Broadband circularly polarized antenna

Abstract

The invention discloses a broadband circularly polarized antenna which comprises a feed structure and a radiation structure, the feed structure adopts a double-layer dielectric structure, a floor is distributed in the middle of the double-layer dielectric structure, an upper feeder line is distributed between the floor and a top dielectric layer, and a lower feeder line is distributed between the floor and a lower dielectric layer. The upper-layer feeder line is distributed between the floor and the bottom-layer medium, the lower-layer feeder line is distributed between the floor and the bottom-layer medium, the upper-layer feeder line and the lower-layer feeder line are connected through a via hole structure, and the position setting of a total feed port of the antenna meets the condition that the phase difference of the antenna excited by the upper-layer feeder line and the lower-layer feeder line is 90 degrees. According to the invention, the upper and lower layers of transmission lines are connected by adopting a double-layer dielectric plate structure and a via hole mode, and the phase difference of the two sections of transmission lines to excite the antenna is 90 degrees by selecting the position of a port, so that the relatively strong frequency change characteristic and loss caused by the use of an additional multi-section phase shift microstrip line and a power divider structure are avoided; and the complexity and the overall size of the feed structure are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of microstrip antennas, and in particular relates to a broadband circularly polarized antenna. Background Art

[0002] With the development of wireless communication and detection technologies such as radar, satellite communication, and remote sensing, microstrip antennas have been widely used in the above fields due to their advantages of small size, light weight, low profile, easy integration and conformality, low cost, and easy manufacturing. Circularly polarized antennas are insensitive to polarization and can receive incoming waves of any polarization. Their radiated waves can be received by any polarized antenna, and circular polarizations of different rotation directions have greater polarization isolation. Therefore, they have certain advantages and are widely used.

[0003] The impedance bandwidth of the antenna is an important indicator. The bandwidth of a typical microstrip antenna is relatively small. In order to expand the impedance bandwidth of the antenna, DMPozar proposed a slot coupling feeding method. The main advantages of this method are: using a non-contact coupling feeding method, avoiding the inductance introduced in traditional probe feeding, and improving the impedance bandwidth; the manufacturing process is simpler, providing convenience for the structural design of multi-layer dielectrics and multi-layer patches; reducing the radiation of the feeding network part, and the feeding network and antenna structure can be designed and debugged separately; using a multi-layer structure can further improve the impedance bandwidth.

[0004] In addition to the impedance bandwidth of the antenna, the axial ratio bandwidth of the circularly polarized antenna is also an important parameter. In order to achieve circular polarization, single feed point and multi-feed point methods can be used. Among them, the impedance bandwidth and axial ratio bandwidth of the circularly polarized antenna of the single feed point method are not ideal; multi-feed points can be divided into dual feed and quad feed methods, and the dual feed method has a higher cross-polarization rate due to the asymmetry of the feeding structure; compared with the dual feed method, the quad feed method can improve the performance of circular polarization due to the symmetrical excitation of the cross-shaped slot.

[0005] The existing four-feed circularly polarized antenna includes: (1) the dielectric substrate of the feeding structure is a single-layer structure, and three Wilkinson power dividers are used to form a feeding network. By designing a 1-to-2-to-2 microstrip feeding network and selecting a suitable microstrip line length to design a phase extension line, the four ports are finally output with equal amplitudes and phases that differ by 90°. The phase difference between ports 1 and 2 is 90°, the phase difference between ports 3 and 4 is 90°, and the phase difference between the two Wilkinson power dividers is 180°. Since the phase difference is realized by the length of microstrip line, the feeding network belongs to frequency-variable network. Three sections of microstrip phase-shifting structure are introduced in the structure. The phase-shifting line is long, so the frequency-variable characteristics of the feeding network under wide bandwidth are increased; at the same time, the feeding network includes a two-stage power divider circuit of 1:2:2, and a three-stage phase-shifting circuit. The loss of the whole feeding network is high; since the two-stage power division and phase-shifting circuit are realized on a single-layer dielectric board, the overall structure of the feeding network is complex and the size is large; (2) The antenna is coplanarly fed through a 1:4 sequentially rotating equal power division 270° phase-shifting network to form right-hand circular polarization. The feeding network of the antenna is designed according to the 1:4 power distribution of each section of the transmission line. The energy is evenly distributed to the four output ports through the 270° transmission line in turn to produce circular polarization. Since the microstrip line structure used for phase shifting in the feeding network is relatively long, there is also the problem of increased frequency-varying characteristics under wide bandwidth; at the same time, the longer microstrip line generates greater losses, making it difficult to strictly achieve equal power at each port in the design, affecting the circular polarization performance of the antenna. The antenna axial ratio bandwidth and impedance bandwidth are both less than 10%. Summary of the invention

[0006] In order to achieve both high impedance bandwidth and high axial ratio bandwidth of the antenna while having a simple feeding network structure and small size, the present application provides a broadband circularly polarized antenna. The feeding network structure adopted in the present application reduces the number and length of microstrip phase-shifting structures, thereby weakening the frequency-varying characteristics of the feeding network under wide bandwidth and reducing the loss of the entire feeding network. The feeding network structure of the present application is simple and small in size, and can obtain higher impedance bandwidth and axial ratio bandwidth.

[0007] The present invention is achieved through the following technical solutions:

[0008] A broadband circularly polarized antenna, comprising a feeding structure and a radiating structure, wherein the feeding structure adopts a double-layer dielectric structure, a floor is distributed in the middle position of the double-layer dielectric structure, an upper layer feeding line is attached to the surface of a top dielectric layer, and a lower layer feeding line is attached to the surface of a bottom dielectric layer, the upper layer feeding line and the lower layer feeding line are connected through a via structure, and the position of the total feeding port of the antenna is set to meet the phase difference of 90° between the upper layer feeding line and the lower layer feeding line in exciting the antenna.

[0009] The present application adopts a double-layer dielectric plate structure and vias to connect the upper and lower layers of transmission lines, and naturally realizes a phase difference of 90° between the two transmission line excitation antennas by selecting the position of the port, avoiding the use of additional multi-section phase-shifted microstrip lines and power divider structures to produce strong frequency-varying characteristics and losses, and reducing the complexity and overall size of the feeding structure.

[0010] As a preferred embodiment, a coupling gap is provided in the center of the floor of the present application; the upper layer feeder line is composed of transmission line A, transmission line B and transmission line C; the lower layer feeder line is composed of transmission line D, transmission line E and transmission line F; the transmission line A and the transmission line D are connected through a via structure;

[0011] The transmission line A, the transmission line B and the transmission line C form a 1-to-2 power divider, and the transmission line D, the transmission line E and the transmission line F form a 1-to-2 power divider;

[0012] The main feeding port and the transmission line A and the transmission line D form a 1-to-2 power divider;

[0013] The open ends of the transmission line B, the transmission line C, the transmission line E and the transmission line F are symmetrically arranged with respect to the coupling gap.

[0014] The present application adopts a four-feed point symmetrical excitation method to achieve a larger pattern bandwidth and axial ratio bandwidth.

[0015] As a preferred embodiment, there is a spacing between the transmission line B and the transmission line C of the present application, and the transmission line B and the transmission line C intersect with the coupling gap; there is a spacing between the transmission line E and the transmission line F, and the transmission line E and the transmission line F intersect with the coupling gap shown.

[0016] As a preferred embodiment, the coupling gap of the present application is composed of two rectangular gaps, and the two gaps are arranged orthogonally to each other to form a cross-shaped gap.

[0017] As a preferred embodiment, the upper feed line and the lower feed line of the present application have the same size; the total feeding port is arranged so that the absolute value of the length difference between the transmission line A and the transmission line D is one quarter wavelength of the center frequency of the antenna.

[0018] As a preferred embodiment, the via structure of the present application includes a through hole provided on the floor and a cylindrical conductor passing through the through hole.

[0019] As a preferred implementation, the radiation structure of the present application is composed of at least one radiation layer, and at least one radiation layer is located above the feeding structure.

[0020] As a preferred implementation, there is a height difference between at least one of the radiation layers of the present application and the feeding structure shown, and there is also a height difference between at least one of the radiation layers.

[0021] As a preferred embodiment, a radiation patch is distributed in the center of each radiation layer of the present application;

[0022] The radiating patch may be circular or rectangular.

[0023] As a preferred implementation, the feeding structure of the present application is fixed to the radiation structure via a bracket.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] Compared with the traditional circularly polarized antenna structure, there are problems such as complex structure, large size, or unsatisfactory impedance bandwidth and axial ratio bandwidth. The broadband circularly polarized antenna proposed in this application adopts a double-layer dielectric plate structure and a via to connect the upper and lower layers of feed lines, and the position of the total feed port is selected to achieve a phase difference of 90° between the upper and lower layers of feed lines to excite the antenna, avoiding the use of additional multi-stage phase-shifted microstrip lines and power divider structures to produce strong frequency-varying characteristics and losses, reducing the complexity and overall size of the feeding structure, and improving the performance of the antenna. In addition, the broadband circularly polarized antenna proposed in this application adopts a four-feed symmetrical excitation method to obtain a larger radiation pattern bandwidth and axial ratio bandwidth, and adopts slot-coupled feeding and multi-layer radiation patches to obtain a larger impedance bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0027] Figure 1 The figure is a schematic diagram of the structure of a broadband circularly polarized antenna according to an embodiment of the present invention.

[0028] Figure 2 FIG. 4 is a top view of a feeding structure according to an embodiment of the present invention.

[0029] Figure 3 It is a side view of the feeding structure of an embodiment of the present invention.

[0030] Figure 4 1 is a curve showing the change of the broadband circularly polarized antenna S11 with respect to frequency according to an embodiment of the present invention.

[0031] Figure 5 1 is the radiation pattern of the xoz plane of the broadband circularly polarized antenna of the embodiment of the present invention at 0.95, 1.1 and 1.22 GHz.

[0032] Figure 6 1 is the yoz plane radiation pattern of the broadband circularly polarized antenna of the embodiment of the present invention at 0.95, 1.1 and 1.22 GHz.

[0033] Figure 7 The graph is a curve showing the axial ratio of the broadband circularly polarized antenna according to an embodiment of the present invention changing with frequency.

[0034] Reference numerals and corresponding component names:

[0035] 1-transmission line A, 2-transmission line B, 3-transmission line C, 4-transmission line D, 5-transmission line E, 6-transmission line F, 7-via structure, 8-total feeding port, 9-slot A, 10-slot B, 11-feeding structure, 12-radiation structure, 13-radiation layer A, 14-radiation layer B, 15-radiation patch A, 16-radiation patch B. DETAILED DESCRIPTION

[0036] Hereinafter, the term "include" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present invention, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0037] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the words listed at the same time. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0038] The expressions (such as "first", "second", etc.) used in various embodiments of the present invention may modify the various constituent elements in various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing an element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of various embodiments of the present invention, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0039] It should be noted that if it is described that one component element is “connected” to another component element, the first component element may be directly connected to the second component element, and a third component element may be “connected” between the first component element and the second component element. Conversely, when one component element is “directly connected” to another component element, it can be understood that there is no third component element between the first component element and the second component element.

[0040] The terms used in various embodiments of the present invention are only used for the purpose of describing specific embodiments and are not intended to limit various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meaning generally understood by those of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in various embodiments of the present invention.

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0042] Embodiment 1:

[0043] The impedance bandwidth and axial ratio bandwidth of the circularly polarized antenna achieved by the existing single feed point method are not ideal, and the circularly polarized antenna achieved by the multi-feed point method either has a complex overall structure and a large size, or the antenna axial ratio bandwidth and impedance bandwidth are not ideal; based on this, this embodiment proposes a broadband circularly polarized antenna. The broadband circularly polarized antenna proposed in this embodiment adopts a double-layer dielectric plate structure and a via to connect the upper and lower layers of feed lines, and achieves a phase difference of 90° between the two sections of feed lines to excite the antenna by selecting the position of the port, avoiding the use of additional multi-section phase-shifted microstrip lines and power divider structures to produce strong frequency-varying characteristics and losses, reducing the complexity and overall size of the feeding structure, and at the same time, the antenna uses a slot coupling feeding method and a 4-feed point symmetrical excitation method, and has a large impedance bandwidth and axial ratio bandwidth.

[0044] like Figure 1As shown, the broadband circularly polarized antenna proposed in this embodiment is mainly composed of a feeding structure 11 and a radiating structure 12; wherein, the feeding structure 11 adopts a double-layer dielectric structure, the floor is distributed in the middle of the double-layer dielectric structure, the upper layer feeder is attached to the surface of the top dielectric layer (either the upper surface or the lower surface), and the lower layer feeder is attached to the surface of the bottom dielectric layer (either the upper surface or the lower surface); the radiating structure 12 is composed of at least one radiating layer, and is located above the feeding structure; when the radiating structure 12 adopts at least two radiating layers, there is a certain distance between the multiple radiating layers and between the multiple radiating layers and the feeding structure. The radiating structure and the feeding structure can be fixed by, but not limited to, a bracket.

[0045] Specific as Figure 2-3 As shown, a coupling slot is arranged at the center of the metal floor in the feeding structure of this embodiment. The coupling slot is composed of two rectangular slots (ie, slot A9 and slot B10). The two slots are arranged orthogonally to each other and together form a cross-shaped slot.

[0046] The upper layer feeder and the lower layer feeder in the feed structure 11 of the present embodiment have the same size, wherein the upper layer feeder is composed of transmission line A1, transmission line B2 and transmission line C3, and the lower layer feeder is composed of transmission line D4, transmission line E5 and transmission line F6; one end of transmission line B2 and transmission line C3 are both connected to the same end of transmission line A1 to form a 1-to-2 power divider; one end of transmission line E5 and transmission line F6 are both connected to the same end of transmission line D4 to form a 1-to-2 power divider; the open end of transmission line A1 and the open end of transmission line D4 are connected through a via structure 7, and the via structure 7 is composed of a through hole on the floor and a cylindrical conductor passing through the through hole; transmission line B2 and There is a certain distance between the transmission lines C3. Preferably, the transmission lines B2 and C3 can be symmetrically arranged with the gap B10 as the axis of symmetry; the transmission lines B2 and C3 intersect with the gap A9 and their open ends extend beyond the width of the gap A9; there is a certain distance between the transmission lines E5 and F6. Preferably, the transmission lines E5 and F6 can be symmetrically arranged with the gap A9 as the axis of symmetry; the transmission lines E5 and F6 intersect with the gap B10 and their open ends extend beyond the width of the gap B10, so that the open ends of the transmission lines B2, C3, E5 and F6 are symmetrically arranged with the coupling gap to achieve symmetrical excitation of four feed points.

[0047] The total feed port 8 of the antenna forms a 1-to-2 power divider with the transmission line A1 and the transmission line D4. The port position is set at a point where the absolute value of the length difference between the transmission line A1 and the transmission line D4 is a quarter wavelength of the center frequency. Figure 2As shown in the figure, the total feed port 8 is set on the transmission line A1. Since the upper layer feed line and the lower layer feed line have the same size, the total feed port 8 is set on the transmission line A1 and is at a suitable distance from the via structure 7, so that the absolute value of the length difference between the upper and lower layers of feed lines can be achieved to be a quarter wavelength of the center frequency. It should be noted that Figure 2 The figure is only an exemplary illustration and does not limit the position of the main feeding port 8, that is, in other optional embodiments, the main feeding port 8 can also be set at other positions, as long as the absolute value of the length difference between the transmission line A1 and the transmission line D4 is one quarter of the wavelength of the center frequency.

[0048] This embodiment takes a two-layer radiation layer structure as an example to illustrate the radiation structure. Figure 1 As shown, the radiation structure 12 includes a radiation layer A13 and a radiation layer B14, both of which are located above the feed structure 11, and the radiation layer B14 is located between the radiation layer A13 and the feed structure 11; wherein, there is a certain distance between the radiation layer A13 and the radiation layer B14, and there is a certain distance between the radiation layer B14 and the feed structure 11; a radiation patch A15 is distributed at the center of the radiation layer A, and a radiation patch B16 is distributed at the center of the radiation layer B, and the radiation chip can be circular, rectangular, etc. It should be noted that: Figure 1 This is only an example and does not limit the number of radiation layers or the shape of the radiation patch.

[0049] Embodiment 2:

[0050] This embodiment simulates and verifies the broadband circularly polarized antenna proposed in the above embodiment 1, and obtains Figure 4-Figure 7 The electromagnetic simulation results are as follows: Figure 4 is the curve of antenna S11 changing with frequency, Figure 5 and Figure 6 They are the xoz and yoz radiation patterns of the antenna at 0.95, 1.1 and 1.22 GHz, respectively. Figure 7 This is the curve of the antenna's axial ratio changing with frequency.

[0051] The broadband circularly polarized antenna verified in this embodiment includes three layers, which are the bottom feeding structure layer, the radiation layer B and the radiation layer A (such as Figure 1 The antenna center frequency is designed to be 1.1 GHz. The dielectric layer material in the feeding structure is FR-4, the thickness is 1 mm, and the length and width of the dielectric layer and the floor are 150 mm (i.e., a rectangular structure).

[0052] Transmission line A1 and transmission line D4 are microstrip structures with a width of 1.9 mm. Transmission lines B2, C3, E5 and F6 are microstrip structures with a width of 0.4 mm and a length of 60.5 mm. The spacing between transmission line B2 and transmission line C3, and the spacing between transmission line E5 and transmission line F6 are both 15.73 mm. The length of the open section of transmission line B2, transmission line C3, transmission line E5 and transmission line F6 that exceeds the gap width is 11.88 mm. The upper transmission line A1 and the lower transmission line D4 are connected by a via structure 7. The radius of the cylindrical conductor in the via structure 7 is 0.95 mm, and the radius of the through hole hollowed out on the floor is 2.5 mm. The total feeding port 8 is set on the transmission line A1, and the distance between it and the via structure 7 is 19mm. Since the structural dimensions of the upper feeding line and the lower feeding line are consistent, the length of the transmission line D4 is greater than the length of the transmission line A1 by 38mm, which is one quarter of the medium wavelength, and the port normalized impedance is set to 25 ohms.

[0053] The length and width of the dielectric of the radiation layer B14 are both 150mm (i.e., a rectangular structure), and the thickness is 2mm. The length and width of the radiation patch B16 are both 86.3mm (i.e., a rectangular structure), and the height difference with the feeding structure is 20mm. The length and width of the dielectric of the radiation layer A13 are both 150mm (i.e., a rectangular structure), and the thickness is 1.58mm. The length and width of the radiation patch A15 are 77.6mm (i.e., a rectangular structure), and the height difference with the radiation layer B14 is 15.4mm.

[0054] According to the simulation results, we can know that:

[0055] Depend on Figure 4 It can be seen that the -10dB impedance bandwidth is 0.85~1.4GHz, and the impedance bandwidth is 48%.

[0056] Depend on Figure 5-6 It can be seen that the maximum gain of the antenna is 6.8~7.4dB, and does not change significantly with frequency.

[0057] Depend on Figure 7 It can be seen that the axial ratio is less than 3dB in the bandwidth from 0.98 to 1.22GHz, and the axial ratio bandwidth is about 21%.

[0058] Based on the above analysis, it can be seen that the embodiment of the present invention uses a double-layer dielectric plate structure and a via to connect the upper and lower layers of transmission lines, and by selecting the position of the port, the phase difference of the two-segment transmission line excitation antenna is naturally realized to be 90°, avoiding the use of additional multi-segment phase-shifted microstrip lines and power divider structures to produce strong frequency-variable characteristics and losses, and reducing the complexity and overall size of the feeding structure. At the same time, the symmetrical excitation method of 4 feed points is used, the directional pattern bandwidth and axial ratio bandwidth are both large, and it has a large impedance bandwidth.

[0059] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A broadband circularly polarized antenna, comprising a feeding structure and a radiating structure, characterized in that: The feeding structure adopts a double-layer dielectric structure, the floor is distributed in the middle position of the double-layer dielectric structure, the upper feed line is attached to the surface of the top dielectric layer, the lower feed line is attached to the surface of the bottom dielectric layer, the upper feed line and the lower feed line are connected through a via structure, and the position of the total feeding port of the antenna is set to meet the phase difference of 90° between the upper feed line and the lower feed line in exciting the antenna.

2. A broadband circularly polarized antenna according to claim 1, characterized in that: A coupling gap is provided in the center of the floor; the upper layer feeder line is composed of transmission line A, transmission line B and transmission line C; the lower layer feeder line is composed of transmission line D, transmission line E and transmission line F; the transmission line A and the transmission line D are connected through a via structure; The transmission line A, the transmission line B and the transmission line C form a 1-to-2 power divider, and the transmission line D, the transmission line E and the transmission line F form a 1-to-2 power divider; The main feeding port and the transmission line A and the transmission line D form a 1-to-2 power divider; The open ends of the transmission line B, the transmission line C, the transmission line E and the transmission line F are symmetrically arranged with respect to the coupling gap.

3. A broadband circularly polarized antenna according to claim 2, characterized in that: There is a distance between the transmission line B and the transmission line C, and the transmission line B and the transmission line C intersect with the coupling gap; there is a distance between the transmission line E and the transmission line F, and the transmission line E and the transmission line F intersect with the coupling gap.

4. A broadband circularly polarized antenna according to claim 2, characterized in that: The coupling gap is composed of two rectangular gaps, and the two gaps are arranged orthogonally to each other to form a cross-shaped gap.

5. A broadband circularly polarized antenna according to claim 2, characterized in that: The upper layer feed line and the lower layer feed line have the same size; the main feed port is arranged at a position where the absolute value of the length difference between the transmission line A and the transmission line D is a quarter wavelength of the center frequency of the antenna.

6. A broadband circularly polarized antenna according to claim 2, characterized in that: The via structure includes a through hole provided on the floor and a cylindrical conductor passing through the through hole.

7. A broadband circularly polarized antenna according to any one of claims 1 to 6, characterized in that: The radiation structure is composed of at least one radiation layer, and at least one radiation layer is located above the feeding structure.

8. The broadband circularly polarized antenna according to claim 7, characterized in that: There is a height difference between at least one of the radiation layers and the feeding structure, and there is also a height difference between at least one of the radiation layers.

9. The broadband circularly polarized antenna according to claim 7, characterized in that: There are radiation patches distributed in the center of each radiation layer; The radiating patch may be circular or rectangular.

10. A broadband circularly polarized antenna according to any one of claims 1 to 6, characterized in that: The feeding structure and the radiating structure are fixed via a bracket.

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