Array antenna calibration device and array antenna calibration program

Abstract

To reduce the burden of selecting one of two kinds of solutions (K1 solution and K2 solution) as the amplitude and phase of the relative radiated electric field of each antenna element when calibrating each antenna element so as to equalize the amplitude characteristics and the phase characteristics of the radiated electric field of each antenna element using the REV method (element electric field vector rotation method).SOLUTION: When the amplitude and phase of the relative radiated electric field of each antenna element 11-n(n=1 to N) is calculated on the basis of the amplitude and phase of the initial synthesized radiated electric field of all antenna elements 11-1 to 11-N based on the amplitude of the synthesized radiated electric field of the all antenna elements 11-1 to 11-N, it is only assumed that the amplitude of the initial synthesized radiated electric field of all antenna elements 11-1 to 11-N except for each antenna element 11-n is larger (in the case of K1 solution) than the amplitude of the radiated electric field of each antenna element 11-n, without taking into consideration that the amplitude of the initial synthesized radiated electric field is smaller (in the case of K2 solution) than the amplitude of the radiated electric field.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a technique for calibrating each antenna element using the REV method (Rotating element Electric field Vector method) so as to align the amplitude and phase characteristics of the radiated electric field of each antenna element. [Background technology]

[0002] Patent Documents 1 and 2, Non-Patent Document 1, and the like disclose techniques for calibrating each antenna element using the REV method so as to align the amplitude characteristics and phase characteristics of the radiated electric field of each antenna element.

[0003] First, the amplitude of the combined radiated electric field of all antenna elements is measured while rotating the phase of the radiated electric field of each antenna element from the phase of the initial radiated electric field. Next, based on the amplitude of the combined radiated electric field of all antenna elements, the amplitude and phase of the relative radiated electric field of each antenna element are calculated with reference to the amplitude and phase of the initial combined radiated electric field of all antenna elements. Next, based on the amplitude and phase of the relative radiated electric field of each antenna element, each antenna element is calibrated so that the amplitude characteristics and phase characteristics of the radiated electric field of each antenna element are aligned.

[0004] In this way, the amplitude and phase characteristics of the radiated electric field of each element of the phased array antenna can be calibrated by simply measuring the amplitude of the radiated electric field of all antenna elements, without measuring the phase of the radiated electric field of all antenna elements. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 03-038548 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-201526 [Non-patent literature]

[0006] [Non-Patent Document 1] Kiyoji Mano and Takashi Katagi, "Method for Measuring Element Amplitude and Phase of Phased Array Antennas - Element Electric Field Vector Rotation Method," Transactions of the Institute of Electronics, Information and Communication Engineers, May 1982, Vol. B65, No. 5, pp. 555-560. Summary of the Invention [Problem to be solved by the invention]

[0007] Here, depending on whether the amplitude of the initial composite radiated electric field of all antenna elements excluding each antenna element is larger or smaller than the amplitude of the radiated electric field of each antenna element, one of two solutions (K1 solution and K2 solution) must be selected as the amplitude and phase of the relative radiated electric field of each antenna element. As a method for selecting between the two solutions, the following first to third selection methods have been proposed.

[0008] In the first selection method, multiple different states are set for the amplitude and phase (mainly phase) of the initial composite radiated electric field of all antenna elements, and then the K1 and K2 solutions are calculated for the multiple different states, and a solution that has the same meaning in the multiple different states is selected.However, the disadvantage is that there are many items to consider, such as whether any of the multiple solutions have the same meaning, how many different states to set, and how to set the multiple different states.

[0009] In the second selection method, not only is the amplitude of the combined radiated electric field of all antenna elements measured, but the phase of the combined radiated electric field of all antenna elements is also measured, and the K1 solution is selected when the phase of the combined radiated electric field of all antenna elements does not change by more than 180° as the phase of the radiated electric field of each antenna element rotates. However, this method deviates from the concept of the REV method, which is that it is sufficient to only measure the amplitude of the combined radiated electric field of all antenna elements, and it is necessary to measure the phase of the combined radiated electric field of all antenna elements.

[0010] In the third selection method, the phase of the initial radiation field of each antenna element is set so that the amplitude of the initial combined radiation field of all antenna elements excluding each antenna element is always larger than the amplitude of the radiation field of each antenna element, not smaller, and then the K1 solution is selected. However, the third selection method can only be applied when it is possible to guarantee in advance by some method that the phases of the initial radiation fields of each antenna element are somewhat aligned; in other cases, the reliability of the third selection method cannot be guaranteed.

[0011] Therefore, in order to solve the above problem, the present disclosure aims to reduce the burden of selecting one of two solutions (K1 solution and K2 solution) as the amplitude and phase of the relative radiated electric field of each antenna element when calibrating each antenna element using the REV method (element electric field vector rotation method) to align the amplitude and phase characteristics of the radiated electric field of each antenna element. [Means for solving the problem]

[0012] To solve the above problem, the amplitude and phase of the relative radiated electric field of each antenna element are determined by selecting only the K1 solution without selecting the K2 solution, then performing calibration and repeatedly performing the REV method in that state. Here, when the REV method is first performed, the phases of the initial radiated electric fields of each antenna element are generally not aligned (due to variations in the circuit characteristics of each antenna element, etc.), resulting in a high probability of the K2 solution occurring and a high probability of the K1 solution being incorrect. However, the radiation characteristics of each antenna element other than the antenna element for which an erroneous determination was made are accurately calibrated. Then, after the REV method is repeated several times, the amplitude of the initial composite radiated electric field of all antenna elements except for each antenna element gradually increases (due to the phases of the initial radiated electric fields of each antenna element being approximately aligned), resulting in a gradually lower probability of the K2 solution occurring and a gradually lower probability of the K1 solution being incorrect. Therefore, the K2 solution can be relatively easily eliminated using the method disclosed herein.

[0013] Specifically, the present disclosure provides an array antenna calibration device that repeatedly applies the following: a radiation field measurement unit that measures the amplitude of a composite radiation field of all elements of the array antenna while rotating the phase of the radiation field of each element of the array antenna from the phase of an initial radiation field; an amplitude / phase calculation unit that, when calculating the amplitude and phase of a relative radiation field of each element based on the amplitude of the composite radiation field of all elements and with reference to the amplitude and phase of the initial composite radiation field of all elements, assumes only the case where the amplitude of the initial composite radiation field of all elements excluding each element is larger than the amplitude of the radiation field of each element, without considering the case where it is smaller; and an amplitude / phase calibration unit that calibrates each element based on the amplitude and phase of the relative radiation field of each element so as to align the amplitude characteristics and phase characteristics of the radiation field of each element.

[0014] The present disclosure also provides an array antenna calibration program that causes a computer to repeatedly execute the following steps: a radiation field measurement step of measuring the amplitude of a composite radiation field of all elements of the array antenna while rotating the phase of the radiation field of each element of the array antenna from the phase of an initial radiation field; an amplitude and phase calculation step of calculating the amplitude and phase of a relative radiation field of each element based on the amplitude of the composite radiation field of all elements and taking the amplitude and phase of the initial composite radiation field of all elements as a reference, assuming only cases where the amplitude of the initial composite radiation field of all elements excluding each element is larger than the amplitude of the radiation field of each element, without considering cases where it is smaller; and an amplitude and phase calibration step of calibrating each element based on the amplitude and phase of the relative radiation field of each element so that the amplitude characteristics and phase characteristics of the radiation field of each element are aligned.

[0015] These configurations can reduce the burden of selecting one of two solutions (K1 solution and K2 solution) for the amplitude and phase of the relative radiation electric field of each antenna element.

[0016] The present disclosure also provides an array antenna calibration device, further comprising a calibration accuracy evaluation unit that evaluates the calibration accuracy across all elements based on the magnitude of the difference between a sum vector across all elements, which is related to the relative radiation electric field vector of each element and is composed of the amplitude and phase of the relative radiation electric field of each element, and an initial composite radiation electric field vector of all elements, which is composed of the amplitude and phase of the initial composite radiation electric field of all elements.

[0017] This configuration makes it possible to investigate the cause of an anomaly, such as selecting an incorrect solution for the amplitude and phase of the relative radiated electric field of each antenna element, without significant cost or know-how. In other words, it is sufficient to simply calculate the difference without checking the calibration coefficients of each antenna element, the radiation patterns of all antenna elements, or the extracted pulse waveforms of all antenna elements.

[0018] The present disclosure also provides an array antenna calibration device, characterized in that the calibration accuracy evaluation unit continues repeated application of the radiated electric field measurement unit, the amplitude / phase calculation unit, and the amplitude / phase calibration unit when the difference remains large compared to a predetermined value, and ends repeated application of the radiated electric field measurement unit, the amplitude / phase calculation unit, and the amplitude / phase calibration unit when the difference becomes small compared to the predetermined value for the first time.

[0019] According to this configuration, in order to select only the K1 solution without selecting the K2 solution as the amplitude and phase of the relative radiation electric field of each antenna element, the REV method needs to be repeated multiple times, but the number of times the REV method is repeated can be quantitatively evaluated.

[0020] The present disclosure also provides an array antenna calibration device, characterized in that the calibration accuracy evaluation unit evaluates the calibration accuracy of each element based on the magnitude of the coefficient of determination between the measurement result of the amplitude of the composite radiation electric field of all the elements relative to the rotation phase of the radiation electric field from the phase of the initial radiation electric field of each element and a sine function or cosine function having an arbitrary amplitude and phase.

[0021] With this configuration, it is possible to investigate the cause of an abnormality without significant cost or know-how, such as whether there was an abnormal operation of each antenna element, whether the S / N ratio during measurement was low, etc. In other words, it is only necessary to calculate the coefficient of determination without checking the calibration coefficient of each antenna element, the radiation patterns of all antenna elements, or the extracted pulse waveforms of all antenna elements.

[0022] The present disclosure also provides an array antenna calibration device, characterized in that the calibration accuracy evaluation unit determines abnormal operation of each of the elements when the coefficient of determination is smaller than a predetermined value, determines normal operation of each of the elements and a spurious solution of the amplitude-phase calculation unit when the coefficient of determination is larger than the predetermined value but the difference is larger than the predetermined value, and determines normal operation of each of the elements and a normal solution of the amplitude-phase calculation unit when the coefficient of determination is larger than the predetermined value and the difference is smaller than the predetermined value.

[0023] According to this configuration, by using the difference and the coefficient of determination in combination, it is possible to determine the cause of the abnormality without significant cost or know-how, whether it is a problem with the REV method algorithm or a problem with the hardware of the array antenna transceiver device. In other words, it is sufficient to simply calculate the difference and the coefficient of determination without checking the calibration coefficients of each antenna element, the radiation patterns of all antenna elements, or the extracted pulse waveforms of all antenna elements.

[0024] The present disclosure also provides an array antenna calibration device, further comprising a calibration accuracy evaluation unit that evaluates the calibration accuracy of each element based on the magnitude of the coefficient of determination between the measurement result of the amplitude of the composite radiation electric field of all the elements relative to the rotation phase of the radiation electric field from the phase of the initial radiation electric field of each element and a sine function or cosine function having an arbitrary amplitude and phase.

[0025] With this configuration, it is possible to investigate the cause of an abnormality without significant cost or know-how, such as whether there was an abnormal operation of each antenna element, whether the S / N ratio during measurement was low, etc. In other words, it is only necessary to calculate the coefficient of determination without checking the calibration coefficient of each antenna element, the radiation patterns of all antenna elements, or the extracted pulse waveforms of all antenna elements. [Effects of the Invention]

[0026] In this way, the present disclosure can reduce the burden of selecting one of two solutions (K1 solution and K2 solution) as the amplitude and phase of the relative radiated electric field of each antenna element when calibrating each antenna element using the REV method (element electric field vector rotation method) to align the amplitude and phase characteristics of the radiated electric field of each antenna element. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an array antenna system according to the present disclosure. [Figure 2] FIG. 10 is a diagram showing the procedure of the array antenna calibration process of the present disclosure. [Figure 3] FIG. 1 is a diagram illustrating an overview of the array antenna calibration process of the present disclosure. [Figure 4] FIG. 10 is a diagram illustrating details of the selection process of the K1 solution or the K2 solution according to the present disclosure. [Figure 5] FIG. 1 is a diagram illustrating an overview of the iterative processing of the REV method of the present disclosure. [Figure 6] FIG. 10 is a diagram showing the occurrence probability of a K2 solution in the iterative processing of the REV method of the present disclosure. [Figure 7] FIG. 10 is a diagram showing the amplitude calibration error of each element in the iterative process of the REV method of the present disclosure. [Figure 8] FIG. 10 is a diagram showing the phase calibration error of each element in the iterative process of the REV method of the present disclosure. [Figure 9] FIG. 10 is a diagram showing the procedure of the calibration accuracy evaluation process of the present disclosure. [Figure 10] FIG. 10 is a diagram showing an overview of a first calibration accuracy evaluation process of the present disclosure. [Figure 11]FIG. 10 is a diagram showing an overview of a second calibration accuracy evaluation process of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0028]

[0023] The following embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of implementation of the present disclosure, and the present disclosure is not limited to the following embodiments.

[0029] (Array antenna calibration process of the present disclosure) The configuration of the array antenna system of the present disclosure is shown in Fig. 1. The array antenna system A includes an array antenna transceiver 1 and an array antenna calibration device 2. The array antenna transceiver 1 includes antenna elements 11-n (n = 1 to N), attenuators 12-n (n = 1 to N), phase shifters 13-n (n = 1 to N), a divider / combiner 14, a transceiver unit 15, and a control unit 16, and can be an all-analog system, an all-digital system, or an analog / digital hybrid system. The array antenna calibration device 2 includes a radiated electric field measurement unit 21, an amplitude / phase calculation unit 22, an amplitude / phase calibration unit 23, and a calibration accuracy evaluation unit 24, and can be implemented by installing the array antenna calibration program shown in Fig. 2 and the calibration accuracy evaluation program shown in Fig. 9 on a computer.

[0030] The procedure for the array antenna calibration process of the present disclosure is shown in Figure 2. An overview of the array antenna calibration process of the present disclosure is shown in Figure 3. Details of the selection process of the K1 solution or K2 solution of the present disclosure are shown in Figure 4.

[0031] The radiated electric field measuring unit 21 measures the amplitude of the combined radiated electric field of all the antenna elements 11-1 to 11-N while rotating the phase of the radiated electric field of each antenna element 11-n from the phase of the initial radiated electric field using each phase shifter 12-n (step S2). In the first stage of FIG. 3, the initial radiated electric field vector E 0、n The power of the initial combined radiation field of all antenna elements 11-1 to 11-N is |E0| 2 (initial composite radiated electric field vector E0) is measured, and the phase Δ m、nWith the rotation of (m=1 to M), the power |E m、n '| 2 (Composite radiation electric field vector E m、n ') is measured.

[0032] In the first stage of FIG. 3, since there are variations in the circuit characteristics of each antenna element 11-n, the amplitude |E 0、n | and phase φ 0、n are not aligned, and the initial radiation electric field vector E 0、n The lengths and directions of the

[0033] The amplitude and phase calculation unit 22 calculates the amplitude and phase of the relative radiation field of each antenna element 11-n based on the amplitude and phase of the initial composite radiation field of all the antenna elements 11-1 to 11-N (step S3). In the second stage of FIG. 3, the phase Δ of the radiation field of each antenna element 11-n is calculated. m、n The power ratio of the combined radiated electric field of all antenna elements 11-1 to 11-N |E m、n '| 2 / |E0| 2 In the third stage of FIG. 3, the amplitude ratio k of the relative radiation electric field of each antenna element 11-n is calculated based on the amplitude |E0| and phase φ0 of the initial composite radiation electric field of all antenna elements 11-1 to 11-N. n =|E 0、n | / |E0| and phase X n =φ 0、n -φ0 is calculated. Details of the second and third stages of FIG.

[0034] The amplitude and phase calibration unit 23 calibrates each antenna element 11-n using the control unit 16 based on the amplitude and phase of the relative radiated electric field of each antenna element 11-n so as to align the amplitude and phase characteristics of the radiated electric field of each antenna element 11-n (step S4). In the fourth stage of FIG. 3, the amplitude |E 0、n ”| and phase φ 0、nThe calibration coefficients (correction amounts of the amplitude and phase of the radiated electric field) of each attenuator 12-n and each phase shifter 13-n are calculated so that " are the same.

[0035] The radiated electric field measuring unit 21, the amplitude / phase calculating unit 22, and the amplitude / phase calibrating unit 23 repeat steps S2 to S4 for all of the antenna elements 11-1 to 11-N (step S5).

[0036] In the fourth row of FIG. 3, even if there are variations in the circuit characteristics of each antenna element 11-n, the amplitude |E 0、n ”| and phase φ 0、n ” are aligned, and the radiation electric field vector E 0、n " are aligned in length and direction.

[0037] In this way, the phase arg(E m、n Without measuring the power |E m、n '| 2 By simply measuring the amplitude and phase characteristics of the radiated electric field of each antenna element 11-n of the phased array antenna, it is possible to calibrate the amplitude and phase characteristics of the radiated electric field of each antenna element 11-n of the phased array antenna.

[0038] In the first stage of FIG. 4, the amplitude |Y n |=|E 0、1 +···+E 0、N -E 0、n | is the amplitude |E of the radiated electric field of each antenna element 11-n m、n Therefore, the relative amplitude ratio k of the radiation electric field of each antenna element 11-n is n =|E 0、n | / |E0| and phase X n =φ 0、n As -φ0, it is necessary to select the K1 solution.

[0039] Here, the relative amplitude ratio k of the radiation electric field of each antenna element 11-n is nis calculated as in Equations 1 and 2, and the phase X of the relative radiation field of each antenna element 11-n is n is calculated as in Equations 1 and 3. Then, Q in Equation 1 n、max and Q n、min is |E m、n '| 2 / |E0| 2 are the maximum and minimum values ​​of Δ m_max、n is |E m、n '| 2 / |E0| 2 Δ gives the maximum value of m、n (In the second row of Figure 3, |E m、n '| 2 / |E0| 2 and Δ m、n The relationship between is approximated by a sine or cosine function.

number

number

number

[0040] In the second stage of FIG. 4, the amplitude |Y n |=|E 0、1 +···+E 0、N -E 0、n | is the amplitude |E of the radiated electric field of each antenna element 11-n m、n Therefore, the relative amplitude ratio k of the radiation electric field of each antenna element 11-n is n =|E 0、n | / |E0| and phase X n =φ 0、n As -φ0, the K2 solution must be selected.

[0041] Here, the relative amplitude ratio k of the radiation electric field of each antenna element 11-n is n is calculated as in Equations 4 and 5, and the phase X of the relative radiation field of each antenna element 11-n is nis calculated as in Equations 4 and 6. Then, Q in Equation 4 n、max and Q n、min is |E m、n '| 2 / |E0| 2 are the maximum and minimum values ​​of Δ m_max、n is |E m、n '| 2 / |E0| 2 Δ gives the maximum value of m、n (In the second row of Figure 3, |E m、n '| 2 / |E0| 2 and Δ m、n The relationship between is approximated by a sine or cosine function.

number

number

number

[0042] However, the amplitude |Y n |=|E 0、1 +···+E 0、N -E 0、n is the amplitude |E of the radiated electric field of each antenna element 11-n. m、n Therefore, it is not obvious whether the amplitude ratio k of the relative radiated electric field of each antenna element 11-n is larger or smaller than |. n =|E 0、n | / |E0| and phase X n =φ 0、n It is not obvious which of the K1 solution and the K2 solution should be selected as -φ0. Therefore, the iterative process of the REV method shown in FIG. 5 is executed.

[0043] An outline of the iterative process of the REV method of the present disclosure is shown in Fig. 5. The amplitude / phase calculation unit 22 assumes only the case where the amplitude of the initial composite radiated electric field of all antenna elements 11-1 to 11-N excluding each antenna element 11-n is larger (K1 solution) than the amplitude of the radiated electric field of each antenna element 11-n, without considering the case where it is smaller (K2 solution) (step S3). The radiated electric field measurement unit 21, amplitude / phase calculation unit 22, and amplitude / phase calibration unit 23 repeat the REV method (steps S2 to S7; steps S6 and S7 will be described later) a set number of times (steps S1, S8 to S10) as described later in Figs. 6 to 8 or 9 and 10. In step S10, the amplitude / phase calibration unit 23 calculates the amplitude |E of the initial radiated electric field of each antenna element 11-n before the next iteration of the REV method. 0、n | and phase φ 0、n are changed to the amplitude and phase of the radiated electric field after the previous calibration using the REV method.

[0044] The first stage of Fig. 5 shows the first time the REV method is executed, and the count of the iterations of the REV method is 0 (step S1). Then, the phase X of the relative radiation field of each antenna element 11-n is n =φ 0、n -φ0 are not uniform (for example, there is variation in the circuit characteristics of each antenna element 11-n). Therefore, the amplitude |Y n |=|E 0、1 +···+E 0、N -E 0、n is the amplitude |E of the radiated electric field of each antenna element 11-n. m、n Therefore, the probability that the K2 solution occurs is high. When the K2 solution is not selected and only the K1 solution is selected, the probability that the K1 solution is incorrect is high.

[0045] The second stage of Fig. 5 shows the case where the REV method has been executed a number of times less than the set value, and the number of repetitions of the REV method is less than the set value (NO in steps S8 and S9). Then, the phase X of the relative radiation electric field of each antenna element 11-n n =φ 0、nTherefore, the amplitude |Y n |=|E 0、1 +···+E 0、N -E 0、n is the amplitude |E of the radiated electric field of each antenna element 11-n. m、n Therefore, the probability of the K2 solution occurring is low. Even if the K2 solution is not selected and only the K1 solution is selected, the error probability of the K1 solution is low.

[0046] The third row in Fig. 5 shows the case where the REV method has been executed the same number of times as the set value, and the count of the repetitions of the REV method is the same as the set value (YES in steps S8 and S9). Then, the phase X n =φ 0、n Therefore, the amplitude |Y n |=|E 0、1 +···+E 0、N -E 0、n is the amplitude |E of the radiated electric field of each antenna element 11-n. m、n The probability that the K2 solution occurs is 0. Even if the K2 solution is not selected and only the K1 solution is selected, the error probability of the K1 solution is 0.

[0047] In this way, it is possible to reduce the burden of selecting one of two solutions (K1 solution and K2 solution) for the amplitude and phase of the relative radiation electric field of each antenna element 11-n.

[0048] In addition, in formulas 1 and 4, Q n、min Since is 0 or negative, r n 2 When the calibration coefficient of each antenna element 11-n is abnormal (YES in step S6), the amplitude-phase calibrator 23 calibrates the phase φ of the initial radiation electric field of each antenna element 11-n. 0、n(step S7), the radiated electric field measurement unit 21, the amplitude / phase calculation unit 22, and the amplitude / phase calibration unit 23 re-execute the REV method without executing step S8. On the other hand, if the calibration coefficients of each antenna element 11-n are normal (NO in step S6), the amplitude / phase calibration unit 23 increments the count of repetitions of the REV method (step S8) without executing step S7, and the radiated electric field measurement unit 21, the amplitude / phase calculation unit 22, and the amplitude / phase calibration unit 23 either repeat the REV method (NO in step S9) or end the REV method (YES in step S9).

[0049] The probability of occurrence of a K2 solution in the iterative processing of the REV method of the present disclosure is shown in Fig. 6. When performing the iterative Monte Carlo simulation of the REV method, the number of antenna elements 11-n was set to 16, 64, or 256, the phase of the initial radiation electric field of each antenna element 11-n was set randomly within a range from 0° to 360°, and the amplitude of the initial radiation electric field of each antenna element 11-n was set randomly within a range from 0 dB to -8 dB or -15 dB.

[0050] When the iteration count of the REV method is 1, the probability of the K2 solution occurring takes a finite value, but when the iteration count of the REV method is 2, the probability of the K2 solution occurring approaches 0 to some extent, and when the iteration count of the REV method is 3 or 4, the probability of the K2 solution occurring becomes almost 0. Therefore, it was found that the necessary and sufficient setting value for the iteration count of the REV method in step S9 should be set to 3 or 4.

[0051] Here, the greater the number of antenna elements 11-n, the lower the probability of the K2 solution occurring even when the iteration count of the REV method is 1, and as the iteration count of the REV method increases to 2 or more, the lower the probability of the K2 solution occurring. This is because the phase of the initial radiation electric field of each antenna element 11-n is set randomly, and the amplitude of the initial radiation electric field of each antenna element 11-n is also set randomly. In other words, to cancel the initial radiation electric field vector of one antenna element 11-n, the initial radiation electric field vector of multiple antenna elements 11-n is required, but conversely, the greater the number of antenna elements 11-n, the more difficult it is to cancel the initial radiation electric field vector of one antenna element 11-n.

[0052] The amplitude calibration error of each element in the iterative processing of the REV method of the present disclosure is shown in Fig. 7. The phase calibration error of each element in the iterative processing of the REV method of the present disclosure is shown in Fig. 8. When performing the iterative Monte Carlo simulation of the REV method, the number of antenna elements 11-n was set to 64 or 256, the phase of the initial radiation electric field of each antenna element 11-n was set randomly within a range from 0° to 360°, and the amplitude of the initial radiation electric field of each antenna element 11-n was set randomly within a range of 3 dB width, and the errors of the amplitude calibration error and the phase calibration error were also evaluated.

[0053] Then, when the iteration count of the REV method is 1, the amplitude calibration error and the phase calibration error take finite values ​​(the errors are also large), but when the iteration count of the REV method is 2, the amplitude calibration error and the phase calibration error approach 0 to some extent (the errors are large), and when the iteration count of the REV method is 3 or 4, the amplitude calibration error and the phase calibration error become almost 0 (the errors are also small). Therefore, it was found that the iteration count of the REV method should be set to 3 or 4 as a necessary and sufficient setting value in step S9.

[0054] 7 and 8, as in FIG. 6, the more elements there are in each antenna element 11-n, the smaller the amplitude calibration error and phase calibration error become (the smaller the error) even when the iteration count of the REV method is 1, and as the iteration count of the REV method increases to 2 or more, the amplitude calibration error and phase calibration error become even smaller (the smaller the error).

[0055] (Calibration accuracy evaluation process of the present disclosure) The procedure of the calibration accuracy evaluation process of the present disclosure is shown in Fig. 9. An outline of the first calibration accuracy evaluation process of the present disclosure is shown in Fig. 10. An outline of the second calibration accuracy evaluation process of the present disclosure is shown in Fig. 11.

[0056] As a first calibration accuracy evaluation process, the calibration accuracy evaluation unit 24 evaluates the calibration accuracy across all antenna elements 11-1 to 11-N based on the magnitude of the difference between the sum vector across all antenna elements 11-1 to 11-N, which is related to the relative radiation electric field vector of each antenna element 11-n and is composed of the amplitude and phase of the relative radiation electric field of each antenna element 11-n, and the initial composite radiation electric field vector of all antenna elements 11-1 to 11-N, which is composed of the amplitude and phase of the initial composite radiation electric field of all antenna elements 11-1 to 11-N (step S11).

[0057] In the first stage of FIG. 10, the phase X of the relative radiation field of each antenna element 11-n is n =φ 0、n -φ0 are not uniform (for example, there is variation in the circuit characteristics of each antenna element 11-n). Therefore, the amplitude |Y n |=|E 0、1 +···+E 0、N -E 0、n is the amplitude |E of the radiated electric field of each antenna element 11-n. m、n Therefore, the probability that the K2 solution occurs is high. When the K2 solution is not selected and only the K1 solution is selected, the probability that the K1 solution is incorrect is high.

[0058] The sum vector of all antenna elements 11-1 to 11-N with respect to the relative radiation electric field vector of each antenna element 11-n can be expressed as a complex number as follows: Σ|E 0、n | / |E0|×exp(j(φ 0、n -φ0))=Σk n exp(jX n ) Theoretically, under the condition that there is no error at all, the initial composite radiation electric field vector of all antenna elements 11-1 to 11-N is expressed as a complex number as |E0| / |E0|×exp(j(φ0-φ0))=1+0j. k n and X n When an incorrect solution is selected as Σk n exp(jX n )≠1.

[0059] In the second stage of FIG. 10, the phase X of the relative radiation field of each antenna element 11-n is n =φ 0、n Therefore, the amplitude |Y n |=|E 0、1 +···+E 0、N -E 0、n is the amplitude |E of the radiated electric field of each antenna element 11-n. m、n Therefore, the probability of the K2 solution occurring is low. Even if the K2 solution is not selected and only the K1 solution is selected, the error probability of the K1 solution is low.

[0060] The sum vector of all antenna elements 11-1 to 11-N with respect to the relative radiation electric field vector of each antenna element 11-n can be expressed as a complex number as follows: Σ|E 0、n | / |E0|×exp(j(φ 0、n -φ0))=Σk n exp(jX n ) Theoretically, under the condition that there is no error at all, the initial composite radiation electric field vector of all antenna elements 11-1 to 11-N is expressed as a complex number as |E0| / |E0|×exp(j(φ0-φ0))=1+0j. k n and X nWhen the correct solution is selected as Σk n exp(jX n )≒1.

[0061] In this way, the cause of an anomaly, such as the selection of an incorrect solution for the amplitude and phase of the relative radiation electric field of each antenna element 11-n, can be investigated without significant cost or know-how. In other words, the difference Σk n exp(jX n )-1. In Equations 1 and 4, Q n、min Since is 0 or negative, r n 2 Being ∞ or negative can also be a cause of anomalies.

[0062] As a second calibration accuracy evaluation process, the calibration accuracy evaluation unit 24 evaluates the calibration accuracy of each antenna element 11-n based on the magnitude of the coefficient of determination between the measurement result of the amplitude of the combined radiation electric field of all antenna elements 11-1 to 11-N relative to the rotation phase of the radiation electric field from the phase of the initial radiation electric field of each antenna element 11-n and a sine function or cosine function having an arbitrary amplitude and phase (step S12).

[0063] 11, each antenna element 11-n is operating abnormally or has a low S / N ratio during measurement. Therefore, the phase Δ m、n When the antenna element 11-1 rotates from the phase of the initial radiation field of 0° to 360° after one rotation, the power |E m、n '| 2 However, it does not match precisely with sine or cosine functions of arbitrary amplitude and phase.

[0064] The phase Δ of the radiated electric field of each antenna element 11-n m、n The power of the combined radiated electric field of all antenna elements 11-1 to 11-N is |E m、n '| 2However, |E m、n '| 2 =A+Bcos(Δ m、n -Δ m_max、n ) is approximated by the coefficient of determination R 2 is 0.852. In the approximation formula, A, B and Δ m_max、n However, since it cannot be calculated accurately, in Equations 1 to 6, Q n、max , Q n、min and Δ m_max、n is not calculated accurately, and k n and X n is not calculated accurately.

[0065] 11, there is no abnormal operation of each antenna element 11-n or the S / N ratio during measurement is high. Therefore, the phase Δ m、n When the antenna element 11-1 rotates from the phase of the initial radiation field of 0° to 360° after one rotation, the power |E m、n '| 2 corresponds accurately to a sine or cosine function with arbitrary amplitude and phase.

[0066] The phase Δ of the radiated electric field of each antenna element 11-n m、n The power of the combined radiated electric field of all antenna elements 11-1 to 11-N is |E m、n '| 2 However, |E m、n '| 2 =A+Bcos(Δ m、n -Δ m_max、n ) is approximated by the coefficient of determination R 2 is 0.997. In the approximation formula, A, B and Δ m_max、n is calculated accurately, so in Equations 1 to 6, Q n、max , Q n、min and Δ m_max、n is calculated exactly, and k n and X n is also calculated accurately.

[0067] In this way, the cause of the abnormality, such as whether there was an abnormal operation of each antenna element 11-n or whether the S / N ratio during measurement was low, can be investigated without a great deal of cost or know-how. In other words, the coefficient of determination R 2 The abnormal operation of each antenna element 11-n may be an abnormal operation of each phase shifter 13-n, an abnormal operation of each attenuator 12-n, or unnecessary electric field / magnetic field coupling from an adjacent antenna element 11-n to each antenna element 11-n.

[0068] Here, when there is an abnormal operation of each antenna element 11-n, or when the S / N ratio during measurement is low, the coefficient of determination R 2 Not only does the difference Σk n exp(jX n )-1 may be large. Therefore, the difference Σk n exp(jX n Based only on the fact that )-1 is large, it is not possible to determine whether an incorrect solution was selected for the amplitude and phase of the relative radiated electric field of each antenna element 11-n, whether there was an abnormal operation of each antenna element 11-n, or whether the S / N ratio during measurement was low. Therefore, the following process is executed.

[0069] The calibration accuracy evaluation unit 24 calculates the coefficient of determination R 2 When is smaller than the predetermined value (step S13, YES), the difference Σk n exp(jX n )-1, the radiated electric field measurement unit 21, the amplitude / phase calculation unit 22, and the amplitude / phase calibration unit 23 correct the abnormal operation of each antenna element 11-n or improve the S / N ratio during measurement, and then execute the REV method again (step S15).

[0070] The calibration accuracy evaluation unit 24 calculates the coefficient of determination R 2 Although is larger than the predetermined value (step S13, NO), the difference Σk nexp(jX n If )-1 is greater than the predetermined value (step S16, YES), the normal operation of each antenna element 11-n and the spurious solution of the amplitude / phase calculation unit 22 are determined (step S17).Then, the repeated application of the radiated electric field measurement unit 21, the amplitude / phase calculation unit 22, and the amplitude / phase calibration unit 23 is continued (step S18).

[0071] The calibration accuracy evaluation unit 24 calculates the coefficient of determination R 2 is larger than the predetermined value (step S13, NO), and the difference Σk n exp(jX n If )-1 is smaller than the predetermined value (step S16, NO), it is determined whether each antenna element 11-n is operating normally and whether the amplitude / phase calculation unit 22 has a normal solution (step S19). Then, the repeated application of the radiated electric field measurement unit 21, the amplitude / phase calculation unit 22, and the amplitude / phase calibration unit 23 is terminated (step S20).

[0072] In this way, the difference Σk n exp(jX n )-1 and the coefficient of determination R 2 By using this method in combination, it is possible to determine without much cost or know-how whether the cause of the abnormality is a problem with the REV method algorithm or a problem with the hardware of the array antenna transceiver 1. In other words, it is possible to calculate the difference Σk without checking the calibration coefficients of each antenna element 11-n, the radiation patterns of all antenna elements 11-1 to 11-N, or the extracted pulse waveforms of all antenna elements 11-1 to 11-N. n exp(jX n )-1 and the coefficient of determination R 2 It is only necessary to calculate

[0073] In order to select only the K1 solution without selecting the K2 solution as the amplitude and phase of the relative radiation electric field of each antenna element 11-n, the REV method needs to be repeated multiple times, and the number of times the REV method is repeated can be quantitatively evaluated. [Industrial Applicability]

[0074] The array antenna calibration device and array antenna calibration program of the present disclosure can reduce the burden of selecting between two types of solutions in the REV method when calibrating each antenna element using the REV method to align the amplitude and phase characteristics of the radiated electric field of each antenna element. [Explanation of symbols]

[0075] A: Array antenna system 1: Array antenna transmitter / receiver 2: Array antenna calibration equipment 11-1, 11-2, 11-3, 11-N: Antenna elements 12-1, 12-2, 12-3, 12-N: Attenuators 13-1, 13-2, 13-3, 13-N: Phase shifter 14:Distributor / Synthesizer 15: Transmitter / receiver 16: Control unit 21: Radiation field measurement unit 22: Amplitude and phase calculation unit 23: Amplitude and phase calibration section 24: Calibration accuracy evaluation unit

Claims

1. A radiation electric field measurement unit that measures the amplitude of a composite radiation electric field of all elements of the array antenna while rotating the phase of the radiation electric field of each element of the array antenna from the phase of the initial radiation electric field using the REV method (element electric field vector rotation method); an amplitude and phase calculation unit that, when calculating the amplitude and phase of the relative radiation electric field of each of the elements using the REV method and based on the amplitude of the composite radiation electric field of all the elements and taking the amplitude and phase of the initial composite radiation electric field of all the elements as a reference, assumes only when the amplitude of the initial composite radiation electric field of all the elements excluding each of the elements is larger (in the case of a K1 solution) than the amplitude of the radiation electric field of each of the elements, without considering when the amplitude is smaller (in the case of a K2 solution); an amplitude and phase calibration unit that calibrates each of the elements based on the amplitude and phase of the relative radiation electric field of each of the elements using the REV method so as to align the amplitude characteristics and phase characteristics of the radiation electric field of each of the elements; is repeatedly applied, gradually decreasing the occurrence probability of the K2 solution, gradually decreasing the error probability of the K1 solution, eliminating the K2 solution, and selecting the K1 solution. Array antenna calibration device.

2. a calibration accuracy evaluation unit configured to evaluate the calibration accuracy of all elements to be lower as the difference between the sum vector across all elements, which is related to the relative radiation electric field vector of each element and is configured from the amplitude and phase of the relative radiation electric field of each element, and the initial composite radiation electric field vector of all elements, which is configured from the amplitude and phase of the initial composite radiation electric field of all elements, is larger.

2. The array antenna calibration device according to claim 1, wherein:

3. When the difference remains larger than a predetermined value, the calibration accuracy evaluation unit continues the repeated application of the radiated electric field measurement unit, the amplitude / phase calculation unit, and the amplitude / phase calibration unit, and when the difference becomes smaller than the predetermined value for the first time, ends the repeated application of the radiated electric field measurement unit, the amplitude / phase calculation unit, and the amplitude / phase calibration unit.

3. The array antenna calibration device according to claim 2.

4. The calibration accuracy evaluation unit evaluates the calibration accuracy of each element lower as the coefficient of determination between the measurement result of the amplitude of the composite radiation electric field of all the elements relative to the rotation phase of the radiation electric field from the phase of the initial radiation electric field of each element and a sine function or cosine function having an arbitrary amplitude and phase becomes smaller.

4. The array antenna calibration device according to claim 2 or 3.

5. The calibration accuracy evaluation unit determines that each of the elements is operating abnormally when the coefficient of determination is smaller than a predetermined value, determines that each of the elements is operating normally and that the amplitude / phase calculation unit has a spurious solution when the coefficient of determination is larger than the predetermined value but the difference is larger than the predetermined value, and determines that each of the elements is operating normally and that the amplitude / phase calculation unit has a normal solution when the coefficient of determination is larger than the predetermined value and the difference is smaller than the predetermined value.

5. The array antenna calibration device according to claim 4.

6. The calibration accuracy evaluation unit further includes a calibration accuracy evaluation unit that evaluates the calibration accuracy of each element to be lower as the coefficient of determination between the measurement result of the amplitude of the composite radiation electric field of all the elements relative to the rotation phase of the radiation electric field from the phase of the initial radiation electric field of each element and a sine function or cosine function having an arbitrary amplitude and phase is smaller.

2. The array antenna calibration device according to claim 1, wherein:

7. A radiation electric field measurement step of measuring the amplitude of a composite radiation electric field of all elements of the array antenna while rotating the phase of the radiation electric field of each element of the array antenna from the phase of the initial radiation electric field using the REV method (element electric field vector rotation method); an amplitude and phase calculation step of calculating the amplitude and phase of the relative radiation electric field of each element using the REV method and the amplitude and phase of the initial composite radiation electric field of all elements as a reference, based on the amplitude of the composite radiation electric field of all elements, the amplitude and phase of the initial composite radiation electric field of all elements excluding each element being larger than the amplitude of the radiation electric field of each element (in the case of a K1 solution), without considering a case where the amplitude of the initial composite radiation electric field of all elements excluding each element is smaller than the amplitude of the radiation electric field of each element (in the case of a K2 solution); an amplitude / phase calibration step of calibrating each of the elements using the REV method based on the amplitude and phase of the relative radiation electric field of each of the elements so as to align the amplitude characteristics and phase characteristics of the radiation electric field of each of the elements; and causing a computer to repeatedly execute the above to gradually decrease the occurrence probability of the K2 solution, gradually decrease the error probability of the K1 solution, eliminate the K2 solution, and select the K1 solution.

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