Gain calculation method based on finite plane near-field sampling external expansion

Abstract

The invention belongs to the technical field of communication, and particularly relates to a gain calculation method based on finite plane near-field sampling external expansion. The method comprises the following steps: (1) acquiring the distribution of an acquired limited cross-section field, a sampling distance and the aperture size of an antenna to be measured; (2) constructing a virtual equivalent array model, and establishing a forward transmission matrix when the size of the virtual array model is greater than the aperture size of the original to-be-measured antenna; (3) performing calculation to obtain excitation distribution meeting section field distribution, and adjusting excitation of the virtual equivalent array to enable forward field distribution of the virtual equivalent array to be matched with original data; (4) constructing a forward transmission matrix of the expansion plane, and calculating to obtain field distribution of a near field of the expansion plane; and (5) calculating a gain value through the field distribution of the expanded planar near field. According to the method, the virtual equivalent array model is constructed to replace an original to-be-measured antenna model, and an infinite or large enough plane field is generated by utilizing expansion of a finite section field, so that the measurement precision and efficiency are improved.

Description

Technical Field

[0001] The invention belongs to the field of communication technology, and in particular relates to a gain calculation method based on finite plane near-field sampling expansion. Background Art

[0002] With the rapid development of wireless technologies such as mobile communications and satellite navigation, antennas have become an indispensable key component in wireless devices. This change has not only promoted the popularization and application of wireless communications, but also put forward higher requirements on the design and performance of antennas. Among the many antenna performance parameters, gain is one of the core indicators of the antenna and has a significant impact on the overall operation quality of the communication system. Gain not only reflects the radiation ability of the antenna in a specific direction, but also is related to the coverage and transmission efficiency of the signal. Therefore, accurate measurement of antenna gain is crucial to optimizing the performance of wireless communication systems.

[0003] The requirements for antenna accuracy and performance indicators make antenna testing increasingly important in the design process, and high-precision measurement methods are also receiving more and more attention. For electrically large-sized antennas, the application of traditional far-field testing methods requires a sufficiently large test space, which is difficult to meet in some cases. In order to solve this problem, near-field measurement methods came into being and have become a modern testing technology widely used at home and abroad. Among them, the planar near-field measurement method can obtain the electromagnetic field distribution data of the antenna in the near-field area, and then derive the far-field characteristics of the antenna through mathematical processing. It is widely used in the near-field measurement of antennas due to its advantages of simple model and convenient sampling.

[0004] When using planar near field to obtain antenna field distribution and calculate performance indicators, the sampling surface size and sampling interval will have a significant impact on measurement accuracy. When applying planar near field technology to calculate the gain of the antenna to be tested, the gain error will gradually increase as the sampling plane decreases. Especially when the sampling surface is smaller than the size of the antenna aperture to be tested, the gain error will deteriorate significantly, resulting in the calculated gain value lacking reference value. The root cause of this phenomenon is that a smaller sampling area will lose some field information. When the sampling surface cannot cover enough field information, the reliability of the gain result will be affected. At the same time, blindly increasing the sampling area can improve measurement accuracy, but it will extend the sampling time, thereby reducing test efficiency. Therefore, how to optimize the sampling surface size while ensuring measurement accuracy is an important challenge facing the current antenna measurement field. This makes it particularly necessary to develop a method that can still calculate high-precision gain values ​​at a smaller sampling area, so as to balance accuracy and efficiency and improve the overall performance of antenna testing. Summary of the invention

[0005] The present invention proposes a method for accurately measuring antenna gain under limited sampling area conditions. The core of this method is to build a virtual array model so that the field distribution generated by its near field can match the field distribution data obtained by the actual small sampling surface. Based on this model, the amplitude and phase distribution of the virtual array are inverted and solved, thereby effectively expanding the field information of the small sampling area to a larger space.

[0006] The technical solution provided by the present invention is a gain calculation method based on finite plane near-field sampling expansion, comprising: (1) Obtain the collected finite cross-section field distribution , sampling distance and the size of the antenna aperture to be tested; (2) Construct a virtual equivalent array model, and ensure that the size of the virtual array model is larger than the size of the original antenna aperture to be tested, and establish a forward transmission matrix ; (3) Based on The calculated field distribution satisfies the finite cross section Incentive distribution , and adjust the excitation of the virtual equivalent array to , so that the forward field distribution of the virtual equivalent array is consistent with the original finite cross-section field distribution match; (4) Construct the forward transmission matrix of the extended plane ,Depend on The extended plane field distribution is calculated ; (5) By extending the plane field distribution Calculate the gain value.

[0007] Preferably, the free space Green's function is used Constructing the forward transfer matrix , Expressed as ,in Represents the complex electric far-field pattern of the virtual array model.

[0008] Preferably, an ideal point source array is used as an equivalent array, and the forward transmission matrix is ​​equivalent to the free space Green's function.

[0009] Compared with the prior art, the present invention has the following beneficial effects: (1) By constructing a virtual array model to be equivalent to the antenna to be tested, the field information of a small sampling area can be effectively expanded to a larger space, solving the problem of inaccurate gain calculation in the planar near field when the sampling range is insufficient; (2) The proposed method also reduces the size of the sampling area and can obtain accurate gain results under a small sampling area, thus reducing the requirements for the test environment and greatly improving the test efficiency. (3) The array elements of the virtual array constructed by the proposed method are flexible, and any antenna such as an ideal point source, dipole antenna, waveguide antenna, Vivaldi antenna, etc. can be selected. The arrangement method is also suitable for arrays of any arrangement type, such as rectangular uniform arrangement, circular arrangement, polygonal arrangement, and random distribution; (4) The method proposed in the present invention is flexible to implement and has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a flow chart of a gain calculation method based on finite plane near-field sampling expansion in an embodiment of the present invention; Figure 2 It is the planar near-field sampling model in Embodiment 1 of the present invention; Figure 3 is the planar near field distribution of the horn antenna in Example 2 of the present invention; Figure 4 is the planar near field distribution of the waveguide array antenna in Embodiment 2 of the present invention; Figure 5 This is the planar near-field distribution of the microstrip array antenna in Example 2 of the present invention. DETAILED DESCRIPTION

[0011] The present invention is further described below in conjunction with specific embodiments and the accompanying drawings. More details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention is obviously capable of being implemented in a variety of other ways different from the description herein. For those skilled in the art, any substitution, improvement or change made to the embodiments of the present invention is within the protection scope of the present invention, and the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0012] Embodiment 1 This embodiment provides a gain calculation method based on finite plane near-field sampling expansion. The flowchart of the method is as follows: Figure 1 As shown, the specific steps include: 1. Collect the planar near-field data of the antenna to be tested. The planar near-field sampling model is as follows: Figure 2 As shown, the operating frequency of the antenna to be tested is The sizes of the mouth surface are and , the direct distance between the antenna to be tested and the sampling plane is The collected planar near-field data is .

[0013] 2. Construct a virtual equivalent array model. The number of array elements is and , the array element spacing is and , and the virtual equivalent array size is larger than the original antenna aperture size to be tested, that is The virtual equivalent array model i Incentives for each unit It can be expressed as ,in For the i The magnitude of the stimulus, For the i The phase of the excitation, j The initial value of each excitation amplitude is set to 1V, and the initial value of the phase is set to 0°.

[0014] 3. Using Free Space Green's Function Constructing the forward transfer matrix ,but It can be expressed as ,in represents the far-field pattern of the complex electric field of the virtual array model. In this embodiment, since the ideal point source array is used as the equivalent array, the forward transfer matrix here is equivalent to the free space Green's function, that is, , the forward transmission matrix of the subsequent expansion plane = .

[0015] according to The calculated field distribution satisfies the finite cross section The excitation distribution of the virtual array model is adjusted to , and replace the original antenna model to be tested with the adjusted new virtual equivalent array model.

[0016] 4. Construct the forward transmission matrix of the extended plane The expanded planar near-field distribution is obtained by calculating the excitation distribution of the adjusted new virtual equivalent array model. ,in .

[0017] 5. Reuse the obtained extended plane field distribution containing enough field information To calculate the final gain value.

[0018] Example 2 In order to verify the feasibility of the method proposed in the present invention, three types of antennas to be tested were simulated and verified using FEKO and MATLAB: (1) Select the horn antenna as the antenna to be tested, and the operating frequency , the direct distance from the sampling surface , the size of the mouth is , virtual array element spacing , the number of array elements is The planar near field distribution is as follows: Figure 3 As shown, the solid line box represents the sampling area. , the dotted box represents the sampling area The dashed box represents the sampling area. .

[0019] The gain errors calculated by the conventional method directly using the original data under three different sampling planes are compared with the gain errors calculated by the method provided by the present invention. The results are shown in Table 1.

[0020] Table 1 Gain errors calculated by two methods under different sampling planes .

[0021] (2) Selection The waveguide array antenna is used as the antenna to be tested, and the operating frequency , the array element spacing is and , direct distance from the sampling surface , the size of the mouth is , virtual array element spacing , the number of array elements is The planar near field distribution is as follows: Figure 4 As shown, the solid line box represents the sampling area. , the dotted box represents the sampling area The dashed box represents the sampling area. ;

[0022] The gain errors calculated by the conventional method directly using the original data under three different sampling planes are compared with the gain errors calculated by the method of the present invention. The results are shown in Table 2.

[0023] Table 2 Gain errors calculated by two methods under different sampling planes .

[0024] (3) Selection The microstrip array antenna is used as the antenna to be tested, and the operating frequency , the array element spacing is and Direct distance from sampling surface , the size of the mouth is , virtual array element spacing , the number of array elements is The planar near field distribution is as follows: Figure 5 As shown, the solid line box represents the sampling area. , the dotted box represents the sampling area The dashed box represents the sampling area. .

[0025] The gain errors calculated by the conventional method directly using the original data under three different sampling planes are compared with the gain errors calculated by the method of the present invention. The results are shown in Table 3.

[0026] Table 3 Gain errors calculated by two methods under different sampling planes .

[0027] According to the above three groups of simulation experiment results, it can be known that for different types of antennas, whether single antennas or array antennas, whether electrically large-size antennas or electrically small-size antennas, the method of the present invention can greatly improve the accuracy of calculating the gain value of the antenna to be measured using planar near-field technology under a limited sampling surface.

Claims

1. A gain calculation method based on finite plane near-field sampling expansion, characterized in that: include: (1) Obtain the collected finite cross-section field distribution , sampling distance and the size of the antenna aperture to be tested; (2) Construct a virtual equivalent array model, and ensure that the size of the virtual array model is larger than the size of the original antenna aperture to be tested, and establish a forward transmission matrix ; (3) Based on The calculated field distribution of the finite cross section is Incentive distribution , and adjust the excitation of the virtual equivalent array to , so that the forward field distribution of the virtual equivalent array is consistent with the original finite cross-section field distribution match; (4) Construct the forward transmission matrix of the extended plane ,Depend on The extended plane field distribution is calculated ; (5) By extending the plane field distribution Calculate the gain value.

2. The gain calculation method based on finite plane near-field sampling expansion according to claim 1 is characterized in that: Using the free-space Green's function Constructing the forward transfer matrix , Expressed as ,in Represents the far-field pattern of the complex electric field of the virtual equivalent array model.

3. The gain calculation method based on finite plane near-field sampling expansion according to claim 2 is characterized in that: Taking the ideal point source array as the equivalent array, the forward transfer matrix is ​​equivalent to the free-space Green's function.

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