A pattern reconfigurable antenna based on common mode and differential mode theory

Abstract

The application belongs to the technical field of reconfigurable antennas, and particularly provides a directional pattern reconfigurable antenna based on common mode and differential mode theory, which is used to solve the problems of existing directional pattern reconfigurable antennas, such as too large size, high cost, complex structure and few reconfiguration states, and further meet the development needs of antenna miniaturization, low cost and multi-state direction. Based on the common mode / differential mode principle, multiple state directional patterns share the same radiation unit, and a double feeding structure is adopted. When a single feeding is adopted, the antenna generates a forward radiation pattern or a conical pattern; when two coupled feeding structures are fed with equal amplitude and in-phase or anti-phase, the antenna generates a left tilt pattern or a right tilt pattern. In summary, the application can realize the reconfiguration between the forward radiation pattern, the conical pattern and the left and right tilt patterns, and the reconfiguration mode is simple and universal. Meanwhile, the antenna has the advantages of simple structure, small size and low cost.

Description

Technical Field

[0001] This invention belongs to the field of reconfigurable antenna technology, specifically providing a pattern reconfigurable antenna based on common-mode and differential-mode theory. Background Technology

[0002] As a new type of antenna, the pattern reconfigurable antenna can switch between different types of radiation patterns compared with traditional antennas. It also has many advantages such as small size, light weight, low cost, and high sensitivity.

[0003] Currently, reconfigurable radiation patterns mainly include conical patterns, end-fire patterns, tilted patterns, broadside patterns, and backfire patterns. Among them, reconfigurable antennas with conical-broadside and tilted-broadside radiation patterns have been studied extensively and can be applied to multiple scenarios, such as vehicle-mounted communication, base station and handheld terminal communication. Their pattern reconfiguration methods mainly employ the characteristic mode method, reconfigurable feed networks, directing / reversing, local excitation, etc. For example, Ren Q et al. (Ren Q, Qian B, Chen X, et al. Linear Antenna Array With Large Element Spacing for Wide-Angle Beam Scanning With Suppressed Grating Lobes[J].IEEE Antennas and Wireless Propagation Letters,2022,21(6):1258-1262.) designed a reconfigurable conical-forward radiation pattern antenna based on the switching principle. By switching the feed port, the reconfiguration between the forward radiation pattern and the conical radiation pattern was achieved. However, the antenna pattern types are still limited, and the antenna size is relatively large, which is not conducive to the design and fabrication of integrated systems, and the cost is high. For example, Wang Z et al. (Wang Z, Dong Y, Peng Z, et al. Hybrid Metasurface, Dielectric Resonator, Low-Cost, Wide-Angle Beam-Scanning Antenna for 5G Base Station Application[J]. IEEE Transactions on Antennas and Propagation, 2022, 70(9): 7646-7658.) proposed a tilt-forward radiation pattern reconfigurable antenna based on Huygens' principle. By switching the feed network, the reconfiguration between the forward radiation pattern and the two tilt patterns can be achieved. However, the ground plane of this antenna is a defective ground structure, which is large in size. At the same time, the Huygens element is implemented in the form of dielectric resonance, which is costly and has limited application scenarios.

[0004] However, there is limited research on reconfigurable antennas with conical-tilted-forward radiation patterns, and existing implementation methods are not universally applicable and have drawbacks such as complex antenna design, high cost, and large size. In addition, in order to be suitable for more complex and diverse application scenarios and to demonstrate the unique advantages of reconfigurable antennas, pattern reconfigurable antennas are developing towards miniaturization, low cost, and multi-state characteristics. Summary of the Invention

[0005] The purpose of this invention is to address the problems of excessive size, high cost, complex structure, and limited reconfiguration states in existing pattern-reconfigurable antennas by providing a pattern-reconfigurable antenna based on common-mode and differential-mode theory. This addresses the development needs for antenna miniaturization, low cost, and multi-state directional capabilities. Based on the common-mode / differential-mode principle, this invention allows multiple pattern configurations to share the same radiating element, enabling reconfiguration between forward radiation patterns, conical patterns, and left / right tilted patterns. Furthermore, the antenna boasts advantages such as simple structure, small size, and low cost, making it highly valuable for applications.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A pattern-reconfigurable antenna based on common-mode and differential-mode theory includes: an upper dielectric substrate 1, a lower dielectric substrate 2, nylon support pillars 3, a first coaxial cable 4, and a second coaxial cable 5. The upper dielectric substrate is disposed above the lower dielectric substrate via the nylon support pillars, and an air gap is formed between the upper and lower dielectric substrates. Its characteristic is that:

[0008] A metal ground 11 is provided on the lower surface of the lower dielectric substrate 2;

[0009] A rectangular radiating patch 6, a central disk 7, and a short stub 8 are disposed on the upper surface of the upper dielectric substrate 1. A left L-shaped branch 9 and a right L-shaped branch 10 are disposed on the lower surface of the upper dielectric substrate 1. A circular groove is formed in the center of the rectangular radiating patch, and the central disk is located in the center of the circular groove. The left L-shaped branch and the right L-shaped branch are symmetrically arranged about the centerline of the lower surface of the upper dielectric substrate. A circular metal connecting piece is disposed at the end of the short branch of the right L-shaped branch. The left L-shaped branch is connected to the short stub through a short-circuit metal post. The left L-shaped branch and the right L-shaped branch are respectively connected to the metal ground through short-circuit metal posts.

[0010] The inner conductor of the first coaxial cable 4 is connected to a short stub and then to the left L-shaped stub. The outer conductor of the first coaxial cable 4 is connected to the right L-shaped stub 10 through a circular metal connecting piece and then to the metal ground. The inner conductor of the second coaxial cable 5 is connected to the central disk 7, and the outer conductor is connected to the metal ground.

[0011] Furthermore, the first coaxial cable 4, the short stub 8, the left L-shaped stub 9, and the right L-shaped stub 10 together form the first coupling power supply structure and provide coupling power supply to the rectangular radiating patch 6; the coaxial cable 5 and the central disk 7 form the second coupling power supply structure and provide coupling power supply to the rectangular radiating patch 6.

[0012] Furthermore, when the first coupled feeding structure is fed alone, the antenna produces a forward radiation pattern; when the second coupled feeding structure is fed alone, the antenna produces a conical pattern; when the first coupled feeding structure and the second coupled feeding structure are fed with equal amplitude and in phase (common-mode feeding), the antenna produces a left-tilted pattern; and when the first coupled feeding structure and the second coupled feeding structure are fed with equal amplitude and out of phase (differential-mode feeding), the antenna produces a right-tilted pattern.

[0013] Furthermore, the radiation dimensions of the pattern-reconfigurable antenna are 0.46λ0×0.23λ0×0.11λ0, where λ0 is the operating wavelength at the center frequency of the antenna.

[0014] In terms of working principle:

[0015] When the first coupled feeding structure is fed alone, the left and right current directions on the antenna radiating patch are consistent, which can be equivalent to a horizontally placed dipole. Due to the presence of the metal ground, a horizontally polarized forward radiation pattern is generated. Similarly, when the second coupled feeding structure is fed alone, the left and right current directions on the antenna radiating patch are opposite, which can be equivalent to a vertically placed monopole. Due to the presence of the metal ground, a vertically polarized conical radiation pattern is generated. Since the forward radiation pattern and the conical radiation pattern are orthogonal in polarization, the first coupled feeding structure and the second coupled feeding structure have a high degree of isolation. When the first and second coupled feeding structures are simultaneously fed with equal amplitude and in phase (common-mode feeding), the current direction on the left side of the antenna radiating patch is consistent, thus enhancing the current, while the current direction on the right side is opposite, thus canceling it out. This can be equivalent to the left side being a radiator and the right side being a reflector, resulting in a radiation pattern tilted to the left. Similarly, when the first and second coupled feeding structures are simultaneously fed with equal amplitude and out of phase (differential-mode feeding), the current direction on the right side of the antenna radiating patch is consistent, thus enhancing the current, while the current direction on the left side is opposite, thus canceling it out. This can be equivalent to the right side being a radiator and the left side being a reflector, resulting in a radiation pattern tilted to the right.

[0016] In summary, based on the above technical solutions, the beneficial effects of the present invention are as follows:

[0017] 1. The reconfigurable antenna provided by this invention can realize four reconfigurable radiation patterns, namely, forward radiation pattern, cone pattern, left-tilted pattern, and right-tilted pattern. The reconfiguration method is simple and universal, and can be applied to a variety of working scenarios, such as Internet of Things (IoT), drone communication, vehicle communication, base station, etc.

[0018] 2. The main radiating structure of the pattern-reconfigurable antenna provided by this invention can be implemented by a printed PCB board, which is low in cost and simple to process; the overall antenna size is 0.46λ0×0.23λ0×0.11λ0, and the overall antenna has obvious miniaturization advantages, which is less than half a wavelength. It can be used not only alone, but also in large beam scanning arrays. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the pattern reconfigurable antenna based on common-mode and differential-mode theory of the present invention.

[0020] Figure 2 This is a schematic diagram of the upper dielectric substrate in the pattern reconfigurable antenna based on common-mode and differential-mode theory of the present invention, wherein (a) is the front structure and (b) is the back structure.

[0021] Figure 3 The diagram shows the simulation results of the return loss of the pattern reconfigurable antenna based on common-mode and differential-mode theory in an embodiment of the present invention.

[0022] Figure 4 The diagram shows the simulation results of the radiating patch current distribution and 3D radiation pattern at the center frequency of the pattern reconfigurable antenna based on common-mode and differential-mode theory in this embodiment of the invention.

[0023] Figure 5 The above diagram shows the simulation results of the peak actual gain of the pattern reconfigurable antenna under various states in the operating frequency band based on common-mode and differential-mode theory in this embodiment of the invention.

[0024] Figure 6 The diagram shows the simulation results of the radiation efficiency of the pattern reconfigurable antenna under various states within the operating frequency band based on common-mode and differential-mode theories in this embodiment of the invention.

[0025] Figure 7 The above are simulation results of the planar radiation pattern at the center frequency of the pattern reconfigurable antenna based on common-mode and differential-mode theory in various states according to an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0027] Example 1

[0028] This embodiment provides a pattern-reconfigurable antenna based on common-mode and differential-mode theory, the structure of which is as follows: Figure 1As shown, it includes: an upper dielectric substrate 1, a lower dielectric substrate 2, nylon support pillars 3, a first coaxial cable 4, and a second coaxial cable 5. The upper dielectric substrate is disposed above the lower dielectric substrate via the nylon support pillars, and an air gap is formed between the upper and lower dielectric substrates; wherein:

[0029] The lower dielectric substrate 2 is a single-layer board (with a metal layer on one side), and its lower surface is printed with an all-metal ground plane 11.

[0030] The upper dielectric substrate 1 is a double-layer board (double-sided metal-coated). The metal patterns printed on its upper surface include: a rectangular radiating patch 6, a central disk 7, and a short stub 8. The metal patterns printed on its lower surface include: a left L-shaped branch 9 and a right L-shaped branch 10. A circular groove is opened in the center of the rectangular radiating patch, and the central disk is located in the center of the circular groove, ensuring that the central disk is separated from the rectangular radiating patch. The left L-shaped branch 9 and the right L-shaped branch 10 are symmetrically arranged about the centerline of the lower surface of the upper dielectric substrate, and the short branch points to the centerline and the long branch is parallel to the wide side of the rectangular radiating patch. A circular metal connecting piece is provided at the end of the short branch of the right L-shaped branch. The left L-shaped branch is connected to the short stub 8 through a short-circuit metal post. The left L-shaped branch and the right L-shaped branch are respectively connected to the metal ground 11 through short-circuit metal posts.

[0031] The first coaxial cable 4 and the second coaxial cable 5 are located between the upper dielectric substrate 1 and the lower dielectric substrate 2. The inner conductor of the first coaxial cable 4 is connected to the short line 8 on the upper surface of the upper dielectric substrate and is connected to the left L-shaped branch 9 on the lower surface of the upper dielectric substrate through the short line 8. The outer conductor of the first coaxial cable 4 is connected to the right L-shaped branch 10 on the lower surface of the upper dielectric substrate through a circular metal connecting piece and is grounded (connected to metal ground 11).

[0032] In the aforementioned reconfigurable antenna, the first coaxial cable 4, the stub 8, the left L-shaped stub 9, and the right L-shaped stub 10 together form the first coupled feeding structure and provide coupled feeding to the radiating patch 6; the inner conductor of the second coaxial cable 5 is connected to the central disk 7 on the upper surface of the upper dielectric substrate, and the outer conductor is connected to the all-metal ground 11. The coaxial cable 5 and the central disk 7 form the second coupled feeding structure and provide coupled feeding to the radiating patch 6.

[0033] When the first and second coupled feed structures are fed separately, two different radiation patterns are generated: a forward radiation pattern and a conical pattern. The specific principle is as follows: when the first coupled feed structure is fed alone, the left and right current directions on the antenna radiating patch are consistent, which can be equivalent to a horizontally placed dipole. Due to the presence of the metal ground, a horizontally polarized forward radiation pattern is generated. Similarly, when the second coupled feed structure is fed alone, the left and right current directions on the antenna radiating patch are opposite, which can be equivalent to a vertically placed monopole. Due to the presence of the metal ground, a vertically polarized conical pattern is generated. Because the polarization of the forward radiation pattern and the conical pattern is orthogonal, the first and second coupled feed structures have a high degree of isolation, exceeding 28.5 dB in the passband.

[0034] When the first and second coupled feeding structures are fed simultaneously, a tilted radiation pattern is generated. The specific principle is as follows: when the first and second coupled feeding structures are fed with equal amplitude and in phase (common-mode feeding) at the same time, the current direction on the left side of the antenna radiating patch is consistent, thus enhancing the antenna, while the current direction on the right side is opposite, thus canceling the current. This can be equivalent to the left side being a radiator and the right side being a reflector, thus generating a radiation pattern tilted to the left. Similarly, when the first and second coupled feeding structures are fed with equal amplitude and opposite phase (differential-mode feeding) at the same time, the current direction on the right side of the antenna radiating patch is consistent, thus enhancing the antenna, while the current direction on the left side is opposite, thus canceling the current. This can be equivalent to the right side being a radiator and the left side being a reflector, thus generating a radiation pattern tilted to the right.

[0035] It should be noted that the short-circuit metal pillars connected between the left L-shaped stub 9 and the metal ground 11, and the right L-shaped stub 10 and the metal ground 11, are used to achieve port impedance matching of the first coupling feed structure. The positions of the connection points on the left L-shaped stub 9 and the right L-shaped stub 10 can be optimized and adjusted according to the port impedance matching situation. In this embodiment, in order to fix the short-circuit metal pillars, they are made to pass through the upper dielectric substrate 1 and be flush with the upper surface of the upper dielectric substrate.

[0036] Furthermore, in this embodiment, the overall dimensions of the pattern reconfigurable antenna based on common-mode and differential-mode theory are 40mm × 20mm × 10mm (0.46λ0 × 0.23λ0 × 0.11λ0); the dielectric substrate is of type F4BM, with a thickness of 0.787mm, a dielectric constant of 4.4, and a loss tangent of 0.0025; the rectangular radiating patch has a length and width of 30mm and 15mm respectively, and the radius of its central circular slot is 2.4mm; the radius of the central disk is 1.4mm; the width of the L-shaped stub and the stub is 1.5mm, the length of the stub is 3mm, and the total length of the L-shaped stub is 8.4mm; the radii of the short-circuit metal pillar and the nylon pillar are 0.5mm and 1mm respectively.

[0037] The dimensions described above are specific dimensions calculated and optimized for this embodiment, used to illustrate the beneficial effects of the present invention, and to perform simulation tests on the pattern reconfigurable antenna in this embodiment.

[0038] like Figure 3 The figure shows the simulation results of antenna return loss in this embodiment. As can be seen from the figure, under the four radiation states of the antenna in the range of 3.32GHz-3.7GHz, the return loss is less than -10dB, the impedance bandwidth is more than 10%, the bandwidth is relatively wide, and the isolation of the two ports is higher than 28.5dB throughout the passband. It has the characteristics of high isolation and is suitable for a variety of scenarios, such as Internet of Things (IoT), drone communication, vehicle communication, base stations, etc.

[0039] like Figure 4 The figure shows the simulation results of the radiating patch current distribution and 3D radiation pattern under different states at the center frequency of the antenna in this embodiment. As can be seen from the figure, at the center frequency f = 3.5 GHz, the rectangular radiating patch is divided into left and right parts by the dashed line. When only the first coupled feeding structure is fed, the current distribution of the left and right parts is in phase, and the antenna operates in the forward radiation pattern. When only the second coupled feeding structure is fed, the current distribution of the left and right parts is out of phase, and the antenna operates in the conical radiation pattern. When the coupled structure is fed in common mode, the current distribution of the left part is in phase, and the current distribution of the right part is out of phase, and the antenna operates in the left tilted radiation pattern. When the coupled structure is fed in differential mode, the current distribution of the right part is in phase, and the current distribution of the left part is out of phase, and the antenna operates in the right tilted radiation pattern.

[0040] like Figure 5 The figure shows the actual simulation results of the peak gain under various states within the antenna's operating frequency band in this embodiment. As can be seen from the figure, at the center frequency point f = 3.5 GHz, the maximum actual gain of the antenna under the four states are 7.8 dBi, 4.98 dBi, 7.45 dBi and 7.44 dBi, respectively.

[0041] like Figure 6 The figure shows the simulation results of the radiation efficiency of the antenna under various states in the operating frequency band of this embodiment. It can be seen from the figure that the maximum radiation efficiency of the antenna exceeds 88.3% at the center frequency point f = 3.5 GHz.

[0042] like Figure 7 The figure shows the simulation results of the planar radiation pattern at the center frequency of the antenna in this embodiment under various states. It can be seen from the figure that the cross polarization of the antenna is better than -14.5dB under different states, and the polarization purity is high. Among them, the beam pointing of the cone pattern is ±48°, and the beam pointing of the left (right) tilted pattern is -30° (30°).

[0043] Therefore, it can be seen that the antenna pattern of the present invention can be a forward radiation pattern, a cone pattern, a left-tilted pattern, and a right-tilted pattern. Figure 4 It can switch between various states, and the implementation method is simple, the antenna structure is compact, the cost is low, and the gain and efficiency are high.

[0044] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A pattern-reconfigurable antenna based on common-mode and differential-mode theory, comprising: The upper dielectric substrate (1), the lower dielectric substrate (2), the nylon support pillar (3), the first coaxial cable (4), and the second coaxial cable (5) are provided. The upper dielectric substrate is positioned above the lower dielectric substrate via the nylon support pillar, and an air gap is formed between the upper and lower dielectric substrates. The feature is that: A metal ground (11) is provided on the lower surface of the lower dielectric substrate (2); A rectangular radiating patch (6), a central disk (7), and a short stub (8) are provided on the upper surface of the upper dielectric substrate (1). A left L-shaped branch (9) and a right L-shaped branch (10) are provided on the lower surface of the upper dielectric substrate (1). A circular groove is opened in the center of the rectangular radiating patch, and the central disk is located in the center of the circular groove. The left L-shaped branch and the right L-shaped branch are symmetrically arranged about the center line of the lower surface of the upper dielectric substrate. A circular metal connecting piece is provided at the end of the short branch of the right L-shaped branch. The left L-shaped branch is connected to the short stub through a short-circuit metal post. The left L-shaped branch and the right L-shaped branch are respectively connected to the metal ground through short-circuit metal posts. The inner conductor of the first coaxial cable (4) is connected to a short stub and then to the left L-shaped stub. The outer conductor of the first coaxial cable (4) is connected to the right L-shaped stub (10) through a circular metal connecting piece and then to the metal ground. The inner conductor of the second coaxial cable (5) is connected to the central disk (7), and the outer conductor is connected to the metal ground. The first coaxial cable, the short stub, the left L-shaped stub, and the right L-shaped stub together form the first coupling feed structure, which couples and feeds the rectangular radial patch; the coaxial cable and the central disk form the second coupling feed structure, which couples and feeds the rectangular radial patch. When the first coupled feeding structure is fed alone, the antenna produces a forward radiation pattern. When the second coupled feeding structure is fed alone, the antenna produces a conical pattern. When the first coupled feeding structure and the second coupled feeding structure are fed with equal amplitude and in phase, the antenna produces a left-tilted pattern. When the first coupled feeding structure and the second coupled feeding structure are fed with equal amplitude and out of phase, the antenna produces a right-tilted pattern.

2. The pattern-reconfigurable antenna based on common-mode and differential-mode theory as described in claim 1, characterized in that, The radiation dimensions of the pattern reconfigurable antenna are 0.46λ0×0.23λ0×0.11λ0, where λ0 is the operating wavelength at the center frequency of the antenna.

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