Low-profile bidirectional end-fire circularly polarized antenna array and adjusting method thereof

Abstract

The invention discloses a low-profile bidirectional end-fire circularly polarized antenna array and an adjusting method thereof, the antenna array comprises 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, and the four left sub-arrays and the four right sub-arrays are arranged on the single-layer F4B dielectric substrate in a central symmetry mode; each sub-array comprises a feed metal column, a short-circuit metal column, a magnetic dipole and an electric dipole, and the adjustment method comprises the steps of introducing polarization constraint conditions, constructing a model, constraining an electric field component in a bidirectional end-fire direction, forming a circularly polarized wave, and accurately adjusting the excitation of each antenna array element according to optimal excitation distribution. The problem of polarization mismatch when a receiving terminal moves among circularly polarized waves in different rotation directions is solved, bidirectional left-hand circularly polarized radiation is flexibly realized, the defect of low end-fire circularly polarized gain of a traditional single electromagnetic dipole is overcome, and bidirectional end-fire gain exceeds 11.5 dBic.

Description

Technical Field

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

[0002] With 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 because they are adapted to the radiation characteristics of such spaces. Circular polarization technology has significant advantages in reducing sensitivity to direction, alleviating multipath interference, and reducing polarization mismatch losses.

[0003] In the past, bidirectional end-fire circularly polarized radiation was mainly achieved by relying on methods based on electric and magnetic complementary dipoles. However, these methods have many problems. When the receiving terminal moves between circularly polarized waves of different rotation directions, polarization mismatch is likely to occur. In addition, there is still much room for improvement in structural design and performance optimization.

[0004] In terms of improving end-fire gain, the traditional single electromagnetic dipole has an omnidirectional radiation pattern in the upward plane, resulting in a relatively low end-fire circular polarization gain, which is difficult to meet the needs of practical applications. To improve this situation, researchers have taken a variety of measures. For example, the introduction of non-driven reflectors and directors to construct a single-fed end-fire CP antenna to improve the unidirectional radiation gain. Although the introduction of reflectors can enhance the unidirectional gain, it also makes it difficult to improve the bidirectional gain at the same time; complementary dipole arrays have complex metal structures and relatively high profiles, and some designs lack the ability to independently control vertical polarization components and orthogonal electric fields, which limits their application in practical scenarios.

[0005] Traditional array antenna design is usually based on the principle of array factor and radiation pattern superposition. When dealing with the mutual coupling problem between array elements, either this coupling effect is ignored or a bulky decoupling structure is introduced. There is a lack of a systematic and efficient design method, which makes it difficult to meet the strict requirements of modern wireless communications on antenna performance. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a low-profile bidirectional end-fire circularly polarized antenna array and an adjustment method thereof to address 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 and are arranged in a centrally symmetrical manner on the single-layer F4B dielectric substrate. 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 to generate end-fire circularly polarized waves. The one-to-sixteen radio frequency circuit is connected to each sub-array through a feeding metal column and a short-circuit metal column.

[0008] Furthermore, the width of the subarray is , the length of the subarray is , the distance between the two center back-to-back units is , the distance between a pair of electric dipoles and magnetic dipoles in the same direction is The radius of the magnetic dipole is R .

[0009] Furthermore, 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] Furthermore, the operating frequency of the antenna array is 2.45 GHz.

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

[0012] Furthermore, the eight sub-arrays include 16 elements in total, and each magnetic dipole and each electric dipole is one element.

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

[0014] Furthermore, 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 It indicates that the electric dipole produces a horizontal polarization 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.

[0015] Furthermore, 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.

[0016] Furthermore, the optimal excitation distribution in step S3 is expressed as: , in, represents the normalized incident wave to the transmit antenna array, represents the conjugate transpose, A Represents the energy distribution characteristics of the array.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention uses electric dipoles and magnetic dipoles to construct an antenna array, and optimizes the amplitude and phase of the horizontal and vertical polarization components in the bidirectional end-fire direction to achieve precise polarization control. On the one hand, it solves the polarization mismatch problem when the receiving terminal moves between circularly polarized waves of different rotation directions, and can flexibly realize bidirectional left-handed circularly polarized radiation to meet diverse communication needs; on the other hand, it effectively improves the end-fire gain, overcomes the defect of low end-fire circular polarization gain of a traditional single electromagnetic dipole, and achieves a bidirectional end-fire gain of more than 11.5 dBic. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a low-profile bidirectional end-fire circularly polarized antenna array; Figure 2 is a schematic diagram of the structure of the subarray; Figure 3 It is a side view of a low-profile bidirectional end-fire circularly polarized antenna array; Figure 4 The simulated and measured radiation patterns at 2.45 GHz, (a) is the xy plane radiation pattern in the bidirectional left-hand circular polarization state; (b) is the yz plane radiation pattern in the bidirectional left-hand circular polarization state. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0020] like Figure 1 As shown, the low-profile bidirectional end-fire 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 arranged in a centrally symmetrical manner on the single-layer F4B dielectric substrate 5, as shown in FIG. Figure 2 As shown, each subarray includes a feed 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 an end-fire circularly polarized wave. The one-to-sixteen RF circuit is connected to each subarray through the feed metal column 1 and the short-circuit metal column 2, as shown in FIG. Figure 3 The figure shows a side view of a low-profile bidirectional end-fire circularly polarized antenna array, where 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 help to achieve a low-profile design of the antenna, making the overall structure of the antenna compact and easy to integrate and install.

[0021] The eight subarrays consist of 16 elements in total, with each magnetic dipole and each electric dipole having two centers, and the distance between back-to-back elements is set to , the distance between a pair of electric and magnetic dipoles in the same direction is set to , after optimization , ,in, Represents the width of the array structure, ; Represents the length of the array structure, . represents the distance between two center back-to-back units, ; represents the distance between electromagnetic dipoles in the same direction, , R represents the radius of the magnetic dipole, R =22.1 mm.

[0022] The length, width and other parameters of the electric dipole and the related dimensions of the magnetic dipole of the present invention are optimized according to the working frequency of the antenna 2.45 GHz and the desired radiation performance to ensure that the required horizontal and vertical polarization components can be effectively generated.

[0023] The 1:16 RF circuit is connected to the antenna array. The circuit includes a rheostat, an attenuator, and a phase shifter. In actual operation, these devices adjust the excitation of the 16 antenna elements according to the results of the following calculations, thereby achieving bidirectional left-hand circular polarization.

[0024] The adjustment method of the low-profile bidirectional end-fire circularly polarized antenna array described in the present invention comprises the following steps: (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 and introducing the polarization constraint, the constructed model 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 It indicates that the electric dipole produces a horizontal polarization 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.

[0025] (2) Constrain the electric field component in the bidirectional end-fire direction to form a circularly polarized wave; In the design of bidirectional end-fire left-hand circular polarization radiation, a specific electric field amplitude and phase relationship must be met to achieve bidirectional left-hand circular polarization. That is, when the electric field amplitudes of vertically polarized radiation and horizontally polarized radiation are equal and the phase difference is Circularly polarized waves can be formed when , so the electric field component in the bidirectional end-fire direction is constrained, and its expression is: , And the following conditions must be met to ensure that ideal circularly polarized waves can be generated in the bidirectional end-fire direction.

[0026] , in, Indicates the phase, represents the amplitude, e represents the phase of the electromagnetic wave, j Indicates a complex number, and the subscripts “+” and “-” indicate two opposite end-fire directions.

[0027] (3) 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; In order to find the optimal solution under the above constraints, the present invention uses the Lagrange multiplier method to obtain the following formula: , The above formula calculates It is the optimal excitation distribution of 16 antenna elements in different states.

[0028] (4) Accurately adjust the excitation of each antenna array element based on the optimal excitation distribution.

[0029] Through the variable resistor, attenuator and phase shifter in the one-to-sixteen RF circuit, the above formula is calculated The amplitude and phase information of each element in the antenna is used to accurately adjust the excitation of each antenna element. Example

[0030] A 2.45GHz electric dipole-magnetic dipole combined bidirectional end-fire low-profile left-hand circularly polarized antenna array was constructed. Its eight subarrays are arranged symmetrically on a single-layer F4B dielectric substrate, and the electric dipoles and magnetic dipoles of each subarray work normally.

[0031] In this embodiment, , The one-to-sixteen RF circuit provides each antenna element with the optimal excitation distribution in a bidirectional left-hand circular polarization state based on the calculation results.

[0032] like Figure 4 As shown in the figure, the radiation performance of the antenna is simulated and analyzed by electromagnetic simulation software, and it is found that at the operating frequency of 2.45GHz, the bidirectional end-fire gain of the antenna reaches 11.8dBic, and the axial ratio is 0.4dB. Among them, (a) is the xy plane radiation pattern in the bidirectional left-hand circular polarization state; (b) is the yz plane radiation pattern in the bidirectional left-hand circular polarization state, the half-power beamwidth in the xy plane and yz plane are 36° and 38° respectively, and the 3-dB AR beamwidth is 40° and 39° respectively.

[0033] The antenna array was physically manufactured and tested using professional testing 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 beamwidths 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 an end-fire circularly polarized wave. The one-to-sixteen radio frequency circuit is connected to each sub-array via the feeding metal column (1) and the short-circuit metal column (2).

2. The low-profile bidirectional end-fire circularly polarized antenna array according to claim 1, characterized in that: The width of the subarray is , the length of the subarray is , the distance between the two center back-to-back units is , the distance between a pair of electric dipoles and magnetic dipoles in the same direction is The radius of the magnetic dipole is R .

3. 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.

4. 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.

5. 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.

6. The low-profile bidirectional end-fire circularly polarized antenna array according to claim 1, characterized in that: The eight sub-arrays include a total of 16 elements, with each magnetic dipole (3) and each electric dipole (4) being one element.

7. 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 6, 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.

8. The method for adjusting a low-profile bidirectional end-fire circularly polarized antenna array according to claim 7, 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.

9. The method for adjusting a low-profile bidirectional end-fire circularly polarized antenna array according to claim 7, 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.

10. The adjustment method of the low-profile bidirectional end-fire circularly polarized antenna array according to claim 7, characterized in that: The optimal excitation distribution in step S3 is expressed as: ， in, represents the normalized incident wave to the transmit antenna array, represents the conjugate transpose, A Represents the energy distribution characteristics of the array.

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