Ultra-wideband low-profile composite structure monopole antenna

Abstract

The application discloses a kind of ultra-wideband low profile composite structure monopole antenna, including antenna radiator, metal short-circuit column, lumped loading module, metal floor and coaxial connector;The center position of the metal floor is provided with coaxial connector;Coaxial connector is connected with the bottom of antenna radiator;The antenna radiator is located above the center of metal floor and there is a certain spacing between the bottom and the metal floor, metal short-circuit column is set at equal intervals around the antenna radiator, and the bottom of metal short-circuit column is installed on the lumped loading module, and the lumped loading module is located on the metal floor.The application has the characteristics of ultra-wideband, low profile and omnidirectional radiation.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically relating to an ultra-wideband low-profile composite structure monopole antenna. Background Technology

[0002] In recent years, with the rapid development of information and communication technologies, more and more wireless communication modes have emerged, requiring antennas to operate simultaneously in multiple frequency bands. However, simply increasing the number of antennas to expand the operating frequency band not only leads to increased antenna size and complex layout, but may also cause coupling effects between multiple antennas, affecting antenna performance. Against this backdrop, ultra-wideband technology has been widely applied, becoming an effective solution to address the need for multi-band operation. Traditional monopole antennas are relatively large in low-frequency bands (e.g., 0.1 GHz), with a theoretical length reaching 750 mm, which limits their application in compact devices. However, low-profile ultra-wideband monopole antennas, through optimized design, significantly reduce size while maintaining excellent performance. Compared to traditional monopole antennas, low-profile ultra-wideband monopole antennas can substantially shorten antenna length, meeting the demands of modern communication equipment for miniaturization, high integration, and high performance.

[0003] Low-profile monopole antennas, while meeting the requirement of compact size, need to address technical challenges such as ultra-wideband impedance matching and stable radiation patterns. Common design methods include using graded radiators, adding matching networks, or parasitic elements.

[0004] Graded radiator design optimizes an antenna's frequency response and impedance matching by gradually changing the shape of its radiator. This design improves bandwidth, efficiency, and pattern stability by optimizing the current distribution and electromagnetic radiation patterns of the antenna structure at different frequencies. Common graded radiator shapes include linear or nonlinear width variations, such as a tapered structure that transitions from narrow to wide, or a V-shaped radiator. This transitional design helps reduce impedance discontinuities at different frequencies, thereby improving wideband matching performance. However, this improvement has limitations. For some applications with very high ultra-wideband requirements, graded radiators alone may not meet sufficiently wide bandwidth needs, requiring the combination of other design methods to further extend the bandwidth.

[0005] Loading techniques are a common antenna design method widely used in antenna miniaturization. By loading specific structures onto the antenna, such as top loading and short-circuit loading, the antenna's electrical characteristics can be effectively adjusted, achieving size reduction and optimizing low-frequency resonant performance. Lumped element loading introduces lumped elements such as inductors, capacitors, or resistors into the antenna, adjusting its electrical characteristics to optimize performance. However, whether top loading, short-circuit loading, or lumped element loading, all increase the complexity of the antenna structure and may introduce more parasitic effects and losses, affecting the overall performance of the antenna. Therefore, a comprehensive consideration of various factors is necessary.

[0006] The paper 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 novel 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, with the overall structure resembling an inverted hat. This design effectively reduces the antenna's electrical size, with a profile height of only λ / 39, a relative bandwidth of 190%, and an antenna gain from -25 to 5dBi. However, the antenna's highest frequency can only reach 2GHz, failing to cover a higher frequency range.

[0007] The paper B.-l. Jia, Y.-j. Zhao and L. Xing, "Ultra-wideband monopole antenna with lumped elements," 2017 Sixth 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 that achieves wideband impedance characteristics by loading lumped resistive and inductive elements at appropriate locations on the antenna and a disk loaded on top. The lumped element loading and top-loading structure enables it to operate in the ultra-wideband range of 20MHz to 4GHz, achieving a relative bandwidth of 198%, and a maximum antenna gain from -20 to 15dBi, although the profile height of λ / 15 is still relatively high.

[0008] The literature 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, introduces an electrically small top-loaded mono-cone antenna with a height of 49.53 mm. The main radiator is a monocone structure with a ring structure at the top. Grounded short-circuit pins and cylinders are introduced on the monocone and ring structures, respectively. The antenna achieves miniaturization through the grounded short-circuit pins and cylinders. The antenna profile height is λ / 11, and it operates in the frequency range of 0.52 GHz to 1.74 GHz with a relative bandwidth of 107%. However, this antenna suffers from a relatively narrow bandwidth, limiting its coverage to a wider range of frequencies.

[0009] In summary, traditional monopole antennas, when achieving ultra-wideband coverage, suffer from large size, poor pattern stability, and limited bandwidth expansion, making it difficult to meet the demands of modern communication equipment for miniaturization, high performance, and multi-band coverage. Antenna miniaturization, ultra-wideband coverage, and high gain are mutually influential and restrictive, making it challenging to simultaneously satisfy all three. Therefore, achieving both ultra-wideband coverage and miniaturization while maintaining antenna gain is the main research direction and breakthrough point. Summary of the Invention

[0010] In order to overcome the shortcomings of the existing technology, the present invention aims to provide a composite structure monopole antenna, which has the characteristics of ultra-wideband, low profile and omnidirectional radiation.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] An ultra-wideband low-profile composite monopole antenna includes an antenna radiator, a metal short-circuit post, a lumped loading module, a metal ground plane, and a coaxial connector.

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

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

[0015] The antenna radiator is located directly above the metal floor. The outline of the vertical cross-section of the antenna radiator is a composite curve, including a conical structure composed of linear curves and a disk structure composed of elliptical curves. The top edge of the conical structure and the bottom edge of the disk structure are spliced ​​together.

[0016] A circular ring structure is provided 7mm to 8mm outward from the top of the antenna radiator and connected to the antenna radiator. 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, arranged in a centrally symmetrical manner, and are arranged in a vertically rotating manner around the center of the antenna radiator.

[0020] The lumped loading module includes a dielectric substrate, a rectangular microstrip line, a circular cross-section metallized via, a resistor, and an inductor.

[0021] The dielectric substrate has rectangular microstrip lines and circular cross-section metallized vias arranged on it. The circular cross-section metallized vias are located on the cuboid microstrip lines and are arranged in an N-column periodic pattern to ensure that the lumped loading module is grounded; N is greater than or equal to 1.

[0022] The resistors and inductors are in series circuit structure, and the microstrip lines are arranged in three groups of rectangles with a spacing of less than 2mm in horizontal alignment.

[0023] The coaxial connector located at the center of the metal floor is used for power supply, and the inner conductor of the coaxial connector passes through the metal floor and connects to the antenna radiator.

[0024] The metal floor has a central perforation, allowing the inner conductor of the coaxial connector to pass through.

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

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

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

[0028] The beneficial effects of this invention are:

[0029] This invention effectively broadens antenna bandwidth by altering the current distribution through short-circuit post loading and top loading, without changing the antenna's physical height. This indirectly adjusts the antenna's equivalent impedance, enabling it to cover a wider communication frequency band while maintaining a low profile. This invention is suitable for scenarios requiring miniaturized devices, high-frequency coverage, and wideband capabilities.

[0030] The structure of this invention ensures miniaturization through a low-profile monopole structure design, while using a loading method to compensate for impedance changes caused by antenna miniaturization, ensuring good signal transmission between the antenna and the transmission line, and providing better gain and lower VSWR.

[0031] This invention relates to a low-profile monopole antenna operating in the 0.1 GHz to 6 GHz frequency band, exhibiting significant performance improvements, particularly in low-frequency bandwidth. The antenna structure employs a unique profile combination, utilizing short-circuit post loading and lumped loading designs, effectively adding specific impedance elements to the antenna circuit. This allows for adjustment of the antenna's input impedance to match the impedance of the coaxial feed line, reducing signal reflection and improving impedance matching across different frequency bands. Consequently, the antenna's performance across the frequency range is effectively optimized, especially in terms of matching effect and radiation directivity within the 0.1 GHz to 6 GHz band, maintaining a relatively uniform omnidirectional radiation pattern over a wide frequency range.

[0032] The antenna structure of this invention is relatively simple, easy to manufacture, and has a low cost. Compared with traditional monopole antenna designs, the low-profile monopole antenna of this invention improves performance while reducing space occupation, making it very suitable for compact, high-performance small wireless devices and systems. Attached Figure Description

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

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

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

[0036] Figure 4 The VSWR of this invention is 0.1 to 2 GHz.

[0037] Figure 5 The VSWR of this invention is 2-6 GHz.

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

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

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

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

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

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

[0044] Figure 12 This is the 4GHz radiation pattern of the present invention. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings.

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

[0047] This invention designs a low-profile composite antenna with omnidirectional radiation characteristics within a compact space of 300mm in diameter and 150mm in height, capable of covering an ultra-wide frequency band from 0.1GHz to 6GHz, thus balancing miniaturization and stable performance in various scenarios. This is achieved by modifying the monopole's profile shape, top loading, short-circuit post loading, and lumped loading.

[0048] This invention proposes an ultra-wideband composite low-profile monopole antenna. The antenna is small in size, with a profile height of only 142 mm (λ / 21), achieving a bandwidth coverage ratio of over 1:60 and a relative bandwidth of 193%, exhibiting omnidirectional radiation characteristics. This invention is highly suitable for small communication and detection devices and IoT terminals, achieving ultra-wideband coverage while meeting the design requirements of miniaturization and high performance, providing a solution for wireless communication systems.

[0049] Example

[0050] like Figures 1-3 As shown, a low-profile ultra-wideband monopole antenna mainly consists of five parts, from top to bottom: antenna radiator 1, metal short-circuit post 2, lumped loading module 3, metal ground plane 4, and coaxial connector 5.

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

[0052] Furthermore, the antenna radiator 1 is located 4mm above the center of the metal floor 4. The antenna radiator 1 is the main radiating structure of the antenna. The profile of its vertical cross-section is a composite curve, consisting of linear and elliptical curves. Combinations of different curve shapes can alter the antenna's input impedance characteristics, enabling better impedance matching over a wider frequency range. Simultaneously, a circular ring structure is loaded at the top, increasing the current path while connecting the antenna radiator 1 and the metal shorting post 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 onto the z-axis is 66mm.

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

[0055] Furthermore, the metal short-circuit posts 2 are arranged in a rotating pattern 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 3mm, connecting the antenna radiator 1 and the lumped loading module 3.

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

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

[0058] The dielectric substrate 301 is an FR4 dielectric substrate with a dielectric constant of 4.4 and a thickness of 1.5 mm. Rectangular microstrip lines 302 and circular cross-section metallized vias 303 are arranged on the dielectric substrate 301. The circular cross-section metallized vias 303 are located on the cuboid microstrip lines 302 and are arranged in a 4-column periodic arrangement to ensure that the lumped loading module 3 is grounded.

[0059] Resistor 304 and inductor 305 are connected in series on microstrip line 302, which consists of three groups of rectangular horizontally arranged lines spaced 1.25 mm apart.

[0060] Furthermore, the metal floor 4 has a central perforation, allowing the inner conductor of the coaxial connector 5 to pass through.

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

[0062] Working principle of the invention:

[0063] The antenna of this invention uses a 50Ω coaxial center feed and changes the profile shape of the monopole. Its current distribution will be adjusted with the frequency, so that the input impedance of the antenna changes more smoothly over a wider frequency range, thereby effectively widening the antenna's operating bandwidth and reducing the antenna profile height.

[0064] The top-loaded thin circular ring increases the antenna's electrical length, expands the current flow path, lowers the antenna's resonant frequency, and extends the low-frequency bandwidth. Simultaneously, the loading through short-circuit posts and lumped elements alters the current distribution on the antenna, thereby changing its impedance at low frequencies, achieving impedance matching, and enabling the antenna to operate in the low-frequency range.

[0065] Figure 4 and Figure 5 This is the standing wave ratio (VSWR) 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 VSWR of less than 3 throughout the entire frequency band, which can effectively transmit energy and reduce reflection loss.

[0066] Figure 6 , Figure 7 This is the horizontal gain curve of the antenna of the present invention. In the low-frequency band of 0.1–1.2 GHz, the maximum horizontal gain of the antenna is greater than -20 dBi. In the high-frequency band of 1.2–6 GHz, the maximum horizontal gain of the antenna reaches the range of 0–6 dBi. The antenna of the present invention has lower gain in the low-frequency band, but it meets practical requirements. It has higher gain in the high-frequency band, which can meet the needs of wireless applications with different frequency bands and different communication requirements. Figures 8 to 12 The radiation patterns of the present invention in the horizontal and vertical planes at certain frequencies are shown. It can be seen that the antenna exhibits omnidirectional radiation characteristics across the entire 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 shaped like an "8". The gain value changes relatively little at various angles, and it can radiate signals relatively uniformly in all directions.

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

[0069] Figures 11 to 12 The curve shape becomes complex in the vertical direction (XOZ plane), but the fluctuations are not significant in the horizontal direction (XOY plane), and it can maintain basic uniform radiation characteristics, indicating that the antenna can still maintain omnidirectionality at high frequencies.

Claims

1. A super-wideband low-profile composite monopole antenna, characterized in that, It includes an antenna radiator (1), a metal short-circuit post (2), a lumped loading module (3), a metal ground plane (4), and a coaxial connector (5); The lumped loading module (3) includes several microstrip lines (302) connected in series with resistors (304) and inductors (305). One microstrip line (302) at one end of the series structure is connected to the antenna radiator (1) through the metal short-circuit post (2), and the other microstrip line (302) at the other end of the series structure is connected to the metal ground plane (4). The outer shaft of the coaxial connector (5) is connected to the metal ground plate (4), and the inner shaft is connected to the antenna radiator (1). The antenna radiator (1) is located directly above the metal floor (4). The outline of the vertical cross section of the antenna radiator (1) is a composite curve, including a conical structure (6) composed of linear curves and a disk structure (7) composed of elliptical curves. The top edge of the conical structure (6) and the bottom edge of the disk structure (7) are spliced ​​together. 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 4 groups, and are centrally symmetrically distributed. The metal short-circuit posts (2) are arranged vertically and rotate around the center of the antenna radiator (1). The lumped loading module (3) is located on the metal floor (4), and is arranged in four groups around the center of the antenna radiator (1) in a circular symmetrical distribution. The lumped loading module (3) includes a dielectric substrate (301), a rectangular microstrip line (302), a circular cross-section metallized via (303), a resistor (304), and an inductor (305). A rectangular microstrip line (302) and a circular cross-section metallized via (303) are arranged on the dielectric substrate (301). The circular cross-section metallized via (303) is located on the cuboid microstrip line (302) and presents an N-column periodic arrangement structure to ensure that the grounding N of the lumped loading module (3) is greater than or equal to 1.

2. The ultra-wideband low-profile composite monopole antenna according to claim 1, characterized in that, The antenna radiator (1) extends outward by 7mm~8mm from the top and is provided with a circular structure, which is connected to the antenna radiator (1). The top of the metal short-circuit post (2) is in contact with the outer side of the circular structure.

3. The ultra-wideband low-profile composite monopole antenna according to claim 2, characterized in that, The antenna radiator (1) is a hollow structure, and the antenna radiator (1) and the ring structure are made of the same material.

4. The ultra-wideband low-profile composite monopole antenna according to claim 1, characterized in that, The resistor (304) and inductor (305) are in series circuit structure, and the microstrip line (302) is arranged in three groups of rectangles with a spacing of less than 2mm.

5. The ultra-wideband low-profile composite monopole antenna according to claim 1, characterized in that, The coaxial connector (5) located at the center of the metal floor (4) is powered, and the inner conductor of the coaxial connector (5) passes through the metal floor (4) and connects to the antenna radiator (1); The metal floor (4) has a central perforation, allowing the inner conductor of the coaxial connector (5) to pass through.

6. The application of an ultra-wideband low-profile composite structure monopole antenna according to any one of claims 1-5, characterized in that, The ultra-wideband low-profile composite monopole antenna is used in radar detection, Sub-6GHz communication, and industrial IoT.

7. The application according to claim 6, characterized in that, The ultra-wideband low-profile composite structure monopole antenna is used in the 0.1G~6GHz operating frequency band.

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