHz.

[0052] Furthermore, the antenna radiator 1 is located above the center of the metal floor 4 and at a distance of 4 mm. The antenna radiator 1 is the main radiation structure of the antenna. The profile of the vertical cross section of the antenna radiator 1 is a combination curve, that is, it is composed of a linear curve and an elliptical curve. The combination of curves of different shapes can change the input impedance characteristics of the antenna, so that it can achieve better impedance matching in a wider frequency band. At the same time, a ring structure is loaded on the top to increase the current path while connecting the antenna radiator 1 and the metal short-circuit column 2.

[0053] The slope of the linear curve is 1.03, the z-axis is perpendicular to the metal floor, and the length of the linear curve projected on the z-axis is 66 mm.

[0054] The semi-major axis of the elliptic curve is a=79mm, and the semi-minor axis is b=72mm.

[0055] Furthermore, the metal short-circuit posts 2 are arranged in a rotational manner around the center of the antenna radiator 1 and are evenly distributed in four groups in a circularly symmetrical distribution. The metal short-circuit posts 2 are cylinders with a diameter of 3 mm, and connect the antenna radiator 1 with the lumped loading module 3 .

[0056] Furthermore, the lumped loading modules 3 are located on the metal floor 4 and are also arranged in four groups around the center of the antenna radiator 1 in a circularly symmetrical distribution.

[0057] The lumped loading module 3 includes a dielectric plate 301, a rectangular microstrip line 302, a circular cross-section metallized through hole 303, a resistor 304 and an inductor 305;

[0058] The dielectric plate 301 is a FR4 dielectric plate with a dielectric constant of 4.4 and a thickness of 1.5 mm. A rectangular microstrip line 302 and a circular cross-section metallized through hole 303 are arranged on the dielectric plate 301. The circular cross-section metallized through hole 303 is located on the rectangular microstrip line 302 and presents a 4-row periodic arrangement structure to ensure that the lumped loading module 3 is grounded.

[0059] The resistor 304 and the inductor 305 are connected in series on the microstrip line 302. The microstrip line 302 is three groups of rectangles arranged horizontally with an interval of 1.25 mm.

[0060] Furthermore, the metal floor 4 has a central hole so that the inner conductor of the coaxial connector 5 can pass through.

[0061] Furthermore, the coaxial connector 5 is located at the center of the metal floor 4 , and the inner conductor of the coaxial connector 5 is connected to the antenna radiator 1 through the aperture position of the metal floor 4 .

[0062] Working principle of the present invention:

[0063] The antenna of the present invention adopts 50Ω coaxial center feeding, changes the contour shape of the monopole, and its current distribution is adjusted with the change of frequency, so that the input impedance of the antenna changes more smoothly in a wider frequency range, thereby effectively widening the working bandwidth of the antenna and reducing the profile height of the antenna.

[0064] The top loading thin ring increases the electrical length of the antenna, increases the current flow path, reduces the antenna's resonant frequency, and expands the low-frequency bandwidth. At the same time, through the short-circuit column and lumped element loading, the current distribution on the antenna changes, thereby changing the impedance of the antenna at low frequency, achieving impedance matching, and enabling the antenna to work in the low-frequency range.

[0065] Figure 4 and Figure 5 It is the standing wave ratio curve of the antenna of the present invention. The antenna can cover an ultra-wide frequency range of 0.1 to 6 GHz, and achieves a standing wave characteristic of VSWR (voltage standing wave ratio) lower than 3 in the entire frequency band, and can effectively transmit energy and reduce reflection loss.

[0066] Figure 6 , Figure 7 The horizontal plane gain curve of the antenna of the present invention shows that in the low frequency band of 0.1 to 1.2 GHz, the maximum horizontal plane gain of the antenna is greater than -20 dBi, and in the high frequency band of 1.2 to 6 GHz, the maximum horizontal plane gain of the antenna reaches the range of 0 to 6 dBi. The antenna of the present invention has a lower gain in the low frequency band, but meets the actual needs. The high frequency band has a higher gain and can meet the wireless applications of different frequency bands and different communication needs. Figures 8 to 12 The radiation patterns of the present invention in the horizontal and vertical planes at some frequencies are shown. It can be seen that the antenna exhibits omnidirectional radiation characteristics in the full frequency band.

[0067] like Figure 8 As shown, the curve in the horizontal direction (XOY plane) is circular, and the curve in the vertical direction (XOZ plane) is roughly in the shape of an "8", and the gain value changes at each angle are relatively small, and the signal can be radiated more evenly in all directions.

[0068] Figures 9 and 10 , the curves of the XOY and XOZ planes are relatively regular. Overall, the radiation uniformity can be maintained, indicating that the antenna has good omnidirectional radiation characteristics at low frequencies.

[0069] Figure 11 to Figure 12 , the curve shape becomes complicated in the vertical direction (XOZ plane), but it does not fluctuate much in the horizontal direction (XOY plane), and can maintain basic uniform radiation characteristics, indicating that the antenna can still maintain omnidirectionality under high frequency conditions.

Claims

1. An ultra-wideband low-profile composite structure monopole antenna, characterized in that: It comprises an antenna radiator (1), a metal short-circuit post (2), a lumped loading module (3), a metal floor (4) and a coaxial connector (5); The lumped loading module (3) includes a plurality of microstrip lines (302) connected in series with a resistor (304) and an inductor (305), wherein a microstrip line (302) at one end of the series structure is connected to the antenna radiator (1) through the metal short-circuit column (2), and a microstrip line (302) at the other end of the series structure is connected to the metal floor (4); The outer axis of the coaxial connector (5) is connected to the metal floor (4), and the inner axis is connected to the antenna radiator (1).

2. The ultra-wideband low-profile composite structure monopole antenna according to claim 1, characterized in that: The antenna radiator (1) is located directly above the metal floor (4); the profile of the vertical cross section of the antenna radiator (1) is a combined curve, including a cone structure (6) formed by a linear curve and a disk structure (7) formed by an elliptical curve; the top edge of the cone structure (6) and the bottom edge of the disk structure (7) are spliced ​​and connected.

3. The ultra-wideband low-profile composite structure monopole antenna according to claim 1, characterized in that: The top of the antenna radiator (1) extends outward by 7 mm to 8 mm to form a circular ring structure connected to the antenna radiator (1), and the top of the metal short-circuit column (2) contacts the outside of the circular ring structure.

4. The ultra-wideband low-profile composite structure monopole antenna according to claim 3, characterized in that: The antenna radiator (1) is a hollow structure, and the antenna radiator (1) and the circular ring structure are made of the same material.

5. The ultra-wideband low-profile composite structure monopole antenna according to claim 1, characterized in that: The antenna radiator (1) is coaxially arranged with the center of the metal floor (4); The metal short-circuit posts (2) are evenly distributed in four groups in a centrally symmetrical distribution, and the metal short-circuit posts (2) are arranged in a vertical rotation around the center of the antenna radiator (1).

6. The ultra-wideband low-profile composite structure monopole antenna according to claim 1, characterized in that: The lumped loading module (3) comprises a dielectric plate (301), a rectangular microstrip line (302), a circular cross-section metallized through hole (303), a resistor (304) and an inductor (305); A rectangular microstrip line (302) and a circular cross-section metallized through hole (303) are arranged on the dielectric plate (301); the circular cross-section metallized through hole (303) is located on the rectangular microstrip line (302) and presents an N-row periodic arrangement structure to ensure that the grounding N of the lumped loading module (3) is greater than or equal to 1.

7. The ultra-wideband low-profile composite structure monopole antenna according to claim 6, characterized in that: The resistor (304) and the inductor (305) are in a series circuit structure, and the microstrip line (302) is in three groups of rectangular horizontal arrangements with intervals less than 2 mm.

8. The ultra-wideband low-profile composite structure monopole antenna according to claim 1, characterized in that: A coaxial connector (5) located at the center of the metal floor (4) is fed, and an inner conductor of the coaxial connector (5) passes through the metal floor (4) and is connected to the antenna radiator (1); The metal floor (4) has a central hole, so that the inner conductor of the coaxial connector (5) can pass through.

9. Application of an ultra-wideband low-profile composite structure monopole antenna according to any one of claims 1 to 8, characterized in that: The ultra-wideband low-profile composite structure monopole antenna is used in radar detection, Sub-6GHz communication and industrial Internet of Things.

10. The use according to claim 9, characterized in that: The ultra-wideband low-profile composite structure monopole antenna is used in a 0.1G to 6GHz operating frequency band.

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