A multi-objective antenna array optimization design method

Abstract

The present invention discloses a multi-objective antenna array optimization design method in the field of antenna transmission efficiency, comprising the following steps: establishing a transmitting antenna array and a receiving antenna array model in a simulation software; performing a full-wave simulation, and obtaining a scattering matrix S of the antenna system after the simulation is completed; calculating the optimal excitation distribution of the antenna corresponding to the desired focusing effect; and calculating the corresponding antenna system transmission efficiency T. array ; Verify whether the expected focus effect is obtained. The method of the present invention adopts the weighted constrained maximum power transmission efficiency method to maximize the system power transmission efficiency while generating the desired focusing electric field distribution pattern in the open area, wherein the number of focuses and their spatial positions can be controlled by modifying the power weight coefficient received by the receiving antenna, which can meet the array antenna design under specific scenario requirements. Compared with other methods for optimizing antenna power transmission efficiency, the calculation time is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of antenna transmission efficiency, and in particular relates to a multi-objective antenna array optimization design method. Background Art

[0002] In recent years, wireless power transmission based on focused antennas has been an active research field. Currently, this technology has been widely used in communication systems, smart homes, and microwave hyperthermia. Most of the previous research in this area focused on the design of wireless power transmission systems with single-focus antennas. However, in real life, we often encounter scenarios where multiple targets and the power allocation between each target must be adjustable, such as wireless information transmission for multiple target users, microwave hyperthermia for multiple target tumors, etc. Therefore, multi-target and power-adjustable wireless power transmission has important research value and practical significance.

[0003] At present, the optimal feeding excitation distribution for wireless power transmission is mainly obtained through optimization algorithms, such as the Levenberg-Marquardt algorithm and the artificial neural network algorithm. However, these methods require huge computing power to support a large number of iterations. If the number of antenna units is large, it takes a lot of time. Another method to achieve wireless power transmission is to use the time reversal (TR) method. In DS Zhao and M. Zhu. Generating microwave spatial fields with arbitrary patterns [J]. IEEE Antennas and Wireless Propagation Letters, 2016, (15): 1739-1742 and DS Zhao. Shaping microwave field of arbitrary intensity patterns in bounded area by time reversal mirror [C]. 2016 Progress in Electromagnetic Research Symposium (PIERS), 2016, 4428-4428., several TR focusing fields have been successfully realized in a closed metal cavity with a synthetic excitation distribution. However, most wireless power transmission scenarios are not in metal cavities, but in open space. In 2019, in JWWu, RYWu, XCBo, L.Bao, XJFu, and TJCui.Synthesis algorithm for near-field power pattern control and its experimental verification via metasurfaces[J].IEEE Transactions on Antennas and Propagation, 2019, (67): 1073–1083., a near-field power pattern synthesis algorithm in open space was proposed. A new coding element surface was used to achieve the best phase distribution, covering the entire 2π with a slight amplitude fluctuation, but this method still requires a lot of time for iterative calculations. At the same time, the distance between the source and the metasurface is 30λ0 (λ0 refers to the wavelength of free space), which is too long for low-frequency applications.

[0004] In terms of improving the power transmission efficiency of the system, the existing method is the maximum power transmission efficiency method, that is, taking the power transmission efficiency between the two antenna arrays as the objective function to optimize the excitation distribution array antenna design method of the transmitting array and the receiving array. However, this maximum power transmission efficiency method cannot meet the array antenna design requirements in certain specific scenarios, such as the need for different beams in multi-beam antennas to have specific gains, and the need for the array antenna used in phased array weather radars to have as small a gain fluctuation in the main lobe as possible. Summary of the invention

[0005] In view of the deficiencies of the prior art, an object of the present invention is to provide a multi-objective antenna array optimization design method to solve the problems raised in the above background technology.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A multi-objective antenna array optimization design method includes the following steps:

[0008] Establish the transmitting antenna array and receiving antenna array models in the simulation software;

[0009] Perform full-wave simulation, and after the simulation is completed, obtain the scattering matrix S of the antenna system;

[0010] Calculate the optimal excitation distribution of the antenna corresponding to the desired focusing effect;

[0011] Calculate the corresponding antenna system transmission efficiency T array ;

[0012] Check the electric field distribution at the target position in the simulation software to verify whether the expected focusing effect is achieved.

[0013] Preferably, the transmitting antenna array uses rectangular microstrip patch antennas as array elements, and arranges the antenna units equidistantly on the dielectric substrate with a spacing of λ / 2, where λ is the wavelength in air. The receiving antenna array uses metal half-wave dipoles as units, which are also equidistantly arranged above the transmitting antenna array with a spacing of λ / 2.

[0014] Preferably, the scattering matrix is ​​as follows:

[0015]

[0016] Preferably, the optimal excitation distribution in step 3 is obtained by S in the scattering matrix S in step 2. rt Substitute the following formula and set the matrix W according to your needs to solve the optimal excitation distribution a of the antenna system t :

[0017] a t =A-1 S rt H (S rt A -1 S rt H ) -1 Wy.

[0018] Where A=[S rt ] H [S rt ]. The superscripts T and H represent matrix transpose and matrix conjugate transpose respectively. y is the column vector of control weights, which is set to all 1s by default. W is the introduced diagonal matrix of weighted coefficients. Each weighted coefficient on the diagonal of the weighted diagonal matrix corresponds to the location of a receiving antenna.

[0019] Preferably, by modifying the diagonal data of the matrix W and adjusting the weight of the receiving antenna, the position of the energy focus point emitted by the antenna can be arbitrarily adjusted so that the focus forms different patterns.

[0020] Preferably, the transmission efficiency of the antenna system is array It is the ratio of the power received by the receiving antenna array to the power input to the transmitting antenna array, expressed as follows:

[0021]

[0022] When all elements of the receiving antenna array are matched, [a r ]=0, we get the following formula:

[0023]

[0024] Beneficial effects of the present invention:

[0025] 1. The method of the present invention adopts a weighted constrained maximum power transmission efficiency method to maximize the system power transmission efficiency while generating a desired focused electric field distribution pattern in an open area. The number of foci and their spatial positions can be controlled by modifying the power weight coefficient received by the receiving antenna, which can meet the array antenna design requirements under specific scenarios. Compared with other methods for optimizing antenna power transmission efficiency, the calculation time is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 is a flow chart of the method of the present invention;

[0028] Figure 2 It is a diagram of the antenna model in the present invention;

[0029] Figure 3 is a return loss effect diagram of the antenna system in the present invention;

[0030] Figure 4 It is the antenna numbering diagram in the present invention;

[0031] Figure 5 It is the operation diagram of the simulation software in the present invention;

[0032] Figure 6 It is the meaning diagram of the scattering matrix in the present invention;

[0033] Figure 7 It is the first code effect diagram in the present invention;

[0034] Figure 8 It is the second code effect diagram of the present invention;

[0035] Fig. 9 It is the best excitation distribution diagram in the present invention;

[0036] Fig.10 It is the plane R diagram of the present invention;

[0037] Fig.11 It is an operation setting interface diagram in the present invention;

[0038] Fig.12 It is a three-dimensional effect diagram of the X electric field in the present invention;

[0039] Fig.13 It is a three-dimensional effect diagram of the Y electric field in the present invention;

[0040] Fig.14 It is a three-dimensional effect diagram of the L electric field in the present invention;

[0041] Fig.15 It is a top view effect diagram of the X electric field in the present invention;

[0042] Fig.16 It is a top view effect diagram of the Y electric field in the present invention;

[0043] Fig.17 It is a top view effect diagram of the L electric field in the present invention;

[0044] Fig.18 It is the measured electric field distribution diagram of the actual antenna in the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] See also Figure 1 As shown, the present invention proposes a multi-objective antenna array optimization design method, comprising the following steps:

[0047] Step 1: Create an antenna model in the simulation software:

[0048] In the simulation software (taking HFSS18.2 as an example, the following operations are all performed in HFSS18.2), establish the transmitting antenna array and receiving antenna array models, such as Figure 2 As shown, the antenna system is in an impedance matching state, that is, the return loss (ratio of incident wave power to reflected wave power) of the antenna system is less than -10dB. The specific effect is shown in Figure 3 ;

[0049] The transmitting antenna array uses rectangular microstrip patch antennas as array elements, and arranges the antenna units equidistantly in a 6×6 manner on a dielectric substrate with a spacing of λ / 2, where λ is the wavelength in the air. The receiving antenna array uses metal half-wave dipoles as units, which are equidistantly arranged in a 3×3 manner at a position 150 mm above the transmitting antenna array with a spacing of λ / 2, where λ is the wavelength in the air.

[0050] Antenna number as Figure 4 As shown, please note that in HFSS, when setting a lumped port (Lumped port is a type of antenna port in HFSS, where the antenna inputs or outputs signals) for the antenna in the antenna model, you need to follow Figure 4 The given numbers are set sequentially.

[0051] Step 2: Get the scattering matrix S of the antenna system:

[0052] Perform full-wave simulation in the simulation software, and derive the scattering matrix S of the antenna system from the simulation software after the simulation is completed, such as Figure 5 As shown, save it in MATLAB file format.

[0053] Among them, the meaning of the scattering matrix S is explained as follows Figure 6 As shown:

[0054] consider Figure 6 The general antenna transceiver system shown in FIG. 1 is composed of an n tport transmit antenna array and an n r The entire wireless system can be regarded as an n-port receiving antenna array. t +n r port network, can be used with a (n t +n r )×(n t +n r ) scattering matrix S is expressed as:

[0055]

[0056] Among them, the normalized incident wave and transmitted wave of the transmitting antenna array and the receiving antenna array are defined as follows:

[0057]

[0058] The scattering matrix is:

[0059]

[0060] Step 3: Calculate the optimal excitation distribution of the three antennas corresponding to the three shapes of "X", "Y" and "L" that the energy focus forms:

[0061] The S in the scattering matrix S derived from the simulation rt Substitute the following formula and set the matrix W according to your needs to solve the optimal excitation distribution a of the antenna system t , the solution process is carried out with the help of MATLAB software; (the meaning of the optimal excitation distribution is that the power transmission efficiency of the antenna system is the largest under this excitation, so it is called the optimal excitation distribution. When the formula is derived, the constraint condition that maximizes the power transmission efficiency of the system is added, so the formula calculates the optimal excitation distribution corresponding to the maximum power transmission efficiency):

[0062] a t =A -1 S rt H (S rt A -1 S rt H ) -1 Wy. (4)

[0063] Where A=[S rt ] H [S rt The superscripts T and H represent matrix transpose and matrix conjugate transpose respectively. rtSee step 2, y is the column vector of the control weight, which is set to all 1 by default, and W is the diagonal matrix of the introduced weight coefficients. Each weight coefficient on the diagonal of the weight diagonal matrix corresponds to the location of a receiving antenna. If you want to focus on a receiving antenna, increase the number of the corresponding position of the receiving antenna in W to control the distribution of energy at the target position (focus).

[0064] For example, in this example, we placed 9 receiving antennas (3×3) 150 mm above the antenna, numbered 1-9. See the corresponding relationship for details. Figure 4 If you want the energy emitted by the antenna to be focused on the receiving antenna 1, modify the diagonal data of the matrix W in the code, increase the first data on the diagonal (the physical meaning is to increase the weight of the first receiving antenna), and keep the other data on the diagonal at 1. See the code effect. Figure 7 , where the vector v is the diagonal vector of the weight matrix W.

[0065] When adjusting the weight of matrix W, increase it to 100 or 200. The specific value needs to be adjusted continuously. For example, first set it to 100, and then feel that the focus is not large enough, then increase the data a little bit until you get the appropriate focusing effect.

[0066] In this example, three focus conditions were tested. In these three focusing effects, the focus formed the shapes of the letters X, Y, and L, which are called X, Y, and Z types. To get the X-type focusing effect, the weights of the receiving antennas 1, 3, 5, 7, and 9 must be increased, so that the energy emitted by the transmitting antenna is focused near these receiving antennas to form the shape of the letter "X". Similarly, the Y-type is to increase the weights of the receiving antennas 1, 3, 5, and 8, and the L-type is to increase the weights of the receiving antennas 1, 4, 7, 8, and 9. The specific diagonal data (weights) of the matrix W are shown in Table 1, and the effects in the code are shown in Figure 8 .

[0067] Table 1

[0068]

[0069] After setting the three weights of X, Y, and L, the optimal excitation distribution a corresponding to the three focus shapes of "X", "Y", and "L" is obtained in MATLAB using formula (4): t ,like Fig. 9 shown.

[0070] Step 4: Calculate the transmission efficiency T of the antenna system corresponding to X-type, Y-type, and L-type array :

[0071] The ratio of the power received by the receiving antenna array to the power input to the transmitting antenna array is defined as the power transfer efficiency T between the transmitting antenna array and the receiving antenna array. array , which can be expressed as follows:

[0072]

[0073] Assuming that each element of the receiving antenna array is matched, then [a r ]=0, substituting this condition into formula (5) yields:

[0074]

[0075] Among them, S rt and A are the same as defined in formula (4).

[0076] Substitute the optimal excitation distribution a for the three types of X, Y, and L calculated in step 3 into t , we can calculate the power transmission efficiency of the system in the three cases, which is also the maximum power transmission efficiency. (Because the excitation distribution we calculated by formula (4) is the optimal excitation distribution, the corresponding transmission efficiency is the maximum transmission efficiency that the antenna system can achieve. This is the outstanding advantage of this design method: while achieving the desired focusing effect, the power transmission efficiency of the entire system is the maximum power transmission efficiency).

[0077] The calculated simulated power transfer efficiencies for the X-, Y-, and L-shaped patterns are 13.4%, 14.9%, and 10.9%, respectively.

[0078] Step 5: Check the electric field distribution at the target location (i.e., where you want to focus, in this case, the plane 150mm above the transmitting antenna) in the simulation software to verify whether the expected effect is achieved:

[0079] Step 5.1: Delete the receiving antenna and place plane R at the target location to view the electric field distribution:

[0080] To check the electric field distribution of the antenna, there is no need for the receiving antenna. The purpose of placing the receiving antenna is to focus the energy emitted by the antenna near the receiving antenna where it is desired to be focused. The optimal excitation distribution and maximum power transmission efficiency in this case are calculated. The calculations have been completed in steps 3 and 4, so here we delete 9 test antennas from the original antenna model.

[0081] In HFSS software, to view the electric field distribution at a certain position, you need to draw a line or a plane at this position first, and then view the electric field distribution on the line or plane. Fig.10 shown.

[0082] Step 5.2: Set the antenna excitation and distribute the three best excitation distributions a t Input simulation software:

[0083] Input a signal to the antenna to make it emit electromagnetic waves. The corresponding operation in the simulation software is to set the amplitude and phase of the input signal to the input port (lumped port) of the transmitting antenna. The setting operation interface is shown in Fig.11 , where the left column is the name of the 36 antenna ports, and the right four columns are filled with the amplitude, amplitude unit, phase, and phase unit corresponding to each antenna port. Here, the amplitude and phase values ​​calculated by equation (6) in MATLAB are used ( Fig. 9 Enter the values ​​in the table, and then click OK. The excitation data of the 36 transmitting antennas will be saved in the HFSS simulation model.

[0084] If you need to view the electric field distribution of X type, enter the optimal excitation distribution corresponding to X type. If you need to view the electric field distribution of Y type, enter the optimal excitation distribution corresponding to Y type.

[0085] Step 5.3: Check the electric field distribution:

[0086] Use the built-in function of HFSS software to view the electric field distribution on the plane R drawn in step 5.1. The three-dimensional effects of X-type, Y-type and L-type are shown in Fig.12 , 13 , 14, top view renderings see Fig.15 , 16 , 17, respectively forming focus distributions in the shape of English letters “X”, “Y”, and “L”, achieving the desired effect.

[0087] Then, we conduct physical tests, use a three-dimensional near-field test system to test the antenna, put the measured electric field data into MATLAB, and draw the measured electric field distribution diagram, see Fig.18 ,and Fig.15 , 16 , and the simulated electric field distribution diagrams of 17 are basically consistent. The measured power transmission efficiencies of X-type, Y-type, and L-type are 12.5%, 14.1%, and 11.8%, respectively, which are consistent with the simulated power transmission efficiencies of 13.4%, 14.9%, and 10.9%.

[0088] In the actual experiment, a rectangular array of LEDs was introduced to visualize the focusing effect. The energy emitted by the antenna array was successfully focused on the points corresponding to the X-shape, Y-shape, and L-shape, with high power density. The LED lights at the focal position can be lit through wireless energy transmission, demonstrating that the antenna has a good focusing effect.

[0089] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0090] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A multi-objective antenna array optimization design method, characterized in that: The following steps are involved: Step 1: Establish the transmitting antenna array and receiving antenna array models in the simulation software; Step 2: Perform full-wave simulation and obtain the scattering matrix of the antenna system after the simulation is completed. ; Step 3: Calculate the optimal excitation distribution of the antenna corresponding to the desired focusing effect; Step 4: Calculate the corresponding antenna system transmission efficiency ; Step 5: Check the electric field distribution at the target position in the simulation software to verify whether the expected effect is achieved; In step 1, the transmitting antenna array uses rectangular microstrip patch antennas as array elements, and the antenna units are equidistantly arranged on the dielectric substrate with a spacing of λ / 2, where λ is the wavelength in air. The receiving antenna array uses metal half-wave dipoles as units, which are also equidistantly arranged above the transmitting antenna array with a spacing of λ / 2; The scattering matrix in step 2 is as follows: ； The optimal excitation distribution in step 3 is obtained by using the scattering matrix in step 2 In Substitute the following formula and set the matrix according to your needs , solve the optimal excitation distribution of the antenna system : ； in, , the superscript H represents matrix transpose and matrix conjugate transpose, is a column vector controlling weights, which is set to all 1s by default. To introduce a diagonal matrix of weighted coefficients, each weighted coefficient on the diagonal of the diagonal matrix corresponds to the location of a receiving antenna; The transmission efficiency of the antenna system in step 4 It is the ratio of the power received by the receiving antenna array to the power input to the transmitting antenna array, expressed as follows: When all elements of the receiving antenna array are matched, , we get the following formula: 。 2. The multi-objective antenna array optimization design method according to claim 1, characterized in that: By modifying the matrix By adjusting the diagonal data of the receiving antenna and adjusting the weight of the receiving antenna, the energy focus point position emitted by the antenna can be adjusted arbitrarily to make the focus form different graphics.

3. The multi-objective antenna array optimization design method according to claim 1, characterized in that: The step 5 comprises: Step 5.1: Delete the receiving antenna and place plane R at the target location to view the electric field distribution; Step 5.2: Set the antenna excitation and obtain the best excitation distribution Input simulation software; Step 5.3: Check the electric field distribution on plane R in step 5.1.

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