A broadband elliptic cylindrical omnidirectional antenna coupled to a feed

Abstract

The application relates to a broadband elliptic cylindrical omnidirectional antenna coupled with a feeder, which comprises an elliptic metal sheet, an elliptic dielectric tube, a rectangular dielectric plate and an elliptic metal sleeve; wherein the outer surface of the elliptic dielectric tube is attached with a radiation patch, a short-circuit branch and a matching resistor, and the elliptic dielectric tube is vertically fixed on a metal base; a coupling strip line is printed on the dielectric plate and located inside the hollow elliptic dielectric tube, and the coupling strip line and the short-circuit branch jointly form a feeding balun; the elliptic metal sleeve is located between the elliptic dielectric tube and an elliptic antenna cover, and is connected with the metal base. The application can be used in an airborne environment, realizes broadband matching of an airborne ultrashort wave antenna, improves the gain of the low-frequency band of the antenna, improves the non-circularity of the high-frequency directional diagram, and improves the communication distance and stability of an airborne ultrashort wave communication system.

Description

Technical Field

[0001] This invention belongs to the field of ultra-shortwave antenna technology, and particularly relates to an airborne ultra-shortwave broadband omnidirectional antenna. Background Technology

[0002] Airborne antennas are conversion devices used for electromagnetic energy exchange between aircraft systems and other systems, and are an integral part of the aircraft's communication system. The quality of airborne antennas determines the quality of the entire communication system, making the study of airborne antennas of great significance.

[0003] Due to the requirements of the carrier's flight performance and structural performance, airborne antennas are mostly planar printed antennas, often shaped like airfoils, to avoid affecting the aerodynamic performance of the carrier aircraft. When considering the antenna's electrical performance, such as standing wave ratio and gain, the antenna height should also be minimized.

[0004] In existing technologies, most broadband omnidirectional antennas are designed using a blade antenna. To reduce antenna height, resistive loading is often employed. Appropriate resistive loading can effectively broaden the antenna's operating bandwidth, but it also introduces some gain loss. The well-known Type 506-3 airborne VHF antenna exhibits low low-frequency gain (only -9 dBi) after resistive loading, and also suffers from significant non-circularity, reducing the system's communication stability.

[0005] In summary, existing airborne antennas suffer from significant gain loss when using resistive loading to achieve broadband impedance matching, and the planar structure results in a large non-circularity of the horizontal radiation pattern, making it difficult to meet the application requirements of complex aircraft operating attitudes. Summary of the Invention

[0006] Technical problems to be solved

[0007] To overcome the shortcomings of existing technologies, this invention provides a vertically polarized airborne omnidirectional antenna with low height, wide bandwidth, high efficiency (high gain), and low non-circularity. This invention can be used in airborne environments to achieve broadband matching of airborne VHF antennas, improve the gain of the antenna in the low-frequency band, improve the non-circularity of the high-frequency radiation pattern, and enhance the communication distance and stability of airborne VHF communication systems.

[0008] Technical solution

[0009] A coupled-fed broadband elliptical cylindrical omnidirectional antenna is characterized by comprising an elliptical metal sheet, an elliptical dielectric tube, a rectangular dielectric plate, an elliptical radome, an elliptical metal sleeve, a metal base, and a coaxial RF connector; the elliptical metal sheet is located at the top of the antenna and contacts the top of the elliptical radome; the elliptical dielectric tube, the rectangular dielectric plate, and the elliptical metal sleeve are all located inside the elliptical radome, with the rectangular dielectric plate located inside the elliptical dielectric tube and the elliptical metal sleeve located outside the elliptical dielectric tube; the outer surface of the elliptical dielectric tube is covered with a radiating patch, a short-circuit stub, and a matching resistor; the rectangular dielectric plate is printed with a coupling feed line and is electrically connected to the coaxial RF connector; the elliptical dielectric tube, the rectangular dielectric plate, the elliptical metal sleeve, and the coaxial RF connector are all fixed on the metal base.

[0010] A further technical solution of the present invention: the elliptical metal sheet is an elliptical thin sheet, which is electrically connected to the top of the radiating patch.

[0011] A further technical solution of the present invention: when the radiating patch is unfolded, it is a thin metal sheet, divided into three segments, and each segment has a chamfer at the adjacent vertices; the upper part of the upper segment of the radiating patch is connected to an elliptical metal sheet, and the lower part of the lower segment is connected to a metal base.

[0012] A further technical solution of the present invention: the short-circuit stub is attached to the outer surface of the elliptical dielectric tube, and the coupling feed line is printed on the rectangular dielectric plate, the two forming a balanced feed balun similar to a dipole.

[0013] A further technical solution of the present invention: the matching resistor is attached to the outer surface of the elliptical dielectric tube, and is connected to the lower end of the upper section and the upper end of the middle section of the radiation patch, respectively.

[0014] A further technical solution of the present invention: the elliptical metal sleeve is located outside the elliptical medium tube and maintains the same major-minor axis ratio as the elliptical medium tube.

[0015] A further technical solution of the present invention: the height of the elliptical metal sleeve is 0.025λ. L ~0.05λ L , where λ L This is the operating frequency band.

[0016] A further technical solution of the present invention: the coupled power supply line is a gradient power supply line.

[0017] Beneficial effects

[0018] This invention provides a coupled-fed broadband elliptical cylindrical omnidirectional antenna. Through matching resistor loading and top loading, the antenna can be significantly miniaturized, greatly reducing its profile height. Feeding using a balun composed of a coupled feed line and short-circuit stubs generates new resonant points, expanding the antenna's impedance bandwidth, further optimizing impedance matching, reducing losses, and improving antenna efficiency and gain. By attaching a radiating patch to the outer surface of the elliptical dielectric tube, a wider width is achieved, increasing the antenna's operating bandwidth and miniaturizing it. This also reduces the antenna's non-circularity in the horizontal plane radiation pattern, especially at high frequencies. The elliptical dielectric tube has an external height of 0.025λ. L ~0.05λ L The elliptical metal sleeve can expand the impedance bandwidth of the antenna and reduce the degree of antenna beam tilt.

[0019] By employing a variety of measures to optimize impedance matching and improve pattern non-circularity, this antenna not only has wide bandwidth performance but also achieves low height and high gain. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0021] Figure 1 This is a three-dimensional view of a coupled-fed broadband elliptical cylindrical omnidirectional antenna according to the present invention.

[0022] Figure 2 This is a three-dimensional view of the patch unfolding and roll-up of a coupled-fed broadband elliptical cylindrical omnidirectional antenna according to the present invention.

[0023] Figure 3 This is a schematic diagram showing the relative positions of a rectangular dielectric substrate inside a hollow elliptical dielectric tube in a coupled-fed broadband elliptical cylindrical omnidirectional antenna according to the present invention.

[0024] Figure 4 The voltage standing wave ratio (VSWR) diagram of a coupled-fed broadband elliptical cylindrical omnidirectional antenna according to the present invention is shown.

[0025] Figure 5 The vertical plane gain pattern of a coupled-fed broadband elliptical cylindrical omnidirectional antenna of the present invention at 108MHz.

[0026] Figure 6 The vertical plane gain pattern of a coupled-fed broadband elliptical cylindrical omnidirectional antenna of the present invention at 225MHz.

[0027] Figure 7 The image shows the gain pattern of a coupled-fed broadband elliptical cylindrical omnidirectional antenna in the vertical plane at 400MHz, according to the present invention.

[0028] Figure 8 This is a horizontal plane gain characteristic diagram of a coupled-fed broadband elliptical cylindrical omnidirectional antenna according to the present invention.

[0029] Figure 9 This is a diagram showing the non-circularity characteristic of the horizontal plane radiation pattern of a coupled-fed broadband elliptical cylindrical omnidirectional antenna according to the present invention.

[0030] Among them, 1-elliptical metal sheet; 2-matching resistor; 3-radiating patch; 4-elliptical dielectric tube; 5-elliptical radome; 6-rectangular dielectric board; 7-coupled feed line; 8-short-circuit stub; 9-elliptical metal sleeve; 10-coaxial RF connector; 11-metal base. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0032] like Figures 1-3 As shown, the coupled-fed broadband elliptical cylindrical omnidirectional antenna provided in this embodiment of the invention includes: an elliptical metal sheet 1, a matching resistor 2, a radiating patch 3, an elliptical dielectric tube 4, an elliptical radome 5, a rectangular dielectric substrate 6, a coupled-fed strip 7, a short-circuit stub 8, an elliptical metal sleeve 9, a coaxial RF connector 10, and a metal base 11.

[0033] A hollow elliptical dielectric tube 4 is vertically fixed on a metal base. A matching resistor 2, a radiating patch 3, and a short-circuit stub 8 are attached to the outer surface of the elliptical dielectric tube 4. A rectangular dielectric plate 6 is placed inside the elliptical dielectric tube 4 and is vertically fixed to the bottom metal base 11, just like the elliptical dielectric tube 4. The surface of the rectangular dielectric plate 6 is placed along the long axis of the elliptical dielectric tube 4 and is shifted along the short axis of the elliptical dielectric tube 4 towards the resistor loading side to be close to the inner wall of the hollow elliptical dielectric tube 4. A coupling feed line 7 is printed on one side of the rectangular dielectric plate 6. The coupling feed line 7 is a gradient feed line, and its lower end is connected to the core wire of the coaxial RF connector 10 for power feeding. The coaxial RF connector 10 is fixed to the lower surface of the metal base 11. An elliptical metal piece 1 is located at the top of the elliptical radome 5 and is electrically connected to the top of the radiating patch 3. An elliptical metal sleeve 9 is placed outside the elliptical dielectric tube 4, with a flange extending from the bottom, and is vertically fixed to the metal base 11.

[0034] When unfolded, the radiating patch 3 is a three-segment rectangular metal sheet with chamfered corners, named upper segment, middle segment, and lower segment from top to bottom. The upper and lower segments are relatively short. The lower segment is connected to the upper surface of the metal base 11. The chamfered corners are symmetrical. The vertical length of the lower chamfer of the middle segment is longer, while the vertical lengths of the chamfers of the upper side of the middle segment, the lower side of the upper segment, and the upper side of the lower segment are shorter. When unfolded, the width of the radiating patch 3 is slightly smaller than the circumference of the elliptical dielectric tube 4, which has a wider width, can improve the working bandwidth of the antenna and enable miniaturization. When attached to the outer surface of the elliptical dielectric tube 4, it improves the non-circularity of the high-frequency radiation pattern of the antenna.

[0035] Among them, the lower end of the short-circuit stub 8 is connected to the bottom of the lower section of the radiating patch 3, and the upper end is connected to one of the lower chamfers of the middle section radiating patch. The coupled feed line 7 and the short-circuit stub 8 form a balanced feed balun, which adds a new resonant point in the antenna's operating frequency band and improves the antenna's impedance matching.

[0036] Among them, the matching resistor 2 is located between the upper section patch and the middle section patch. The matching resistor 2 is connected to the lower end of the upper section of the radiating patch 3 and to the upper end of the middle section of the radiating patch 3.

[0037] The height of the elliptical metal sleeve 9 is 0.04λ. L Located outside the elliptical dielectric tube 4 and connected to the metal base, it can improve antenna impedance matching and reduce the antenna beam tilt.

[0038] Among them, the elliptical antenna cover 5 is located outside the elliptical metal sleeve, with an elliptical metal sheet covering the upper end and the lower end fixed on the metal base;

[0039] The coaxial RF connector 10 is fixed to the lower surface of the metal base, and its inner conductor is electrically connected to the lower end of the coupling feed line 7 to feed the antenna.

[0040] The antenna structure employed in this embodiment of the invention realizes a low-height, wideband airborne VHF antenna. The use of resistive loading, radiating patch curling and chamfering, balanced feed balun, elliptical metal plate loading, and elliptical metal sleeve structural designs significantly improves antenna performance, reducing antenna height while widening impedance bandwidth, and simultaneously ensuring low-frequency gain. The overall antenna height is as low as 0.133λ. L Width 0.05λ L Compared with traditional airborne antennas, the antenna structure used in this embodiment has higher low-frequency gain and better high-frequency non-circularity, which greatly increases the communication stability and communication distance of the airborne antenna.

[0041] refer to Figures 4 to 9 The voltage standing wave ratio, gain pattern, gain variation with frequency, and horizontal plane pattern non-circularity variation with frequency of the antenna in the above embodiment were simulated and calculated using simulation software. The simulation results are as follows:

[0042] Figure 4 This is the characteristic of voltage standing wave ratio (VSWR) changing with operating frequency obtained from antenna simulation in the example. Figure 4 It can be seen that an impedance bandwidth with a standing wave ratio of <2.5 can be achieved at 3.7 times the frequency (108MHz~400MHz).

[0043] Figures 5-7 The image shows the gain patterns of the antenna at 108MHz, 225MHz, and 400MHz. As can be seen from the image, the antenna exhibits good symmetry about the z-axis in the entire space, with minimal non-circularity on the horizontal plane. At 108MHz, a gain of -3.7dBi can be achieved.

[0044] Figure 8 This is a graph showing the horizontal gain of the antenna as a function of frequency in an example embodiment. Figure 8 As can be seen, the gain of this antenna is higher than that of other similar antennas.

[0045] Figure 9 This is a graph showing the variation of the horizontal plane radiation pattern non-circularity of the antenna as a function of frequency, as illustrated in the example. Figure 9 As can be seen, the non-circularity of the horizontal radiation pattern of this antenna is smaller compared to that of a blade antenna.

[0046] Simulation results show that the antenna can achieve the effects of low height, wide bandwidth, high gain and small non-circularity.

[0047] In summary, the coupled-fed broadband elliptical cylindrical omnidirectional antenna provided by this invention achieves broadband high gain through matching resistor loading, rolled-up radiating patches, balanced feeding baluns, and an elliptical metal sleeve. Miniaturization is achieved by increasing the antenna's port resistance using matching resistor loading; broadband is achieved by improving port impedance through rolled-up radiating patches and balanced feeding baluns; high-frequency beam warping is reduced by the elliptical metal sleeve, while impedance smoothing is improved; and high-frequency non-circularity is reduced by the overall elliptical structure of the antenna. Through these measures, this coupled-fed broadband elliptical cylindrical omnidirectional antenna can achieve high gain at low frequencies and a stable radiation pattern at high frequencies, ensuring stable communication in the omnidirectional angular domain and significantly increasing the communication range of airborne antennas.

[0048] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A coupled-fed broadband elliptical cylindrical omnidirectional antenna, characterized in that... Includes an elliptical metal sheet (1), a matching resistor (2), a radiating patch (3), an elliptical dielectric tube (4), an elliptical radome (5), a rectangular dielectric board (6), a coupling feed line (7), a short-circuit stub (8), an elliptical metal sleeve (9), a coaxial RF connector (10), and a metal base (11). A hollow elliptical dielectric tube (4) is vertically fixed on a metal base. A matching resistor (2), a radiating patch (3), and a short-circuit stub (8) are attached to the outer surface of the elliptical dielectric tube (4). A rectangular dielectric plate (6) is placed inside the elliptical dielectric tube (4) and is vertically fixed on the bottom metal base (11) along with the elliptical dielectric tube (4). The surface of the rectangular dielectric plate (6) is placed along the long axis of the elliptical dielectric tube (4), and the surface of the rectangular dielectric plate (6) is shifted along the short axis of the elliptical dielectric tube (4) towards the side where the resistor is applied, close to the hollow elliptical dielectric tube. 4) Inner wall; a coupling feed line (7) is printed on one side of the rectangular dielectric plate (6). The coupling feed line (7) is a gradient feed line. The lower end is connected to the core wire of the coaxial RF connector (10) for power feeding. The coaxial RF connector (10) is fixed to the lower surface of the metal base (11). The elliptical metal piece (1) is located at the top of the elliptical radome (5) and is electrically connected to the top of the radiating patch (3). The elliptical metal sleeve (9) is placed outside the elliptical dielectric tube (4) with a flange extending from the bottom and vertically fixed on the metal base (11). When the radiation patch (3) is unfolded, it is a three-section rectangular metal sheet with chamfered corners, named as upper section, middle section and lower section from top to bottom respectively; the upper section and lower section are relatively short; the lower section is connected to the upper surface of the metal base (11); the chamfered corners are symmetrical from left to right, the lower chamfered corner of the middle section has a longer vertical length, and the upper chamfered corners of the middle section, the lower chamfered corner of the upper section and the upper chamfered corner of the lower section have shorter vertical lengths. Among them, the lower end of the short-circuit stub (8) is connected to the bottom of the lower section of the radiating patch (3), and the upper end is connected to one of the lower chamfers of the middle section radiating patch. The coupled feed line (7) and the short-circuit stub (8) form a balanced feed balun, which adds a new resonant point in the working frequency band of the antenna and improves the impedance matching of the antenna. Among them, the matching resistor (2) is located between the upper section patch and the middle section patch. The matching resistor (2) is connected to the lower end of the upper section of the radiating patch (3) and to the upper end of the middle section of the radiating patch (3). The height of the elliptical metal sleeve (9) is 0.025λ. L ~0.05λ L , where λ L Operating frequency band; Located outside the elliptical dielectric tube (4) and connected to the metal base, it can improve the antenna impedance matching and reduce the beam tilt of the antenna. Among them, the elliptical radome (5) is located outside the elliptical metal sleeve, with the upper end covered by an elliptical metal sheet and the lower end fixed to the metal base; The coaxial RF connector (10) is fixed on the lower surface of the metal base, and its inner conductor is electrically connected to the lower end of the coupling feed line (7) to feed the antenna.

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