A low sidelobe phased array optimization method with controllable channel power loss

Abstract

The present invention discloses a low sidelobe phased array optimization method with controllable channel power loss, which relates to the field of phased array antennas and solves the problems of high channel power loss, low power amplifier efficiency and complex feeding network. The present invention includes a phased array antenna scanning beam sharing excitation amplitude, optimizing the normal beam and several scanning beams to minimize the sidelobe level, controlling the channel power loss at the same time during the optimization process of minimizing the sidelobe level, converting the constraint on the channel power loss into a constraint on the excitation amplitude, using convex optimization iterative calculation for the converted constraint problem, judging whether a given threshold is met, or terminating the iteration when the maximum number of iterations is reached, and outputting the directional diagrams of several scanning beams of the phased array antenna and the shared excitation amplitude distribution that meets the requirements. The present invention saves costs, improves power amplifier efficiency, and has high engineering practical value.

Description

Technical Field

[0001] The present invention relates to the field of phased array antennas, and in particular to a low sidelobe phased array optimization method with controllable channel power loss. Background Art

[0002] Phased array antennas are increasingly widely used in modern communication systems and radar systems due to their flexible beam scanning characteristics. They can be used to form a certain radiation beam at the required scanning angle, or to achieve rapid beam scanning within a certain spatial angle range. In engineering applications, in order to improve the anti-interference ability of array antennas to factors such as noise, the sidelobe level of their radiation pattern needs to be as low as possible. On the other hand, in order to improve the radiation efficiency of the antenna, higher requirements are also placed on the design of the phased array feeding system, and reducing channel power loss can not only improve the efficiency of the power amplifier but also simplify the feeding network.

[0003] Chinese patent 202110181871.8 discloses a phased array antenna sidelobe fast calculation method and sidelobe reduction method [1]. This method combines genetic algorithm to achieve low sidelobe synthesis of the array factor of the phased array. However, this patent only integrates the array factor and ignores the influence of the unit mutual coupling effect. Therefore, this patent is only applicable to cases with small scanning angles (such as scanning angles within ±30°). When the required scanning angle is wide-angle scanning, the mutual coupling of the unit becomes non-negligible. Chinese patent 202010010677.9 discloses an irregular subarray optimization method for ultra-large scanning angles [2]. This method can achieve a larger scanning angle with fewer TR components. However, this method adjusts the amplitude and phase of the excitation at different scanning angles. This requires the phased array system to add an amplitude modulation module (such as an attenuator) to achieve the beam scanning effect, which makes the feeding network complicated. Reference Y. Aslan, J. Puskely, A. Roederer, and A. Yarovoy, “Synthesis of multiple beam linear arrays with uniform amplitudes,” in Proc. 12th Eur. Conf. Antennas Propag. (EuCAP), April 2018. [3] discussed how to achieve wide-angle scanning of multiple beams while minimizing side lobes through position optimization. In this process, the array elements are uniformly excited, and the amplifiers that power the array can achieve high energy efficiency. However, in practical applications, there is another requirement, that is, the position of the array elements is fixed and the amplitude is not adjusted during beam scanning, that is, the amplitudes of different beams are shared. If the channel power loss can be further reduced on this basis, the power amplifier efficiency can be improved and costs can be saved. Summary of the invention

[0004] The technical problems to be solved by the present invention are: high channel power loss, low power amplifier efficiency and complex feeding network. The present invention provides a low sidelobe phased array optimization method with controllable channel power loss to solve the above problems.

[0005] The basic idea of ​​the present invention is as follows:

[0006] The sidelobe level of the normal beam and several scanning beams is optimized simultaneously. In this process, the power loss of the channel is controlled to find the minimum sidelobe level value that can be achieved when the amplitudes of multiple beams are shared under the constraint condition. In addition, the present invention can conveniently take mutual coupling into consideration by using the active unit directional diagram. In the specific implementation process of the present invention, an iterative convex optimization idea is introduced to transform the non-convex constraint conditions of the channel power loss in the original comprehensive problem, and indirectly transform it into iterative constraints on the excitation amplitude, thereby converting the non-convex problem into an iterative convex optimization problem, and after the convex optimization is completed, the judgment conditions for the channel power loss obtained in this iteration are added, so as to finally achieve the control of the channel power loss.

[0007] That is, the normal beam and scanning beam of the phased array antenna share the excitation amplitude, the normal beam of the phased array is phase-shifted to obtain a number of scanning beams, the normal beam and the several scanning beams are optimized to minimize the sidelobe level, and the channel power loss is simultaneously controlled during the optimization process of minimizing the sidelobe level, and the constraint on the channel power loss is converted into a constraint on the excitation amplitude. The converted constraint problem is iteratively calculated using convex optimization to determine whether the channel power loss value of the excitation obtained in each iteration meets a pre-given threshold. If the given threshold is met or the maximum number of iterations is reached, the iteration is terminated, and the directional patterns of the several scanning beams of the phased array antenna and the shared excitation amplitude distribution that meets the requirements are output.

[0008] The present invention is achieved as follows through the following technical solutions:

[0009] Combine the problem of minimizing the side lobes of multiple beams under the condition of feed amplitude sharing with the control channel power loss, and express the comprehensive problem in mathematical form;

[0010] Since the constraint of channel power loss is a non-convex constraint, the present invention adopts the idea of ​​iterative convex optimization to transform the constraint of power loss;

[0011] In each iteration, the constraint on the channel power loss is transformed into a constraint on the excitation amplitude, thus converting the synthesis problem into a convex optimization problem;

[0012] After each convex optimization is completed, it is added to determine whether the channel power loss value of the excitation obtained in this iteration meets the condition of a given threshold;

[0013] The condition for the termination of the iteration is that the comprehensive channel power loss value meets the given threshold or reaches the maximum number of iterations; if the iteration termination condition is met, the directional diagrams of several scanning beams and the common excitation amplitude distribution that meets the requirements are output, otherwise the iteration continues.

[0014] The channel power loss can be defined as the ratio of the sum of the actual power required by each channel when the array antenna radiates a certain pattern to the total power fed to each channel by the power amplifier, that is,

[0015]

[0016] Among them, w n is the excitation of the nth array element when the array points to the normal beam, and N is the total number of array elements. Since the excitation amplitudes of multiple beams are shared in the present invention, the array channel power loss is the same for different beams.

[0017] Furthermore, the problem of minimizing the side lobes of multiple beams is combined with the control channel power loss, and the mathematical form can be expressed as:

[0018]

[0019] Among the constraints in formula (2), from top to bottom, constraint 1 is for normal beam pointing Constraint 2 controls the channel power loss, where P(w) represents the channel power loss, δ max is the threshold given by the user; constraint 3 is to optimize the side lobes of K beams simultaneously, where is the kth beam of the array, K is the total number of beamformed beams, and τ is the K beams in the corresponding sidelobe area. The last constraint defines the excitation of the kth beam, which is calculated from the excitation corresponding to the normal beam through the phase relationship, where is the excitation of the nth array element corresponding to the kth beam, represents the position vector of the array element, Represents the direction vector corresponding to the maximum pointing angle of the kth beam. The above comprehensive problem is a non-convex problem because the constraint condition of the channel power loss is a non-convex constraint.

[0020] Furthermore, the above transformation into a constraint on the excitation amplitude is as follows: in the lth iteration, the excitation amplitude of each array element is constrained to be less than or equal to the product of the maximum excitation amplitude obtained in the (l-1)th iteration and a coefficient. In mathematical form, it can be described as

[0021] |w n (l) |≤ε·max{|w1(l-1) |,|w2 (l-1) |, ..., |w N (l-1) |},for n=1,…,N (3)

[0022] Where ε is a positive real number less than 1. At this time, if the excitation of the (l-1)th iteration is obtained, the array synthesis problem of the lth iteration is transformed into a convex optimization problem.

[0023] Furthermore, the condition for judging whether the channel power loss meets a given threshold is to judge P(w (l) )≤δ max Whether it satisfies the above P(w (l) ) can be calculated as

[0024]

[0025] The present invention has the following advantages and beneficial effects:

[0026] The present invention controls the power loss of the channel when optimizing the side lobes of several scanning beams of the phased array antenna, which can reduce the transmission power loss and improve the effective transmission power on the one hand; and simplify the feeding network and save costs on the other hand.

[0027] The present invention is not limited to the structure of the antenna and can include the influence of mutual coupling of array elements and platform effect, thus having high engineering practical value for phased array design. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0029] Figure 1 The figure is a flow chart of the method of the present invention.

[0030] Figure 2 An antenna unit diagram designed for verifying the proposed algorithm in an embodiment of the present invention.

[0031] Figure 3 Schematic diagram of the scanning beam when there is no channel power loss control in the embodiment of the present invention.

[0032] Figure 4 In the embodiment of the present invention Figure 3 Corresponding excitation amplitude distribution diagram.

[0033] Figure 5 1 is a scanning beam pattern obtained when controlling channel power loss in an embodiment of the present invention.

[0034] Figure 6 In the embodiment of the present invention Figure 5 Corresponding excitation amplitude distribution diagram. DETAILED DESCRIPTION

[0035] Hereinafter, the term "include" or "may include" used in various embodiments of the present invention indicates the presence of the invented function, operation or element, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present invention, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0036] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the words listed at the same time. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0037] The terms used in various embodiments of the present invention are only used for the purpose of describing specific embodiments and are not intended to limit various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise limited, all terms used here (including technical terms and scientific terms) have the same meaning as the meaning generally understood by those of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as the terms defined in the dictionary generally used) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in various embodiments of the present invention.

[0038] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0039] Step 1: Calculate the channel power loss. The channel power loss can be defined as the ratio of the sum of the actual power required by each channel when the array antenna radiates a certain pattern to the total power fed to each channel by the power amplifier, that is,

[0040]

[0041] Among them, w nis the excitation of the nth array element when the array points to the normal beam, and N is the total number of array elements. Since the excitation amplitudes of multiple beams are shared in the present invention, the array channel power loss is the same for different beams.

[0042] Step 2: Combine the comprehensive problem of minimizing the sidelobes of multiple beams with feed amplitude sharing and the control channel power loss and formulate it mathematically.

[0043] For an N-element array of any form, the radiation pattern of the k-th scanning beam can be expressed as

[0044]

[0045] In the formula

[0046]

[0047]

[0048] in, is the active unit radiation pattern of the nth array element, including the influence of array element mutual coupling and installation platform, etc. It can be obtained through testing or electromagnetic simulation software. is the position vector of the nth array element, represents the direction vector of the spatial radiation angle, is the excitation vector of the kth beam.

[0049] In engineering applications, if we want to obtain multiple beams through phase scanning, and the amplitudes of multiple beams are shared, then the excitation of the kth beam can be expressed as

[0050]

[0051] Where K is the total number of beams required, w = [w1,w2,…,w N ] T is the excitation vector corresponding to the normal beam, is the direction vector of the kth beam.

[0052] The comprehensive problem of low sidelobe phased array antenna with controllable channel power loss can be expressed as:

[0053]

[0054] The optimization goal is to find the minimum sidelobe level that can be achieved by several beams at the same time. The above condition 1 constrains the normal beam pointing direction. Condition 2 controls the channel power loss, where δ max is a user-defined threshold; condition 3 optimizes the side lobes of K beams simultaneously. is the sidelobe area of ​​the kth beam, and τ is the sidelobe level to be optimized. The last condition constrains the excitation of the kth beam, which is obtained by phase scanning of the excitation corresponding to the normal beam. is the direction vector corresponding to the maximum pointing angle of the kth beam; the above comprehensive problem is a non-convex problem because the constraint condition of channel power loss is a non-convex constraint.

[0055] Step 3: Since the constraint of channel power loss is a non-convex constraint, the present invention adopts the idea of ​​iterative convex optimization to transform the non-convex constraint. In the lth iteration, the excitation amplitude of each array element is constrained to be less than or equal to the product of the maximum excitation amplitude obtained in the (l-1)th iteration and a coefficient. In mathematical form, it can be described as

[0056] |w n (l) |≤ε·max{|w1 (l-1) |,|w2 (l-1) |,…,|w N (l-1) |},for n=1,…,N (11)

[0057] Where ε is a positive real number less than 1. Empirically, ε is generally between 0.8 and 0.99. If the excitation of the (l-1)th iteration is obtained, the array synthesis problem of the lth iteration is transformed into a convex optimization problem, that is,

[0058]

[0059] Step 4: Add judgment P(w (l) )≤δ max Whether the conditions are met,

[0060]

[0061] Step 5: The condition for the termination of the iteration is that the comprehensive channel power loss value meets the given threshold or reaches the maximum number of iterations; if the iteration termination condition is met, the common excitation amplitude and corresponding excitation phase of several scanning beams are output, otherwise step 3 is iteratively executed.

[0062] Specific simulation example:

[0063] A 20-element uniform linear array arranged on the z-axis with an element spacing of 15 mm is taken as an example to verify the effectiveness of the present invention. Figure 2The dimensions of the antenna unit used in the array are given. The antenna unit is a commonly used microstrip patch antenna, and the operating frequency is 10GHz. In the pattern synthesis process, the present invention considers the influence of coupling by using the active unit pattern. It is assumed that the phased array needs to achieve a scanning range of ±45°, and the amplitude of each scanning pattern is shared and the phase is switched quickly. Figure 3 The directional diagram without constraint on channel power loss is given. Figure 3 In the figure, the horizontal axis is the angle θ (°), and the vertical axis is the power pattern (dB); Figure 3 The corresponding scanning angles of the middle beam curve from left to right are 45°, 60°, 75°, 90°, 105°, 120°, and 135°. As can be seen from the figure, the maximum gain of the beam is 19.57dB, the pointing of each beam is completely accurate, and the maximum sidelobe level is -25dB. The corresponding excitation amplitude distribution is as follows: Figure 4 ,exist Figure 4 In the figure, the horizontal axis is the array element position (λ), and the vertical axis is the excitation amplitude. The channel power loss obtained according to the excitation amplitude distribution is 2.73dB. The method proposed in the present invention is used to constrain the channel power loss. Here, the maximum loss that the system can accept is set to 1.5dB, and the other conditions remain unchanged. The comprehensive directional diagram and the corresponding excitation amplitude distribution are: Figure 5 and Figure 6 .exist Figure 5 In the figure, the horizontal axis is the angle θ (°), and the vertical axis is the power pattern (dB); Figure 6 In the figure, the horizontal axis is the array element position (λ) and the vertical axis is the excitation amplitude.

[0064] At this time, the maximum gain obtained is 19.87dB, the sidelobe level is raised to -21dB, and the channel power loss is reduced to 1.45dB, which meets the given constraints. When the given maximum allowable power loss is smaller, the degree of freedom of the excitation will also be smaller, and generally, the comprehensive sidelobe will be higher. The above results verify the effectiveness of the method proposed in the present invention.

[0065] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A low sidelobe phased array optimization method with controllable channel power loss, characterized in that: The steps include: The scanning beams of the phased array antenna share the excitation amplitude, the normal beam of the phased array is phase-shifted to obtain several scanning beams, the normal beam and the several scanning beams are optimized to minimize the sidelobe level, and the channel power loss is controlled simultaneously during the optimization process of minimizing the sidelobe level, and the constraint on the channel power loss is converted into a constraint on the excitation amplitude. The converted constraint problem is subjected to convex optimization iterative calculation to determine whether the channel power loss value of the excitation obtained in each iteration meets a predetermined threshold. If the threshold is met or the maximum number of iterations is reached, the iteration is terminated, and the directional patterns of the several scanning beams of the phased array antenna and the shared excitation amplitude distribution that meets the requirements are output; Among them, the sidelobe level minimization of the normal beam and several scanning beams is optimized, that is, the minimum sidelobe level that the normal beam and several scanning beams can achieve at the same time is found. The optimization problem can be expressed as Represents the constrained normal beam pointing angle P(w)≤δ max In the example, P(w) represents the channel power loss, δ max is the threshold given by the user, The side lobes of K beams are optimized simultaneously, where is the kth beam of the array, K is the total number of beamformed beams, and τ is the K beams in the corresponding sidelobe area. The minimum sidelobe level that can be achieved simultaneously within the represents the excitation of the nth array element corresponding to the kth beam, The excitation corresponding to the normal beam is obtained by calculating the phase relationship, represents the position vector of the array element, Represents the direction vector corresponding to the maximum pointing angle of the kth beam.

2. The low sidelobe phased array optimization method with controllable channel power loss according to claim 1, characterized in that: The channel power loss is the ratio of the sum of the actual power required by each channel when the array antenna radiates a certain pattern to the total power fed to each channel by the power amplifier, that is, Among them, w n is the excitation of the nth array element when the array points to the normal beam, and N is the total number of array elements.

3. The low sidelobe phased array optimization method with controllable channel power loss according to claim 2, characterized in that: In the above transformation into the constraint on the excitation amplitude, in the lth iteration, the excitation amplitude of each array element is constrained to be less than or equal to the product of the maximum excitation amplitude obtained in the (l-1)th iteration and a coefficient, that is, |w n (l) |≤ε·max{|w1 (l-1) |,|w2 (l-1) |,…,|w N (l-1) |},for n=1,…,N(3) Among them, ε is a positive real number less than 1. At this time, if the excitation of the l-1th iteration is obtained, the array synthesis problem of the lth iteration is transformed into a convex optimization problem.

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