CN102998665A - Target radar cross section measuring and calibrating processing method - Google Patents

Abstract

The invention provides a target radar cross section measuring and calibrating processing method. The method includes measuring and acquiring a test field background echo SBC (f,t1) at the moment of t1 after a calibration member support is installed, wherein SBC (f, t) is equal to HC(f, t1) * BC (f, t1); measuring and acquiring a calibration member echo SC (f, t2) at the moment of t2 after a calibration member is installed; measuring and acquiring a test field background echo SBT (f, t3) at the moment of t3 after a target support is installed, wherein SBT (f, t3) is equal to HT(f, t3) * BT (f, t3); and measuring and acquiring a target echo ST (f, t4) at the moment of t4 after a target is installed. The formula (1) is used for performing calibrating processing. By means of the target radar cross section measuring and calibrating processing method, the problem that measuring calibrating errors caused by many time varying factors in outfield testing are large can be solved.

Description

Target radar scattering cross-section is measured the method for processing with calibration

Technical field

The present invention relates to Radar Signal Processing Technology, (Radar Cross Section is called for short: RCS) measure the method for processing with calibration to relate in particular to a kind of target radar scattering cross-section.

Background technology

The rcs measurement technology is one of important means of goal in research radar scattering characteristic.RCS can determine according to accurate RCS value, calibration constant under the different distance condition and the echoed signal of radar target and calibration body of calibration body.At present, when the echoed signal of instrumentation radar target and calibration body, usually need to adopt metal support support radar target and calibration body.

In the prior art, the step of rcs measurement is: lay and measure the standard type support, measure the checkout area background return B of this moment _C(f); The calibration body is installed, is measured calibration body echo S _C(f); Lay Metal pylon, measure the checkout area background return B of this moment _T(f); Installation targets, measurement target echo S _T(f); And according to formula (8) calculating target RCS σ _T(f)

${\mathrm{\σ}}_T\left(f\right)=K\·{\left|\frac{S_T\left(f\right)-B_T\left(f\right)}{S_C\left(f\right)-B_C\left(t\right)}\right|}^2{\mathrm{\σ}}_C\left(f\right)---\left(8\right).$

Wherein, S _T(f) and S _CThe echoed signal that radar received when (f) expression was surveyed target and measured standard type respectively, K is the calibration constant under the different distance condition, B _T(f) and B _CBackground return when (f) expression is surveyed target and measured standard type respectively, σ _TBe target RCS, σ _CBe the RCS of calibration body, f is radar frequency.

Prior art has following shortcoming: (1) will not introduce measuring error with the variation characteristic of the condition such as meteorology in time if do not consider checkout area in full-scale target quiescent test outfield.Especially, for the ground flat field, because it has utilized the multiple scattering characteristic on checkout area ground, the variation of environment and meteorological condition will cause the variation of ground complex reflection coefficient, electric dimensions length etc., and then affect the variation of checkout area field strength distribution characteristic and echo amplitude phase place, its result not only affects calibration precision, and affects the background subtracting effect, causes the target RCS measurement error to increase.(2) any again instrumentation radar system of precision, always there is certain system drifting, under the condition that indoor environment temperature etc. is strictly controlled, perhaps, system drifting does not produce material impact, but under outdoor checkout area condition, it is obvious that this system drifting may become, although adopt the continuous calibration in strange land can elimination amplitude calibration error, but the amplitude of measuring system and phase drift can cause equally that the accurate background phasor is subtracted each other can't be realized and produce the residue background error, causes the target RCS measuring error to increase.

Summary of the invention

The invention provides a kind of target radar scattering cross-section and measure the method for processing with calibration, the unit for electrical property parameters, the drift of radar system generation phase and magnitude and the checkout area environmental factor that are used for solving checkout area change the problem that the target RCS measuring error that causes increases.

The invention provides a kind of target radar scattering cross-section and measure the method for processing with calibration, comprising:

At t ₁Constantly, measure the checkout area background return S that obtains after body support frame is calibrated in installation _BC(f, t ₁), S _BC(f, t ₁)=H _C(f, t ₁) B _C(f, t ₁);

At t ₂Constantly, measure the calibration body echo S that obtains after body is calibrated in installation _C(f, t ₂);

At t ₃Constantly, measure the checkout area background return S obtain behind the installation targets support _BT(f, t ₃), S _BT(f, t ₃)=H _T(f, t ₃) B _T(f, t ₃);

At t ₄Constantly, measure the target echo S obtain behind the installation targets _T(f, t ₄);

Adopting formula (1) to carry out the RCS calibration processes:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=\frac{S_T(f,t_4)-S_{\mathrm{BT}}(f,t_3)}{S_C(f,t_2)-S_{\mathrm{BC}}(f,t_1)}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(1\right)$

Wherein, described H _T(f, t ₁) and H _C(f, t ₃) transport function of measuring system-checkout area when expression is surveyed target and measured standard type respectively; Described f is radar frequency; Described

The multiple scattering function in broadband that represents respectively target and calibration body; Described B _T(f, t ₃) and B _C(f, t ₃) intrinsic backscatter when expression is surveyed target and measured standard type respectively.

Aforesaid target radar scattering cross-section is measured the method for processing with calibration, and preferably, described employing formula (1) carries out the analysis of RCS calibration error, is specially:

Adopt formula (2), (3), (4) to obtain the calibration result:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=\frac{H_T(f,t_4)}{H_C(f,t_2)}\·\frac{T\left(f\right)+{\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})}{C\left(f\right)+{\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(2\right)$

${\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})=B_C(f,t_2)-\frac{H_C(f,t_2)}{H_C(f,t_1)}\·B_C(f,t_1)---\left(3\right)$

${\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})=B_T(f,t_4)-\frac{H_T(f,t_3)}{H_T(f,t_4)}\·B_T(f,t_3)---\left(4\right)$

Wherein, described T (f) and C (f) represent respectively target and the true scattered field of calibration body under given attitude, described Δ _C(f, Δ t ₁₂) and Δ _T(f, Δ t ₃₄) be the residue background error after background is offset processing.

Aforesaid target radar scattering cross-section is measured the method for processing with calibration, preferably,

Described H _T(f, t) adopts formula (5) to determine:

$H_T(f,t)=\sqrt{\frac{G_{\mathrm{Tt}}(f,t)G_{\mathrm{Tr}}(f,t)F_{\mathrm{Tt}}(f,t)F_{\mathrm{Tr}}(f,t)}{{\left(4\mathrm{\π}\right)}^3{L}_{\mathrm{Tt}}(f,t)L_{\mathrm{Tr}}(f,t)}}\·\frac{1}{R_{\mathrm{Tt}}\left(t\right)R_{\mathrm{Tr}}\left(t\right)}\·\frac{c}{f}---\left(5\right)$

Described H _C(f, t) adopts formula (6) to determine:

$H_C(f,t)=\sqrt{\frac{G_{\mathrm{Ct}}(f,t)G_{\mathrm{Cr}}(f,t)F_{\mathrm{Ct}}(f,t)F_{\mathrm{Cr}}(f,t)}{{\left(4\mathrm{\π}\right)}^3{L}_{\mathrm{Ct}}(f,t)L_{\mathrm{Cr}}(f,t)}}$ $\left(6\right)$

$\·\frac{1}{R_{\mathrm{Ct}}\left(t\right)R_{\mathrm{Cr}}\left(t\right)}\·\frac{c}{f}\·\exp [-j\frac{4\mathrm{\πf}}{c}\mathrm{\ΔR}\left(t\right)]$

Wherein, G _tAnd G _rBe respectively the gain of transmitting radar antenna and receiving antenna, F _tAnd F _rBe the direction of propagation factor; R _tAnd R _rBe respectively the distance between transmitting radar antenna and the receiving antenna; L _tAnd L _rBe respectively the loss of radar emission passage and radar receiving cable; λ is radar wavelength, and c is velocity of propagation, and f is radar frequency, the parameter when T and C represent respectively to survey target and measure standard type; T and r represent respectively to transmit and receive; R _Tt(t) be the distance of target and emitting antenna, R _Tr(t) be the distance of target and receiving antenna, R _Ct(t) for calibrating the distance of body and emitting antenna, R _Cr(t) for calibrating the distance of body and receiving antenna, Δ R (t)=R _Tt(t)+R _Tr(t)-R _Ct(t)-R _Cr(t) be target with and the calibration body between range difference.

Aforesaid target radar scattering cross-section is measured the method for processing with calibration, preferably,

Described employing formula (2), (3), (4) obtain the calibration result, are specially:

Adopt formula (7) to carry out RCS calibration analysis on Uncertainty, and then find the concrete disposal route that reduces uncertainty:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=H_m(f,\mathrm{\Δ}{t}_{24})\·\frac{T\left(f\right)+{\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})}{C\left(f\right)+{\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})}\·\frac{1}{H_0\left(f\right)}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(7\right)$

Wherein, described H _m(f, Δ t ₂₄) be illustrated in and measure during calibration body and the measurement target, checkout area-measuring system transport function changes the measuring uncertainty that causes with the test duration; Described Δ _T(f, Δ t ₃₄) and Δ _C(f, Δ t ₁₂) represent respectively to survey target and measure in the standard type process measuring uncertainty that the residue background error that checkout area and radar system transport function temporal evolution produce brings; Described T (f) and C (f) represent respectively target and the true scattered field of calibration body under given attitude; Described H ₀(f) being can be by measure geometry relation and definite amplitude and the linear phase factor of radar parameter in the transport function.

Aforesaid target radar scattering cross-section is measured the method for processing with calibration, preferably, if target and calibration body on same support, described H then ₀(f)=1;

If target and calibration body be not on same support, then

Described K ₀Be the calibration constant.

Target radar scattering cross-section provided by the invention is measured the method for processing with calibration, by introducing the multiple scattering function in target broadband, and the time dependent transport function of instrumentation radar system and checkout area is introduced background phasor that electromagnetic scattering measures subtract each other and calibrate processing, with instrumentation radar, the checkout area environmental change, target scattering, the calibration volume scattering, target area and calibration district's backscatter etc. link up, thereby more intactly characterized WB-RCS than classic method and measure the impact that total system and overall process are processed RCS test and calibration, can solve the measurement calibration error large problem that the change factor causes when many in the field testing.

Description of drawings

Fig. 1 is the process flow diagram that target radar scattering cross-section of the present invention is measured the embodiment of the method for processing with calibration;

Fig. 2 is the position relationship synoptic diagram that middle target radar scattering cross-section embodiment illustrated in fig. 1 is measured.

Embodiment

Fig. 1 is the process flow diagram that target radar scattering cross-section of the present invention is measured the embodiment of the method for processing with calibration, and Fig. 2 is the position relationship synoptic diagram that middle target radar scattering cross-section embodiment illustrated in fig. 1 is measured, and in conjunction with Fig. 1, Fig. 2, the method comprises:

S101 is at t ₁Constantly, measure the checkout area background return S that obtains after body support frame 2 is calibrated in installation _BC(f, t ₁), S _BC(f, t ₁)=H _C(f, t ₁) B _C(f, t ₁);

H wherein _C(f, t) is the transport function of measuring system-checkout area when measuring standard type, B _C(f, t) is the intrinsic backscatter when measuring standard type, and t changes in time.

S102 is at t ₂Constantly, measure the calibration body echo S that obtains after body 1 is calibrated in installation _C(f, t ₂);

Specifically, suppose that rcs measurement satisfies the high s/n ratio measuring condition, i.e. the impact of noise can be ignored.If introduce measuring system-checkout area the time become transport function radar received the impact of echo, then measure mutually for the broadband frequency sweep width of cloth, radar echo signal can be expressed as S when measuring standard type _C(f, t ₂)=H _C(f, t ₂) [C (f)+B _C(f, t ₂)];

C in the formula (f) is the calibration true scattered field of body under given attitude, time to time change not under given attitude and radar parameter condition.

S103 is at t ₃Constantly, measure the checkout area background return S obtain behind the installation targets support 4 _BT(f, t ₃), S _BT(f, t ₃)=H _T(f, t ₃) B _T(f, t ₃);

Wherein, H _T(f, t) is the transport function of measuring system-checkout area when surveying target, B _TThe intrinsic backscatter that target is surveyed in (f, t) expression.

S104 is at t ₄Constantly, measure the target echo S obtain behind the installation targets 3 _T(f, t ₄);

Wherein, suppose that rcs measurement satisfies the high s/n ratio measuring condition, i.e. the impact of noise can be ignored.If introduce measuring system-checkout area the time become transport function radar received the impact of echo, then measure mutually for the broadband frequency sweep width of cloth, the radar echo signal when surveying target can be expressed as:

S _T(f,t ₄)=H _T(f,t ₄)·[T(f)+B _T(f,t ₄)];

T in the formula (f) is the true scattered field of target under given attitude, time to time change not under given attitude and radar parameter condition.

S105, adopt formula (1) to carry out the RCS calibration and process:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=\frac{S_T(f,t_4)-S_{\mathrm{BT}}(f,t_3)}{S_C(f,t_2)-S_{\mathrm{BC}}(f,t_1)}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(1\right)$

Wherein, described H _T(f, t) and H _CThe transport function of measuring system-checkout area when (f, t) represents respectively to survey target and measure standard type; Described f is radar frequency; Described

The multiple scattering function in broadband that represents respectively target and calibration body; Described B _T(f, t) and B _CIntrinsic backscatter when (f, t) represents respectively to survey target and measure standard type.

Specifically, the multiple scattering function in the broadband in the present embodiment

For:

$\sqrt{\mathrm{\σ}\left(f\right)}=\underset{R\→\∞}{\lim }\sqrt{4\mathrm{\π}}R\·\frac{E_s\left(f\right)}{E_i\left(f\right)}$

Wherein, E _i(f) and E _s(f) represent respectively radar incident field (target place) and target scattering field (radar antenna place); It with the pass between the RCS is

When specific implementation, suppose that rcs measurement satisfies the high s/n ratio measuring condition, i.e. the impact of noise can be ignored.If introduce measuring system-checkout area the time become transport function radar received the impact of echo, then measure mutually for the broadband frequency sweep width of cloth, separately radar echo signal can be expressed as respectively when surveying target and calibration body:

S _T(f,t)=H _T(f,t)·[T(f)+B _T(f,t)]

S _C(f,t)=H _C(f,t)·[C(f)+B _C(f,t)]

Wherein, H _T(f, t) and H _CThe transport function of measuring system-checkout area changed in time slowly when (f, t) represented respectively to survey target and measure standard type, had reflected over time characteristic of instrumentation radar system drifting and checkout area type and electrical quantity characteristic thereof; S _T(f, t) and S _C(f, t) represents respectively target echo and the calibration body echo that radar receives, and both become the impact of transport function when all being subject to instrumentation radar-checkout area; T (f) and C (f) represent respectively target and the calibration true scattered field of body under given attitude, time to time change not under given attitude and radar parameter condition; B _T(f, t) and B _C(f, intrinsic backscatter when t) expression survey target is with the mensuration standard type respectively, both are in time t variation all, and expression is owing to target or calibrate body with the coupling scattering between the support or the change of background state, when causing drop target support and empty support to measure, the variation of intrinsic backscatter.

Therefore, formula (1) can be changed to:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=\frac{H_T(f,t_4)}{H_C(f,t_2)}\·\frac{T\left(f\right)+{\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})}{C\left(f\right)+{\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(2\right)$

${\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})=B_C(f,t_2)-\frac{H_C(f,t_2)}{H_C(f,t_1)}\·B_C(f,t_1)---\left(3\right)$

${\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})=B_T(f,t_4)-\frac{H_T(f,t_3)}{H_T(f,t_4)}\·B_T(f,t_3)---\left(4\right)$

In the formula, T (f) and C (f) represent respectively target and the true scattered field of calibration body under given attitude, Δ _C(f, Δ t ₁₂) and Δ _T(f, Δ t ₃₄) be the residue background error after background is offset processing.

Therefore, adopt formula (1) to carry out the RCS calibration among the above-mentioned S105 and process, can be specially and adopt formula (2), (3) and (4) to carry out RCS calibration processing.

Present embodiment, by introducing the multiple scattering function in target broadband, and the time dependent transport function of instrumentation radar system and checkout area is introduced background phasor that electromagnetic scattering measures subtract each other and calibrate processing, instrumentation radar, checkout area environmental change, target scattering, calibration volume scattering, target area and the backscatter of calibration district etc. are linked up, thereby more intactly characterized WB-RCS than classic method and measure the impact that total system and overall process are processed RCS test and calibration, can solve the measurement calibration error large problem that the change factor causes when many in the field testing.

Particularly, above-described embodiment in actual applications, measuring system-checkout area the time become transport function and can derive by radar equation.As shown in Figure 2, the reception echo power P of calibration body and target to be measured _rAll satisfy radar equation (10):

$P_r=\frac{P_t{G}_t{G}_r{F}_t{F}_r{\mathrm{\λ}}^2}{{\left(4\mathrm{\π}\right)}^3{R_t}^2{R}_r^2{L}_t{L}_r}\·\mathrm{\σ}---\left(10\right)$

Wherein, P _tBe radar emission power, G _tAnd G _rBe respectively the gain of transmitting radar antenna and receiving antenna, F _tAnd F _rBe the direction of propagation factor; R _tAnd R _rBe respectively the distance between transmitting radar antenna and the receiving antenna; L _tAnd L _rBe respectively the loss of radar emission passage and radar receiving cable, described L _tAnd L _rComprise system loss and loss;

Be radar wavelength, σ is the RCS of testee.

If supposition is take target's center as the phase reference center, by radar equation (20), the transport function when surveying target and measuring standard type can be expressed as respectively:

$H_T(f,t)=\sqrt{\frac{G_{\mathrm{Tt}}(f,t)G_{\mathrm{Tr}}(f,t)F_{\mathrm{Tt}}(f,t)F_{\mathrm{Tr}}(f,t)}{{\left(4\mathrm{\π}\right)}^3{L}_{\mathrm{Tt}}(f,t)L_{\mathrm{Tr}}(f,t)}}\·\frac{1}{R_{\mathrm{Tt}}\left(t\right)R_{\mathrm{Tr}}\left(t\right)}\·\frac{c}{f}---\left(5\right)$

$H_C(f,t)=\sqrt{\frac{G_{\mathrm{Ct}}(f,t)G_{\mathrm{Cr}}(f,t)F_{\mathrm{Ct}}(f,t)F_{\mathrm{Cr}}(f,t)}{{\left(4\mathrm{\π}\right)}^3{L}_{\mathrm{Ct}}(f,t)L_{\mathrm{Cr}}(f,t)}}$ $\left(6\right)$

$\·\frac{1}{R_{\mathrm{Ct}}\left(t\right)R_{\mathrm{Cr}}\left(t\right)}\·\frac{c}{f}\·\exp [-j\frac{4\mathrm{\πf}}{c}\mathrm{\ΔR}\left(t\right)]$

Parameter when T and C represent respectively to survey target and measure standard type; T and r represent respectively to transmit and receive; R _Tt(t) be the distance of target and emitting antenna, R _Tr(t) be the distance of target and receiving antenna, R _Ct(t) for calibrating the distance of body and emitting antenna, R _Cr(t) for calibrating the distance of body and receiving antenna, Δ R (t)=R _Tt(t)+R _Tr(t)-R _Ct(t)-R _Cr(t) be target with and the calibration body between range difference.And, suppose that the antenna gain item has comprised the impact that radar transmitter and transmitter antenna gain (dBi) drift, receiver gain and receiving antenna gain in time drift about in time simultaneously.

In the actual measurement process, can change accordingly according to the difference of measuring situation to formula (1) and formula (2), and the result after changing can also be used for the generation of Analysis deterrmination uncertain factor, present embodiment just is measured as example with single station.

Measure when adopting list to stand, and in the situation of duplexer, G in the present embodiment _Tt=G _Tr=G _Ct=G _Cr=G, R _Tt=R _Tr=R _T, R _Ct=R _Cr=R _C, L _Tr=L _Tr=L _T, L _Ct=L _Cr=L _C, F _Tt=F _Tr=F _TAnd F _Ct=F _Cr=F _CSo formula (5) can be reduced to:

$H_T(f,t)=\sqrt{\frac{1}{{\left(4\mathrm{\π}\right)}^3}}\·\frac{G(f,t)F_T(f,t)}{L_T(f,t)R_T^2\left(t\right)}\·\frac{c}{f}---\left(11\right)$

Formula (6) can be reduced to:

$H_C(f,t)=\sqrt{\frac{1}{{\left(4\mathrm{\π}\right)}^3}}\·\frac{G(f,t)F_C(f,t)}{L_C(f,t)R_C^2\left(t\right)}\·\frac{c}{f}\·\exp [-j\frac{4\mathrm{\πf}}{c}\mathrm{\ΔR}\left(t\right)]---\left(12\right)$

In formula (11) and (12):

G (f, t) has comprised the system-gain impact that transmitter power and phase drift cause;

R _T(t) and R _C(t) be apart from the factor, insensitive over time to systematic parameter, so can think time-independent constant, can be designated as R _T(t)=R _T, R _C(t)=R _C

L _T(f, t), L _C(f, t) is decay factor, and be generally insensitive to the time variation, but change with the radar frequency of operation, can note by abridging to be L _T(f) and L _C(f);

The subtle change of Δ R (t) causes the phase generate that changes with frequency linearity to change, be equivalent to the small translation of target reference center, can not produce substantial effect to the target RCS measurement result, so also can be assumed to time-independent constant, can not affect the analysisanddiscusion to contingency question, can be designated as Δ R (t)=Δ R.

Like this, formula (11) and formula (12) can further be reduced to:

$H_T(f,t)=\sqrt{\frac{1}{{\left(4\mathrm{\π}\right)}^3}}\·\frac{c}{L_T\left(f\right)\·R_T^2\·f}\·G(f,t)\·F_T(f,t)---\left(13\right)$

$H_C(f,t)=\sqrt{\frac{1}{{\left(4\mathrm{\π}\right)}^3}}\·\frac{c}{L_C\left(f\right)\·R_C^2\·f}\·G(f,t)\·F_C(f,t)\·\exp [-j\frac{4\mathrm{\πf}}{c}\mathrm{\ΔR}]---\left(14\right)$

Therefore,

$\frac{H_T(f,t_n)}{H_C(f,t_m)}=\frac{G(f,t_n)}{G(f,t_m)}\·\frac{F_T(f,t_n)}{F_C(f,t_m)}\·H_0\left(f\right)---\left(15\right)$

H in the formula ₀(f) being can be by measure geometry relation and definite amplitude and the linear phase factor of radar parameter in the transport function, does not pass in time and changes.

$H_0\left(f\right)={\left(\frac{R_C}{R_T}\right)}^2\·\frac{L_C\left(f\right)}{L_T\left(f\right)}\·\exp [-j\frac{4\mathrm{\πf}}{c}\mathrm{\ΔR}]$ $\left(16\right)$

$=A\left(f\right)\exp [-j\frac{4\mathrm{\πf}}{c}\mathrm{\ΔR}]$

When calibrating together situation: target and calibration body are placed on the same support, measure sequentially in time.Calibrate together if in the RCS test, adopt, R is arranged _C=R _T, L _C(f)=L _T(f), have A (f)=1 this moment, and Δ R=0 is so have

H ₀(f)=1 (16a)

When situation is calibrated in the strange land continuously: calibration body and target are placed on the different distance, utilize two range gate realizations to calibrate bodies, target echo signal gathers simultaneously and calibrate continuously measurement.At this moment, the close together in the general test process between calibration body and the target, and the relative bandwidth of radar system less (otherwise being difficult to contentedly facial plane field condition) are so can think

Be approximately equal to constant, therefore have

$H_0\left(f\right)\≈K_0\·\exp [-j\frac{4\mathrm{\πf}}{c}\mathrm{\ΔR}]---\left(16b\right)$

Described K ₀Be the calibration constant.

Owing in the RCS calibration is processed, can concern and radar parameter according to measure geometry, and accurately calculate H according to radar equation ₀(f), so this transport function generally can not introduced obvious calibration process errors.

Like this, actual rcs measurement and process in can do following correction to formula (1):

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=\frac{S_T(f,t)-S_{\mathrm{BT}}(f,t)}{S_C(f,t)-S_{\mathrm{BC}}(f,t)}\·\frac{1}{H_0\left(f\right)}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(17\right)$

In the following formula only first fraction be time dependent.Note Δ t _Mn=t _n-t _m, expression t _mAnd t _nThe time interval between twice different measuring (m, n=1,, 2,3,4).Like this, formula (2) can be rewritten as:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=H_m(f,\mathrm{\Δ}{t}_{24})\·\frac{T\left(f\right)+{\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})}{C\left(f\right)+{\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})}\·\frac{1}{H_0\left(f\right)}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(7\right)$

In formula (7), H _m(f, Δ t ₂₄) be illustrated in and measure calibration body (t ₂Constantly) with measurement target (t ₄Constantly), checkout area-measuring system transport function changes the measuring uncertainty that causes, Δ with the test duration _T(f, Δ t _T) and Δ _C(f, Δ t _C) represent respectively to survey target and measure in the standard type process measuring uncertainty that the residue background error that checkout area and radar system transport function temporal evolution produce brings.

Particularly, in the formula (7), invariant is

T (f), C (f) and Residue H _m(f, Δ t ₂₄), Δ _T(f, Δ t ₃₄) and Δ _C(f, Δ t ₁₂) be uncertain variables, in measurement result, can specifically analyze, determine which factor can affect measurement result, H when the single station of the below's concrete analysis is measured _m(f, Δ t ₂₄), Δ _T(f, Δ t _T) and Δ _C(f, Δ t _C) uncertain factor of bringing and the method for eliminating uncertain factor.

By the next formula (7) of formula (2) conversion, wherein H _m(f, Δ t ₂₄) can be used to eliminate the impact of instrumentation radar system drifting and checkout area environment electrical property change, in the present embodiment because single station is measured, so H _m(f, Δ t ₂₄) be

$H_m(f,\mathrm{\Δ}{t}_{24})=\frac{H_T(f,t_4)}{H_C(f,t_2)}=\frac{G(f,t_4)}{G(f,t_2)}\·\frac{F_T(f,t_4)}{F_C(f,t_2)}---\left(18\right)$

$=H_G(f,\mathrm{\Δ}{t}_{24})\·H_F(f,\mathrm{\Δ}{t}_{24})$

Wherein

$H_G(f,\mathrm{\Δ}{t}_{24})=\frac{G(f,t_4)}{G(f,t_2)}---\left(19\right)$

Be the uncertainty that instrumentation radar system (containing antenna) causes with frequency drift in time, the antenna gain variable effect is very little usually, and uncertainty mainly is that transmitter and receiver drifts about and causes.

$H_F(f,\mathrm{\Δ}{t}_{24})=\frac{F_T(f,t_4)}{F_C(f,t_2)}---\left(20\right)$

Be checkout area inconsistent uncertainty that causes of propagation factor between the two when surveying target and measuring standard type, mainly because the checkout area electrical quantity changes with the condition such as meteorology in time causes.

If can derive transfer function H by testing process design or subsidiary means in the test process _m(f, Δ t ₂₄), then in processing, calibration uses 1/H _m(f, Δ t ₂₄) compensating processing, the impact of instrumentation radar system drifting and checkout area environment electrical property change is eliminated.

By the next formula (7) of formula (2) conversion, wherein Δ _T(f, Δ t _T) and Δ _C(f, Δ t _C) can be used to eliminate the impact of background subtracting remainder error.

The measuring uncertainty that the residue background error brings in the formula (7) can be expressed as follows:

${\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_T)=[1-\frac{H_T(f,t_3)}{H_T(f,t_4)}]\·B_T\left(f\right)$

$=[1-\frac{G(f,t_3)}{G(f,t_4)}\·\frac{F_T(f,t_3)}{F_T(f,t_4)}]\·B_T\left(f\right)---\left(21\right)$

$=[1-H_G(f,\mathrm{\Δ}{t}_{34})\·H_{\mathrm{FT}}(f,\mathrm{\Δ}{t}_{34})]\·B_T\left(f\right)$

${\mathrm{\Δ}}_C(f,{\mathrm{\Δt}}_C)=[1-\frac{H_C(f,t_1)}{H_C(f,t_2)}]\·B_C\left(f\right)$

$=[1-\frac{G(f,t_1)}{G(f,t_2)}\·\frac{F_C(f,t_1)}{F_C(f,t_2)}]\·B_C\left(f\right)---\left(22\right)$

$=[1-H_G(f,{\mathrm{\Δt}}_{12})\·H_{\mathrm{FC}}(f,\mathrm{\Δ}{t}_{12})]\·B_C\left(f\right)$

In the formula,

$H_{\mathrm{FT}}(f,\mathrm{\Δ}{t}_{34})=\frac{F_T(f,t_3)}{F_T(f,t_4)}---\left(23\right)$

The uncertainty that causes for surveying the destination path propagation factor;

$H_{\mathrm{FC}}(f,\mathrm{\Δ}{t}_{12})=\frac{F_C\left(f{,t}_1\right)}{F_C(f,t_2)}---\left(24\right)$

The uncertainty that causes for measuring standard type propagated factor variations.

As seen, background is offset remainder error and is subject to radar system drift H _G(f, Δ t ₃₄) (the radar system drift during surveying the Metal pylon background and surveying target), H _G(f, Δ t ₁₂) (the radar system drift during measuring mark support background and measuring standard type), H _FT(f, Δ t ₃₄) (the propagated factor variations during surveying the Metal pylon background and surveying target) and H _FC(f, Δ t ₁₂) impact of (measuring mark support background and the propagated factor variations of measuring during the standard type) four.

If in test, can lead H by testing process design or subsidiary means _G(f, Δ t ₁₂) H _FC(f, Δ t ₁₂) and H _G(f, Δ t ₃₄) H _FT(f, Δ t ₃₄), then before background subtracting is processed, can compensate processing to background data, thereby eliminate the residue background error.

In addition, can see also from formula (7) that accurate calibration is processed and also required the time-independent transfer function H of accurate Calculation ₀The theoretical value of magnitude-phase characteristics (f), the multiple scattering function in accurate Calculation calibration body broadband

And the error in pointing of elimination calibration body and target etc.

This shows, target radar scattering cross-section proposed by the invention has been measured with the method expressed intact of calibrating processing temporal evolution and the time-independent various factors of impact test uncertainty in RCS test and the processing procedure, and the method can be used for instructing definite test and the flow process of processing, the extraction of formation background clutter and accurate background to subtract each other disposal route and algorithm, also is used for simultaneously the principal element of analyzing influence outfield uncertainty of measurement.

It should be noted that at last: above each embodiment is not intended to limit only in order to technical scheme of the present invention to be described; Although with reference to aforementioned each embodiment the present invention is had been described in detail, those of ordinary skill in the art is to be understood that: it still can be made amendment to the technical scheme that aforementioned each embodiment puts down in writing, and perhaps some or all of technical characterictic wherein is equal to replacement; And these modifications or replacement do not make the essence of appropriate technical solution break away from the scope of various embodiments of the present invention technical scheme.

Claims (5)

1. a target radar scattering cross-section is measured the method for processing with calibration, it is characterized in that, comprising:

At t ₁Constantly, measure the checkout area background return S that obtains after body support frame is calibrated in installation _BC(f, t ₁), S _BC(f, t ₁)=H _C(f, t ₁) B _C(f, t ₁);

At t ₂Constantly, measure the calibration body echo S that obtains after body is calibrated in installation _C(f, t ₂);

At t ₃Constantly, measure the checkout area background return S obtain behind the installation targets support _BT(f, t ₃), S _BT(f, t ₃)=H _T(f, t ₃) B _T(f, t ₃);

At t ₄Constantly, measure the target echo S obtain behind the installation targets _T(f, t ₄);

Adopting formula (1) to carry out the RCS calibration processes:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=\frac{S_T(f,t_4)-S_{\mathrm{BT}}(f,t_3)}{S_C(f,t_2)-S_{\mathrm{BC}}(f,t_1)}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(1\right)$

Wherein, described H _T(f, t ₁) and H _C(f, t ₃) transport function of measuring system-checkout area when expression is surveyed target and measured standard type respectively; Described f is radar frequency; Described

The multiple scattering function in broadband that represents respectively target and calibration body; Described B _T(f, t ₃) and B _C(f, t ₃) intrinsic backscatter when expression is surveyed target and measured standard type respectively.

2. method according to claim 1 is characterized in that, described employing formula (1) carries out the analysis of RCS calibration error, is specially:

Adopting formula (2), (3), (4) to carry out the RCS calibration processes:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=\frac{H_T(f,t_4)}{H_C(f,t_2)}\·\frac{T\left(f\right)+{\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})}{C\left(f\right)+{\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(2\right)$

${\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})=B_C(f,t_2)-\frac{H_C(f,t_2)}{H_C(f,t_1)}\·B_C(f,t_1)---\left(3\right)$

${\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})=B_T(f,t_4)-\frac{H_T(f,t_3)}{H_T(f,t_4)}\·B_T(f,t_3)---\left(4\right)$

Wherein, described T (f) and C (f) represent respectively target and the true scattered field of calibration body under given attitude, described Δ _C(f, Δ t ₁₂) and Δ _T(f, Δ t ₃₄) be the residue background error after background is offset processing.

3. method according to claim 2 is characterized in that, described H _T(f, t) adopts formula (5) to determine:

$H_T(f,t)=\sqrt{\frac{G_{\mathrm{Tt}}(f,t)G_{\mathrm{Tr}}(f,t)F_{\mathrm{Tt}}(f,t)F_{\mathrm{Tr}}(f,t)}{{\left(4\mathrm{\π}\right)}^3{L}_{\mathrm{Tt}}(f,t)L_{\mathrm{Tr}}(f,t)}}\·\frac{1}{R_{\mathrm{Tt}}\left(t\right)R_{\mathrm{Tr}}\left(t\right)}\·\frac{c}{f}---\left(5\right)$

Described H _C(f, t) adopts formula (6) to determine:

$H_C(f,t)=\sqrt{\frac{G_{\mathrm{Ct}}(f,t)G_{\mathrm{Cr}}(f,t)F_{\mathrm{Ct}}(f,t)F_{\mathrm{Cr}}(f,t)}{{\left(4\mathrm{\π}\right)}^3{L}_{\mathrm{Ct}}(f,t)L_{\mathrm{Cr}}(f,t)}}$ $\left(6\right)$

$\·\frac{1}{R_{\mathrm{Ct}}\left(t\right)R_{\mathrm{Cr}}\left(t\right)}\·\frac{c}{f}\·\exp [-j\frac{4\mathrm{\πf}}{c}\mathrm{\ΔR}\left(t\right)]$

Wherein, G _tAnd G _rBe respectively the gain of transmitting radar antenna and receiving antenna, F _tAnd F _rBe the direction of propagation factor; R _tAnd R _rBe respectively the distance between transmitting radar antenna and the receiving antenna; L _tAnd L _rBe respectively the loss of radar emission passage and radar receiving cable; λ is radar wavelength, and c is velocity of propagation, and f is radar frequency, the parameter when T and C represent respectively to survey target and measure standard type; T and r represent respectively to transmit and receive; R _Tt(t) be the distance of target and emitting antenna, R _Tr(t) be the distance of target and receiving antenna, R _Ct(t) for calibrating the distance of body and emitting antenna, R _Cr(t) for calibrating the distance of body and receiving antenna, Δ R (t)=R _Tt(t)+R _Tr(t)-R _Ct(t)-R _Cr(t) be target with and the calibration body between range difference.

4. method according to claim 3 is characterized in that, RCS calibration analysis on Uncertainty is carried out in described employing formula (2), (3), (4), and then finds the effective ways that reduce uncertainty.Be specially:

Adopting formula (7) to carry out the RCS calibration processes:

$\sqrt{{\mathrm{\σ}}_T\left(f\right)}=H_m(f,\mathrm{\Δ}{t}_{24})\·\frac{T\left(f\right)+{\mathrm{\Δ}}_T(f,\mathrm{\Δ}{t}_{34})}{C\left(f\right)+{\mathrm{\Δ}}_C(f,\mathrm{\Δ}{t}_{12})}\·\frac{1}{H_0\left(f\right)}\·\sqrt{{\mathrm{\σ}}_C\left(f\right)}---\left(7\right)$

Wherein, described H _m(f, Δ t ₂₄) be illustrated in and measure during calibration body and the measurement target, checkout area-measuring system transport function changes the measuring uncertainty that causes with the test duration; Described Δ _T(f, Δ t ₃₄) and Δ _C(f, Δ t ₁₂) represent respectively to survey target and measure in the standard type process measuring uncertainty that the residue background error that checkout area and radar system transport function temporal evolution produce brings; Described T (f) and C (f) represent respectively target and the true scattered field of calibration body under given attitude; Described H ₀(f) being can be by measure geometry relation and definite amplitude and the linear phase factor of radar parameter in the transport function.

5. method according to claim 4 is characterized in that, if target and calibration body on same support, described H then ₀(f)=1;

If target and calibration body be not on same support, then

Described K ₀Be the calibration constant.

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