A broadband quasi-isotropic antenna radiator based on mode compression

Abstract

The application discloses a broadband quasi-isotropic antenna radiator based on mode compression, which comprises a planar antenna layer, a dielectric substrate and a metal ground layer arranged in sequence from top to bottom, wherein the planar antenna layer is provided with a folded dipole radiation structure, a matching network and a feeding structure, a capacitive loading structure is arranged in a high-order mode current zero point area of the folded dipole radiation structure, the base mode working frequency is shifted upward by changing the base mode current path and the equivalent boundary condition, the equivalent radiation resistance is improved by changing the equivalent electrical length of the side wall and the current phase distribution, the reverse current far field cancellation is weakened, and the broadband impedance matching and quasi-isotropic radiation of 2.17GHz to 2.95GHz are realized. The application has simple structure and does not need a complex feeding network, and is suitable for Internet of Things terminals and attitude-insensitive communication equipment.

Description

Technical Field

[0001] This invention belongs to the field of microwave antenna technology, and specifically relates to a broadband quasi-isotropic antenna radiator based on mode compression. Background Technology

[0002] With the development of the Internet of Things, wireless sensor networks, mobile terminals, and short-range wireless communication devices, the placement, installation posture, and relative position of terminal devices exhibit significant randomness. To reduce the impact of device posture changes on wireless link stability, quasi-isotropic antennas with full-space coverage capabilities have important application value.

[0003] Existing quasi-isotropic antennas are typically implemented by combining multiple discrete radiating elements, synthesizing multiple electric dipoles or monopoles, orthogonally exciting complementary electric / magnetic dipoles, or using bent or ring radiators. While these methods can improve the radiation null problem near a certain frequency, they often suffer from drawbacks such as large structural size, complex feeding networks, narrow bandwidth, difficulty in impedance matching, or high integration difficulty with small terminals.

[0004] For broadband antenna design, existing technologies also employ multimode resonance or mode compression to extend the bandwidth of dipole antennas. For example, loading a capacitive structure near the zero point of the higher-order mode current in a thin, straight dipole radiator shifts the resonant frequency of the lower-order modes and brings them closer to the higher-order modes in frequency, thereby improving the impedance bandwidth. This type of method is mainly aimed at linear or near-linear dipole radiating structures, and its technical focus is typically on compressing the frequency spacing between multiple resonant modes to obtain a wider impedance matching bandwidth.

[0005] However, the aforementioned method for broadbanding thin straight dipoles does not fully consider the spatial radiation uniformity problem prevalent in quasi-isotropic terminal antennas. Particularly in folded dipole radiators with metal ground planes or terminal ground structures, the main radiating arm and the sidewall radiation paths together form a bent current path. Since opposite current components are easily generated on adjacent paths or sidewall paths, these opposing current components partially cancel each other out in the far field, reducing the equivalent radiation resistance and further leading to lower input impedance, difficulty in broadband matching, and increased fluctuations in actual gain throughout the entire space.

[0006] Furthermore, in folded dipole-type quasi-isotropic radiators, simply adjusting the length of the radiating arms or introducing a conventional matching network can improve impedance matching at local frequencies, but it is difficult to simultaneously control the frequency distribution of the fundamental and higher-order modes, the phase distribution of the sidewall currents, and the overall radiation uniformity. How to simultaneously achieve broadband impedance matching, reduce far-field cancellation of reverse currents, and improve quasi-isotropic radiation characteristics while maintaining a simple structure and facilitating planar integration remains a technical problem that needs to be solved.

[0007] Therefore, it is necessary to propose a mode control structure suitable for folded dipole-type quasi-isotropic radiators, which can not only extend the impedance bandwidth, but also improve the sidewall current distribution, increase the equivalent radiation resistance, and maintain good full-space radiation uniformity over a wide frequency band. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a broadband quasi-isotropic antenna radiator based on mode compression. This antenna achieves broadband impedance matching and quasi-isotropic radiation by setting a capacitive loading structure in the high-order mode current zero region and coordinating the fundamental and high-order modes of the radiator. This allows multiple matched modes to be distributed close together within the target frequency band.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a broadband quasi-isotropic antenna radiator based on mode compression, comprising a planar antenna layer, a dielectric substrate, and a metal ground plane layer arranged sequentially from top to bottom;

[0011] The planar antenna layer is provided with a folded dipole radiation structure, a matching network, and a feeding structure.

[0012] The folded dipole radiation structure includes a main radiation arm and a sidewall radiation path.

[0013] A capacitive loading structure is provided on the folded dipole radiation structure. The capacitive loading structure is located in the high-order mode current zero-point region or the near-current zero-point region of the folded dipole radiation structure. The term "near-current zero-point region" in this invention does not require that the amplitude of the high-order mode surface current at that location be strictly zero in a mathematical sense. Rather, it refers to the region where, under the combined effects of actual finite size, bent structure, dielectric substrate, metal ground plane, and feed / matching network, the change in high-order mode resonant frequency is less than the change in fundamental mode resonant frequency.

[0014] The capacitive loading structure is used to change the fundamental mode current path and equivalent boundary conditions, so that the fundamental mode operating frequency is shifted to a higher frequency. At the same time, it weakens the cancellation effect of the reverse current component in the far field in the sidewall radiation path, thereby improving the equivalent radiation resistance and realizing broadband impedance matching and quasi-isotropic radiation.

[0015] Furthermore, the higher-order mode is a third-order mode, and the capacitive loading structure is arranged in the third-order mode current zero-point region of the folded dipole radiation structure.

[0016] Furthermore, the capacitive loading structure is disposed in the bent top region of the main radiating arm.

[0017] Furthermore, the capacitive loading structure includes at least one of gap capacitor, lumped capacitor, interdigitated capacitor, and patch coupling capacitor.

[0018] Furthermore, the capacitive loading structure is a gap capacitor formed on the metal conductor of the planar antenna layer.

[0019] Furthermore, the main radiating arm and the side wall radiating path cooperate to form a U-shaped folded current radiating path.

[0020] Furthermore, the matching network includes a first lumped inductor, a second lumped inductor, a first lumped capacitor, and a second lumped capacitor. The matching network is connected between the feed structure and the folded dipole radiating structure and is used to transform the impedance and compensate the reactance between the feed structure and the folded dipole radiating structure.

[0021] Furthermore, the dielectric substrate is made of F4BM material; the thickness of both the planar antenna layer and the metal ground layer is 0.035 mm.

[0022] This invention places the capacitive structure in the zero-point region of the third-order mode current, so that it has less disturbance to the distribution of the third-order mode main current. At the same time, it changes the fundamental mode current path and equivalent boundary conditions, so that the fundamental mode operating frequency shifts to a higher frequency, the equivalent electrical length of the sidewall and the current phase distribution change, the reverse current cancellation effect is weakened, the equivalent radiation resistance increases, and broadband impedance matching is formed.

[0023] Furthermore, the operating bandwidth of the antenna radiator covers 2.17 GHz to 2.95 GHz.

[0024] Secondly, the present invention provides the application of the above-mentioned pattern compression-based broadband quasi-isotropic antenna radiator in Internet of Things terminals, wireless sensor nodes, or mobile communication attitude-insensitive wireless communication devices.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) By setting a capacitive loading structure in the zero-point region of the higher-order mode current, this invention achieves mode compression of the fundamental mode and higher-order modes, making multiple resonant modes more closely distributed in frequency and expanding the impedance bandwidth. On the other hand, by changing the equivalent electrical length and current phase distribution of the sidewall radiation path, it fundamentally weakens the far-field cancellation of the sidewall reverse current inherent in the folded dipole, thus significantly improving the equivalent radiation resistance. The above two effects are accomplished synergistically by the same capacitive loading structure, rather than by separate additional measures, achieving a synergistic effect of mode compression and sidewall current regulation.

[0027] (2) This invention adopts a three-layer structure: the top layer is a planar antenna structure, the middle layer is an F4BM substrate, and the bottom layer is a metal ground plane. The structure is simple and easy to process and integrate with planar circuits. This invention only requires setting gap capacitors or lumped capacitors in the planar antenna layer, without the need for complex multi-port feed networks or additional absorption / reflection structures. Compared with the prior art that only performs mode compression for linear dipoles, this invention is specifically designed for three-dimensional folded radiating structures with metal ground planes. While achieving a wide impedance bandwidth, it effectively overcomes the far-field cancellation and full-space gain dip defects unique to folded structures.

[0028] (3) Thanks to the effective suppression of reverse current in the sidewalls, this invention can achieve broadband operation in the 2.17GHz to 2.95GHz frequency band, with a wide coverage bandwidth, and is suitable for wireless devices that require broadband coverage and attitude-insensitive communication. The terminal device can maintain stable communication link quality under any placement orientation, solving the industry pain point that traditional broadband antennas only focus on horizontal omnidirectionality and ignore the deep null point (radiation dead zone) of the full space gain. This invention maintains effective radiation in multiple spatial directions in a wide frequency band and has quasi-isotropic radiation characteristics.

[0029] In summary, the structure of this invention combines the advantages of broadband high performance, quasi-isotropic coverage, and low-cost planar integration. Attached Figure Description

[0030] Figure 1 This is a three-dimensional structural schematic diagram of the designed broadband quasi-isotropic antenna radiator based on mode compression.

[0031] Figure 2 This is a top view schematic diagram of the designed broadband quasi-isotropic antenna radiator based on mode compression;

[0032] Figure 3 This is a schematic diagram of the matching network structure of the designed broadband quasi-isotropic antenna radiator based on mode compression.

[0033] Figure 4 This is a partially enlarged schematic diagram of the capacitively loaded structure of the broadband quasi-isotropic antenna radiator based on mode compression, when a GAP gap capacitor is used.

[0034] Figure 5 This is a schematic diagram of the third-order mode current zero of the broadband quasi-isotropic antenna radiator designed based on mode compression.

[0035] Figure 6 The simulation parameters of the designed broadband quasi-isotropic antenna radiator based on mode compression are compared before and after the capacitor is loaded.

[0036] Figure 7This is a comparison diagram of the fundamental mode current distribution before and after loading a capacitive structure onto the designed broadband quasi-isotropic antenna radiator based on mode compression.

[0037] Figure 8 The parameter scan results of the designed broadband quasi-isotropic antenna radiator based on mode compression under different gap widths are shown in the figure.

[0038] Figure 9 These are the maximum and minimum actual gain plots of the designed mode-compression-based broadband quasi-isotropic antenna radiator in the target operating frequency band.

[0039] Figure 10 The figure shows the actual gain range of the designed mode-compression-based broadband quasi-isotropic antenna radiator in the target operating frequency band.

[0040] Figure 11 The figure shows the simulation results of the overall efficiency of the designed broadband quasi-isotropic antenna radiator based on mode compression.

[0041] The diagram is labeled as follows: 1. Planar antenna layer; 2. Dielectric substrate; 3. Metal ground plane layer; 4. Folded dipole radiating structure; 41. Main radiating arm; 42. Sidewall radiating path; 5. Capacitive loading structure; 6. Matching network; 7. Feeding structure; 81. First lumped inductor; 82. Second lumped inductor; 83. First lumped capacitor; 84. Second lumped capacitor. Detailed Implementation

[0042] To clearly illustrate the technical solution, design purpose, and advantages of the present invention, the present invention will be described below in conjunction with embodiments and accompanying drawings. The specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of protection of the present invention.

[0043] In the description of the embodiments of the present invention, it should be noted that the terms "upper", "lower", "first", "second", etc. are only used to facilitate the description based on the orientation or positional relationship shown in the drawings, and should not be construed as limiting the structural orientation or protection scope of the present invention.

[0044] like Figures 1 to 4 As shown, this embodiment provides a broadband quasi-isotropic antenna radiator based on mode compression. The antenna radiator has a three-layer structure, comprising, from top to bottom, a planar antenna layer 1, a dielectric substrate 2, and a metal ground plane layer 3. The planar antenna layer 1 is disposed on the upper surface of the dielectric substrate 2, and the metal ground plane layer 3 is disposed on the lower surface of the dielectric substrate 2. The dielectric substrate 2 is made of F4BM material with a dielectric constant of approximately 2.65, a loss tangent of approximately 0.002, and a thickness of H1 = 1 mm. The thicknesses of both the planar antenna layer 1 and the metal ground plane layer 3 are H2 = 0.035 mm.

[0045] The planar antenna layer 1 includes a folded dipole radiating structure 4, a capacitive loading structure 5, a matching network 6, and a feeding structure 7. The folded dipole radiating structure 4 includes a main radiating arm 41 and a sidewall radiating path 42. The matching network 6 includes a first lumped inductor 81 and a second lumped inductor 82, a first lumped capacitor 83, and a second lumped capacitor 84, used to transform the impedance and compensate the reactance between the feeding structure 7 and the folded dipole radiating structure 4 to achieve broadband impedance matching within the target operating frequency band. The sidewall radiating path 42 and the main radiating arm 41 together form a folded current path.

[0046] Furthermore, the dimensions of the planar antenna layer 1, the dielectric substrate 2, and the metal ground layer 3 are all W0×L0=70mm×70mm. The main radiating arm 41 of the folded dipole radiating structure 4 disposed on the planar antenna layer 1 has a length L1=43.2mm, the sidewall radiating path 42 has a length L2=40mm, and the width of both is W2=3.7mm.

[0047] Furthermore, the total length of the matching network 6 is L3 = 12.3 mm, and the width is W3 = 1 mm. The gap width is G2 = G3 = 0.4 mm. The first collective inductance 81 (Lm1) is 1 nH; the second collective inductance 82 (Lm2) is 19 nH; the first collective capacitance 83 (C1) is 0.3 pF; and the second collective capacitance 84 (C2) is 1.6 pF.

[0048] Without capacitive loading, there are opposite current components in the sidewall radiation path 42 of the folded dipole radiation structure 4. These opposing current components partially cancel each other out in the far field, reducing the equivalent radiation resistance and limiting the impedance matching and radiation uniformity of the antenna over a wide bandwidth. This reverse current cancellation phenomenon is one of the essential characteristics that distinguishes the folded dipole from the conventional thin straight dipole: the current in a conventional thin straight dipole is distributed along a single axis, and there is no far-field cancellation mechanism caused by the reverse current in adjacent paths. Therefore, its broadbanding method does not need to consider the deterioration of the equivalent radiation resistance.

[0049] like Figure 4 As shown, the capacitive loading structure 5 is disposed in the third-order mode current zero region or approximately current zero region of the folded dipole radiation structure 4, with a gap width G1 = 1 mm. The capacitive loading structure 5 can be a gap capacitor, a small lumped capacitor connected across the gap, or other structures capable of forming an equivalent capacitive loading.

[0050] Figures 5 to 8 This illustration demonstrates the impact of the capacitively loaded structure on the antenna mode distribution, impedance matching characteristics, and key structural parameters in this embodiment. Specifically, Figure 5 This is a schematic diagram of the third-order mode current zero of the radiator designed in this invention. Figure 5 It can be seen that the capacitive loading structure is set in the zero-point region or near-zero-point region of the third-order mode current, so it has little disturbance to the distribution of the third-order mode main current, while it can change the fundamental mode current path and equivalent boundary conditions.

[0051] further, Figure 6 The figure shows a comparison of simulation results (S11) with and without the capacitive structure. Figure 6 It can be seen that after setting the capacitive loading structure 5, the -10dB impedance bandwidth of the antenna radiator covers 2.17GHz to 2.95GHz; compared with the unloaded structure, the impedance matching bandwidth after loading is significantly increased, indicating that the capacitive loading structure 5 can effectively regulate the mode distribution and expand the working bandwidth.

[0052] Furthermore, by Figure 7 It can be seen that after setting the capacitive loading structure 5, the current phase distribution in the sidewall region of the folded dipole radiation structure changes, and the far-field cancellation effect caused by the reverse current in the sidewall is weakened, which is beneficial to improving the equivalent radiation resistance and improving the broadband radiation performance.

[0053] Furthermore, by Figure 8 It is known that the gap width of the capacitively loaded structure affects the resonant frequency position and impedance matching degree of the antenna. By reasonably selecting the gap width, multiple matching modes can be distributed close together within the target operating frequency band, thereby achieving mode compression and broadband impedance matching. In summary, Figures 5 to 8 Together, they demonstrate that the present invention, by setting a capacitive loading structure in the zero-point region of the third-order mode current, regulates the distribution of the fundamental mode while minimizing disturbance to the higher-order mode, weakens the reverse current cancellation, and achieves broadband matching within the target frequency band.

[0054] like Figures 9 to 11 As shown, this embodiment verifies the quasi-isotropic radiation performance of the antenna radiator within the target operating frequency band from aspects such as actual gain distribution, gain fluctuation, and efficiency characteristics. The quasi-isotropic radiation performance is characterized by full-space gain fluctuation, which is the difference between the maximum and minimum gain in the same frequency space. Figure 9 The maximum and minimum gain curves across the entire 2.1 GHz to 3 GHz frequency band are shown.

[0055] further, Figure 10 The maximum and minimum gain fluctuation curves across the entire space within the 2.1 GHz to 3 GHz frequency band are displayed. Within the target operating frequency band, the actual gain range of the antenna radiator remains within a relatively small range, indicating that its radiation distribution across the entire space is relatively uniform. This reduces the impact of terminal device attitude changes on communication link stability, thus demonstrating quasi-isotropic radiation characteristics.

[0056] further, Figure 11 The figure shows the simulation results of the overall efficiency of the antenna radiator within the target operating frequency band. Figure 11 It can be seen that the antenna radiator maintains high efficiency within the operating frequency band without significant efficiency collapse, indicating that this embodiment can maintain good energy radiation capability while achieving broadband impedance matching and quasi-isotropic radiation.

[0057] In summary, the mode-compression-based broadband quasi-isotropic antenna radiator described in this invention not only achieves broadband impedance matching within the 2.17 GHz to 2.95 GHz operating frequency band, but also maintains a relatively stable maximum practical gain, a high minimum practical gain, small overall spatial practical gain fluctuations, and good efficiency characteristics within this band. Therefore, this invention can achieve good overall spatial coverage and attitude-insensitive radiation performance over a wide frequency band, making it suitable for IoT terminals, wireless sensor nodes, mobile communication terminals, and other wireless devices requiring broadband coverage and spatial radiation uniformity.

[0058] The above description is merely one embodiment of the present invention and does not limit the scope of protection of the present invention. For those skilled in the art, equivalent substitutions or improvements can be made to the form, size, loading position, power supply method, substrate material, metal layer size, and ground plane shape of the capacitive loading structure without departing from the principle of the present invention, and all such equivalent substitutions or improvements should fall within the scope of protection of the present invention.

Claims

1. A broadband quasi-isotropic antenna radiator based on mode compression, characterized in that, It includes a planar antenna layer (1), a dielectric substrate (2), and a metal ground layer (3) arranged from top to bottom. The planar antenna layer (1) is provided with a folded dipole radiation structure (4), a matching network (6), and a feeding structure (7). The folded dipole radiation structure (4) includes a main radiation arm (41) and a sidewall radiation path (42). A capacitive loading structure (5) is provided on the folded dipole radiation structure (4). The capacitive loading structure (5) is located in the high-order mode current zero region or the approximate current zero region of the folded dipole radiation structure (4). The approximate current zero region is defined as: the region where the change in high-order mode resonant frequency is less than the change in fundamental mode resonant frequency. The capacitive loading structure (5) is used to change the fundamental mode current path and equivalent boundary conditions, so that the fundamental mode operating frequency moves to a higher frequency, while weakening the cancellation effect of the reverse current component in the far field in the side wall radiation path (42), so as to improve the equivalent radiation resistance and realize broadband impedance matching and quasi-isotropic radiation.

2. The broadband quasi-isotropic antenna radiator based on mode compression according to claim 1, characterized in that, The higher-order mode is a third-order mode, and the capacitive loading structure is arranged in the third-order mode current zero-point region of the folded dipole radiation structure.

3. The broadband quasi-isotropic antenna radiator based on mode compression according to claim 2, characterized in that, The capacitive loading structure (5) is disposed in the bent top region of the main radiating arm (41).

4. The broadband quasi-isotropic antenna radiator based on mode compression according to claim 1, characterized in that, The capacitive loading structure (5) includes at least one of the following: gap capacitor, lumped capacitor, interdigitated capacitor, and patch coupling capacitor.

5. The broadband quasi-isotropic antenna radiator based on mode compression according to claim 4, characterized in that, The capacitive loading structure (5) is a gap capacitor formed on the metal conductor of the planar antenna layer (1).

6. The broadband quasi-isotropic antenna radiator based on mode compression according to claim 1, characterized in that, The main radiating arm (41) and the side wall radiating path (42) cooperate to form a U-shaped folded current radiating path.

7. The broadband quasi-isotropic antenna radiator based on mode compression according to claim 1, characterized in that, The matching network (6) includes a first lumped inductor (81), a second lumped inductor (82), a first lumped capacitor (83), and a second lumped capacitor (84). The matching network (6) is connected between the feed structure (7) and the folded dipole radiation structure (4) and is used to transform the impedance and compensate the reactance between the feed structure (7) and the folded dipole radiation structure (4).

8. The broadband quasi-isotropic antenna radiator based on mode compression according to claim 1, characterized in that, The dielectric substrate (2) is made of F4BM material with a dielectric constant of 2.65, a loss tangent of 0.002, and a thickness of 1 mm; the thickness of the planar antenna layer (1) and the metal ground layer (3) is 0.035 mm.

9. The application of the mode compression-based broadband quasi-isotropic antenna radiator as described in any one of claims 1-8 in Internet of Things terminals, wireless sensor nodes, or mobile communication attitude-insensitive wireless communication devices.

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