CN102353949A - Radar cross-section (RCS) estimation correction method for target based on water vapor absorption loss - Google Patents

Abstract

The invention provides a radar cross-section (RCS) estimation correction method for a target based on water vapor absorption loss. On the premise that the detection distance and a detection radar are determined and the detection frequency is known, the RCS estimation correction method for K wave band targets and millimeter wave band targets is provided according to relevance between the water vapor absorption loss and a radar equation so as to provide reference for remote sensing and detection of the target in a water vapor absorption environment.

Description

Target RCS based on water-vapour absorption loss is estimated modification method

Technical field

The present invention relates to a kind of target RCS and estimate modification method based on water-vapour absorption loss.

Background technology

Atmosphere is to have absorbing phenomenon as a kind of medium for electromagnetic wave propagation, and therefore just there is the certain absorption loss in the electromagnetic wave of wherein propagating.At present, basically all be under the free space environmental baseline for RCS (Radar Cross-Section, the RCS) pre-estimating technology of each class targets, do not consider the loss influence of Atmospheric Absorption.Along with the extension of detection range, the influence of atmospheric absorption loss increases gradually, does not consider that this factor will influence the precision of estimating of target RCS.Generally, atmospheric envelope is that water vapor absorbs and causes to one of principal element of electro-magnetic wave absorption, and water vapor to absorption of electromagnetic wave mainly near the 22.235GHz with more than the 100GHz (being K wave band and millimere-wave band).

Summary of the invention

The technical matters that the present invention will solve is to provide a kind of target RCS based on water-vapour absorption loss to estimate modification method.

The technical scheme that the unresolved above-mentioned technical matters of the present invention is taked is: estimate modification method based on the target RCS of water-vapour absorption loss, it is characterized in that: it may further comprise the steps:

Step 1, according to electromagnetic theory, providing water vapor is the absorption coefficient ξ of 22.235GHz ± 0.1GHz in absorption frequency ₂₂(h) and the above absorption coefficient ξ of 100GHz _Res(h) formula, thus the water-vapour absorption loss in the detection process obtained:

$\mathrm{Lw}={\∫}_0^h({\mathrm{\ξ}}_{22}\left(h\right)+{\mathrm{\ξ}}_{\mathrm{res}}\left(h\right))\mathrm{dh},$ Wherein h is a detection range;

Step 2, according to L _wTarget echo power to detection radar receiving antenna place is revised, and provides the echo power that detection radar can receive under the water vapor absorbing environmental, i.e. the target echo power at detection radar receiving antenna place;

Step 3, according to radar equation, the echo power that detection radar can receive under the tie water steam absorbing environmental is revised the RCS of target.

The target echo power at described detection radar receiving antenna place and the relational expression of water-vapour absorption loss are:

101gP _r＝101gP ₀-2L _w，

Wherein, P _rBe the target echo power at detection radar receiving antenna place, P ₀For surveying the target echo power at radar receiving antenna place under the free space condition.

Described radar equation is:

$\mathrm{\σ}=\frac{{\left(4\mathrm{\π}\right)}^3{P}_{r}h}{P_t{G}^2{\mathrm{\λ}}^2},$

σ is a target RCS, and λ is for surveying wavelength, and G is a radar antenna gain, P _tEmissive power for radar.Described water vapor is the absorption coefficient ξ of 22.235GHz ± 0.1GHz in absorption frequency ₂₂(h) be:

${\mathrm{\ξ}}_{22}\left(h\right)=0.002535\left\{{\mathrm{fP}}_w{\left(\frac{300}{T}\right)}^{3.5}\exp \right[20144(1-\frac{300}{T})\left]F\right\};$

Water vapor is the absorption coefficient ξ more than the 100GHz in absorption frequency _Res(h) formula is:

ξ _res(h)＝0.007347ρPT ^-2.5f ²；

Wherein P is an atmospheric pressure, and T is a steam temperature, and f is a look-in frequency, and ρ is an atmospheric density, P _wBe power factor, F is that the frequency ratio factor, Δ f are the difference on the frequency factor;

$P_w=\frac{\mathrm{\ρT}}{288.75},$ $F=\frac{f}{f_r}(\frac{\mathrm{\Δf}}{{(f_r-f)}^2+{\left(\mathrm{\Δf}\right)}^2}+\frac{\mathrm{\Δf}}{{(f_r+f)}^2+{\left(\mathrm{\Δf}\right)}^2}),$

$\mathrm{\Δf}=0.01799(P_w\frac{300}{T}+0.20846(0.75P-P_w){\left(\frac{300}{T}\right)}^{0.63}).$

Beneficial effect of the present invention is:

1, along with the extension of detection range, the influence of atmospheric absorption loss increases gradually, and the present invention considers atmospheric envelope to one of principal element of electro-magnetic wave absorption---water-vapour absorption loss, to improve the precision of estimating of target RCS.

2, confirm to detection range, detection radar; Under the known prerequisite of look-in frequency; According to the relevance between water-vapour absorption loss and radar equation, propose K wave band and millimere-wave band target RCS and estimate modification method, for remote sensing, the detection of target under the water vapor absorbing environmental provides reference frame.

Embodiment

Suppose the distance h=200km of a certain target and detection radar, look-in frequency f is 22.235GHz, and P is 1 atmospheric pressure, and T is 300k.The target RCS that obtains under this acquisition mode of free space environmental baseline calculates through existing target RCS pre-estimating technology, is 8.7dB.

1) according to electromagnetic theory, providing water vapor is the absorption coefficient ξ of 22.235GHz ± 0.1GHz in absorption frequency ₂₂(h) be:

${\mathrm{\ξ}}_{22}\left(h\right)=0.002535\left\{{\mathrm{fP}}_w{\left(\frac{300}{T}\right)}^{3.5}\exp \right[20144(1-\frac{300}{T})\left]F\right\}(\mathrm{dB}/\mathrm{km})---\left(1\right);$

Water vapor is the absorption coefficient ξ more than the 100GHz in absorption frequency _Res(h) formula is:

ξ _res(h)＝0.007347ρPT ^-2.5f ²(dB/km) (2)；

Wherein P is an atmospheric pressure, and T is a steam temperature, and f is a look-in frequency, and ρ is an atmospheric density, P _wBe power factor, F is that the frequency ratio factor, Δ f are the difference on the frequency factor;

$P_w=\frac{\mathrm{\ρT}}{288.75}---\left(3\right),$

$F=\frac{f}{f_r}(\frac{\mathrm{\Δf}}{{(f_r-f)}^2+{\left(\mathrm{\Δf}\right)}^2}+\frac{\mathrm{\Δf}}{{(f_r+f)}^2+{\left(\mathrm{\Δf}\right)}^2})---\left(4\right),$

$\mathrm{\Δf}=0.01799(P_w\frac{300}{T}+0.20846(0.75P-P_w){\left(\frac{300}{T}\right)}^{0.63})---\left(5\right).$

With formula (3), (4), (5) substitution formula (1) and (2), the following formula of substitution (6) and give known parameters again obtains the water-vapour absorption loss in the detection process:

$\mathrm{Lw}={\∫}_0^h({\mathrm{\ξ}}_{22}\left(h\right)+{\mathrm{\ξ}}_{\mathrm{res}}\left(h\right))\mathrm{dh}=0.18\mathrm{dB}---\left(6\right),$

2) according to L _wTarget echo power to detection radar receiving antenna place is revised, and provides the echo power that detection radar can receive under the water vapor absorbing environmental, i.e. the target echo power at detection radar receiving antenna place, and the relationship of the two formula is:

101gP _r＝101gP ₀-2L _w (7)，

Wherein, P _rTarget echo power for detection radar receiving antenna place; P ₀For surveying the target echo power at radar receiving antenna place under the free space condition.

3) according to radar equation, the echo power that detection radar can receive under the tie water steam absorbing environmental is revised the RCS of target.Radar equation is:

$\mathrm{\σ}=\frac{{\left(4\mathrm{\π}\right)}^3{P}_{r}h}{P_t{G}^2{\mathrm{\λ}}^2}---\left(8\right),$

σ is a target RCS, and λ is for surveying wavelength, and G is a radar antenna gain, P _tEmissive power for radar.Because detection radar is known, then λ, G and P _tBe known parameters.

With formula (6) substitution formula (7) back substitution formula (8), obtain the target RCS value and be corrected for 8.34dB.

Therefore, target RCS that obtains under the situation of consideration water-vapour absorption loss and the target RCS under the free space environmental baseline differ 0.36dB.Correction to target RCS has very big meaning to Electro Magnetic Compatibility under this environment of follow-up judgement etc.

Claims (4)

1. estimate modification method based on the target RCS of water-vapour absorption loss, it is characterized in that: it may further comprise the steps:

Step 1, according to electromagnetic theory, providing water vapor is the absorption coefficient ξ of 22.235GHz ± 0.1GHz in absorption frequency ₂₂(h) and the above absorption coefficient ξ of 100GHz _Res(h) formula, thus the water-vapour absorption loss in the detection process obtained:

$\mathrm{Lw}={\∫}_0^h({\mathrm{\ξ}}_{22}\left(h\right)+{\mathrm{\ξ}}_{\mathrm{res}}\left(h\right))\mathrm{dh},$ Wherein h is a detection range;

Step 2, according to L _wTarget echo power to detection radar receiving antenna place is revised, and provides the echo power that detection radar can receive under the water vapor absorbing environmental, i.e. the target echo power at detection radar receiving antenna place;

Step 3, according to radar equation, the echo power that detection radar can receive under the tie water steam absorbing environmental is revised the RCS of target.

2. the target RCS based on water-vapour absorption loss according to claim 1 is estimated modification method, it is characterized in that: the target echo power at described detection radar receiving antenna place and the relational expression of water-vapour absorption loss are:

101gP _r＝101gP ₀-2L _w，

Wherein, P _rBe the target echo power at detection radar receiving antenna place, P ₀For surveying the target echo power at radar receiving antenna place under the free space condition.

3. the target RCS based on water-vapour absorption loss according to claim 2 is estimated modification method, it is characterized in that: described radar equation is:

$\mathrm{\σ}=\frac{{\left(4\mathrm{\π}\right)}^3{P}_{r}h}{P_t{G}^2{\mathrm{\λ}}^2},$

σ is a target RCS, and λ is for surveying wavelength, and G is a radar antenna gain, P _tEmissive power for radar.

4. estimate modification method according to claim 1 or 2 or 3 described target RCS based on water-vapour absorption loss, it is characterized in that: described water vapor is the absorption coefficient ξ of 22.235GHz ± 0.1GHz in absorption frequency ₂₂(h) be:

Water vapor is the absorption coefficient ξ more than the 100GHz in absorption frequency _Res(h) formula is:

ξ _res(h)＝0.007347ρPT ^-2.5f ²；

Wherein P is an atmospheric pressure, and T is a steam temperature, and f is a look-in frequency, and ρ is an atmospheric density, P _wBe power factor, F is that the frequency ratio factor, Δ f are the difference on the frequency factor;

$P_w=\frac{\mathrm{\ρT}}{288.75},$ $F=\frac{f}{f_r}(\frac{\mathrm{\Δf}}{{(f_r-f)}^2+{\left(\mathrm{\Δf}\right)}^2}+\frac{\mathrm{\Δf}}{{(f_r+f)}^2+{\left(\mathrm{\Δf}\right)}^2}),$

$\mathrm{\Δf}=0.01799(P_w\frac{300}{T}+0.20846(0.75P-P_w){\left(\frac{300}{T}\right)}^{0.63}).$