A polarization information driven microwave correlation imaging method

Abstract

The application discloses a kind of polarized information driven microwave correlation imaging methods in the field of radar signal processing technology.The polarized information driven microwave correlation imaging method includes the following steps: constructing full polarization frequency hopping radar matrix;Form horizontal polarization and vertical polarization space-time random radiation field;Iterative imaging using the orthogonal complement space of random radiation field.The polarized information driven microwave correlation imaging method can use polarization information to image target with high resolution and high robustness, and perform instantaneous polarization measurement while imaging, simple to implement, has strong engineering application potential, can be popularized to map reconnaissance, target identification and other practical scenarios, quickly and accurately obtain target area imaging and target polarization information.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar signal processing, in particular to a polarization information driven microwave correlation imaging method. BACKGROUND

[0002] The most commonly used technology in the current radar imaging method is the synthetic aperture imaging technology and the Doppler sharpening technology, but the method is dependent on the range-doppler effect, the azimuth resolution is limited by the aperture size, and there is an imaging blind area, that is, the imaging effect is poor in the direction without relative motion (forward-looking, oblique forward-looking), and the new microwave correlation imaging method is not dependent on the Doppler information, has a high imaging potential, and expands a new direction for the development of traditional radar imaging.

[0003] Microwave correlation imaging comes from the classic correlation imaging in optics, and the classic correlation imaging in optics is a technology for imaging a target to be measured by using quantum correlation principle and correlating two spatially related light beams, also known as "ghost imaging". Microwave correlation imaging borrows the principle and extends the idea of optical correlation to the microwave field to form a microwave correlation imaging technology. Microwave correlation imaging is to image by correlating the highly random radiation field in the time domain, space domain and frequency domain with the echo information after the radiation target. In addition to the time domain, space domain and frequency domain, the polarization domain is also an important part of the description of electromagnetic signals. By introducing polarization information, the randomness of the radiation field in microwave correlation imaging and the imaging quality of the microwave correlation imaging method can be further improved. However, there is a great gap in the research on polarization microwave correlation imaging at home and abroad. The related research only uses polarization antennas to generate radiation fields, and does not study the application of polarization information in the whole imaging process. Therefore, in view of the above problems, it is urgent to design a polarization information driven microwave correlation imaging method. SUMMARY

[0004] In order to solve the above problems, the purpose of the present application is to provide a polarization information driven microwave correlation imaging method, which solves the technical problems that there is a great gap in the research on polarization microwave correlation imaging in the prior art, and the application of polarization information in the whole imaging process is not studied, can use polarization information to image the target with high resolution and high robustness, and can perform instantaneous polarization measurement while imaging, has simple engineering implementation, has strong engineering application potential, can be popularized to practical scenes such as map reconnaissance and target identification, and can quickly and accurately obtain target area imaging and target polarization information.

[0005] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0006] The present application provides a polarization information driven microwave correlation imaging method, comprising the following steps:

[0007] S1. Constructing a full polarization frequency hopping radar matrix;

[0008] S2. Forming horizontal polarization and vertical polarization space-time random radiation field;

[0009] S3. Iterative imaging using the orthogonal complement space of the random radiation field.

[0010] Further, the S1 includes the following steps:

[0011] S11. The antennas of the frequency hopping radar are arranged equidistantly along the aircraft wing direction to form a column of multi-transmit single-receive form of frequency hopping radar array;

[0012] S12. The horizontal polarization antennas and the vertical polarization antennas are respectively distributed on both sides of the middle full polarization receiving antenna as a boundary;

[0013] S13. The target imaging area of the frequency hopping radar is changed from a square area to a diamond area.

[0014] Further, the S2 includes the following steps:

[0015] S21. Let the position vector from the center of the radar array to the target scattering point be The M full polarization transmitting and receiving antennas are divided into H antennas and V antennas, and the H antennas and the V antennas are arranged on both sides of the antenna array respectively;

[0016] S22. Obtaining the incident field intensity of the entire antenna array on the imaging area;

[0017] S23. Constructing horizontal polarization and vertical polarization space-time random radiation field by transmitting random frequency hopping signals through antennas with different polarization directions and receiving random sampling by antennas.

[0018] Further, the S22 includes the following steps:

[0019] S221. The incident field intensity of the i-th transmitting antenna to the target area is as follows:

[0020]

[0021]

[0022] Where, f Hi (t) and f Vi (t) are the random frequencies of the H antennas and the V antennas respectively, γ i (t) is a random horizontal polarization angle, η i (t) is a random vertical polarization angle, is the antenna position vector;

[0023] S222. Then the incident field intensity of the whole antenna array to the imaging area is:

[0024]

[0025]

[0026] Further, the S23 comprises the following steps:

[0027] S231. The random radiation field of the target area is formed as follows:

[0028]

[0029]

[0030] S232. In the microwave correlation forward-looking imaging process, the random radiation field irradiates the target to form a return wave, which is received by the receiving antenna to obtain the target return wave E Hr , Vr as follows:

[0031]

[0032]

[0033]

[0034]

[0035] S233. The target scattering characteristics and the target polarization scattering characteristics can be obtained by inversion:

[0036]

[0037] Further, the S3 comprises the following steps:

[0038] S31. If the polarization information is not considered, the TSVD processing is performed on the insufficiently random spatio-temporal radiation field, then the return wave and the spatio-temporal random radiation field are compressed and correlated, and finally the target scattering characteristic matrix is obtained to realize the correlation imaging. In the case of not considering the noise, the formula is simplified as r = E s σ.

[0039] S32. If the polarization scattering matrix of the target is considered, the microwave correlation imaging method is used to solve the instantaneous polarization scattering matrix of the target.

[0040] Further, the return wave of the instantaneous polarization scattering matrix in the S32 is expressed as:

[0041] E Hr = EHs S HH +E Vs S HV

[0042] E Vr =E Hs S HV +E Vs S VV

[0043] If you want to solve the above formula, the H antenna radiation field and the V antenna radiation field are orthogonal, that is:

[0044] E Vs E Hs =0

[0045] Further, the S32 comprises the following steps:

[0046] S321. Obtain the horizontal polarization and vertical polarization radiation field orthogonal complement matrix by QR decomposition and cross multiply it with the echo information;

[0047] S322. Construct a new correlation equation with the radiation field processed in step S321 and iterate imaging.

[0048] Further, the S321 comprises the following steps:

[0049] S3211. Use QR decomposition on the radiation field matrix of the target, calculate the orthogonal complement space E Hs and E Vs of the radiation field matrix E Hsb and E Vsb ;

[0050] S3212. Multiply the target HV echo with the HV radiation field orthogonal complement space respectively to obtain:

[0051] E Hsb E Hr =E Hsb E Hs S HH +E Hsb E Vs S HV

[0052] E Vsb E Hr =E Vsb E Hs S HH +E Vsb E Vs S HV

[0053] E Hsb E Vr =EHsb E Hs S VH +E Hsb E Vs S VV

[0054] E Vsb E Vr =E Vsb E Hs S VH +E Vsb E Vs S VV

[0055] From the characteristics of the orthogonal complementary matrix:

[0056] E Hsb E Hs =0

[0057] E Vsb E Vs =0

[0058] That is:

[0059]

[0060] With the above technical solution, the application has the following advantages:

[0061] The application provides a polarized information driven microwave correlation imaging method, divides antennas of a frequency hopping radar array into H antennas and V antennas, generates horizontal polarization and vertical polarization radiation fields by random frequency modulation and random sampling of each antenna respectively, cross multiplies echo information by using orthogonal complementary spaces of HV antenna radiation fields, then forms a new correlation formula with radiation fields processed in the same way and iteratively images, can perform high-resolution and high-robustness imaging on a target by using polarized information, and performs instantaneous polarization measurement while imaging, is better than a traditional instantaneous polarization measurement method in effect under a low time-frequency product, improves anti-interference capability of microwave correlation imaging, is simple in engineering implementation, has strong engineering application potential, can be popularized to practical scenes such as map reconnaissance and target identification, and quickly and accurately obtains target area imaging and target polarized information. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 is a flowchart of the polarized information driven microwave correlation imaging method of the application;

[0063] Figure 2 is a geometric imaging schematic diagram of an application scene of the polarized information driven microwave correlation imaging of the application;

[0064] Figure 3 is a simulation diagram of the polarized information driven microwave correlation imaging of the application;

[0065] Figure 4 Figure 1 is a PSL and I comparison chart of the polarized microwave correlation imaging of the present application and traditional instantaneous polarization measurement;

[0066] Figure 5 Figure 2 is an anti-interference effect comparison chart of the polarized microwave correlation imaging method of the present application and the traditional microwave correlation imaging method. DETAILED DESCRIPTION

[0067] The technical solutions of the present application are described in detail below in conjunction with the accompanying drawings of the specification. It should be noted that, in this document, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or device.

[0068] Figure 1 Figure 1 is a flow chart of the polarized information driven microwave correlation imaging method proposed in the present application. The method is further explained below in conjunction with Figure 1 the present application. The specific steps and effects of the present application are as follows:

[0069] Figure 2 Figure 1 is a flow chart of the polarized information driven microwave correlation imaging method proposed in the present application. The method is further explained below in conjunction with

[0070] S1. Construct a full polarization frequency hopping radar matrix;

[0071] S1 includes the following specific steps:

[0072] S11. As shown in Figure 2 , arrange the frequency hopping radar in a row of antennas (1, 2,..., N) with equal intervals in the direction of the aircraft wing to form a frequency hopping radar array, constituting a row of multiple transmission single reception form;

[0073] S12. With the middle full polarization receiving antenna A as the boundary, respectively distribute the horizontal polarization antenna H and the vertical polarization antenna V on both sides, which can effectively suppress left-right ambiguity and has simple structure and strong practicability;

[0074] S13. At the same time, change the target imaging area B from a general square area to a diamond area, which can effectively reduce the spatial correlation of the random radiation field generated by the radar array arranged in the direction of the aircraft wing at each scattering unit, thereby improving the imaging effect.

[0075] S2. Forming horizontal polarization and vertical polarization space-time random radiation field;

[0076] S2 includes the following specific steps:

[0077] S21. Let the position vector from the center of the radar array to the target scattering point be Divide the M full polarization transceiving antennas into H antennas and V antennas, the H antennas and the V antennas are arranged on both sides of the antenna array respectively, and the random frequencies of the two kinds of antennas are different;

[0078] S22. Obtain the incident field intensity of the entire antenna array on the imaging area;

[0079] The S22 includes the following steps:

[0080] S221. The random frequencies of the H antennas and the V antennas are f Hi (t) and f Vi (t) respectively, the random horizontal polarization angle is γ i (t), the random vertical polarization angle is η i (t), and the antenna position vector is Therefore, the incident field intensity of the i-th transmitting antenna on the target area is as follows:

[0081]

[0082]

[0083] S222. Then the incident field intensity of the entire antenna array on the imaging area is:

[0084]

[0085]

[0086] S23. Forming horizontal polarization and vertical polarization space-time random radiation field by transmitting random frequency hopping signals independently through antennas with different polarization directions and receiving random sampling by receiving antennas.

[0087] S23 includes the following specific steps:

[0088] S231. Forming the random radiation field of the target area as follows:

[0089]

[0090]

[0091] S232. In the process of microwave correlation forward-looking imaging, the random radiation field reflects to form echoes after irradiating the target, and the echoes are received by receiving antennas to obtain the target echoes E Hr , EVr As follows:

[0092]

[0093]

[0094]

[0095]

[0096] S233. The target scattering characteristics and the target polarization scattering characteristics can be obtained by inversion:

[0097]

[0098] S3. Iterative imaging is performed by using the orthogonal complement space of the random radiation field.

[0099] S31. If the polarization information is not considered, the TSVD processing is performed on the insufficiently random space-time radiation field, the echo and the space-time random radiation field are compressed and correlated, and finally the target scattering characteristic matrix is obtained to realize the correlation imaging. In the case of not considering the noise, formula (11) can be simplified as:

[0100] E r = E s σ (12)

[0101] S32. If the polarization scattering matrix of the target is considered, the polarization scattering matrix of the target is obtained while the target is imaged, the above formula cannot be solved, and the characteristics of different HV antenna radiation fields must be considered to perform the calculation. The solution of the polarization scattering matrix of the target is equivalent to the instantaneous polarization measurement, which can be understood as solving the instantaneous polarization scattering matrix of the target by using the method of microwave correlation imaging.

[0102] At this time, the echo can be represented as:

[0103] E Hr = E Hs S HH +E Vs S HV (13)

[0104] E Vr = E Hs S HV +E Vs S VV (14)

[0105] If the above formula is to be solved, the best effect is that the H antenna radiation field and the V antenna radiation field are orthogonal, that is:

[0106] E Vs EHs = 0 (15)

[0107] But for microwave correlation imaging, the radiation field irradiated to the target is random and uncontrollable, and even if the radiation field is directly generated by using a mask and other tools, it cannot be ensured that the HV radiation fields at the target are mutually orthogonal, so another auxiliary matrix must be selected to deform the HV radiation field in calculation.

[0108] S32 includes the following specific steps:

[0109] S321. Obtain the orthogonal complement matrix of the horizontal polarization and vertical polarization radiation field by QR decomposition and cross-multiply it with the echo information;

[0110] S321 includes the following steps:

[0111] S3211. Use QR decomposition on the radiation field matrix of the target to calculate the orthogonal complement space E Hs and E Vs of the radiation field matrix E Hsb and E Vsb ;

[0112] S3212. Multiply the target HV echo with the HV radiation field orthogonal complement space respectively to obtain:

[0113] E Hsb E Hr = E Hsb E Hs S HH + E Hsb E Vs S HV (16)

[0114] E Vsb E Hr = E Vsb E Hs S HH + E Vsb E Vs S HV (17)

[0115] E Hsb E Vr = E Hsb E Hs S VH + E Hsb E Vs S VV (18)

[0116] E Vsb E Vr = E Vsb E Hs S VH + EVsb E Vs S VV (19)

[0117] From the property of the orthogonal complementary matrix, we have:

[0118]

[0119] That is:

[0120]

[0121] S322. Construct a new correlation equation with the processed radiation field of the matrix obtained in step S321 and iteratively image.

[0122] That is, formula (21) can be solved in the manner of solving formula (12), so that the target instantaneous polarization scattering matrix is measured while imaging the target.

[0123] In order to verify the effect of the present application, the method proposed in the present application is preliminarily verified in combination with simulation. Figure 3 The simulation diagram of the polarization information driven microwave correlation imaging of the present application is shown; it should be understood that Figure 3 The simulation described is only used to represent the present application and does not limit the present application. Assuming that the frequency hopping signal bandwidth B = 1 GHz, the pulse width T p = 0.2us, the carrier frequency f0 = 5GHz, the sampling rate f s = 10GHz, the number of antennas is 24, the plane distance is 500m, and the imaging area is set to a plane of 20x20m, the simulation results and analysis are as follows.

[0124] Figure 3 (a) is the simulation target state of the present application, which shows the polarization distribution of the target scattering, the rows and columns represent the spatial distribution of the target in the imaging area, different target types are represented by line and point, and the polarization scattering matrix of the target is randomly generated each time; Figure 3 (b) shows the spatial correlation of the random radiation field of one pulse, which is the spatial and temporal correlation of one sampling radiation field, from Figure 3 As can be seen from (b), the spatial correlation of the radiation field is in the form of a sharp peak, representing its high autocorrelation, which meets the radiation field condition of microwave correlation imaging; Figure 3 (c) shows the microwave correlation imaging result, that is, the cross-sectional condition of one microwave correlation imaging, from Figure 3 (c) can intuitively represent the imaging accuracy and resolution; Figure 3 (d) shows the target polarization scattering imaging, which is the result of the entire polarization information driven microwave correlation imaging, and as can be seen from the comparison with the target, the microwave correlation imaging basically achieves the expectation.

[0125] The measured results of the target polarization scattering matrix are shown in Table 1,

[0126] Table 1 Measured results of the target polarization scattering matrix

[0127]

[0128] As can be seen from Table 1, the measured target polarization scattering matrix has slight errors, but is basically consistent, indicating that the method can measure the instantaneous polarization matrix while imaging the target.

[0129] Figure 4 Fig. 1 is a comparison diagram of the polarization microwave correlation imaging of the present application and traditional instantaneous polarization measurement PSL and I; in order to further reflect the advantages of the polarization information driven microwave correlation imaging method of the present application in the aspect of instantaneous polarization measurement, the method is compared with the traditional instantaneous polarization measurement method. The instantaneous polarization measurement mainly uses the difference between the H and V antenna signals to measure, so the difference between the two signals is an important basis for comparing the instantaneous polarization measurement effect, and the difference is often measured by the autocorrelation and cross-correlation of the two signals; Giuli defines two parameters, isolation (I) and peak sidelobe level (PSL) to describe them in his research, wherein the isolation I describes the signal orthogonality by the cross-correlation of the signals, and the peak sidelobe level PSL describes the influence of the sidelobe of the autocorrelation function of the signal on the polarization scattering matrix measurement, so the PSL and I of the present application are compared with the positive and negative linear frequency modulation signals used in the general instantaneous polarization measurement to evaluate the instantaneous polarization measurement performance thereof. The PSL and I are specifically defined as follows:

[0130]

[0131]

[0132] In the above formula, i and j represent the transmission channels of the HV polarization signals, is the autocorrelation function of the signal, under the condition that the time width T is 0.2 μs and the bandwidth is from 0.5 GHz to 2.5 GHz, the two-way radiation fields of the HV antenna are calculated according to the above formula, and the results are shown in Fig. 2, Figure 4 Figure 4 Fig. 3 shows the changes of PSL and I with the signal time-frequency product, wherein a line represents PSL-polarization microwave correlation imaging; b line represents I-polarization microwave correlation imaging; c line represents I-traditional instantaneous polarization measurement; and d line represents PSL-traditional instantaneous polarization measurement. Through Figure 4 Figure 4 ​​From the PSL and I contrast of the two ways of the polarization microwave correlation imaging and the traditional instantaneous polarization measurement, it can be seen that, when the time-frequency product is small (Bτ<340), the peak side lobe level (PSL) and the isolation (I) of the two-way signal of the HV antenna of the polarization microwave correlation imaging method are averagely higher than those of the positive and negative linear frequency modulation signal used in the general method by about 13dB and 3dB, which indicates that the polarization microwave correlation imaging method has better instantaneous polarization measurement effect in this time-frequency product section. Figure 4 It can be seen that, the polarization microwave correlation method for instantaneous polarization measurement is different from the general instantaneous polarization measurement method, and the correlation of the PSL and the signal time-frequency product is not strong, which is determined by the randomness of the radiation field in the microwave correlation imaging. The microwave correlation imaging itself has a high requirement for the randomness of the radiation field, and is in a high random state in the time domain and the frequency domain. Therefore, the change of the time-frequency product has a small influence on the randomness of the radiation field, and the change amplitude is less than 0.4dB in the total time-frequency product section (100>Bτ<500). Therefore, under the condition of low time-frequency product, the polarization microwave correlation imaging has greater advantages in the instantaneous polarization measurement than the traditional instantaneous polarization measurement.

[0133] In order to further embody the anti-interference ability of the polarization information driven microwave correlation imaging method, the method is compared with the traditional microwave correlation imaging method under the same parameters (SNR=10dB). Figure 5 The anti-interference effect comparison diagram of the polarization microwave correlation imaging method and the traditional microwave correlation imaging method is shown, and the simulation result is Figure 5 , Figure 5 (a) is the simulation target; Figure 5 (b) is the traditional microwave correlation imaging result; Figure 5 (c) is the polarization microwave correlation imaging result; Figure 5 (d) is the error comparison of the traditional microwave correlation imaging method and the polarization microwave correlation imaging method of the application, wherein, Figure 5 The e change curve of (d) represents the NMSE change curve of the traditional microwave correlation imaging method with the SNR, and the f curve represents the NMSE change curve of the polarization microwave correlation imaging method of the application with the SNR. Figure 5 It can be seen that, under the white noise interference, the polarization microwave correlation imaging method has stronger anti-interference ability and higher imaging quality, because the polarization scattering matrix of the target is calculated at the same time of the imaging, which is equivalent to correcting the calculation result of the correlation for many times, and effectively avoiding the influence of the interference. Meanwhile, the influence of the polarization antenna on the noise interference is not considered in this simulation, and the anti-interference ability will be stronger in the actual application process, because the polarization antenna can only receive the signal in the predetermined polarization direction.

[0134] Finally, it should be pointed out that although the present application has been described with reference to the current specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not used as a limitation to the present application, and various equivalent changes or replacements can be made without departing from the concept of the present application, therefore, any changes or modifications to the above embodiments within the scope of the spirit of the present application will fall within the scope of the claims of the present application.

Claims

1. A polarimetric information driven microwave correlative imaging method, characterized in that, The method comprises the following steps: S1. Constructing a full polarization frequency hopping radar matrix; The S1 comprises the following steps: S11. Equidistantly arranging the antennas of the frequency hopping radar along the direction of the aircraft wing to form a column of the frequency hopping radar array in the form of multiple transmitting and single receiving; S12. Distributing the horizontally polarized antennas and the vertically polarized antennas on the two sides of the middle full polarization receiving antenna respectively; S13. Changing the target imaging area of the frequency hopping radar from a square area to a diamond area; S2. Forming a horizontally polarized and vertically polarized space-time random radiation field; The S2 comprises the following steps: S21. Let the position vector from the radar array center to the target scattering point be The M full polarization transceiving antennas are divided into H antennas and V antennas, and the H antennas and the V antennas are arranged on two sides of the antenna array respectively. S22. Obtaining the incident field intensity of the entire antenna array on the imaging area; S23. Constructing the horizontally polarized and vertically polarized space-time random radiation field through the independent transmission of random frequency hopping signals by the antennas with different polarization directions and the random sampling of receiving antennas; S3. Iterative imaging by using the orthogonal complementary space of the random radiation field.

2. The polarimetric information driven microwave correlation imaging method of claim 1, wherein, The S22 comprises the following steps: S221. The incident field intensity of the ith transmitting antenna on the target area is as follows: where f Hi (t) and f Vi (t) are the random frequencies of the H and V antennas, respectively, γ i (t) is a random horizontal polarization angle, η i (t) is a random vertical polarization angle, is the antenna position vector; S222. Then the incident field intensity of the entire antenna array on the imaging area is as follows:

3. The polarimetric information driven microwave correlation imaging method of claim 1, wherein, The S23 comprises the following steps: S231. Forming the random radiation field of the target area as follows: S232.In the microwave correlation forward-looking imaging process, the random radiation field irradiates the target after reflection to form a return wave, which is received by the receiving antenna to obtain the target return wave E Hr 、 E Vr The following formula: S233. Through inversion, the target scattering characteristics and the target polarization scattering characteristics can be obtained:

4. The polarimetric information driven microwave correlation imaging method of claim 1, wherein, The S3 comprises the following steps: S31. If the polarization information is not considered, the spatio-temporal radiation field with insufficient randomness is processed by TSVD, and then the echo and the spatio-temporal random radiation field are compressed and correlated, and finally the target scattering characteristic matrix is obtained, the correlation imaging is realized, and the target scattering characteristic matrix is simplified to E r = E s σ; S32. If the polarization scattering matrix of the target is considered, the instantaneous polarization scattering matrix of the target is solved by using the method of microwave correlation imaging.

5. The polarimetric information driven microwave correlation imaging method of claim 4, wherein, The instantaneous polarization scattering matrix in the S32 is expressed as: E Hr = E Hs S HH + E Vs S HV E Vr = E Hs S HV + E Vs S VV If the above formula is solved, the H antenna radiation field and the V antenna radiation field are orthogonal, that is: E Vs E Hs = 0.

6. The polarimetric information driven microwave correlation imaging method of claim 4, wherein, The S32 comprises the following steps: S321. Obtaining the orthogonal complementary matrix of the horizontally polarized and vertically polarized radiation fields through QR decomposition and cross-multiplying the matrix with the echo information; S322. Constructing a new correlation formula by using the matrix obtained in the step S321 and the processed radiation field, and iteratively imaging.

7. The polarimetric information driven microwave correlation imaging method of claim 6, wherein, The S321 comprises the following steps: S3211. Using QR decomposition on the radiation field matrix of the target, the radiation field matrix E is calculated Hs and E Vs the orthogonal complement space E Hsb and E Vsb ; S3212. Multiplying the HV echo of the target with the orthogonal complementary space of the HV radiation field to obtain: E Hsb E Hr = E Hsb E Hs S HH + E Hsb E Vs S HV E Vsb E Hr = E Vsb E Hs S HH + E Vsb E Vs S HV E Hsb E Vr = E Hsb E Hs S VH + E Hsb E Vs S VV E Vsb E Vr = E Vsb E Hs S VH + E Vsb E Vs S VV From the characteristics of the orthogonal complementary matrix, the following formula can be obtained: E Hsb E Hs = 0 E Vsb E Vs = 0 That is:

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