CN104614715A

CN104614715A - Measurement calibration and polarimetric calibration device for target bistatic radar cross section and measurement calibration method thereof

Info

Publication number: CN104614715A
Application number: CN201510097351.3A
Authority: CN
Inventors: 许小剑; 唐建国
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2015-03-05
Filing date: 2015-03-05
Publication date: 2015-05-13
Anticipated expiration: 2035-03-05
Also published as: CN104614715B

Abstract

The invention discloses a device (abbreviated as BPARC) and a measurement and calibration method that can be used for the measurement calibration and polarization calibration of the target bistatic radar cross section (RCS). The source polarimetric radar calibration (PARC) device can simultaneously solve the problems of target bi-station RCS calibration and target bi-station polarization scattering matrix measurement polarization calibration under the condition of bi-station scattering measurement. As a calibration device for dual-station RCS measurement, BPARC can overcome the shortcomings of existing technologies and devices, and ensure the stability of RCS calibration values under different dual-station angles; as a polarization calibration device for dual-station polarization scattering matrix measurement, BPARC is both All the advantages of the existing single-station polarization calibration PARC device are retained, and at the same time, it can be used for dual-station polarization calibration, and the dual-station RCS calibration and dual-station polarization calibration functions of the traditional PARC device are added.

Description

A Calibration and Polarization Calibration Device and Measurement Calibration Method Used for Bistatic Radar Cross Section Measurement of Targets

技术领域technical field

本发明涉及目标的雷达散射截面(RCS)测量与处理的技术领域，特别是涉及一种可用于目标双站雷达散射截面(RCS)测量定标与极化校准装置(简称为BPARC)及其测量校准方法。The present invention relates to the technical field of radar cross section (RCS) measurement and processing of targets, in particular to a calibration and polarization calibration device (abbreviated as BPARC) and its measurement which can be used for target bistatic radar cross section (RCS) measurement Calibration method.

背景技术Background technique

双站雷达散射截面(RCS)测量几何关系示意图如图1所示。双站雷达方程可表示为：The schematic diagram of the geometric relationship of the bistatic radar cross section (RCS) measurement is shown in Fig. 1. The bistatic radar equation can be expressed as:

${P P}_{r r} = = \frac{{P P}_{t t} {G G}_{t t} {G G}_{r r} {λ λ}^{22}}{{((44 π π))}^{33} {R R}_{t t}^{22} {R R}_{r r}^{22} {L L}_{t t} {L L}_{r r}} {σ σ}_{T T}^{b b} - - - - - - ((11))$

式中，P_r为接收机输入端功率(W)；P_t为发射机功率(W)；G_r,G_t分别为接收天线与发射天线的增益(无因次)；L_t为发射通道总的损耗(无因次)；L_r为接收通道总的损耗(无因次)；R_t,R_r分别为目标到发射天线、接收天线的距离(m)；为目标双站散射截面(m²)；λ为雷达工作波长(m)。In the formula, P _r is the receiver input power (W); P _t is the transmitter power (W); G _r , G _t are the gains of the receiving antenna and the transmitting antenna (dimensionless); L _t is the transmitting channel The total loss (dimensionless); L _r is the total loss of the receiving channel (dimensionless); R _t and R _r are the distances from the target to the transmitting antenna and the receiving antenna (m); is the target bi-station scattering cross section (m ² ); λ is the radar operating wavelength (m).

根据相对定标原理(参见文献[1]黄培康主编，《雷达目标特征信号》，第6章，宇航出版社，1993.)，由双站雷达方程可推导出双站RCS测量定标方程为：According to the principle of relative calibration (refer to literature [1] Huang Peikang editor-in-chief, "Radar Target Characteristic Signal", Chapter 6, Aerospace Press, 1993.), from the bistatic radar equation, the bistatic RCS measurement calibration equation can be deduced as:

${σ σ}_{T T}^{b b} = = {K K}_{b b} \cdot &Center Dot; \frac{{P P}_{rT rT}}{{P P}_{rC rC}} \cdot \cdot {σ σ}_{C C}^{b b} = = {K K}_{b b} \cdot &Center Dot; {| | \frac{{S S}_{T T}}{{S S}_{C C}} | |}^{22} \cdot &Center Dot; {σ σ}_{C C}^{b b} - - - - - - ((22))$

式中为目标双站RCS，为定标体的双站RCS；P_rC和P_rT分别为测定标体和测目标时雷达接收到的回波功率；S_T和S_C分别为单次RCS测量采样中，测量目标和测量定标体时的雷达复回波信号；K_b为同双站测量几何关系相对应的定标常数，有：In the formula For the target dual-station RCS, is _the dual-station RCS of the calibration body; P _rC and _P _rT are the echo powers received by the radar when measuring the target and the target, respectively; The radar complex echo signal at the target time; K _b is the calibration constant corresponding to the geometric relationship of the bi-station measurement, which is:

${K K}_{b b} = = {((\frac{{R R}_{tT TT} {R R}_{rT rT}}{{R R}_{tC tC} {R R}_{rC rC}}))}^{22} \cdot &Center Dot; \frac{{L L}_{tT TT} {L L}_{rT rT}}{{L L}_{tC tC} {L L}_{rC rC}} - - - - - - ((33))$

式中R_tT和R_tC分别表示发射通道的目标距离和定标体距离；R_rT和R_rC分别表示接收通道的目标距离和定标体距离；L_tT和L_tC分别表示测目标和测定标体时发射通道的总损耗；L_rT和L_rC分别表示测目标和测定标体时接收通道的总损耗。只要测试中目标距离和定标体距离是确定的，双站几何关系保持不变，则K_b值也是确定的常数。In the formula, R _tT and R _tC represent the target distance of the transmitting channel and the calibration object distance respectively; R _rT and R _rC represent the target distance of the receiving channel and the calibration object distance respectively; L _tT and L _tC represent the measuring target and the measuring target respectively The total loss of the transmitting channel when measuring the body; L _rT and L _rC respectively represent the total loss of the receiving channel when measuring the target and measuring the object. As long as the distance between the target and the calibration body is determined during the test and the geometric relationship between the two stations remains unchanged, the K _b value is also a definite constant.

在选择双站RCS测量定标体时，要求定标体的散射特性随着测量双站角的变化能够稳定在一个相对较小的电平范围内，以保证足够高的双站定标精度。When selecting a calibration body for bi-station RCS measurement, it is required that the scattering characteristics of the calibration body can be stabilized within a relatively small level range with the change of the measurement bi-station angle, so as to ensure a sufficiently high bi-station calibration accuracy.

然而，一些传统的单站RCS测量定标体如金属球、金属圆柱体、二面角和三面角反射器、金属平板等，随着双站角的增大，其散射特性均呈现振荡特性，当双站角较大时，不适宜用作为标准定标体。例如，通过Mie精确解对金属球定标体的双站散射进行计算，当ka值为20时的归一化RCS随双站角的变化特性如图2所示。很明显，对于小双站角测量，金属球用于双站RCS定标仍然是合适的，但随着双站角超过90°以后，其振荡特性越来越严重，这将在很大程度上影响定标精度。However, some traditional single-station RCS measurement calibration bodies, such as metal spheres, metal cylinders, dihedral and trihedral reflectors, and metal plates, etc., as the double-station angle increases, their scattering characteristics show oscillation characteristics. When the double station angle is large, it is not suitable to be used as a standard calibration body. For example, the bistatic scattering of the metal sphere calibration body is calculated through the Mie exact solution. When the ka value is 20, the variation characteristics of the normalized RCS with the bistatic angle are shown in Figure 2. Obviously, for small bistatic angle measurement, metal balls are still suitable for bistatic RCS calibration, but as the bistatic angle exceeds 90°, its oscillation characteristics become more and more serious, which will largely affect the calibration accuracy.

可见，如何找到或者设计合适的双站散射定标体，是双站RCS测量定标的技术难题。It can be seen that how to find or design a suitable bistatic scattering calibration body is a technical problem in bistatic RCS measurement calibration.

与本发明相关的现有技术分析如下：The prior art analysis relevant to the present invention is as follows:

现有技术-1:采用传统具有简单形状的定标体Prior art-1: adopt traditional calibration body with simple shape

这是目前双站RCS测量定标中最常采用的技术。Bradley等人(参见文献[2]C.J.Bradley，P.J.Collins，et.al，"An investigation of bistatic calibration objects，"IEEE Trans.onGeoscience and Remote Sensing，Vol.43，No.10，Oct.2005:2177-2184.及文献[3]C.J.Bradley，P.J.Collins，et.al，"An investigation of bistatic calibration techniques，"IEEE Trans.on Geoscience and Remote Sensing，Vol.43，No.10，Oct.2005:2185-2190.)针对欧洲遥感特征信号实验室(EMSL)测量条件下的双站定标问题进行了研究，重点分析了给定双站角时金属圆柱体、二面角和三面角反射器、金属圆盘和金属丝网等定标体的定标特性。This is the most commonly used technique in bistation RCS measurement calibration at present. Bradley et al. (see literature [2] C.J.Bradley, P.J.Collins, et.al, "An investigation of bistatic calibration objects," IEEE Trans.onGeoscience and Remote Sensing, Vol.43, No.10, Oct.2005:2177- 2184. and literature [3] C.J.Bradley, P.J.Collins, et.al, "An investigation of bistatic calibration techniques," IEEE Trans.on Geoscience and Remote Sensing, Vol.43, No.10, Oct.2005:2185-2190 .) The bi-station calibration problem under the measurement conditions of the European Remote Sensing Signature Laboratory (EMSL) is studied, focusing on the analysis of metal cylinders, dihedral and trihedral reflectors, and metal discs when the bi-station angle is given Calibration characteristics of calibration bodies such as wire mesh and wire mesh.

现有技术-1的缺陷：Bradley等人只是研究了一些传统定标体的定标特性及其在双站测量定标中的适用性，并没有解决随着双站角增大，定标体的双站散射呈现随双站角振荡起伏、造成大的定标误差这一关键问题。Defect of existing technology-1: Bradley et al. only studied the calibration characteristics of some traditional calibration bodies and their applicability in bi-station measurement calibration, but did not solve the problem of calibration body with the increase of bi-station angle The key problem of the bistatic scattering is that it fluctuates with the bistatic angle, resulting in large calibration errors.

现有技术-2:设计专用的双站定标体Existing technology-2: Design a dedicated dual-station calibration body

Monzon提出一种双站定标体设计(参见文献[4]C.Monzon，"A cross-polarized bistaticcalibration device for RCS measurements，"IEEE Trans.on Antennas and Propagation，Vol.51，No.4，April 2003:833-839.)，将金属导电线在介质圆柱体上按一定倾角β螺旋绕制而成。数值计算表明这种定标体具有较好的双站散射特性和交叉极化散射特性。Monzon proposed a bi-station calibration body design (see literature [4]C.Monzon, "A cross-polarized bistaticcalibration device for RCS measurements," IEEE Trans.on Antennas and Propagation, Vol.51, No.4, April 2003 :833-839.), the metal conductive wire is helically wound on a dielectric cylinder at a certain inclination angle β. Numerical calculations show that this calibration body has better bistatic and cross-polarization scattering properties.

现有技术-2的缺陷：导致这种定标体设计迄今并未见真正付诸工程实用的主要技术缺陷包括三个方面：(1)由于需要严格按照某种倾角将金属导电线绕制在介质圆柱体上，实体加工制造比较困难；(2)这种定标装置的理论散射值的精确计算存在一定困难；(3)加工误差如何影响定标精度难以解析分析。Defects of the prior art-2: the main technical defects that cause this calibrator design to be practically put into practice so far include three aspects: (1) due to the need to wind the metal conductive wire in strict accordance with a certain inclination angle On the dielectric cylinder, it is more difficult to manufacture the entity; (2) there are certain difficulties in the accurate calculation of the theoretical scattering value of this calibration device; (3) it is difficult to analyze how the processing error affects the calibration accuracy.

现有技术-3：采用两部发射和接收机，通过两次单站测量导出双站测量的定标函数Existing technology-3: Using two transmitters and receivers, the calibration function of the bi-station measurement is derived from two single-station measurements

Alexander和Currie等人(参见文献[5]N.T.Alexander，N.C.Currie，M.T.Tuley，"Calibration of bistatic RCS measurements，"Proc.of Antenna Measurement TechniquesAssociation 1995 Symposium，Columbus，OH，Nov.1995:166-171.及[6]N.C.Currie，N.T.Alexander，M.T.Tuley，"Unique calibration issues for bistatic radar reflectivitymeasurements，"Proc.IEEE 1996 National Radar Conference，An Arbor，Michigan，May1996:142-147.)在解决美国空军国立散射测试场(RATSCAT)双站相参测量系统(BICOMS)的双站RCS定标问题时，提出在双站测量中采用两部发射和接收机(如图4所示)，通过对定标体的两次单站测量导出双站定标函数，并分析了其定标不确定度。Alexander and Currie et al. (referring to literature [5] N.T.Alexander, N.C.Currie, M.T.Tuley, "Calibration of bistatic RCS measurements," Proc.of Antenna Measurement Techniques Association 1995 Symposium, Columbus, OH, Nov.1995:166-171. and [6] N.C.Currie, N.T.Alexander, M.T.Tuley, "Unique calibration issues for bistatic radar reflectivity measurements," Proc.IEEE 1996 National Radar Conference, An Arbor, Michigan, May1996:142-147.) in solving the US Air Force National Scattering Test Site (RATSCAT) bistation coherent measurement system (BICOMS) bistation RCS calibration problem, it is proposed to use two transmitters and receivers in the bistation measurement (as shown in Figure 4), through the calibration body twice The bi-station calibration function is derived from the single-station measurement, and its calibration uncertainty is analyzed.

现有技术-3的主要优点：可以采用传统的单站定标体，例如金属球、金属圆柱体、角反射器、平板等作为双站定标体，只需经过两次单站和两次双站测量，即可完成双站RCS测量和定标，其定标体不确定度容易满足工程应用要求，不会受到大双站角条件下定标双站散射起伏大的不良影响，因为定标体RCS理论值只需采用单站RCS理论值。The main advantage of prior art-3: traditional single-station calibration bodies can be used, such as metal balls, metal cylinders, corner reflectors, flat plates, etc. Dual-station measurement can complete the dual-station RCS measurement and calibration. The uncertainty of the calibration body can easily meet the requirements of engineering applications, and will not be adversely affected by the large fluctuation of the calibration dual-station scattering under the condition of a large dual-station angle, because the calibration The standard RCS theoretical value only needs to use the single-station RCS theoretical value.

现有技术-3的主要缺陷：(1)普通双站RCS测量只需一部发射机和一部接收机，放置在需要的位置(如图1所示)，而采用这种定标技术则必须使用两部性能基本一致的RCS测量雷达(包括发射机和接收机)，导致系统成本成倍提高；(2)由于需要通过对定标体的两次单站测量和两次双站测量数据才能导出定标函数，增加了影响定标误差的因素，同采用单个发射机和接收机的定标方法相比，增大了RCS定标不确定度。The main defect of prior art-3: (1) only one transmitter and one receiver are needed for ordinary bi-station RCS measurement, and they are placed in the desired position (as shown in Fig. 1 ), while using this calibration technique will Two RCS measurement radars (including transmitters and receivers) with basically the same performance must be used, resulting in a multiplied increase in system cost; (2) due to the need to pass two single-station measurements and two bi-station measurement data on the calibration body The calibration function can only be derived, which increases the factors that affect the calibration error. Compared with the calibration method using a single transmitter and receiver, the RCS calibration uncertainty is increased.

现有技术-4：采用有源极化雷达定标装置(PARC)Prior Art-4: Using Active Polarization Radar Calibration Device (PARC)

有源极化校准器(Polarimetric Active Radar Calibrators，PARC)多用于极化散射测量中的极化通道校准和RCS定标。Active polarization calibrator (Polarimetric Active Radar Calibrators, PARC) is mostly used for polarization channel calibration and RCS calibration in polarization scattering measurement.

假设雷达的接收通道传输矩阵R、发射通道传输矩阵T以及背景杂波I会导致目标的测量极化散射矩阵S^m与目标真实极化散射矩阵S存在偏差。实测值S^m和目标PSM真实值S满足以下关系式(参见文献[7]肖志河，巢增明，蒋欣，王晨，雷达目标极化散射举着测量技术[J].系统工程与电子技术，1996，(3):13-32.)It is assumed that the transmission matrix R of the receiving channel, the transmission matrix T of the transmitting channel of the radar, and the background clutter I will cause a deviation between the measured polarization scattering matrix S ^m of the target and the real polarization scattering matrix S of the target. The measured value S ^m and the real value S of the target PSM satisfy the following relationship (see literature [7] Xiao Zhihe, Chao Zengming, Jiang Xin, Wang Chen, radar target polarization scattering measurement technology [J]. System Engineering and Electronic Technology, 1996, (3):13-32.)

S^m＝R·S·T+I (4)S ^m =R·S·T+I (4)

极化校准的目的是从实测数据中尽可能不失真地还原出目标的真实PSM，求解方程为The purpose of polarization calibration is to restore the real PSM of the target as undistorted as possible from the measured data, and the solution equation is

S＝R^-1·(S^m-I)·T^-1 (5)S＝R ^-1 ·( ^Sm -I)·T ^-1 (5)

可见，必须同时求得系统的收发通道传输矩阵R、T和背景杂波I，才能实现对任意目标的校准。It can be seen that the transmission matrix R, T and background clutter I of the system must be obtained at the same time in order to realize the calibration of any target.

极化校准的通常做法是：控制测试环境的背景杂波足够低从而可忽略其对测量的影响，近似地有I＝0，或者直接测得背景杂波矩阵I并进行背景向量相减处理，在此基础上利用理论PSM已知的目标作为极化校准体，结合对其实测的PSM数据，通过式(4)建立理论PSM与经过背景抵消后的测量值之间的量化关系，有：The usual method of polarization calibration is: control the background clutter of the test environment to be low enough so that its influence on the measurement can be ignored, and approximately have I=0, or directly measure the background clutter matrix I and perform background vector subtraction processing, On this basis, the target known by the theoretical PSM is used as the polarization calibration object, combined with the measured PSM data, the quantitative relationship between the theoretical PSM and the measured value after background offset is established by formula (4), as follows:

M＝S^m-I＝R·S·T (6)M=S ^m -I=R·S·T (6)

来求解雷达测量系统的校准参数R、T，从而有以下简化公式to solve the calibration parameters R and T of the radar measurement system, so that the following simplified formula

S＝R^-1·M·T^-1 (7)S＝R ^-1 ·M·T ^-1 (7)

最基本的PARC是带有光纤延时线的有源转发器，其简单的结构示意图如图5所示(参见文献[8]K.Sarabandi，F.T.Ulaby，“Performance characterization of polarimetric active radarcalibrators and a new single antenna design，”IEEE Transactions on Antennas and Propagation，1992，40(10):1147-1154.)。工作过程为：接收天线从空间接收雷达信号，该信号经放大器放大处理后，由带通滤波器滤除雷达工作频段以外的杂波；通过调节延时线的延时大小来等效改变测量距离，这样，可以去除固定距离上的背景杂波使得近似地有I＝0；最后再经转发天线转发出去，从而被雷达接收和处理。The most basic PARC is an active transponder with an optical fiber delay line, and its simple structural diagram is shown in Figure 5 (see [8] K.Sarabandi, F.T.Ulaby, "Performance characterization of polarimetric active radarcalibrators and a new single antenna design," IEEE Transactions on Antennas and Propagation, 1992, 40(10):1147-1154.). The working process is: the receiving antenna receives the radar signal from the space, and after the signal is amplified by the amplifier, the clutter outside the radar working frequency band is filtered out by the band-pass filter; the measurement distance is equivalently changed by adjusting the delay of the delay line , in this way, the background clutter at a fixed distance can be removed so that approximately I=0; finally, it is retransmitted through the retransmitting antenna to be received and processed by the radar.

与无源定标体相比，PARC的雷达散射截面不受物理尺寸限制，且其大小可以通过调节衰减器来改变，其理论计算值为：Compared with the passive calibration body, the radar cross section of PARC is not limited by physical size, and its size can be changed by adjusting the attenuator. The theoretical calculation value is:

$σ σ = = {G G}_{Loop Loop} \cdot &Center Dot; \frac{{G G}_{T T} \cdot &Center Dot; {G G}_{R R} \cdot &Center Dot; {λ λ}^{22}}{44 π π} - - - - - - ((88))$

式中，G_T和G_R分别为PARC转发天线和接收天线的增益，G_Loop为图5中除天线外，整个回路的总增益。一般也可通过相对定标的方法测得其RCS大小。In the formula, G _T and G _R are the gains of the PARC forwarding antenna and receiving antenna, respectively, and G _Loop is the total gain of the entire loop except the antenna in Figure 5. Generally, the RCS size can also be measured by relative calibration.

PARC的收发天线一般采用喇叭天线，天线具有单一的线极化方式。如图6所示，我们称天线的线极化状态与水平X轴(水平向右)的夹角为天线的极化角。若PARC接收天线的极化角为θ_r，转发天线的极化角为θ_t，则PARC的理论PSM为：The transmitting and receiving antenna of PARC generally adopts the horn antenna, and the antenna has a single linear polarization mode. As shown in Figure 6, we call the angle between the linear polarization state of the antenna and the horizontal X-axis (horizontal to the right) the polarization angle of the antenna. If the polarization angle of the PARC receiving antenna is θ _r and the polarization angle of the transponder antenna is θ _t , then the theoretical PSM of PARC is:

${S S}_{P P} = = \frac{11}{44} \sqrt{\frac{σ σ}{π π}} \cdot &Center Dot; {h h}_{t t} \cdot &Center Dot; {h h}_{r r}^{T T} = = \frac{11}{44} \sqrt{\frac{σ σ}{π π}} \cdot &Center Dot; [\begin{matrix} cos cos {θ θ}_{t t} \cdot &Center Dot; cos cos {θ θ}_{r r} & cos cos {θ θ}_{t t} \cdot &Center Dot; sin sin {θ θ}_{r r} \\ sin sin {θ θ}_{t t} \cdot &Center Dot; cos cos {θ θ}_{r r} & sin sin {θ θ}_{t t} \cdot &Center Dot; sin sin {θ θ}_{r r} \end{matrix}] - - - - - - ((99))$

式中，h_t＝[cosθ_t sinθ_t]^T和h_r＝[cosθ_r sinθ_r]^T分别为PARC转发天线和接收天线的Jones矢量，上标T表示矩阵或向量的转置运算。In the formula, h _t ＝[cosθ _t sinθ _t ] ^T and h _r ＝[cosθ _r sinθ _r ] ^T are the Jones vectors of the PARC forwarding antenna and receiving antenna respectively, and the superscript T represents the transposition operation of the matrix or vector.

由式(9)可见，若采用双天线PARC设计，通过改变接收天线的极化角θ_r和转发天线的极化角θ_t，可以获得PARC各种极化角组合的理论极化散射矩阵S_P1，S_P2，…，S_Pn，结合对应的极化散射矩阵测量值M_p1，M_p2，…，M_pn，根据式(7)可列写出若干方程组，进而可求解出收发通道传输矩阵R和T，从而完成极化校准参数的获取。这正是本项发明的基本出发点。It can be seen from Equation (9) that if the dual-antenna PARC design is adopted, by changing the polarization angle θ _r of the receiving antenna and the polarization angle θ _t of the forwarding antenna, the theoretical polarization scattering matrix S of various combinations of PARC polarization angles can be obtained _P1 , S _P2 ,..., S _Pn , combined with the corresponding measured values of the polarization scattering matrix M _p1 , M _p2 ,..., M _pn , according to formula (7), several equations can be written, and then the transmission of the transceiver channel can be solved Matrix R and T, so as to complete the acquisition of polarization calibration parameters. This is the basic starting point of this invention.

实际应用中，所得到的极化校准参数其精度在很大程度上取决于极化校准测量中所选用校准体的理论PSM是否精确，以及极化校准参数求解方程是否具有稳健性。In practical applications, the accuracy of the obtained polarization calibration parameters depends largely on whether the theoretical PSM of the calibration body selected in the polarization calibration measurement is accurate, and whether the equations for solving the polarization calibration parameters are robust.

单天线PARC：Single antenna PARC:

文献[8]中提出了一种单天线PARC的结构，其原理框图参见图5所示。在天线口面内部有一对相互正交放置的馈源，分别用于接收信号和转发信号，这样，接收和转发信号的极化方式始终是相互正交的，如图7所示。通过将天线绕雷达视线旋转至不同的角位置，天线的收发极化状态也随之而改变，从而获得不同的极化散射矩阵。A single-antenna PARC structure is proposed in [8], and its block diagram is shown in Figure 5. There is a pair of feed sources placed orthogonal to each other inside the antenna interface, which are respectively used for receiving signals and transmitting signals. In this way, the polarization modes of receiving and transmitting signals are always mutually orthogonal, as shown in Figure 7. By rotating the antenna around the radar line-of-sight to different angular positions, the transmitting and receiving polarization states of the antenna are also changed, thereby obtaining different polarization scattering matrices.

采用这种PARC极化校准的基本步骤为[8]：The basic steps to adopt this kind of PARC polarization calibration are [8]:

(1)计算两种姿态下单天线PARC的极化散射矩阵的理论值S_P1、S_P2；(1) Calculate the theoretical values S _P1 and S _P2 of the polarization scattering matrix of the single-antenna PARC under two attitudes;

(2)测量两种姿态下的单天线PARC的测量值Μ_p1、Μ_p2，在测量中，经延时线处理使得接收回波被延时到远离PARC所在的距离处，从而可消除背景杂波I的影响；(2) Measure the measured values Μ _p1 and Μ _p2 of the single-antenna PARC under the two attitudes. In the measurement, the received echo is delayed to a distance away from the PARC through delay line processing, so that background noise can be eliminated. The effect of wave I;

(3)将上述Μ_P1、Μ_P2、S_P1及S_P2通过式(7)建立方程组，求解收发共天线的单站雷达系统的收发通道传输矩阵R和T。(3) The above M _P1 , M _P2 , S _P1 and S _P2 are used to establish an equation group through formula (7) to solve the transmit and receive channel transmission matrices R and T of the monostatic radar system with a common antenna for transmitting and receiving.

虽然文献[8]提出的单天线PARC结构简单且能够较好地完成极化校准工作，但仍存在以下缺点：Although the single-antenna PARC proposed in [8] has a simple structure and can complete the polarization calibration well, it still has the following disadvantages:

(1)PARC天线的接收极化方式和发射极化方式始终是相互正交的，收发天线极化不能任意组合，这大大减少了其理论极化散射矩阵的形式，很多特殊形式的极化散射矩阵无法通过这种单天线PARC得到，比如单位矩阵，从而限制了其应用范围；(1) The receive polarization and transmit polarization of the PARC antenna are always orthogonal to each other, and the polarization of the transmit and receive antennas cannot be combined arbitrarily, which greatly reduces the form of its theoretical polarization scattering matrix, and many special forms of polarization scattering The matrix cannot be obtained by this single-antenna PARC, such as the identity matrix, which limits its application range;

(2)由于该方案是对某几个天线转角的PARC进行测量而获得实测数据，当测量中存在微小转角误差时，会对校准的精度产生影响；(2) Since the solution is to measure the PARC of several antenna rotation angles to obtain the measured data, when there is a small rotation angle error in the measurement, it will affect the calibration accuracy;

(3)采用这种PARC的极化校准参数提取算法的稳健性较差：一旦校准过程中某时刻的系统测量值存在异常值或较大误差时，就会大大降低所提取校准参数的精度；(3) The robustness of the polarization calibration parameter extraction algorithm using this PARC is poor: once there is an abnormal value or a large error in the system measurement value at a certain moment during the calibration process, the accuracy of the extracted calibration parameters will be greatly reduced;

(4)由于一对正交极化馈源同时工作，无法采用极化滤波装置来提高天线的极化隔离度，在很大程度上影响了极化校准精度。(4) Since a pair of orthogonally polarized feed sources work at the same time, it is impossible to use a polarization filter device to improve the polarization isolation of the antenna, which greatly affects the polarization calibration accuracy.

双天线PARC：Dual Antenna PARC:

文献[9](M.He，Y.Z.Li，S.P.Xiao，et al.，“Scheme of dynamic polarimetriccalibration，”Electronics Letters，2012，48(4):237-238.)提出一种基于数字射频存储器的PARC系统，其总体设计框图如图5所示。该系统对接收到的信号进行离散化采样，将离散的信号存储在数字射频存储器中，所有对信号的相关处理都是对存储器中的离散信号进行操作，处理后再由D/A转换器将信号转换成模拟信号进行转发。通过转台控制PARC的接收天线与转发天线以不同的角速度旋转，在雷达测量过程中，PARC收发天线始终在转，基于此PARC结构提出了基于频域的有源极化校准方法。Literature [9] (M.He, Y.Z.Li, S.P.Xiao, et al., "Scheme of dynamic polarimetric calibration," Electronics Letters, 2012, 48(4):237-238.) proposed a PARC based on digital radio frequency memory The overall design block diagram of the system is shown in Figure 5. The system performs discrete sampling on the received signal, stores the discrete signal in the digital radio frequency memory, and all related processing of the signal is to operate on the discrete signal in the memory, and after processing, the D/A converter converts The signal is converted to an analog signal for retransmission. The PARC receiving antenna and transponder antenna are controlled to rotate at different angular velocities through the turntable. During the radar measurement process, the PARC transceiver antenna is always rotating. Based on this PARC structure, an active polarization calibration method based on the frequency domain is proposed.

采用这种PARC其极化校准的基本步骤为：The basic steps of polarization calibration using this PARC are:

(1)PARC收发天线分别以角速度ω_r和ω_t旋转，测量其测量值Μ_P；(1) PARC transceiver antenna rotates with angular velocity ω _r and ω _t respectively, and measures its measured value Μ _P ;

(2)将PARC理论极化散射矩阵S_P及测量值Μ_P改写为4x1的向量和 ${\tilde{M}}_{P} = {[m_{P}^{hh}, m_{P}^{vh}, m_{P}^{hv}, m_{P}^{vv}]}^{T},$ 并将式(3)所描述的误差模型改写为 ${\tilde{M}}_{P} = E_{r} \cdot {\tilde{S}}_{P},$ 其中 $E_{r} = T^{T} &CircleTimes; R$ （为Kroneker积)，它全面的描述了雷达系统校准参数；(2) Rewrite the PARC theoretical polarization scattering matrix S _P and the measured value M _P into a 4x1 vector and ${\tilde{m}}_{P} = {[m_{P}^{hh}, m_{P}^{vh}, m_{P}^{hv}, m_{P}^{vv}]}^{T},$ And rewrite the error model described in formula (3) as ${\tilde{m}}_{P} = {E.}_{r} &Center Dot; {\tilde{S}}_{P},$ in ${E.}_{r} = T^{T} &CircleTimes; R$ ( is the Kroneker product), which comprehensively describes the radar system calibration parameters;

(3)将两边同时取傅里叶变换，可以求得且该解只有在PARC接收天线与转发天线的旋转角速度不相等时成立；(3) Will Taking Fourier transform on both sides at the same time, we can get And the solution is only valid when the rotational angular velocity of the PARC receiving antenna and the transmitting antenna are not equal;

文献[9]基于双天线数字式PARC结构所提出的频率动态极化校准方法，理论上可以实现对雷达系统的校准，但其存在的缺点如下：The frequency dynamic polarization calibration method proposed in [9] based on the dual-antenna digital PARC structure can theoretically realize the calibration of the radar system, but its shortcomings are as follows:

(1)技术设计非常复杂。这种数字式PARC对A/D及D/A的采样速率要求非常高，数字射频存储器电路的时序逻辑复杂，信号的写入与读出以及延迟处理等操作都需要时钟来进行控制，在高速运转的电路中，容易出现竞争、冒险，以致整个系统不能稳定正常的工作；(1) The technical design is very complicated. This kind of digital PARC has very high requirements on the sampling rate of A/D and D/A. The timing logic of the digital radio frequency memory circuit is complex, and the writing and reading of signals and delay processing and other operations need to be controlled by clocks. In the running circuit, it is easy to have competition and risk, so that the whole system cannot work stably and normally;

(2)校准参数求解过程和算法复杂；(2) The calibration parameter solution process and algorithm are complicated;

(3)成本高、可靠性及稳定性有待验证，目前未见其真实产品和实际应用报道。(3) The cost is high, the reliability and stability need to be verified, and there are no real products and practical application reports.

现有技术-4的缺陷：采用上述单天线或双天线设计的两种PARC装置均属于单站极化校准PARC装置，不能用于双站测量RCS定标和双站测量极化校准，故没有解决双站测量RCS定标与极化校准问题。Defect of prior art-4: The two PARC devices designed with the above-mentioned single antenna or dual antenna are both single-station polarization calibration PARC devices, and cannot be used for dual-station measurement RCS calibration and dual-station measurement polarization calibration, so there is no Solve the problem of RCS calibration and polarization calibration for dual-station measurement.

发明内容Contents of the invention

本发明所要解决的技术问题为：本发明提出一种采用带双轴旋转控制机构的双天线PARC装置及其测量校准方法，可同时解决双站散射测量条件下目标双站RCS定标和目标双站极化散射矩阵测量极化校准问题。作为双站RCS测量定标装置，可以克服前述已有技术-1～4的全部缺点，保证不同双站角下RCS定标值的稳定性；作为双站极化散射矩阵测量的极化校准装置，既保留了已有单站极化校准PARC装置的全部优点，同时又可用于双站极化校准，增加了传统PARC装置的双站RCS定标和双站极化校准功能。The technical problem to be solved by the present invention is: the present invention proposes a dual-antenna PARC device with a dual-axis rotation control mechanism and its measurement and calibration method, which can simultaneously solve the target dual-station RCS calibration and target dual-station RCS calibration under the dual-station scattering measurement condition. Polarization Calibration Problem for Station Polarimetric Scattering Matrix Measurements. As a dual-station RCS measurement and calibration device, it can overcome all the shortcomings of the aforementioned prior art -1 to 4, and ensure the stability of the RCS calibration value under different dual-station angles; as a polarization calibration device for dual-station polarization scattering matrix measurement , not only retains all the advantages of the existing single-station polarization calibration PARC device, but also can be used for dual-station polarization calibration, adding the dual-station RCS calibration and dual-station polarization calibration functions of the traditional PARC device.

本发明采用的技术方案为：一种雷达目标双站散射测量RCS定标与极化校准装置，该装置包括接收天线、发射天线、两个方位-视线双轴旋转单元、方位旋转驱动与控制器、俯仰旋转驱动与控制器、射频组合以及电源组合，其中：The technical solution adopted in the present invention is: a radar target dual-station scattering measurement RCS calibration and polarization calibration device, the device includes a receiving antenna, a transmitting antenna, two azimuth-line-of-sight dual-axis rotation units, an azimuth rotation drive and a controller , pitching and rotating drive and controller, radio frequency combination and power supply combination, of which:

所述的接收天线，用于接收双站测量雷达发射天线的辐射信号，由射频电缆馈给射频组合；The receiving antenna is used to receive the radiation signal of the dual-station measuring radar transmitting antenna, and is fed to the radio frequency combination by the radio frequency cable;

所述的射频组合：其包括依次连接的放大器、滤波器、延时线和衰减器，其完成对所述的接收天线所收到的双站测量雷达辐射信号的放大、滤波、延时处理后得到输出信号，并经衰减器对输出信号电平调节后，由射频电缆馈给发射天线；The radio frequency combination: it includes an amplifier, a filter, a delay line and an attenuator connected in sequence, after completing the amplification, filtering and delay processing of the dual-station measurement radar radiation signal received by the receiving antenna The output signal is obtained, and after the output signal level is adjusted by the attenuator, it is fed to the transmitting antenna by the radio frequency cable;

所述的发射天线，用于完成射频信号向双站测量雷达接收天线的辐射；The transmitting antenna is used to complete the radiation of the radio frequency signal to the receiving antenna of the dual-station measuring radar;

所述的两个方位-视线双轴旋转单元：其中一个用于放置所述的接收天线，另一个用于放置所述的发射天线，The two azimuth-line-of-sight dual-axis rotation units: one is used to place the receiving antenna, and the other is used to place the transmitting antenna,

所述的方位旋转驱动与控制器：用于控制所述的方位-视线双轴旋转单元绕方位向的转动；The azimuth rotation drive and controller: used to control the rotation of the azimuth-line-of-sight dual-axis rotation unit around the azimuth direction;

所述的视线旋转驱动与控制器：用于控制所述的方位-视线双轴旋转单元绕视线轴的转动；The line-of-sight rotation drive and controller: used to control the rotation of the azimuth-line-of-sight dual-axis rotation unit around the line-of-sight axis;

所述的电源组合：用于该装置的电源供给。The power combination: used for the power supply of the device.

进一步的，所述的接收天线和所述的发射天线各由一个喇叭天线组成，同时，为了尽可能减小天线交叉极化耦合误差、提高极化隔离比，在每个天线口面处加装微带极化滤波器装置，每个喇叭天线均安装在一个带有角度编码的方位-视线双轴旋转单元上，由方位旋转驱动与控制器和视线旋转驱动与控制器控制每个天线可独立地绕雷达视线旋转和绕方位转动，带有角度编码的方位-视线双轴旋转单元同时可给出天线的视线转角和方位转角的精确位置信息。Further, the receiving antenna and the transmitting antenna are each composed of a horn antenna. At the same time, in order to minimize the antenna cross-polarization coupling error and improve the polarization isolation ratio, a Microstrip polarization filter device, each horn antenna is installed on an azimuth-line-of-sight dual-axis rotation unit with angle encoding, controlled by azimuth rotation drive and controller and line-of-sight rotation drive and controller Each antenna can be independently The ground rotates around the radar line of sight and around the azimuth, and the azimuth-line-of-sight dual-axis rotation unit with angle encoding can simultaneously provide the precise position information of the antenna's line-of-sight rotation angle and azimuth rotation angle.

进一步的，所述的方位-视线双轴旋转单元：主要由视线转动步进电机、视线角度编码器、方位转台、方位角度编码器以及同天线之间的匹配安装接口组成；其中“视线”系指双站测量雷达发射机与接收天线之间、或双站测量雷达接收机与发射天线之间的连线；“方位”系指测量雷达架设于xOy平面内时，在xOy平面内的转角，通过视线旋转与驱动控制器，可以实时精确地控制每个天线绕雷达天线视线的旋转速度及转角位置，通过方位旋转与驱动控制器，可以实时精确地控制每个天线绕方位角平面雷达天线视线的旋转速度及转角位置，在工作状态下，双站散射测量RCS定标与极化校准装置的接收和发射天线在方位向分别转动到对准双站测量雷达的发射机和接收机天线。Further, the azimuth-line-of-sight dual-axis rotation unit is mainly composed of a line-of-sight rotation stepper motor, a line-of-sight angle encoder, an azimuth turntable, an azimuth-angle encoder, and a matching installation interface with the antenna; where "line-of-sight" means Refers to the connection between the bi-station measurement radar transmitter and the receiving antenna, or between the bi-station measurement radar receiver and the transmission antenna; "Azimuth" refers to the rotation angle in the xOy plane when the measurement radar is erected in the xOy plane, Through the line-of-sight rotation and drive controller, the rotation speed and angular position of each antenna around the radar antenna line-of-sight can be accurately controlled in real time. Through the azimuth rotation and drive controller, the radar antenna line-of-sight of each antenna around the azimuth plane can be precisely controlled in real time. In the working state, the receiving and transmitting antennas of the bistatic scattering measurement RCS calibration and polarization calibration device are rotated in azimuth to align with the transmitter and receiver antennas of the bistatic measurement radar.

进一步的，所述的方位旋转驱动与控制器，通过控制方位转台，完成对接收天线和发射天线在方位向的转动，并通过方位角编码器给出每个天线的方位位置信息，方位旋转驱动与控制器可通过远程控制接口由双站散射测量系统控制器远程控制。Further, the azimuth rotation drive and the controller complete the rotation of the receiving antenna and the transmitting antenna in the azimuth direction by controlling the azimuth turntable, and provide the azimuth position information of each antenna through the azimuth encoder, and the azimuth rotation drive The controller can be remotely controlled by the dual-station scatterometry system controller through the remote control interface.

进一步的，所述的视线旋转驱动与控制器：通过控制视线旋转电机，完成对接收天线和发射天线绕视线轴的转动，并通过视线角编码器给出每个天线的视线转角位置信息，视线旋转驱动与控制器可通过远程控制接口由双站散射测量系统控制器远程控制。Further, the line-of-sight rotation drive and controller: by controlling the line-of-sight rotation motor, the rotation of the receiving antenna and the transmitting antenna around the line-of-sight axis is completed, and the line-of-sight corner position information of each antenna is given by the line-of-sight angle encoder. The rotary drive and controller can be remotely controlled by the dual station scatterometry system controller through the remote control interface.

与上述可用于目标双站雷达散射截面测量定标与极化校准装置相对应的双站测量与校准处理的方法，其具体步骤如下：The method for bi-station measurement and calibration processing corresponding to the above-mentioned bi-station radar cross-section measurement calibration and polarization calibration device that can be used for the target, the specific steps are as follows:

步骤-1：BPARC装置调校，包括：Step-1: BPARC device tuning, including:

调节BPARC接收天线与转发天线的视线旋转机构，使得两个天线的初始极化角调为一致，并控制两旋转机构的转速，使收发天线保持一样的转速w_r匀速旋转，其中w_r＝w_t，单位rad/s，以保证在整个测量过程中BPARC的收发天线极化始终是完全一致的，为此，旋转机构可采用步进电机，保证天线每转到一个角度时停下，雷达测量一组数据，然后控制天线转到下一个角位置，如此重复控制和测量，即可保证收发天线的极化是同步变化的；Adjust the line-of-sight rotation mechanism of the BPARC receiving antenna and the transponder antenna so that the initial polarization angles of the two antennas are adjusted to be consistent, and control the rotation speed of the two rotation mechanisms so that the receiving and transmitting antennas maintain the same rotation speed w _r and rotate at a constant speed, where w _r =w _t , the unit is rad/s, to ensure that the polarization of the transmitting and receiving antenna of BPARC is always completely consistent during the whole measurement process. For this reason, the rotating mechanism can use a stepping motor to ensure that the antenna stops when it turns to an angle, and the radar measurement A set of data, and then control the antenna to the next angular position, and repeat the control and measurement to ensure that the polarization of the transmitting and receiving antenna changes synchronously;

角度编码器准确的记录下天线转过的角度γ，则BPARC转过的圈数可由N＝γ/360°计算得出。测量中，可以控制BPARC双天线进行整圈的测量，这样保证了初始极化角的选取对整个校准过程没有影响；The angle encoder accurately records the angle γ that the antenna turns, and the number of turns that the BPARC turns can be calculated by N=γ/360°. During the measurement, the BPARC dual antennas can be controlled to measure the entire circle, which ensures that the selection of the initial polarization angle has no effect on the entire calibration process;

步骤-2：BPARC装置的安装，包括：Step-2: Installation of BPARC device, including:

将本发明所提出的BPARC极化校准装置安装于标校支架上，按照测量雷达系统的要求调整其延时参数；The BPARC polarization calibration device proposed by the present invention is installed on the calibration bracket, and its delay parameter is adjusted according to the requirements of the measurement radar system;

针对当前给定的双站测量的双站角，控制方位转台，使BPARC接收天线对准测量雷达的发射天线，BPARC转发天线对准测量雷达的接收天线，每次改变测量双站角时，均需重复此BPARC安装步骤；For the currently given bistatic angle of bistatic measurement, control the azimuth turntable so that the BPARC receiving antenna is aligned with the transmitting antenna of the measuring radar, and the BPARC forwarding antenna is aligned with the receiving antenna of the measuring radar. This BPARC installation step needs to be repeated;

步骤-3：极化校准测量和数据录取Step-3: Polarization Calibration Measurements and Data Acquisition

维持已按照给定测量双站角调节好的方位转台位置固定不动，控制BPARC的视线旋转机构，使BPARC的两个天线匀速慢速旋转，假设共转过N圈，测量雷达发射信号并接收BPARC转发天线辐射的回波信号，录取BPARC天线绕测量雷达视线旋转过程中不同位置下全部极化通道的回波信号，得到的全部测量数据；Keep the position of the azimuth turntable that has been adjusted according to the given measurement double-station angle fixed, and control the line-of-sight rotation mechanism of BPARC to make the two antennas of BPARC rotate at a constant and slow speed. BPARC forwards the echo signal radiated by the antenna, records the echo signal of all polarization channels at different positions during the rotation of the BPARC antenna around the measurement radar line of sight, and obtains all the measurement data;

每次改变测量双站角时，均需重复此BPARC测量和数据录取步骤；This BPARC measurement and data acquisition step needs to be repeated every time the measurement double station angle is changed;

步骤-4：极化校准参数提取Step-4: Polarization Calibration Parameter Extraction

通过步骤-3中的测量数据求解得到测量雷达系统的全部极化校准参数；Obtain all polarization calibration parameters of the measurement radar system by solving the measurement data in step-3;

每次改变测量双站角时，均需利用对该双站角下的BPARC测量数据求解测量雷达系统的校准参数；Every time the measurement double station angle is changed, it is necessary to use the BPARC measurement data under the double station angle to solve the calibration parameters of the survey radar system;

步骤-5：目标双站极化测量Step-5: Target Bi-Station Polarization Measurement

安装待测目标，并由双站测量雷达录取所有极化通道的目标回波；Install the target to be measured, and record the target echoes of all polarization channels by the dual-station measurement radar;

同一双站角下，可以采用相同的测量雷达对多个相同或不同目标进行双站测量；Under the same dual-station angle, the same measurement radar can be used for dual-station measurement of multiple identical or different targets;

步骤-6：极化校准处理Step-6: Polarization Calibration Processing

根据步骤-4中已得到的极化校准参数和步骤-5中测得的目标测量值，应用式(6-1)即可完成所测目标的极化校准，得到目标的真实极化散射矩阵值；According to the polarization calibration parameters obtained in step-4 and the target measurement value measured in step-5, the polarization calibration of the measured target can be completed by applying formula (6-1), and the real polarization scattering matrix of the target can be obtained value;

${S S}_{t t} = = \frac{11}{((11 - - {ϵ ϵ}_{R R}^{H h} \cdot &Center Dot; {ϵ ϵ}_{R R}^{V V}))} \cdot &Center Dot; \frac{11}{((11 - - {ϵ ϵ}_{T T}^{H h} \cdot &Center Dot; {ϵ ϵ}_{T T}^{V V}))} \cdot &Center Dot; [\begin{matrix} 11 & - - {ϵ ϵ}_{R R}^{H h} \\ - - {ϵ ϵ}_{R R}^{V V} & 11 \end{matrix}] \cdot &Center Dot; [\begin{matrix} \frac{{M m}_{t t}^{HH HH}}{{R R}_{HH HH} \cdot &Center Dot; {T T}_{HH HH}} & \frac{{M m}_{t t}^{HV HV}}{{R R}_{HH HH} \cdot &Center Dot; {T T}_{VV VV}} \\ \frac{{M m}_{t t}^{VH VH}}{{R R}_{VV VV} \cdot &Center Dot; {T T}_{HH HH}} & \frac{{M m}_{t t}^{VV VV}}{{R R}_{VV VV} \cdot &Center Dot; {T T}_{VV VV}} \end{matrix}] \cdot &Center Dot; [\begin{matrix} 11 & - - {ϵ ϵ}_{T T}^{H h} \\ - - {ϵ ϵ}_{T T}^{V V} & 11 \end{matrix}] - - - - - - ((66 - - 11))$

式中 $M_{t} = [\begin{matrix} M_{t}^{HH} & M_{t}^{HV} \\ M_{t}^{VH} & M_{t}^{VV} \end{matrix}]$ 为待校准目标的4个极化组合下的测量值；S_t为待校准目标真实极化散射矩阵；R_HH和R_VV分别为测量系统HH极化和VV极化接收通道的增益因子，T_HH及T_VV分别为测量系统HH极化和VV极化发射通道的增益因子，为测量系统的交叉极化因子，这8个参数为需要通过步骤-1～步骤-5对BPARC测量并对测量数据进行处理来求解的测量系统极化校准参数；In the formula $m_{t} = [\begin{matrix} m_{t}^{HH} & m_{t}^{HV} \\ m_{t}^{VH} & m_{t}^{VV} \end{matrix}]$ is the measured value under the four polarization combinations of the target to be calibrated; S _t is the real polarization scattering matrix of the target to be calibrated; R _HH and R _VV are the gain factors of the HH polarization and VV polarization receiving channels of the measurement system, T _HH and T _VV are the gain factors of the HH polarization and VV polarization transmission channels of the measurement system, respectively, is the cross-polarization factor of the measurement system, and these 8 parameters are the polarization calibration parameters of the measurement system that need to be solved by measuring BPARC through steps-1~step-5 and processing the measurement data;

同一双站角下，采用相同的测量雷达对多个相同或不同目标进行双站测量时，可以用同一组校准参数进行极化校准处理；Under the same dual-station angle, when the same measurement radar is used to perform dual-station measurements on multiple identical or different targets, the same set of calibration parameters can be used for polarization calibration processing;

如果只做双站RCS测量和定标，则上述6个步骤可进一步简化，不需要提取极化校准参数，只需按照式(6-2)所给出的双站定标方程进行测量和RCS定标计算，If only the bi-station RCS measurement and calibration is done, the above six steps can be further simplified, and there is no need to extract the polarization calibration parameters, only the measurement and RCS calibration calculation,

${σ σ}_{T T}^{b b} = = {K K}_{b b} \cdot &Center Dot; \frac{{P P}_{rT rT}}{{P P}_{rC rC}} \cdot &Center Dot; {σ σ}_{C C}^{b b} = = {K K}_{b b} \cdot \cdot {| | \frac{{S S}_{T T}}{{S S}_{C C}} | |}^{22} \cdot &Center Dot; {σ σ}_{C C}^{b b} - - - - - - ((66 - - 22))$

式中为目标双站RCS，为BPARC的理论双站RCS；P_rC和P_rT分别为测定标体和测目标时雷达接收到的回波功率；S_T和S_C分别为单次RCS测量采样中，测量目标和测量定标体时的雷达复回波信号；K_b为同双站测量几何关系相对应的定标常数；In the formula For the target dual-station RCS, _is the theoretical two-station RCS of BPARC; P _rC and P _rT are the echo power received by the radar when measuring the object and the target, respectively; ST and S _C are the measurement target and measurement calibration in a single RCS measurement sample, respectively The radar complex echo signal in body time; K _b is the calibration constant corresponding to the geometric relationship of the two-station measurement;

BPARC的理论双站RCS值计算公式为；Theoretical bistatic RCS value of BPARC The calculation formula is;

${σ σ}_{C C}^{b b} = = {G G}_{Loop Loop} \cdot \cdot \frac{{G G}_{T T} \cdot \cdot {G G}_{R R} \cdot &Center Dot; {λ λ}^{22}}{44 π π} - - - - - - ((66 - - 33))$

式中，G_T和G_R分别为BPARC转发天线和接收天线的增益，G_Loop为BPARC中除天线外，整个回路的总增益；BPARC的理论RCS值也可通过采用另一个RCS值已知的定标体通过相对定标测量的方法来测得；In the formula, G _T and G _R are the gains of the BPARC forwarding antenna and receiving antenna respectively, and G _Loop is the total gain of the entire loop in BPARC except the antenna; the theoretical RCS value of BPARC can also be obtained by using another RCS value The calibration body is measured by the method of relative calibration measurement;

同双站测量几何关系相对应的定标常数K_b的计算则根据双站测量几何关系由式(6-4)完成：The calculation of the calibration constant K _b corresponding to the geometric relationship of the bi-station measurement is completed by formula (6-4) according to the geometric relationship of the bi-station measurement:

${K K}_{b b} = = {((\frac{{R R}_{tT TT} {R R}_{rT rT}}{{R R}_{tC tC} {R R}_{rC rC}}))}^{22} \cdot &Center Dot; \frac{{L L}_{tT TT} {L L}_{rT rT}}{{L L}_{tC tC} {L L}_{rC rC}} - - - - - - ((66 - - 44))$

式中R_tT和R_tC分别表示发射通道的目标距离和定标体距离；R_rT和R_rC分别表示接收通道的目标距离和定标体距离；L_tT和L_tC分别表示测目标和测定标体时发射通道的总损耗；L_rT和L_rC分别表示测目标和测定标体时接收通道的总损耗；只要测试中目标距离和定标体距离是确定的，双站几何关系保持不变，则K_b值是确定的常数。In the formula, R _tT and R _tC represent the target distance of the transmitting channel and the calibration object distance respectively; R _rT and R _rC represent the target distance of the receiving channel and the calibration object distance respectively; L _tT and L _tC represent the measuring target and the measuring target respectively The total loss of the transmitting channel when measuring the body; _LrT and _LrC respectively represent the total loss of the receiving channel when measuring the target and measuring the object; as long as the distance between the target and the calibration object is determined in the test, the geometric relationship between the two stations remains unchanged, Then the K _b value is a definite constant.

本发明技术方案带来的有益效果为：The beneficial effects brought by the technical solution of the present invention are:

1)本发明中所提出的可旋转双天线有源校准装置BPARC保留了已有PARC装置的全部优点，同时又解决了双站RCS测量定标和极化校准问题，具有传统定标体和PARC装置所没有的一系列重要优点。1) The rotatable dual-antenna active calibration device BPARC proposed in the present invention retains all the advantages of the existing PARC device, and at the same time solves the problems of dual-station RCS measurement calibration and polarization calibration, and has traditional calibration bodies and PARC A series of important advantages that the device does not have.

2)与文献[2，3，4]中传统的简单定标体(现有技术-1和)相比：由于BPARC的收发天线指向可控，可以同双站测量雷达的发射和接收天线精确对准，故不收测量双站角大小的影响，解决了传统简单定标体的RCS随双站角增大出现大的起伏、难以完成大双站角RCS测量精确定标问题。2) Compared with the traditional simple calibration body (prior art-1 and ) in literature [2, 3, 4]: since the direction of the transmitting and receiving antenna of BPARC is controllable, it can be precisely compared with the transmitting and receiving antennas of the dual-station measurement radar. Alignment, so it does not accept the influence of the measurement of the double station angle, which solves the problem that the RCS of the traditional simple calibration body has large fluctuations with the increase of the double station angle, and it is difficult to complete the precise calibration of the large double station angle RCS measurement.

3)与文献[5，6]中技术(现有技术-3)相比：采用BPARC作为双站测量定标和校准装置时，双站测量雷达不再需要两套发射和接收机，只需一部发射机和一部接收机，即可完成双站测量、定标和极化校准。3) Compared with the technology in literature [5, 6] (existing technology-3): when BPARC is used as the bistatic measurement calibration and calibration device, the bistatic measurement radar no longer needs two sets of transmitters and receivers, and only needs One transmitter and one receiver can complete bi-station measurement, calibration and polarization calibration.

4)与文献[8]中的单天线PARC(现有技术-4)相比：(1)本项发明BPARC的优点包括可用于完成双站测量RCS定标和极化校准：(2)可加装极化滤波器，使得PARC天线的极化隔离度大大提高，有利于提供测量校准精度；(3)收发极化组合形式多样，可提供更多样化的极化散射特征信号，使得极化校准测量和处理方案的选择可多样化，确保在不同工程应用中均具有可实现性。4) Compared with the single-antenna PARC (prior art-4) in literature [8]: (1) The advantages of BPARC in this invention include that it can be used to complete bi-station measurement RCS calibration and polarization calibration: (2) it can The addition of a polarization filter greatly improves the polarization isolation of the PARC antenna, which is conducive to providing measurement and calibration accuracy; (3) There are various forms of transmission and reception polarization combinations, which can provide more diverse polarization scattering characteristic signals, making the polar The selection of calibration measurement and processing schemes can be diversified to ensure the feasibility in different engineering applications.

5)与文献[9]中数字式PARC(现有技术-4)相比：(1)本项发明BPARC可用于完成双站测量RCS定标和极化校准；(2)无需对射频信号作A/D和D/A处理，保证接收和转发的信号不失真；(3)结构简单，性能稳定，研发成本较低，工程上容易实现；(4)收发极化组合形式多样，可提供更多样化的极化散射特征信号，使得极化校准测量和处理方案的选择可多样化，确保在不同工程应用中均具有可实现性。5) Compared with the digital PARC (prior art-4) in document [9]: (1) BPARC of this invention can be used to complete bi-station measurement RCS calibration and polarization calibration; (2) there is no need for RF signal A/D and D/A processing ensure that the received and forwarded signals are not distorted; (3) simple structure, stable performance, low research and development costs, and easy engineering implementation; (4) various forms of transceiver polarization combinations can provide more Diversified polarization scattering characteristic signals make the selection of polarization calibration measurement and processing schemes diverse, ensuring the feasibility in different engineering applications.

附图说明Description of drawings

图1为双站RCS测量几何关系示意图；Figure 1 is a schematic diagram of the geometric relationship of the two-station RCS measurement;

图2为金属球的归一化RCS随双站角的变化特性；Figure 2 shows the variation characteristics of the normalized RCS of the metal ball with the dual station angle;

图3为Monzon的设计双站定标装置；Figure 3 is the design of Monzon's dual-station calibration device;

图4为采用两部发射机和接收机的双站RCS测量定标示意图；Figure 4 is a schematic diagram of the calibration of the bi-station RCS measurement using two transmitters and receivers;

图5为PARC结构框图；Figure 5 is a block diagram of the PARC structure;

图6为双天线PARC天线正视图；Figure 6 is a front view of the dual-antenna PARC antenna;

图7为单天线PARC天线正视图；Figure 7 is a front view of a single-antenna PARC antenna;

图8为双天线数字式PARC结构框图；Figure 8 is a block diagram of a dual-antenna digital PARC structure;

图9为双站散射测量RCS定标与极化校准装置的总体结构示意图；Figure 9 is a schematic diagram of the overall structure of the dual-station scatterometry RCS calibration and polarization calibration device;

图10为双站散射测量RCS定标与极化校准装置在具体测量中同双站测量雷达之间的几何关系示意图。Fig. 10 is a schematic diagram of the geometric relationship between the bistatic scatterometry RCS calibration and polarization calibration device and the bistatic measurement radar in the specific measurement.

具体实施方式Detailed ways

下面结合附图以及具体实施例进一步说明本发明。The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

本发明所提出的一种可用于目标双站雷达散射截面测量定标与极化校准装置的总体结构示意图如图9所示。A schematic diagram of the overall structure of a target bistatic radar cross-section measurement calibration and polarization calibration device proposed by the present invention is shown in FIG. 9 .

图9中，双站散射测量RCS定标与极化校准装置由接收天线、发射天线、两个方位-视线双轴旋转单元、方位旋转驱动与控制器、俯仰旋转驱动与控制器、射频组合、电源组合、相关匹配安装接口以及远程控制接口等功能模块组成。其中：In Fig. 9, the dual-station scatterometry RCS calibration and polarization calibration device consists of a receiving antenna, a transmitting antenna, two azimuth-line-of-sight dual-axis rotation units, azimuth rotation drive and controller, pitch rotation drive and controller, radio frequency combination, It is composed of functional modules such as power supply combination, related matching installation interface and remote control interface. in:

接收和发射天线：接收天线用于接收双站测量雷达发射天线的辐射信号，由射频电缆馈给射频组合，经放大、滤波、延时和衰减器对输出信号电平调节后，由射频电缆馈给发射天线完成射频信号向双站测量雷达接收天线的辐射，如图10所示。接收和发射天线各由一个喇叭天线组成，同时，为了尽可能减小天线交叉极化耦合误差、提高极化隔离比，在每个天线口面处加装微带极化滤波器装置(参见文献[10]M.Kuloglu，C-C Chen，“Ultrawidebandelectromagnetic polarization filter(UWB-EMPF)applications to conventional horn antennas forsubstantial cross-polarization level reduction，”IEEE Antennas and Propagation Magazine，2013，55(2):280-288.)。每个喇叭天线均安装在一个带有角度编码的方位-视线双轴旋转机构上，由控制器控制每个天线可独立地绕雷达视线旋转和绕方位转动，同时可给出天线的视线转角和方位转角的精确位置信息。Receiving and transmitting antenna: the receiving antenna is used to receive the radiation signal of the dual-station measurement radar transmitting antenna, which is fed to the radio frequency combination by the radio frequency cable, and is fed by the radio frequency cable after the output signal level is adjusted by the amplification, filtering, delay and attenuator. Complete the radiation of the radio frequency signal to the dual station measurement radar receiving antenna for the transmitting antenna, as shown in Figure 10. The receiving and transmitting antennas are each composed of a horn antenna. At the same time, in order to reduce the antenna cross-polarization coupling error as much as possible and improve the polarization isolation ratio, a microstrip polarization filter device is installed at each antenna interface (see literature [10] M. Kuloglu, C-C Chen, "Ultrawidebandelectromagnetic polarization filter (UWB-EMPF) applications to conventional horn antennas for substantial cross-polarization level reduction," IEEE Antennas and Propagation Magazine, 2013, 55(2):280-288. . Each horn antenna is installed on an azimuth-line-of-sight dual-axis rotation mechanism with angle coding, and each antenna can be independently rotated around the radar line of sight and around the azimuth by the controller, and at the same time, the line-of-sight angle and the line-of-sight angle of the antenna can be given. Accurate position information of azimuth and rotation angle.

方位-视线双轴旋转单元：主要由视线转动步进电机、视线角度编码器、方位转台、方位角度编码器以及同天线之间的匹配安装接口等组成。其中“视线”系指图10中双站测量雷达发射机与本发明装置接收天线之间、或双站测量雷达接收机与本发明装置发射天线之间的连线；“方位”系指图10中测量雷达架设于xOy平面内时，在xOy平面内的转角，如图10中所示的θ角。通过视线旋转与驱动控制器，可以实时精确地控制每个天线绕雷达天线视线的旋转速度及转角位置。通过方位旋转与驱动控制器，可以实时精确地控制每个天线绕方位角平面雷达天线视线的旋转速度及转角位置。在工作状态下，双站散射测量RCS定标与极化校准装置的接收和发射天线在方位向分别转动到对准双站测量雷达的发射机和接收机天线，而在视线轴旋转转到不同位置时的典型极化组合正视图可参见图6所示。Azimuth-line-of-sight dual-axis rotation unit: mainly composed of line-of-sight rotation stepper motor, line-of-sight angle encoder, azimuth turntable, azimuth angle encoder, and matching installation interface with the antenna. Wherein "line of sight" refers to the connection line between the dual-station measurement radar transmitter and the device receiving antenna of the present invention or between the dual-station measurement radar receiver and the device transmission antenna of the present invention in Fig. 10; "Azimuth" refers to Fig. 10 When the medium-measurement radar is erected in the xOy plane, the rotation angle in the xOy plane is the angle θ shown in Figure 10. Through the line-of-sight rotation and drive controller, the rotation speed and angular position of each antenna around the line-of-sight of the radar antenna can be precisely controlled in real time. Through the azimuth rotation and drive controller, the rotation speed and rotation angle position of each antenna around the azimuth plane radar antenna line of sight can be precisely controlled in real time. In the working state, the receiving and transmitting antennas of the bistatic scatterometry RCS calibration and polarization calibration device are rotated in azimuth to align with the transmitter and receiver antennas of the bistatic measurement radar, and rotated to different positions in the line of sight axis. The front view of a typical polarization combination in position can be seen in Figure 6.

方位旋转驱动与控制器：通过控制方位转台，完成对本发明装置的接收和发射天线在方位向的转动，并通过方位角编码器给出每个天线的方位位置信息。方位旋转驱动与控制器可通过远程控制接口由双站散射测量系统控制器远程控制。Azimuth rotation drive and controller: By controlling the azimuth turntable, the receiving and transmitting antennas of the device of the present invention are rotated in the azimuth direction, and the azimuth position information of each antenna is given by the azimuth encoder. The azimuth rotation drive and the controller can be remotely controlled by the dual-station scatterometry system controller through the remote control interface.

视线旋转驱动与控制器：通过控制视线旋转电机，完成对本发明装置的接收和发射天线绕视线轴的转动，并通过视线角编码器给出每个天线的视线转角位置信息。视线旋转驱动与控制器可通过远程控制接口由双站散射测量系统控制器远程控制。Line-of-sight rotation drive and controller: By controlling the line-of-sight rotation motor, the rotation of the receiving and transmitting antennas of the device of the present invention around the line-of-sight axis is completed, and the line-of-sight angle position information of each antenna is given by the line-of-sight angle encoder. The line-of-sight rotary drive and controller can be remotely controlled by the dual-station scatterometry system controller through the remote control interface.

射频组合：完成对接收天线所收到的双站测量雷达发射信号的放大、滤波、延时，并经衰减器对输出信号电平调节后，馈给发射天线以完成向双站测量雷达接收机天线的信号辐射。图10中的放大器、滤波器、衰减器、延时线、电源等的工作原理同传统的PARC无异，在此不作讨论。Radio frequency combination: complete the amplification, filtering, and delay of the bistation measurement radar transmission signal received by the receiving antenna, and after the output signal level is adjusted by the attenuator, it is fed to the transmission antenna to complete the transmission to the bistation measurement radar receiver Signal radiation from the antenna. The working principle of the amplifier, filter, attenuator, delay line, power supply, etc. in Figure 10 is the same as that of the traditional PARC, and will not be discussed here.

电源组合：完成本装置全部单元和组件的电源供给。Power combination: complete the power supply of all units and components of the device.

以下我们称本发明所设计的装置为双站有源极化校准器(Bistatic Polarimetric ActiveRadar Calibrators)，简称为BPARC装置，以区别于传统的仅能用于单站测量RCS定标和极化校准的PARC装置。Below we call the device designed by the present invention Bistatic Polarimetric Active Radar Calibrators, referred to as BPARC device, to be different from traditional ones that can only be used for single-station measurement RCS calibration and polarization calibration PARC device.

由于采用本发明所设计的装置BPARC，当测量双站角改变时，可以通过同步控制BPARC的方位转台转动，使得BPARC的接收天线永远保持同测量雷达的发射天线视线相一致，而BPARC的转发天线永远同测量雷达的发射天线视线保持一致。因此，无论测量双站角多大，BPARC的理论RCS值和极化特性均不随双站角发生变化，从而保证了BPARC装置可用于完成单站、双站RCS测量和极化校准各种应用场合。Owing to adopting the device BPARC designed in the present invention, when the measurement double-station angle changes, the azimuth turntable of BPARC can be controlled synchronously to rotate, so that the receiving antenna of BPARC is always consistent with the line of sight of the transmitting antenna of the measuring radar, while the forwarding antenna of BPARC Always keep in line with the transmitting antenna line of sight of the measuring radar. Therefore, no matter how large the dual-station angle is, the theoretical RCS value and polarization characteristics of BPARC will not change with the dual-station angle, thus ensuring that the BPARC device can be used to complete single-station, dual-station RCS measurement and polarization calibration in various applications.

BPARC装置的收发天线可以工作在各种极化组合，通过BPARC模拟实现多种常用无源定标体的极化散射矩阵，从而可大大扩展BPARC的应用范围。此外，通过在收、发天线口面加装极化滤波器，可大大提高交叉极化隔离度，解决单天线PARC所存在的交叉极化耦合给极化校准所带来的消极影响。The transceiver antenna of the BPARC device can work in various polarization combinations, and the polarization scattering matrix of a variety of commonly used passive calibration objects can be realized through BPARC simulation, which can greatly expand the application range of BPARC. In addition, by installing polarization filters on the interface of the receiving and transmitting antennas, the cross-polarization isolation can be greatly improved, and the negative impact of the cross-polarization coupling in the single-antenna PARC on polarization calibration can be solved.

同已有的PARC装置相比，本发明的另一个重要优点是，由于采用了可旋转双天线设计，收、发天线的不同姿态组合可构成不同的极化组合，由此可设计出不同的极化校准测量方案和校准算法，讨论如下。Compared with the existing PARC device, another important advantage of the present invention is that due to the adoption of a rotatable dual-antenna design, different posture combinations of the receiving and transmitting antennas can form different polarization combinations, thus different polarization combinations can be designed. The polarization calibration measurement scheme and calibration algorithm are discussed below.

双站极化测量校准原理与方案介绍如下：The principle and scheme of dual-station polarization measurement calibration are introduced as follows:

由于定量极化测量与校准过程一般要求完成对4个极化通道进行校准，保证最终得到的目标极化散射矩阵测量是精确的，这也意味着同时完成了4个极化组合下目标RCS的测量定标。因此，以下我们不单独讨论双站RCS测量定标问题，而是重点讨论极化测量校准的原理和方案。Since the quantitative polarization measurement and calibration process generally requires the completion of the calibration of the four polarization channels to ensure that the final measurement of the target polarization scattering matrix is accurate, this also means that the target RCS under the four polarization combinations is completed at the same time. Measurement calibration. Therefore, in the following, we will not discuss the calibration of dual-station RCS measurements separately, but focus on the principles and schemes of polarization measurement calibration.

式(3)的极化校准模型改写成矩阵形式有：The polarization calibration model of formula (3) is rewritten into matrix form as follows:

$[\begin{matrix} {M m}_{HH HH} & {M m}_{HV HV} \\ {M m}_{VH VH} & {M m}_{VV VV} \end{matrix}] = = [\begin{matrix} {R R}_{HH HH} & {R R}_{HV HV} \\ {R R}_{VH VH} & {R R}_{VV VV} \end{matrix}] \cdot \cdot [\begin{matrix} {S S}_{HH HH} & {S S}_{HV HV} \\ {S S}_{VH VH} & {S S}_{VV VV} \end{matrix}] \cdot \cdot [\begin{matrix} {T T}_{HH HH} & {T T}_{HV HV} \\ {T T}_{VH VH} & {T T}_{VV VV} \end{matrix}] - - - - - - ((88))$

可将式(8)分解如下：Formula (8) can be decomposed as follows:

$[\begin{matrix} {M m}_{HH HH} & {M m}_{HV HV} \\ {M m}_{VH VH} & {M m}_{VV VV} \end{matrix}] = = [\begin{matrix} {R R}_{HH HH} & 00 \\ 00 & {R R}_{VV VV} \end{matrix}] \cdot &Center Dot; [\begin{matrix} 11 & {ϵ ϵ}_{R R}^{H h} \\ {ϵ ϵ}_{R R}^{V V} & 11 \end{matrix}] \cdot &Center Dot; [\begin{matrix} {S S}_{HH HH} & {S S}_{HV HV} \\ {S S}_{VH VH} & {S S}_{VV VV} \end{matrix}] \cdot &Center Dot; [\begin{matrix} 11 & {ϵ ϵ}_{T T}^{V V} \\ {ϵ ϵ}_{T T}^{H h} & 11 \end{matrix}] \cdot &Center Dot; [\begin{matrix} {T T}_{HH HH} & 00 \\ 00 & {T T}_{VV VV} \end{matrix}] - - - - - - ((99))$

式中， $ϵ_{R}^{H} = \frac{R_{HV}}{R_{HH}}, ϵ_{R}^{V} = \frac{R_{VH}}{R_{VV}}, ϵ_{T}^{H} = \frac{T_{VH}}{T_{HH}}, ϵ_{T}^{V} = \frac{T_{HV}}{T_{VV}}$ 为测量系统的交叉极化因子。In the formula, $ϵ_{R}^{h} = \frac{R_{HV}}{R_{HH}}, ϵ_{R}^{V} = \frac{R_{VH}}{R_{VV}}, ϵ_{T}^{h} = \frac{T_{VH}}{T_{HH}}, ϵ_{T}^{V} = \frac{T_{HV}}{T_{VV}}$ is the cross-polarization factor of the measurement system.

根据式(9)，在极化校准中，只要通过一系列的测量和解算求得参数R_HH、R_VV、T_HH及T_VV，即可完成极化校准，而通过本发明所提出的BPARC获得上述极化校准参数的方法可多种多样。下面介绍其中3种典型方案，其中每一种方案的讨论，都是针对给定测量双站角而进行的，当改变测量双站角时，因为通过控制BPARC的两个方位转台可使其接收天线和转发天线分别对准双站测量雷达的发射天线和接收天线，因此，不同双站角下的极化测量和校准原理及过程是完全一样的。According to formula (9), in polarization calibration, it is only necessary to obtain the parameters through a series of measurements and calculations R _HH , R _VV , T _HH and T _VV can complete the polarization calibration, and there are various methods for obtaining the above polarization calibration parameters through the BPARC proposed by the present invention. Three typical schemes are introduced below, and the discussion of each scheme is carried out for a given measurement double-station angle. When changing the measurement double-station angle, because the two azimuth turntables of BPARC can be controlled to make it receive The antenna and the transponder antenna are aimed at the transmitting antenna and receiving antenna of the bistatic measuring radar respectively. Therefore, the principle and process of polarization measurement and calibration under different bistatic angles are exactly the same.

方案-1：plan 1:

BPARC收、发天线中，保持其中一个天线固定(也即工作在固定的极化状态)、另一个天线可作0～360°旋转(也即极化状态可在0～360°范围内变化)。举例说明如下：In the BPARC receiving and transmitting antennas, keep one of the antennas fixed (that is, work in a fixed polarization state), and the other antenna can be rotated from 0 to 360° (that is, the polarization state can be changed within the range of 0 to 360°) . Examples are as follows:

首先，转发天线保持45°线极化不变，即θ_t＝45°，接收天线在0～360°范围内旋转。由式(6)可知，此时PARC的PSM为：First, the forwarding antenna keeps the 45° linear polarization unchanged, that is, θ _t =45°, and the receiving antenna rotates within the range of 0° to 360°. It can be seen from formula (6) that the PSM of PARC at this time is:

${S S}_{c c 11}^{P P} = = β β \cdot &Center Dot; [\begin{matrix} cos cos {θ θ}_{r r} & sin sin {θ θ}_{r r} \\ cos cos {θ θ}_{r r} & sin sin {θ θ}_{r r} \end{matrix}] - - - - - - ((1010))$

其中，这一系数可在极化校准前，根据其他定标体对PARC进行定标得到，也可通过式(5)计算得到，在本文中均视为已知量。可见，在该种情况下，PARC的极化散射矩阵各分量是随接收天线的极化角θ_r呈正余弦规律变化。in, This coefficient can be obtained by calibrating PARC according to other calibration bodies before polarization calibration, and can also be calculated by formula (5), which is regarded as a known quantity in this paper. It can be seen that, in this case, each component of the polarization scattering matrix of PARC changes with the polarization angle θ _r of the receiving antenna in a sinine-cosine law.

取θ_r＝90°和θ_r＝0°，则由式(8)可知，对应姿态下的理论PSM分别为：Taking θ _r = 90° and θ _r = 0°, then it can be known from formula (8) that the theoretical PSMs under the corresponding attitudes are:

${S S}_{c c 1,1 1,1}^{P P} = = β β \cdot &Center Dot; [\begin{matrix} 00 & 11 \\ 00 & 11 \end{matrix}] - - - - - - ((1111 a a))$

${S S}_{c c 11,, 22}^{P P} = = β β \cdot &Center Dot; [\begin{matrix} 11 & 00 \\ 11 & 00 \end{matrix}] - - - - - - ((1111 b b))$

将式(11a)和式(11b)分别代入式(8)展开，有：Substituting formula (11a) and formula (11b) into formula (8) to expand, we have:

${M m}_{c c 1,1 1,1}^{P P} = = R R \cdot \cdot {S S}_{c c 1,1 1,1}^{P P} \cdot &Center Dot; T T = = β β \cdot &Center Dot; [\begin{matrix} {T T}_{VH VH} \cdot \cdot (({R R}_{HH HH} + + {R R}_{HV HV})) & {T T}_{VV VV} \cdot &Center Dot; (({R R}_{HH HH} + + {R R}_{HV HV})) \\ {T T}_{VH VH} \cdot \cdot (({R R}_{VH VH} + + {R R}_{VV VV})) & {T T}_{VV VV} \cdot &Center Dot; (({R R}_{VH VH} + + {R R}_{VV VV})) \end{matrix}] - - - - - - ((1212 a a))$

${M m}_{c c 11,, 22}^{P P} = = R R \cdot &Center Dot; {S S}_{c c 11,, 22}^{P P} \cdot \cdot T T = = β β \cdot \cdot [\begin{matrix} {T T}_{HH HH} \cdot \cdot (({R R}_{HH HH} + + {R R}_{HV HV})) & {T T}_{HV HV} \cdot \cdot (({R R}_{HH HH} + + {R R}_{HV HV})) \\ {T T}_{HH HH} \cdot \cdot (({R R}_{VH VH} + + {R R}_{VV VV})) & {T T}_{HV HV} \cdot &Center Dot; (({R R}_{VH VH} + + {R R}_{VV VV})) \end{matrix}] - - - - - - ((1212 b b))$

有have

${ϵ ϵ}_{T T}^{H h} = = \frac{{T T}_{VH VH}}{{T T}_{HH HH}} = = \frac{{M m}_{c c 1,1 1,1}^{P P,, HH HH}}{{M m}_{c c 1,2 1,2}^{P P,, HH HH}} - - - - - - ((1313 a a))$

${ϵ ϵ}_{T T}^{V V} = = \frac{{T T}_{HV HV}}{{T T}_{VV VV}} = = \frac{{M m}_{c c 11,, 22}^{P P,, VV VV}}{{M m}_{c c 11,, 11}^{P P,, VV VV}} - - - - - - ((1313 b b))$

其次，接收天线保持45°线极化不变，即θ_r＝45°，转发天线在0～360°范围内旋转。Secondly, the receiving antenna keeps the 45° linear polarization unchanged, that is, θ _r =45°, and the forwarding antenna rotates within the range of 0-360°.

取θ_t＝90°和θ_t＝0°，则对应姿态下的理论PSM分别为：Taking θ _t = 90° and θ _t = 0°, the theoretical PSM under the corresponding attitudes are respectively:

${S S}_{c c 11,, 33}^{P P} = = β β \cdot \cdot [\begin{matrix} 00 & 00 \\ 11 & 11 \end{matrix}] - - - - - - ((1414 a a))$

${S S}_{c c 11,, 44}^{P P} = = β β \cdot &Center Dot; [\begin{matrix} 11 & 11 \\ 00 & 00 \end{matrix}] - - - - - - ((1414 b b))$

将式(14a)和式(14b)分别代入式(8)展开，有：Substituting formula (14a) and formula (14b) into formula (8) to expand, we have:

${M m}_{c c 11,, 33}^{P P} = = R R \cdot &Center Dot; {S S}_{c c 11,, 33}^{P P} \cdot &Center Dot; T T = = β β \cdot &Center Dot; [\begin{matrix} {R R}_{HV HV} \cdot &Center Dot; (({T T}_{HH HH} + + {T T}_{VH VH})) & {R R}_{HV HV} \cdot &Center Dot; (({T T}_{HV HV} + + {T T}_{VV VV})) \\ {R R}_{VV VV} \cdot &Center Dot; (({T T}_{HH HH} + + {T T}_{VH VH})) & {R R}_{VV VV} \cdot &Center Dot; (({T T}_{HV HV} + + {T T}_{VV VV})) \end{matrix}] - - - - - - ((1515 a a))$

${M m}_{c c 11,, 44}^{P P} = = R R \cdot &Center Dot; {S S}_{c c 11,, 44}^{P P} \cdot &Center Dot; T T = = β β \cdot &Center Dot; [\begin{matrix} {R R}_{HH HH} \cdot \cdot (({T T}_{HH HH} + + {T T}_{VH VH})) & {R R}_{HH HH} \cdot &Center Dot; (({T T}_{HV HV} + + {T T}_{VV VV})) \\ {R R}_{VH VH} \cdot &Center Dot; (({T T}_{HH HH} + + {T T}_{VH VH})) & {R R}_{VH VH} \cdot &Center Dot; (({T T}_{HV HV} + + {T T}_{VV VV})) \end{matrix}] - - - - - - ((1515 b b))$

有have

${ϵ ϵ}_{R R}^{H h} = = \frac{{R R}_{HV HV}}{{R R}_{HH HH}} = = \frac{{M m}_{c c 11,, 33}^{P P,, HH HH}}{{M m}_{c c 11,, 44}^{P P,, HH HH}} - - - - - - ((1616 a a))$

${ϵ ϵ}_{R R}^{V V} = = \frac{{R R}_{VH VH}}{{R R}_{VV VV}} = = \frac{{M m}_{c c 11,, 44}^{P P,, VV VV}}{{M m}_{c c 11,, 33}^{P P,, VV VV}} - - - - - - ((1616 b b))$

将与代入式(9)，展开可求得：Will and Substituting into formula (9), the expansion can be obtained:

${R R}_{HH HH} {T T}_{HH HH} = = \frac{11}{β β} \cdot &Center Dot; \frac{{M m}_{c c 1,2 1,2}^{P P,, HH HH}}{11 - - {ϵ ϵ}_{r r}^{H h}} - - - - - - ((1717 a a))$

${R R}_{HH HH} {T T}_{VV VV} = = \frac{11}{β β} \cdot &Center Dot; \frac{{M m}_{c c 1,2 1,2}^{P P,, HV HV}}{{ϵ ϵ}_{t t}^{H h} ((11 - - {ϵ ϵ}_{r r}^{H h}))} - - - - - - ((1717 b b))$

${R R}_{HH HH} {T T}_{HH HH} = = \frac{11}{β β} \cdot \cdot \frac{{M m}_{c c 1,2 1,2}^{P P,, VH VH}}{{ϵ ϵ}_{r r}^{V V} - - 11} - - - - - - ((1717 c c))$

${R R}_{HH HH} {T T}_{HH HH} = = \frac{11}{β β} \cdot \cdot \frac{{M m}_{c c 1,2 1,2}^{P P,, VV VV}}{{ϵ ϵ}_{t t}^{H h} (({ϵ ϵ}_{r r}^{V V} - - 11))} - - - - - - ((1717 d d))$

至此，系统的所有校准参数均已求出，可以完成对任意待校准目标的校准工作。假设待校准目标测量值为M_t，待校准目标真实极化散射矩阵S_t，由式(10)和式(11)可知，有以下极化校准方程：So far, all the calibration parameters of the system have been obtained, and the calibration of any target to be calibrated can be completed. Assuming that the measured value of the target to be calibrated is M _t , and the real polarization scattering matrix S _t of the target to be calibrated, it can be known from equations (10) and (11), the following polarization calibration equations are given:

${S S}_{t t} = = \frac{11}{((11 - - {ϵ ϵ}_{R R}^{H h} \cdot &Center Dot; {ϵ ϵ}_{R R}^{V V}))} \cdot &Center Dot; \frac{11}{((11 - - {ϵ ϵ}_{T T}^{H h} \cdot \cdot {ϵ ϵ}_{T T}^{V V}))} \cdot &Center Dot; [\begin{matrix} 11 & - - {ϵ ϵ}_{R R}^{H h} \\ - - {ϵ ϵ}_{R R}^{V V} & 11 \end{matrix}] \cdot \cdot [\begin{matrix} \frac{{M m}_{t t}^{HH HH}}{{R R}_{HH HH} \cdot \cdot {T T}_{HH HH}} & \frac{{M m}_{t t}^{HV HV}}{{R R}_{HH HH} \cdot &Center Dot; {T T}_{VV VV}} \\ \frac{{M m}_{t t}^{VH VH}}{{R R}_{VV VV} \cdot &Center Dot; {T T}_{HH HH}} & \frac{{M m}_{t t}^{VV VV}}{{R R}_{VV VV} \cdot &Center Dot; {T T}_{VV VV}} \end{matrix}] \cdot \cdot [\begin{matrix} 11 & - - {ϵ ϵ}_{T T}^{H h} \\ - - {ϵ ϵ}_{T T}^{V V} & 11 \end{matrix}] - - - - - - ((1818))$

方案-2：Scenario 2:

保持转发天线与接收天线极化方式相同，且两天线在0～360°范围内同步旋转。此时，PARC的极化散射矩阵为：Keep the forwarding antenna and the receiving antenna in the same polarization mode, and the two antennas rotate synchronously within the range of 0-360°. At this time, the polarization scattering matrix of PARC is:

${S S}_{c c 22}^{P P} = = \frac{β β}{\sqrt{22}} \cdot \cdot [\begin{matrix} cos cos 22 {θ θ}_{r r} & sin sin 22 {θ θ}_{r r} \\ sin sin 22 {θ θ}_{r r} & - - cos cos 22 {θ θ}_{r r} \end{matrix}] + + \frac{β β}{\sqrt{22}} \cdot \cdot [\begin{matrix} 11 & 00 \\ 00 & 11 \end{matrix}] - - - - - - ((1919))$

可见，此时PARC可视为一个既有伪二面角反射器散射特性又兼有金属球散射特性的综合定标体，因此可以仿照传统上采用二面角反射器和金属球的无源极化校准方法实现有源极化校准。具体过程如下。It can be seen that at this time, PARC can be regarded as a comprehensive calibration body that has both the scattering characteristics of pseudo-dihedral reflectors and the scattering characteristics of metal balls, so it can be modeled on the traditional passive electrode with dihedral reflectors and metal balls. Polarization calibration method realizes active polarization calibration. The specific process is as follows.

根据矩阵乘法，式(9)可写为：According to matrix multiplication, formula (9) can be written as:

${M m}_{HH HH} = = {R R}_{HH HH} {T T}_{HH HH} (({S S}_{HH HH} + + {ϵ ϵ}_{T T}^{H h} {S S}_{HV HV} + + {ϵ ϵ}_{R R}^{H h} {S S}_{VH VH} + + {ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{H h} {S S}_{VV VV})) - - - - - - ((2020 a a))$

${M m}_{HV HV} = = {R R}_{HH HH} {T T}_{VV VV} (({{ϵ ϵ}_{T T}^{V V} S S}_{HH HH} + + {S S}_{HV HV} + + {ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{V V} {S S}_{VH VH} + + {ϵ ϵ}_{R R}^{H h} {S S}_{VV VV})) - - - - - - ((2020 b b))$

${M m}_{VH VH} = = {R R}_{VV VV} {T T}_{HH HH} (({{ϵ ϵ}_{R R}^{V V} S S}_{HH HH} + + {{ϵ ϵ}_{R R}^{V V} ϵ ϵ}_{T T}^{H h} {S S}_{HV HV} + + {S S}_{VH VH} + + {ϵ ϵ}_{T T}^{H h} {S S}_{VV VV})) - - - - - - ((2020 c c))$

${M m}_{VV VV} = = {R R}_{VV VV} {T T}_{VV VV} (({{ϵ ϵ}_{R R}^{V V} {ϵ ϵ}_{T T}^{V V} S S}_{HH HH} + + {ϵ ϵ}_{R R}^{V V} {S S}_{HV HV} + + {ϵ ϵ}_{T T}^{V V} {S S}_{VH VH} + + {S S}_{VV VV})) - - - - - - ((2020 d d))$

将式(19)的PARC极化散射矩阵分别带入式(20a)至式(20d)，即对不同旋转角度下的PARC进行测量，得到的测量值为：Put the PARC polarization scattering matrix of formula (19) into formula (20a) to formula (20d), that is, to measure the PARC under different rotation angles, and the measured values obtained are:

${M m}_{c c 22}^{P P,, HH HH} = = {R R}_{HH HH} \cdot \cdot {T T}_{HH HH} \cdot &Center Dot; β β / / \sqrt{22} \cdot &Center Dot; [[((11 - - {ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{H h})) cos cos 22 {θ θ}_{r r} + + (({ϵ ϵ}_{R R}^{H h} + + {ϵ ϵ}_{T T}^{H h})) sin sin 22 {θ θ}_{r r} + + ((11 + + {ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{H h}))]] - - - - - - ((21 twenty one a a))$

${M m}_{c c 22}^{P P,, HV HV} = = {R R}_{HH HH} \cdot &Center Dot; {T T}_{VV VV} \cdot &Center Dot; β β / / \sqrt{22} \cdot &Center Dot; [[(({ϵ ϵ}_{T T}^{V V} - - {ϵ ϵ}_{R R}^{H h})) cos cos 22 {θ θ}_{r r} + + (({11 + + ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{V V})) sin sin 22 {θ θ}_{r r} + + (({ϵ ϵ}_{T T}^{V V} + + {ϵ ϵ}_{R R}^{H h}))]] - - - - - - ((21 twenty one b b))$

${M m}_{c c 22}^{P P,, VH VH} = = {R R}_{VV VV} \cdot \cdot {T T}_{HH HH} \cdot \cdot β β / / \sqrt{22} \cdot \cdot [[(({ϵ ϵ}_{R R}^{V V} - - {ϵ ϵ}_{T T}^{H h})) cos cos 22 {θ θ}_{r r} + + (({11 + + ϵ ϵ}_{R R}^{V V} {ϵ ϵ}_{T T}^{H h})) sin sin 22 {θ θ}_{r r} + + (({ϵ ϵ}_{R R}^{V V} - - {ϵ ϵ}_{T T}^{H h}))]] - - - - - - ((21 twenty one c c))$

${M m}_{c c 22}^{P P,, VV VV} = = {R R}_{VV VV} \cdot &Center Dot; {T T}_{VV VV} \cdot &Center Dot; β β / / \sqrt{22} \cdot &Center Dot; [[(({ϵ ϵ}_{R R}^{V V} {ϵ ϵ}_{T T}^{V V} - - 11)) cos cos 22 {θ θ}_{r r} + + (({ϵ ϵ}_{R R}^{V V} + + {ϵ ϵ}_{T T}^{V V})) sin sin 22 {θ θ}_{r r} + + (({ϵ ϵ}_{R R}^{V V} {ϵ ϵ}_{T T}^{V V} + + 11))]] - - - - - - ((21 twenty one d d))$

以HH极化通道为例，根据测量旋转的PARC得到的测量值进行傅里叶级数展开，有：Taking the HH polarization channel as an example, the measured value obtained according to the PARC that measures the rotation Carry out Fourier series expansion, there are:

${M m}_{c c 22}^{P P,, HH HH} = = {c c}_{00,, HH HH} + + {Σ Σ}_{n no = = 11}^{+ + \infty \infty} (({a a}_{n no,, HH HH} cos cos n no {θ θ}_{r r} + + {b b}_{n no,, HH HH} sin sin n no {θ θ}_{r r})) - - - - - - ((22 twenty two))$

将式(22)提取出常数项及2阶傅里叶系数，并与式(21a)进行比较，易得：Extract the constant term and the second-order Fourier coefficient from formula (22), and compare it with formula (21a), it is easy to get:

${a a}_{22} = = {R R}_{HH HH} \cdot \cdot {T T}_{HH HH} \cdot \cdot β β / / \sqrt{22} \cdot \cdot ((11 - - {ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{H h})) - - - - - - ((23 twenty three a a))$

${b b}_{22} = = {R R}_{HH HH} \cdot \cdot {T T}_{HH HH} \cdot &Center Dot; β β / / \sqrt{22} \cdot &Center Dot; (({ϵ ϵ}_{R R}^{H h} + + {ϵ ϵ}_{T T}^{H h})) - - - - - - ((23 twenty three b b))$

${c c}_{00} = = {R R}_{HH HH} \cdot &Center Dot; {T T}_{HH HH} \cdot &Center Dot; β β / / \sqrt{22} \cdot \cdot ((11 + + {ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{H h})) - - - - - - ((23 twenty three c c))$

将未知量A_HH＝R_HH·T_HH视为一个未知量，可对式(23a)、(23b)和(23c)3个方程构成的方程组进行求解，解得其中的3个未知量A_HH，类似地，对HV，VH，VV极化通道进行傅里叶级数展开和方程组求解，可解得其余未知量A_HV＝R_HH·T_VV，A_VH＝R_VV·T_HH，A_VV＝R_VV·T_VV， Considering the unknown quantity A _HH ＝ R _HH · T _HH as an unknown quantity, the equation system composed of three equations (23a), (23b) and (23c) can be solved, and the three unknown quantities A _HH , Similarly, for the HV, VH, and VV polarization channels, the Fourier series expansion and the solution of the equations can be solved to obtain the remaining unknown quantities A _HV ＝ R _HH · T _VV , A _VH ＝ R _VV · T _HH , A _VV =R _VV T _VV ,

至此，极化测量误差模型中的所有系统参数均求解得到，可对待校准目标进行极化校准。So far, all system parameters in the polarization measurement error model have been solved, and the polarization calibration of the target to be calibrated can be performed.

假设待校准目标测量值为 $M_{t} = [\begin{matrix} M_{t}^{HH} & M_{t}^{HV} \\ M_{t}^{VH} & M_{t}^{VV} \end{matrix}],$ 可知其与待校准目标真实极化散射矩阵 $S_{t} = [\begin{matrix} S_{t}^{HH} & S_{t}^{HV} \\ S_{t}^{VH} & S_{t}^{VV} \end{matrix}]$ 满足Suppose the target measurement value to be calibrated is $m_{t} = [\begin{matrix} m_{t}^{HH} & m_{t}^{HV} \\ m_{t}^{VH} & m_{t}^{VV} \end{matrix}],$ It can be known that it is related to the real polarization scattering matrix of the target to be calibrated $S_{t} = [\begin{matrix} S_{t}^{HH} & S_{t}^{HV} \\ S_{t}^{VH} & S_{t}^{VV} \end{matrix}]$ satisfy

$[\begin{matrix} {M m}_{t t}^{HH HH} & {M m}_{t t}^{HV HV} \\ {M m}_{t t}^{VH VH} & {M m}_{t t}^{VV VV} \end{matrix}] = = [\begin{matrix} {R R}_{HH HH} & {R R}_{HV HV} \\ {R R}_{VH VH} & {R R}_{VV VV} \end{matrix}] \cdot \cdot [\begin{matrix} {S S}_{t t}^{HH HH} & {S S}_{t t}^{HV HV} \\ {S S}_{t t}^{VH VH} & {S S}_{t t}^{VV VV} \end{matrix}] \cdot \cdot [\begin{matrix} {T T}_{HH HH} & {T T}_{HV HV} \\ {T T}_{VH VH} & {T T}_{VV VV} \end{matrix}] - - - - - - ((24 twenty four))$

对式(24)进行整理，可得：Arranging formula (24), we can get:

${S S}_{t t}^{HH HH} = = \frac{11}{X x} ((\frac{{M m}_{t t}^{HH HH}}{{A A}_{HH HH}} - - {ϵ ϵ}_{T T}^{H h} \frac{{M m}_{t t}^{HV HV}}{{A A}_{HV HV}} - - {ϵ ϵ}_{R R}^{H h} \frac{{M m}_{t t}^{VH VH}}{{A A}_{VH VH}} + + {ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{H h} \frac{{M m}_{t t}^{VV VV}}{{A A}_{VV VV}})) - - - - - - ((2525 a a))$

${S S}_{t t}^{HV HV} = = \frac{11}{X x} ((- - {ϵ ϵ}_{T T}^{V V} \frac{{M m}_{t t}^{HH HH}}{{A A}_{HH HH}} + + \frac{{M m}_{t t}^{HV HV}}{{A A}_{HV HV}} + + {ϵ ϵ}_{R R}^{H h} {ϵ ϵ}_{T T}^{V V} \frac{{M m}_{t t}^{VH VH}}{{A A}_{VH VH}} - - {ϵ ϵ}_{R R}^{H h} \frac{{M m}_{t t}^{VV VV}}{{A A}_{VV VV}})) - - - - - - ((2525 b b))$

${S S}_{t t}^{VH VH} = = \frac{11}{X x} ((- - {ϵ ϵ}_{R R}^{V V} \frac{{M m}_{t t}^{HH HH}}{{A A}_{HH HH}} + + {ϵ ϵ}_{R R}^{V V} {ϵ ϵ}_{T T}^{H h} \frac{{M m}_{t t}^{HV HV}}{{A A}_{HV HV}} + + \frac{{M m}_{t t}^{VH VH}}{{A A}_{VH VH}} - - {ϵ ϵ}_{T T}^{H h} \frac{{M m}_{t t}^{VV VV}}{{A A}_{VV VV}})) - - - - - - ((2525 c c))$

${S S}_{t t}^{VV VV} = = \frac{11}{X x} (({ϵ ϵ}_{R R}^{V V} {ϵ ϵ}_{T T}^{V V} \frac{{M m}_{t t}^{HH HH}}{{A A}_{HH HH}} - - {ϵ ϵ}_{R R}^{V V} \frac{{M m}_{t t}^{HV HV}}{{A A}_{HV HV}} - - {ϵ ϵ}_{T T}^{V V} \frac{{M m}_{t t}^{VH VH}}{{A A}_{VH VH}} + + \frac{{M m}_{t t}^{VV VV}}{{A A}_{VV VV}})) - - - - - - ((2525 d d))$

式中可根据求得的系统参数和待校准目标的测量值，通过式(25a)至式(25d)完成待校准目标真实极化散射矩阵的求解。In the formula According to the obtained system parameters and the measured values of the target to be calibrated, the solution of the real polarization scattering matrix of the target to be calibrated can be completed through formula (25a) to formula (25d).

方案-3：Scenario-3:

转发天线与接收天线极化方式相互正交且同步旋转。即始终满足关系：此时，PARC的极化散射矩阵为：The polarization modes of the forwarding antenna and the receiving antenna are orthogonal to each other and rotate synchronously. i.e. the relation is always satisfied: At this time, the polarization scattering matrix of PARC is:

${S S}_{c c 33}^{P P} = = \frac{β β}{\sqrt{22}} \cdot \cdot [\begin{matrix} - - sin sin 22 {θ θ}_{t t} & 11 + + cos cos 22 {θ θ}_{t t} \\ cos cos 22 {θ θ}_{t t} - - 11 & sin sin 22 {θ θ}_{t t} \end{matrix}] - - - - - - ((2626))$

在这种情况下，其极化校准工作过程与文献[2]中所描述的单天线PARC是等效的，如图4所示。In this case, its polarization calibration process is equivalent to the single-antenna PARC described in [2], as shown in Figure 4.

系统的误差模型中参数最多为8个，理论上，任意三组不同姿态组合下的数据都可用于极化校准。例如，为了方便计算，我们选取θ_t,1＝0°、θ_t,2＝45°、θ_t,3＝90°，将θ_t,1、θ_t,2、θ_t,3分别带入式(26)，则对应各姿态的PSM为The maximum number of parameters in the error model of the system is 8. In theory, any three sets of data under different attitude combinations can be used for polarization calibration. For example, for the convenience of calculation, we choose θ _t,1 = 0°, θ _t,2 = 45°, θ _t,3 = 90°, and bring θ _t,1 , θ _t,2 , θ _t,3 into Equation (26), then the PSM corresponding to each attitude is

${S S}_{c c 33,, 11}^{P P} = = \frac{β β}{\sqrt{22}} \cdot &Center Dot; [\begin{matrix} 00 & 22 \\ 00 & 00 \end{matrix}] - - - - - - ((2727 a a))$

${S S}_{c c 33,, 22}^{P P} = = \frac{β β}{\sqrt{22}} \cdot &Center Dot; [\begin{matrix} - - 11 & 11 \\ - - 11 & 11 \end{matrix}] - - - - - - ((2727 b b))$

${S S}_{c c 33,, 33}^{P P} = = \frac{β β}{\sqrt{22}} \cdot &Center Dot; [\begin{matrix} 00 & 00 \\ - - 22 & 00 \end{matrix}] - - - - - - ((2727 c c))$

将分别代入式(9)展开，有：Will Substituting into equation (9) to expand, we have:

${M m}_{c c 33,, 11}^{P P} = = \frac{β β}{\sqrt{22}} \cdot &Center Dot; [\begin{matrix} {22 R R}_{HH HH} \cdot &Center Dot; {T T}_{HH HH} \cdot &Center Dot; {ϵ ϵ}_{T T}^{V V} & 22 {R R}_{HH HH} \cdot &Center Dot; {T T}_{HH HH} \\ 22 {R R}_{HH HH} \cdot &Center Dot; {T T}_{HH HH} \cdot &Center Dot; {ϵ ϵ}_{R R}^{V V} \cdot &Center Dot; {ϵ ϵ}_{T T}^{V V} & 22 {R R}_{VV VV} \cdot &Center Dot; {T T}_{VV VV} \cdot &Center Dot; {ϵ ϵ}_{R R}^{V V} \end{matrix}] - - - - - - ((2828 a a))$

${M m}_{c c 33,, 22}^{P P} = = \frac{β β}{\sqrt{22}} \cdot \cdot [\begin{matrix} {R R}_{HH HH} \cdot \cdot {T T}_{HH HH} \cdot \cdot (({ϵ ϵ}_{T T}^{V V} - - {ϵ ϵ}_{R R}^{H h} + + {ϵ ϵ}_{R R}^{H h} \cdot \cdot {ϵ ϵ}_{T T}^{V V} - - 11)) & {R R}_{HH HH} \cdot \cdot {T T}_{VV VV} \cdot \cdot (({ϵ ϵ}_{R R}^{H h} - - {ϵ ϵ}_{T T}^{H h} - - {ϵ ϵ}_{R R}^{H h} \cdot \cdot {ϵ ϵ}_{T T}^{V V} + + 11)) \\ {R R}_{VV VV} \cdot \cdot {T T}_{HH HH} \cdot \cdot (({ϵ ϵ}_{T T}^{V V} - - {ϵ ϵ}_{R R}^{V V} + + {ϵ ϵ}_{R R}^{V V} \cdot \cdot {ϵ ϵ}_{T T}^{V V} - - 11)) & {R R}_{VV VV} \cdot \cdot {T T}_{VV VV} \cdot \cdot (({ϵ ϵ}_{R R}^{V V} - - {ϵ ϵ}_{T T}^{H h} - - {ϵ ϵ}_{R R}^{V V} \cdot \cdot {ϵ ϵ}_{T T}^{H h} + + 11)) \end{matrix}] - - - - - - ((2828 b b))$

${M m}_{c c 33,, 33}^{P P} = = \frac{β β}{\sqrt{22}} \cdot &Center Dot; [\begin{matrix} - - {22 R R}_{HH HH} \cdot \cdot {T T}_{HH HH} \cdot &Center Dot; {ϵ ϵ}_{R R}^{H h} & - - 22 {R R}_{HH HH} \cdot \cdot {T T}_{VV VV} \cdot \cdot {ϵ ϵ}_{R R}^{H h} \cdot &Center Dot; {ϵ ϵ}_{T T}^{H h} \\ - - 22 {R R}_{VV VV} \cdot \cdot {T T}_{HH HH} & - - 22 {R R}_{VV VV} \cdot &Center Dot; {T T}_{VV VV} \cdot &Center Dot; {ϵ ϵ}_{T T}^{H h} \end{matrix}] - - - - - - ((2828 c c))$

对上述三个矩阵第一个元素(HH分量)作如下处理：The first element (HH component) of the above three matrices is processed as follows:

$\frac{{M m}_{c c 3,2 3,2}^{P P,, HH HH}}{((- - 11 - - {ϵ ϵ}_{R R}^{H h} + + {ϵ ϵ}_{T T}^{V V} + + {ϵ ϵ}_{r r}^{H h} \cdot &Center Dot; {ϵ ϵ}_{t t}^{V V}))} = = \frac{{M m}_{c c 3,1 3,1}^{P P,, HH HH}}{22 {ϵ ϵ}_{T T}^{V V}} &DoubleRightArrow; &DoubleRightArrow; 22 {ϵ ϵ}_{T T}^{V V} \cdot &Center Dot; {M m}_{c c 3,1 3,1}^{P P,, HH HH} = = ((- - 11 - - {ϵ ϵ}_{R R}^{H h} + + {ϵ ϵ}_{T T}^{V V} + + {ϵ ϵ}_{R R}^{H h} \cdot &Center Dot; {ϵ ϵ}_{T T}^{V V})) \cdot &Center Dot; {M m}_{c c 3,2 3,2}^{P P,, HH HH} - - - - - - ((2929))$

$\frac{{M m}_{c c 3,1 3,1}^{P P,, HH HH}}{22 {ϵ ϵ}_{T T}^{V V}} = = \frac{{M m}_{c c 3,3 3,3}^{P P,, HH HH}}{- - 22 {ϵ ϵ}_{R R}^{H h}} &DoubleRightArrow; &DoubleRightArrow; {ϵ ϵ}_{R R}^{H h} = = - - \frac{{M m}_{c c 3,3 3,3}^{P P,, HH HH}}{{M m}_{c c 3,1 3,1}^{P P,, HH HH}} \cdot \cdot {ϵ ϵ}_{T T}^{V V} - - - - - - ((3030))$

将式(30)代入式(29)，整理可得：Substituting formula (30) into formula (29), we can get:

${M m}_{c c 3,3 3,3}^{P P,, HH HH} \cdot \cdot {(({ϵ ϵ}_{T T}^{V V}))}^{22} + + ((22 {M m}_{c c 3,2 3,2}^{P P,, HH HH} - - {M m}_{c c 3,3 3,3}^{P P,, HH HH} - - {M m}_{c c 3,1 3,1}^{P P,, HH HH})) \cdot \cdot {ϵ ϵ}_{T T}^{V V} + + {M m}_{c c 3,1 3,1}^{P P,, HH HH} = = 00 - - - - - - ((3131))$

式(31)为一个一元二次方程，该方程的解为：Equation (31) is a quadratic equation in one variable, and the solution of this equation is:

${ϵ ϵ}_{T T}^{V V} = = \frac{- - ((22 {M m}_{c c 3,2 3,2}^{P P,, HH HH} - - {M m}_{c c 3,3 3,3}^{P P,, HH HH} - - {M m}_{c c 3,1 3,1}^{P P,, HH HH})) &PlusMinus; &PlusMinus; \sqrt{{((22 {M m}_{c c 3,2 3,2}^{P P,, HH HH} - - {M m}_{c c 3,3 3,3}^{P P,, HH HH} - - {M m}_{c c 3,1 3,1}^{P P,, HH HH}))}^{22} - - 44 {M m}_{c c 3,3 3,3}^{P P,, HH HH} \cdot &Center Dot; {M m}_{c c 3,1 3,1}^{P P,, HH HH}}}{22 {M m}_{c c 3,3 3,3}^{P P,, HH HH}} - - - - - - ((3232))$

式(32)中‘±’的选取，遵循使得的原则。The selection of '±' in formula (32) follows such that the rules.

系统其它参数的求解。由式(30)可以直接求得及的求解可以通过以下两种途径来进行求解：(1)通过类似求解的解方程的形式来求解，这样求解过程较麻烦；(2)利用各参数间的特殊关系来进行求解。Solution of other parameters of the system. From formula (30), it can be obtained directly and The solution of can be solved in the following two ways: (1) by similar solution Solve in the form of the solution equation, so the solution process is more troublesome; (2) use the special relationship between each parameter to solve.

这里以采用第二种方法进行求解为例加以说明。Here we take the second method to solve as an example to illustrate.

由式(28)中和联合式(28)可确定From formula (28) and The joint formula (28) can be determined

${ϵ ϵ}_{T T}^{H h} = = \frac{{M m}_{c c 3,1 3,1}^{P P,, HH HH} \cdot \cdot {M m}_{c c 3,3 3,3}^{P P,, HV HV}}{{M m}_{c c 3,3 3,3}^{P P,, HH HH} \cdot \cdot {M m}_{c c 3,1 3,1}^{P P,, HV HV}} \cdot \cdot \frac{11}{{ϵ ϵ}_{T T}^{V V}} - - - - - - ((3333))$

由式(28)中和及可确定From formula (28) and and can be determined

${ϵ ϵ}_{R R}^{V V} = = - - \frac{{M m}_{c c 3,1 3,1}^{P P,, VH VH}}{{M m}_{c c 3,3 3,3}^{P P,, VH VH}} \cdot \cdot \frac{11}{{ϵ ϵ}_{T T}^{V V}} - - - - - - ((3434))$

而and

${R R}_{HH HH} \cdot \cdot {T T}_{HH HH} = = \frac{{M m}_{c c 3,1 3,1}^{P P,, HH HH}}{22 {ϵ ϵ}_{T T}^{V V}} - - - - - - ((3535 a a))$

${R R}_{HH HH} \cdot &Center Dot; {T T}_{VV VV} = = \frac{22 {M m}_{c c 3,1 3,1}^{P P,, HV HV}}{\sqrt{\frac{σ σ}{π π}}} - - - - - - ((3535 b b))$

${R R}_{VV VV} \cdot \cdot {T T}_{HH HH} = = \frac{{M m}_{c c 3,1 3,1}^{P P,, HH HH}}{22 {ϵ ϵ}_{T T}^{V V} \cdot &Center Dot; {ϵ ϵ}_{R R}^{V V}} - - - - - - ((3535 c c))$

${R R}_{VV VV} \cdot &Center Dot; {T T}_{VV VV} = = \frac{{M m}_{c c 3,1 3,1}^{P P,, HH HH}}{22 {ϵ ϵ}_{R R}^{V V}} - - - - - - ((3535 d d))$

至此，系统的所有校准参数均已求出，由式(18)即可实现对任意待校准目标的校准工作。So far, all the calibration parameters of the system have been calculated, and the calibration of any target to be calibrated can be realized by formula (18).

除了以上所列举的三个例子，PARC收、发天线还可以有其它各种组合，从而可获得更多形式的极化散射矩阵用于极化校准，此处不一一列举。In addition to the three examples listed above, the PARC receiving and transmitting antennas can also have other combinations, so that more forms of polarization scattering matrices can be obtained for polarization calibration, which are not listed here.

本发明的实施过程与应用举例介绍如下：Implementation process of the present invention and application example are introduced as follows:

为进一步说明采用本项发明所提出的BPARC在极化校准中如何具体应用，现以上述方案-2为例，说明实施过程。采用其他方案时其测量和校准过程完全类似。In order to further illustrate how the BPARC proposed by this invention is applied in the polarization calibration, the above scheme-2 is taken as an example to illustrate the implementation process. The measurement and calibration process is completely similar for other schemes.

测量和极化校准处理步骤如下：The measurement and polarization calibration process steps are as follows:

步骤-1：BPARC装置调校Step-1: BPARC Device Tuning

调节BPARC接收天线与转发天线的视线旋转机构，使得两个天线的初始极化角调为一致，并控制两旋转机构的转速，使收发天线保持一样的转速w_r(w_r＝w_t，单位rad/s)匀速旋转，以保证在整个测量过程中BPARC的收发天线极化始终是完全一致的。为此，旋转机构可采用步进电机，保证天线每转到一个角度时停下，雷达测量一组数据，然后控制天线转到下一个角位置，如此重复控制和测量，即可保证收发天线的极化是同步变化的。Adjust the line-of-sight rotation mechanism of the BPARC receiving antenna and the transponder antenna so that the initial polarization angles of the two antennas are adjusted to be consistent, and control the rotation speed of the two rotation mechanisms so that the receiving and transmitting antennas maintain the same rotation speed w _r (w _r =w _t , unit rad/s) rotate at a constant speed to ensure that the polarization of the transceiver antenna of BPARC is always completely consistent throughout the measurement process. To this end, the rotating mechanism can use a stepping motor to ensure that the antenna stops every time it turns to an angle, the radar measures a set of data, and then controls the antenna to turn to the next angular position. Repeating the control and measurement in this way can ensure the stability of the sending and receiving antenna. Polarization changes synchronously.

角度编码器准确的记录下天线转过的角度γ，则BPARC转过的圈数可由N＝γ/360°计算得出。测量中，可以控制BPARC双天线进行整圈的测量，这样保证了初始极化角的选取对整个校准过程没有影响。The angle encoder accurately records the angle γ that the antenna rotates, and the number of turns that the BPARC rotates can be calculated by N=γ/360°. During the measurement, the BPARC dual antennas can be controlled to measure the entire circle, which ensures that the selection of the initial polarization angle has no effect on the entire calibration process.

步骤-2：BPARC装置的安装Step-2: Installation of BPARC Device

将本发明所提出的BPARC极化校准装置安装于标校支架上，安照测量雷达系统的要求调整其延时参数。Install the BPARC polarization calibration device proposed by the present invention on the calibration bracket, and adjust its delay parameters according to the requirements of the radar system.

针对当前双站测量的双站角，控制方位转台，使BPARC接收天线对准测量雷达的发射天线，BPARC转发天线对准测量雷达的接收天线，如图10所示。每次改变测量双站角时，均需重复此步骤。For the current bi-station angle of the bi-station measurement, the azimuth turntable is controlled so that the BPARC receiving antenna is aligned with the transmitting antenna of the measuring radar, and the BPARC forwarding antenna is aligned with the receiving antenna of the measuring radar, as shown in Figure 10. This step needs to be repeated each time the measurement double station angle is changed.

维持已调节好的方位转台位置固定不动，控制BPARC的视线旋转机构，使BPARC的两个天线匀速慢速旋转，假设共转过N圈。测量雷达发射信号并接收BPARC转发天线辐射的回波信号，录取BPARC天线绕测量雷达视线旋转过程中不同位置下全部极化通道的回波信号，得到的全部PSM测量数据记为 Keep the adjusted position of the azimuth turntable fixed, and control the line-of-sight rotation mechanism of BPARC to make the two antennas of BPARC rotate at a constant and slow speed, assuming a total of N turns. Measure the radar transmission signal and receive the echo signal radiated by the BPARC forwarding antenna, record the echo signal of all polarization channels at different positions during the rotation of the BPARC antenna around the radar line of sight, and obtain all the PSM measurement data as

将各极化分量分别应用傅里叶级数进行展开，有Will Each polarization component is expanded by Fourier series respectively, and we have

${M m}_{c c 22}^{P P,, wv wv} = = {c c}_{00,, wv wv} + + {Σ Σ}_{n no = = 11}^{+ + \infty \infty} (({a a}_{n no,, wv wv} cos cos n no {θ θ}_{r r} + + {b b}_{n no,, wv wv} sin sin n no {θ θ}_{r r})) - - - - - - ((3636))$

其中wv表示所有的极化状态，提取出常数项与2阶项系数，结合式(21)，令对应项系数相等，按照前述方案-2所述过程即可求得测量雷达系统的全部极化校准参数；where wv represents all the polarization states, extract the coefficients of the constant term and the second-order term, combine the formula (21), make the coefficients of the corresponding terms equal, and follow the process described in the previous scheme-2 to obtain all the polarizations of the measurement radar system Calibration parameters;

安装待测目标，并由双站测量雷达录取所有极化通道的目标回波，假设其PSM测量值为M_t；Install the target to be measured, and record the target echoes of all polarization channels by the dual-station measurement radar, assuming that its PSM measurement value is M _t ;

步骤-6：极化校准处理Step-6: Polarization Calibration Processing

根据步骤-4中已得到的极化校准参数和步骤-5中测得的目标PSM测量值，应用式(18)即可完成所测目标的极化校准，得到目标的真实PSM值S_t。According to the polarization calibration parameters obtained in step-4 and the target PSM measurement value measured in step-5, the polarization calibration of the measured target can be completed by applying formula (18), and the real PSM value S _t of the target can be obtained.

注意到如果只需做双站RCS测量和定标，则上述6个步骤可进一步简化，不需要提取极化校准参数，只需按照式(2)所给出的双站定标方程进行测量和RCS定标计算，其中BPARC的理论RCS值仍由式(8)计算，定标常数K_b的计算则根据双站测量几何关系由式(3)完成。不赘述。Note that if only two-station RCS measurement and calibration are required, the above six steps can be further simplified, and there is no need to extract polarization calibration parameters, only the measurement and RCS calibration calculation, where the theoretical RCS value of BPARC Still calculated by formula (8), the calculation of the calibration constant K _b is completed by formula (3) according to the geometric relationship of the two-station measurement. I won't go into details.

另外，本发明的其他替代方案阐述如下：In addition, other alternatives of the present invention are set forth as follows:

(1)本项发明中PARC所使用的喇叭天线也可由其他类型的线极化天线替代；(1) The horn antenna used by PARC in this invention can also be replaced by other types of linearly polarized antennas;

(2)本项发明中的收发天线极化组合具有无限多种，根据不同的极化组合可设计出不同的极化校准测量方案和极化校准参数提取算法，不限于已经举例指出的3种方案。(2) The polarization combinations of the transmitting and receiving antennas in this invention have an infinite variety, and different polarization calibration measurement schemes and polarization calibration parameter extraction algorithms can be designed according to different polarization combinations, not limited to the three types that have been pointed out by examples plan.

本发明中涉及到的本领域公知技术未详细阐述。The technologies known in the art involved in the present invention are not described in detail.

Claims

1. The utility model provides a can be used to target two-station radar cross section measurement calibration and polarization calibrating device which characterized in that: the device comprises a receiving antenna, a transmitting antenna, two azimuth-sight double-axis rotating units, an azimuth rotating drive and controller, a pitching rotating drive and controller, a radio frequency combination and a power supply combination, wherein:

the receiving antenna is used for receiving radiation signals of the transmitting antenna of the double-station measuring radar, and the radiation signals are fed to the radio frequency combination by the radio frequency cable;

the radio frequency combination comprises the following steps: the system comprises an amplifier, a filter, a delay line and an attenuator which are connected in sequence, wherein the amplifier, the filter, the delay line and the attenuator are used for amplifying, filtering and delaying a double-station measuring radar radiation signal received by a receiving antenna to obtain an output signal, and the output signal is fed to a transmitting antenna through a radio frequency cable after the level of the output signal is adjusted by the attenuator;

the transmitting antenna is used for completing the radiation of the radio frequency signal to the double-station measuring radar receiving antenna;

the two azimuth-sight line biaxial rotation units are as follows: one of them is used for placing the receiving antenna, and the other is used for placing the transmitting antenna;

the azimuth rotation driving and controlling device comprises: the two-axis rotation unit is used for controlling the rotation of the azimuth-sight two-axis rotation unit around the azimuth direction;

the sight line rotation driving and controlling device comprises: the two-axis rotation unit is used for controlling the rotation of the azimuth-sight two-axis rotation unit around a sight line axis;

the power supply combination is as follows: power supply for the device.

2. The calibration and polarization calibration device for the target two-station radar cross section measurement according to claim 1, wherein: the receiving antenna and the transmitting antenna are respectively composed of a horn antenna, meanwhile, in order to reduce cross polarization coupling errors of the antennas and improve polarization isolation ratio as much as possible, a micro-strip polarization filter device is additionally arranged at the opening surface of each antenna, each horn antenna is arranged on an azimuth-sight double-shaft rotating unit with angle codes, each antenna can independently rotate around a radar sight line and rotate around the azimuth under the control of an azimuth rotation driving and controlling device and a sight line rotation driving and controlling device, and the azimuth-sight double-shaft rotating unit with the angle codes can simultaneously give out accurate position information of sight line rotation angles and azimuth rotation angles of the antennas.

3. The calibration and polarization calibration device for the target two-station radar cross section measurement according to claim 1, wherein: the azimuth-sight line biaxial rotation unit comprises: the device mainly comprises a sight line rotating stepping motor, a sight line angle encoder, an azimuth turntable, an azimuth angle encoder and a matching installation interface between the sight line rotating stepping motor and an antenna; wherein the sight line refers to a connecting line between a double-station measuring radar transmitter and a receiving antenna or between a double-station measuring radar receiver and a transmitting antenna; the 'azimuth' refers to the rotation speed and the rotation angle position of each antenna around the sight line of the radar antenna in the xOy plane when the measurement radar is erected in the xOy plane, and can be accurately controlled in real time through the sight line rotation and driving controller.

4. The calibration and polarization calibration device for the target two-station radar cross section measurement according to claim 3, wherein: the azimuth rotation driving and controlling device completes rotation of the receiving antenna and the transmitting antenna in the azimuth direction by controlling the azimuth turntable, gives azimuth position information of each antenna through the azimuth encoder, and can be remotely controlled by the double-station scattering measurement system controller through the remote control interface.

5. The calibration and polarization calibration device for the target two-station radar cross section measurement according to claim 3, wherein: the sight line rotation driving and controlling device comprises: the rotation of the receiving antenna and the transmitting antenna around the sight line axis is completed by controlling the sight line rotating motor, the sight line angle position information of each antenna is given through a sight line angle encoder, and the sight line rotating drive and controller can be remotely controlled by the double-station scattering measurement system controller through a remote control interface.

6. A calibration method for measurement of a scattering cross section of a target double-station radar, according to any one of claims 1 to 5, the calibration and polarization calibration device for measurement of the scattering cross section of the target double-station radar is characterized in that: the method and steps of the two-station measurement and calibration process are as follows:

step-1: a BPARC device calibration comprising:

adjusting the line-of-sight rotation mechanisms of the BPARC receiving antenna and the forwarding antenna to make the initial polarization angles of the two antennas consistent, and controlling the rotation speeds of the two rotation mechanisms to keep the same rotation speed w of the receiving and transmitting antennas_rAt a constant speed, wherein w_r＝w_tThe unit rad/s is used for ensuring that the polarization of a transmitting and receiving antenna of the BPARC is completely consistent all the time in the whole measuring process, therefore, a stepping motor can be adopted as a rotating mechanism, the radar is used for measuring a group of data when the antenna stops when rotating to an angle, then the antenna is controlled to rotate to the next angular position, and the control and the measurement are repeated in such a way, so that the polarization of the transmitting and receiving antenna can be ensured to be changed synchronously;

the angle encoder accurately records the angle gamma of the antenna, and the number of the BPARC turns can be calculated by N-gamma/360 deg. In the measurement, the BPARC double antenna can be controlled to carry out the measurement of a whole circle, so that the selection of the initial polarization angle is ensured to have no influence on the whole calibration process;

step-2: installation of a BPARC device comprising:

the BPARC polarization calibration device provided by the invention is arranged on a calibration bracket, and the time delay parameter of the BPARC polarization calibration device is adjusted according to the requirement of a measuring radar system;

aiming at the current given double-station angle measured by the double stations, the azimuth turntable is controlled, the BPARC receiving antenna is aligned to the transmitting antenna of the measuring radar, the BPARC forwarding antenna is aligned to the receiving antenna of the measuring radar, and the BPARC installing step needs to be repeated every time the measuring double-station angle is changed;

step-3: polarization calibration measurements and data logging:

maintaining the position of an azimuth turntable well adjusted according to a given measurement double-station angle to be fixed, controlling a BPARC sight line rotating mechanism to enable two BPARC antennae to rotate at a constant speed and a low speed, measuring a radar transmitting signal and receiving an echo signal radiated by a BPARC forwarding antenna on the assumption that the two BPARC antennae rotate for N circles in total, recording echo signals of all polarization channels at different positions in the BPARC antenna line rotation process of the measurement radar sight line, and obtaining all measurement data;

repeating the BPARC measurement and data recording steps each time the measurement dual-station angle is changed;

step-4: polarization calibration parameter extraction:

solving through the measurement data in the step-3 to obtain all polarization calibration parameters of the measurement radar system;

when the measurement double-station angle is changed every time, the BPARC measurement data under the double-station angle is required to be used for solving the calibration parameters of the measurement radar system;

step-5: target two-station polarization measurement:

installing a target to be tested, and recording target echoes of all polarization channels by a double-station measuring radar;

under the same two-station angle, the same measuring radar can be adopted to carry out two-station measurement on a plurality of same or different targets;

step-6: polarization calibration process

According to the polarization calibration parameters obtained in the step-4 and the target measurement value measured in the step-5, the polarization calibration of the measured target can be completed by applying the formula (6-1), and the real polarization scattering matrix value of the target is obtained;

in the formula

M_{t} = [\begin{matrix} M_{t}^{HH} & M_{t}^{HV} \\ M_{t}^{VH} & M_{t}^{VV} \end{matrix}]

Measured values under 4 polarization combinations of the target to be calibrated; s_tA true polarization scattering matrix of a target to be calibrated; r_HHAnd R_VVGain factors, T, for HH-polarized and VV-polarized receiving channels of the measurement system, respectively_HHAnd T_VVFor measuring the gain factors of the HH polarized and VV polarized transmit channels of the system,for measuring the cross polarization factor of the system, the 8 parameters are polarization calibration parameters of the measurement system which are required to be solved by measuring the BPARC through the steps-1 to-5 and processing the measurement data;

under the same two-station angle, when the same measuring radar is adopted to carry out two-station measurement on a plurality of same or different targets, the same set of calibration parameters can be used for carrying out polarization calibration processing;

if only the two-station RCS measurement and calibration are carried out, the 6 steps can be further simplified, the polarization calibration parameters do not need to be extracted, only the two-station calibration equation given by the formula (6-2) is needed to carry out the measurement and the RCS calibration calculation,

in the formulaIn order for the target dual-station RCS,theoretical two-station RCS for BPARC; p_rCAnd P_rTRespectively measuring the echo power received by the radar when the target body and the target are measured; s_TAnd S_CRespectively measuring a target and a radar complex echo signal when a calibration body is measured in single RCS measurement sampling; k_bA calibration constant corresponding to the geometric relationship of the two-station measurement;

theoretical two-station RCS value for BPARCThe calculation formula is as follows;

in the formula, G_TAnd G_RGains, G, for the BPARC transmit and receive antennas, respectively_LoopThe total gain of the whole loop except the antenna in the BPARC; the theoretical RCS value of BPARC can also be measured by relative calibration measurements using another calibration standard with known RCS values;

scaling constant K corresponding to geometric relation of two-station measurement_bThe calculation of (2) is then performed by equation (6-4) according to the two-station measurement geometry:

in the formula R_tTAnd R_tCRespectively representing the target distance and the calibration body distance of the transmitting channel; r_rTAnd R_rCRespectively representing the target distance and the calibration body distance of the receiving channel; l is_tTAnd L_tCRespectively representing the total loss of the transmitting channel when the target is measured and the target body is measured; l is_rTAnd L_rCRespectively representing the total loss of a receiving channel when the target is measured and the target body is measured; k if the target distance and the calibration body distance are determined in the test and the two-station geometric relationship remains unchanged_bThe value is a definite constant.