A Low-Profile Bidirectional End-Fire Circularly Polarized Antenna Array and Its Adjustment Method

Abstract

The present invention discloses a low-profile bidirectional end-fire circularly polarized antenna array and an adjustment method thereof. The antenna array includes eight sub-arrays, a single-layer F4B dielectric substrate, and a one-to-sixteen radio frequency circuit. The eight sub-arrays are divided into four left sub-arrays and four right sub-arrays, which are arranged on the single-layer F4B dielectric substrate in a centrosymmetric manner. Each sub-array includes a feeding metal column, a short-circuit metal column, a magnetic dipole, and an electric dipole. The adjustment method includes introducing polarization constraint conditions, constructing a model, constraining the electric field components in the bidirectional end-fire directions to form circularly polarized waves, and precisely adjusting the excitation of each antenna array element according to the optimal excitation distribution. The present invention not only solves the polarization mismatch problem when the receiving terminal moves between circularly polarized waves with different rotation directions, flexibly realizes bidirectional left-handed circular polarization radiation, but also overcomes the defect of low end-fire circular polarization gain of traditional single electromagnetic dipoles, and realizes a bidirectional end-fire gain exceeding 11.5 dBic.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication, and particularly to a low-profile bidirectional end-fire circularly polarized antenna array and an adjustment method thereof. Background Art

[0002] In the process of the continuous development of wireless communication technology, the demand for antenna performance in special environments has become increasingly prominent. Bidirectional end-fire antennas have become one of the key research areas due to their adaptation to the radiation characteristics of such spaces. Circular polarization technology has significant advantages in reducing the sensitivity to direction, alleviating multipath interference, and reducing polarization mismatch loss.

[0003] In the past, in order to achieve bidirectional end-fire circular polarization radiation, methods based on electrically and magnetically complementary dipoles were mainly used. However, these methods have many problems. When the receiving terminal moves between circularly polarized waves with different rotation directions, polarization mismatch is likely to occur; and there is still a large room for improvement in structural design and performance optimization.

[0004] In terms of improving the end-fire gain, the traditional single electromagnetic dipole has a relatively low end-fire circular polarization gain because it presents an omnidirectional radiation pattern in the elevation plane, which is difficult to meet the actual application requirements. To improve this situation, researchers have taken various measures. For example, a non-driven reflector and a director are introduced to construct a single-fed end-fire CP antenna to improve the unidirectional radiation gain. Although the introduction of the reflector can enhance the unidirectional gain, it also makes it difficult to improve the bidirectional gain at the same time; the complementary dipole array has problems such as a complex metal structure and a relatively high profile, and some designs also lack the vertical polarization component and the independent control ability for the orthogonal electric field, which limits its application in actual scenarios.

[0005] Traditional array antenna designs are usually based on the superposition principle of the array factor and the radiation pattern. When dealing with the mutual coupling problem between array elements, either this coupling effect is ignored, or a large decoupling structure is introduced, lacking a systematic and efficient design method, and it is difficult to meet the strict requirements of modern wireless communication for antenna performance. Summary of the Invention

[0006] Object of the Invention: The object of the present invention is to provide a low-profile bidirectional end-fire circularly polarized antenna array and an adjustment method thereof to solve the deficiencies of existing bidirectional end-fire circularly polarized antennas.

[0007] Technical solution: The low-profile bidirectional end-fire circularly polarized antenna array described in the present invention includes eight sub-arrays, a single-layer F4B dielectric substrate, and a one-to-sixteen radio frequency circuit. The eight sub-arrays are divided into four left sub-arrays and four right sub-arrays, which are arranged on the single-layer F4B dielectric substrate in a centrosymmetric manner. Each sub-array includes a feeding metal column, a short-circuit metal column, a magnetic dipole, and an electric dipole. The magnetic dipole provides vertical radiation in the end-fire direction, and the electric dipole provides horizontal radiation in the end-fire direction. The radiation generated by the two forms a pair of orthogonal components, generating an end-fire circularly polarized wave. The one-to-sixteen radio frequency circuit is connected to each sub-array through the feeding metal column and the short-circuit metal column.

[0008] Further, the width of the sub-array is , the length of the sub-array is , the distance between two center-to-back units is , the spacing between a pair of co-directional electric dipoles and magnetic dipoles is , the radius of the magnetic dipole is R .

[0009] Further, the single-layer F4B dielectric substrate has a thickness of 3 mm, a relative dielectric constant of 2.55, and a loss tangent of 0.0015.

[0010] Further, the operating frequency of the antenna array is 2.45 GHz.

[0011] Further, the one-to-sixteen radio frequency circuit includes a variable resistor, an attenuator, and a phase shifter.

[0012] Further, the eight sub-arrays altogether include 16 elements, with each magnetic dipole and each electric dipole being one element.

[0013] The adjustment method of the low-profile bidirectional end-fire circularly polarized antenna array described in the present invention includes the following steps:

[0014] S1: Taking the ratio of the total energy of the transmitting array in the end-fire direction to the total power of the transmitting array as the performance index, introducing polarization constraint conditions, and constructing a model;

[0015] S2: Constraining the electric field components in the bidirectional end-fire directions to form a circularly polarized wave;

[0016] S3: Using the Lagrange multiplier method to solve the optimal solution under the constraint conditions in step S1, which is the optimal excitation distribution of the antenna array in different states;

[0017] S4: Precisely adjusting the excitation of each antenna array element according to the optimal excitation distribution.

[0018] Further, the model constructed in step S1 is:

[0019] ,

[0020] wherein, represents the normalized incident wave of the transmitting antenna array, determining the excitation amplitude and phase information of each antenna element; represents the conjugate transpose, A represents the energy distribution characteristic of the array, , represents the matrix of the field components radiated by the transmitting array; represents the vector of the electric field components for controlling polarization,

[0021] ,

[0022] wherein, and represent that the magnetic dipole generates a vertically polarized component in the far field; and represent that the electric dipole generates a horizontally polarized component, and the subscripts "+" and "-" represent two opposite end-fire directions; represents the field component generated when the i-th antenna element of the transmitting array is excited, wherein , t is the number of transmitting antennas, r is the total number of transmitting and receiving antennas,

[0023] Therefore, it can be obtained that:

[0024] ,

[0025] wherein, T represents the transpose matrix.

[0026] Furthermore, the condition for the step S2 to form a circularly polarized wave is that the electric field amplitudes of the vertically polarized radiation and the horizontally polarized radiation are equal and the phase difference is at that time.

[0027] Furthermore, the optimal excitation distribution of the step S3 is expressed as:

[0028] ,

[0029] wherein, represents the normalized incident wave of the transmitting antenna array, represents the conjugate transpose, A represents the energy distribution characteristic of the array.

[0030] Advantages: Compared with the prior art, the present invention has the following remarkable advantages: By using electric dipoles and magnetic dipoles to construct an antenna array and optimizing the amplitude and phase of the horizontal and vertical polarization components in the broadside direction, precise polarization control is achieved. On the one hand, the polarization mismatch problem when the receiving terminal moves between circularly polarized waves with different rotation directions is solved, and bidirectional left-handed circular polarization radiation can be flexibly realized to meet diverse communication requirements. On the other hand, the broadside gain is effectively improved, overcoming the defect of low broadside circular polarization gain of traditional single electromagnetic dipoles, and achieving a bidirectional broadside gain exceeding 11.5 dBic. Description of the Drawings

[0031] Figure 1 It is a schematic structural diagram of a low-profile bidirectional broadside circularly polarized antenna array;

[0032] Figure 2 It is a schematic structural diagram of a sub-array;

[0033] Figure 3 It is a side view of a low-profile bidirectional broadside circularly polarized antenna array;

[0034] Figure 4 It is the simulated and measured radiation patterns at 2.45 GHz. (a) is the radiation pattern in the xy plane in the state of bidirectional left-handed circular polarization; (b) is the radiation pattern in the yz plane in the state of bidirectional left-handed circular polarization. Detailed Embodiments

[0035] The technical solution of the present invention will be further described below in conjunction with the drawings.

[0036] As Figure 1 shown, the low-profile bidirectional broadside circularly polarized antenna array of the present invention includes eight sub-arrays, a single-layer F4B dielectric substrate 5, and a one-to-sixteen radio frequency circuit. The eight sub-arrays are divided into four left sub-arrays and four right sub-arrays and are arranged symmetrically about the center on the single-layer F4B dielectric substrate 5. As Figure 2 shown, each sub-array includes a feeding metal column 1, a short-circuit metal column 2, a magnetic dipole 3, and an electric dipole 4. The magnetic dipole 3 provides vertical radiation in the broadside direction, and the electric dipole 4 provides horizontal radiation in the broadside direction. The radiation generated by the two forms a pair of orthogonal components to generate broadside circularly polarized waves. The one-to-sixteen radio frequency circuit is connected to each sub-array through the feeding metal column 1 and the short-circuit metal column 2. As Figure 3 shown in the side view of the low-profile bidirectional broadside circularly polarized antenna array, the relative dielectric constant of the single-layer F4B dielectric substrate 5 is 2.55, the loss tangent is 0.0015, and the thickness is 3 mm. This dielectric substrate provides a stable support structure for the antenna array, and its electrical performance parameters contribute to the realization of the low-profile design of the antenna, making the overall structure of the antenna compact and facilitating integration and installation.

[0037] The eight sub-arrays altogether include 16 elements, with each magnetic dipole and each electric dipole being one element. The distance between the two centers of the back-to-back elements is set as , and the spacing between a pair of co-directional electric dipoles and magnetic dipoles is set as , and after optimization , , where represents the width of the array structure, ; represents the length of the array structure, . represents the distance between the two center back-to-back units, ; represents the distance between co-directional electromagnetic dipoles, , R represents the radius of the magnetic dipole, R = 22.1 mm.

[0038] The parameters such as the length and width of the electric dipole of the present invention, as well as the relevant dimensions of the magnetic dipole, are all optimized according to the operating frequency of the antenna, 2.45 GHz, and the desired radiation performance, so as to ensure that the required horizontal and vertical polarization components can be effectively generated.

[0039] A one-to-sixteen radio frequency circuit is connected to the antenna array, and this circuit includes a variable resistor, an attenuator, and a phase shifter. During the actual working process, these devices adjust the excitation of the 16 antenna elements according to the results obtained from the following calculations, thereby realizing bidirectional left-handed circular polarization.

[0040] The adjustment method of the low-profile bidirectional end-fire circular polarization antenna array described in the present invention includes the following steps:

[0041] (1) Taking the ratio of the total energy of the transmitting array in the end-fire direction to the total power of the transmitting array as the performance index, introducing polarization constraint conditions, the constructed model is:

[0042] ,

[0043] where represents the normalized incident wave of the transmitting antenna array, and determines the excitation amplitude and phase information of each antenna element; represents the conjugate transpose, A represents the energy distribution characteristic of the array, , represents the field component matrix radiated by the transmitting array; represents the electric field component vector used to control polarization,

[0044] ,

[0045] Among them, and represent the vertical polarization component generated by the magnetic dipole in the far field; and represent the horizontal polarization component generated by the electric dipole. The subscripts "+" and "-" represent two opposite end-fire directions; represents the field component generated when the i-th antenna element of the transmitting array is excited, where , t is the number of transmitting antennas, r is the total number of transmitting and receiving antennas,

[0046] Therefore, it can be obtained that:

[0047] ,

[0048] Among them, T represents the transposed matrix.

[0049] (2) Constrain the electric field components in the two-way end-fire directions to form a circularly polarized wave;

[0050] In the design of two-way end-fire left-handed circular polarization radiation, specific electric field amplitude and phase relationships need to be satisfied to achieve two-way left-handed circular polarization. That is, when the electric field amplitudes of the vertical polarization radiation and the horizontal polarization radiation are equal and the phase difference is , a circularly polarized wave can be formed. Therefore, the electric field components in the two-way end-fire directions are constrained, and its expression is:

[0051] ,

[0052] And the following conditions need to be satisfied to ensure that an ideal circularly polarized wave can be generated in the two-way end-fire directions.

[0053] ,

[0054] Among them, represents the phase, represents the amplitude, e represents the phase of the electromagnetic wave, j represents a complex number. The subscripts "+" and "-" represent two opposite end-fire directions.

[0055] (3) Use the Lagrange multiplier method to solve the optimal solution under the constraint conditions in step S1, which is the optimal excitation distribution of the antenna array in different states;

[0056] To solve the optimal solution under the above constraint conditions, the present invention uses the Lagrange multiplier method to obtain the following formula:

[0057] ,

[0058] The result calculated by the above formula is the optimal excitation distribution of 16 antenna elements in different states.

[0059] (4) Precisely adjust the excitation of each antenna array element according to the optimal excitation distribution.

[0060] Through the variable resistor, attenuator and phase shifter in the one-to-sixteen RF circuit, according to the amplitude and phase information of each element in the result calculated by the above formula precisely adjust the excitation of each antenna element. Embodiment

[0061] Construct a 2.45 GHz electric dipole-magnetic dipole combined bidirectional end-fire low-profile left-handed circularly polarized antenna array. Its eight sub-arrays are symmetrically arranged on a single-layer F4B dielectric substrate, and the electric dipoles and magnetic dipoles of each sub-array work normally.

[0062] In this embodiment, , . The one-to-sixteen RF circuit provides the optimal excitation distribution for each antenna element to achieve the bidirectional left-handed circular polarization state according to the calculation result.

[0063] As Figure 4 shown, through electromagnetic simulation software, the radiation performance of the antenna is simulated and analyzed. It is obtained that at the operating frequency of 2.45 GHz, the bidirectional end-fire gain of the antenna reaches 11.8 dBic, and the axial ratio is 0.4 dB. Among them, (a) is the radiation pattern in the xy plane in the bidirectional left-handed circular polarization state; (b) is the radiation pattern in the yz plane in the bidirectional left-handed circular polarization state. The half-power beam widths in the xy plane and yz plane are 36° and 38° respectively, and the 3-dB AR beam widths are 40° and 39° respectively.

[0064] Fabricate the physical object of the antenna array and test it using professional test equipment. The test results show that at 2.45 GHz, the bidirectional end-fire gain of the antenna is 11.5 dBic, and the axial ratio is 0.45 dB. The half-power beam widths in the xy plane and yz plane are 37° and 39° respectively, which are basically consistent with the simulation results, verifying the effectiveness of the antenna array design of the present invention.

Claims

1. A low-profile bidirectional end-fire circularly polarized antenna array, characterized in that: The invention comprises eight sub-arrays, a single-layer F4B dielectric substrate (5) and a one-to-sixteen radio frequency circuit. The eight sub-arrays are divided into four left sub-arrays and four right sub-arrays and are arranged on the single-layer F4B dielectric substrate (5) in a centrally symmetrical manner. Each sub-array comprises a feeding metal column (1), a short-circuit metal column (2), a magnetic dipole (3) and an electric dipole (4). The magnetic dipole (3) provides vertical radiation in the end-fire direction, and the electric dipole (4) provides horizontal radiation in the end-fire direction. The radiation generated by the two forms a pair of orthogonal components, generating End-fire circularly polarized waves, a one-to-sixteen radio frequency circuit is connected to each subarray through a feeding metal column (1); the magnetic dipole (3) is a semicircular structure, the short-circuit metal column (2) is arranged on one side of the semicircular structure close to the diameter, the electric dipole (4) is a "┑"-shaped structure spaced a distance from the magnetic dipole (3), and the feeding metal column (1) is respectively arranged on the magnetic dipole (3) and the electric dipole (4); the eight subarrays include a total of 16 elements, each magnetic dipole (3) and each electric dipole (4) being one element.

2. The low-profile bidirectional end-fire circularly polarized antenna array according to claim 1, characterized in that: The single-layer F4B dielectric substrate (5) has a thickness of 3 mm, a relative dielectric constant of 2.55, and a loss tangent of 0.0015.

3. The low-profile bidirectional end-fire circularly polarized antenna array according to claim 1, characterized in that: The operating frequency of the antenna array is 2.45 GHz.

4. The low-profile bidirectional end-fire circularly polarized antenna array according to claim 1, characterized in that: The one-to-sixteen radio frequency circuit includes a variable resistor, an attenuator and a phase shifter.

5. A method for adjusting a low-profile bidirectional end-fire circularly polarized antenna array, implemented by using the low-profile bidirectional end-fire circularly polarized antenna array according to any one of claims 1 to 4, characterized in that: The steps include: S1: Taking the ratio of the total energy of the transmitting array in the end-fire direction to the total power of the transmitting array as the performance index, polarization constraints are introduced to build the model; S2: constrain the electric field component in the bidirectional end-fire direction to form a circularly polarized wave; S3: Use the Lagrange multiplier method to find the optimal solution under the constraints of step S1, that is, the optimal excitation distribution of the antenna array under different states; S4: Accurately adjust the excitation of each antenna array element according to the optimal excitation distribution.

6. The adjustment method of the low-profile bidirectional end-fire circularly polarized antenna array according to claim 5, characterized in that: The model constructed in step S1 is: ， in, The normalized incident wave representing the transmit antenna array determines the excitation amplitude and phase information of each antenna element; represents the conjugate transpose, A represents the energy distribution characteristics of the array, , The field component matrix representing the radiation of the transmitting array; represents the electric field component vector used to control polarization, ， in, and It means that the magnetic dipole produces a vertical polarization component in the far field; and Indicates that the electric dipole produces a horizontally polarized component, and the subscripts "+" and "-" represent two opposite end-fire directions; represents the field component generated when the i-th antenna element of the transmitting array is excited, where , t is the number of transmitting antennas, r is the total number of transmitting antennas and receiving antennas, Therefore, we can get: ， in, T Represents the transposed matrix.

7. The adjustment method of the low-profile bidirectional end-fire circularly polarized antenna array according to claim 5, characterized in that: The condition for forming a circularly polarized wave in step S2 is that the electric field amplitudes of the vertically polarized radiation and the horizontally polarized radiation are equal and the phase difference is hour.

8. The method for adjusting a low-profile bidirectional end-fire circularly polarized antenna array according to claim 5, characterized in that: The optimal excitation distribution in step S3 is expressed as: ， in, represents the normalized incident wave at the transmit antenna array, represents the conjugate transpose, A Represents the energy distribution characteristics of the array; The field component matrix representing the radiation of the transmitting array; represents the electric field component vector used to control polarization.

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