CN103094685B - Large scale radome electrical performance compensation method based on axial defocusing - Google Patents

Abstract

The invention discloses a large scale radome electrical performance compensation method based on axial defocusing which mainly solves the problem that the radome has too much influence on the antenna electrical performance. The technical scheme includes that the method is characterized in that the method calculates an antenna far field according to an aperture field, draws a far-field pattern and extracts the electrical performance index, calculates the aperture field through the radome, calculates the initial adjustment amount of the axial defocusing, calculates the aperture field through the radome during the axial defocusing, calculates the radome far-field before and after the axial defocusing, draws the far-field pattern and extracts the electrical performance index, and compares the antenna with no radome, the far-field pattern of the antenna with the radome and the electrical performance index before and after the axial defocusing. If the requirement of the antenna electrical performance is satisfied, the antenna with no radome, the far-field pattern of the antenna with the radome and the electrical performance index before and after the axial defocusing and the axial defocusing amount are output. If the requirement of the antenna electrical performance is not satisfied, the axial defocusing amount is adjusted slightly, and the process is repeated until the requirement of the electrical performance is satisfied. The method can effectively improve the electrical performance of the antenna system with the radome and be used for the analysis and design of the radome.

Description

Large-scale antenna cover electrical property compensation method based on axial defocusing

Technical field

The invention belongs to Radar Antenna System field, specifically a kind of large-scale antenna cover electrical property compensation method based on axial defocusing, can be used for the electrical property of the reflector antenna system with dielectric interlayer formula radome to compensate.

Technical background

Radome is the wave transparent shell that protection antenna is avoided natural environment influence, is by covering natural or that artificial dielectric's material is made, or the bright window of electromagnetism of the special shape being made up of the dielectric housing of truss support.The radome of excellent in design; except having protectiveness, conductibility, reliability, disguise and the function such as ornamental, can also extend whole system each several part useful life, reduce Life Cost and running cost, simplified design, reduction maintenance cost, ensure antenna surface and position accuracy, create good operational environment to antenna operation personnel.But radome also can exert an influence to the electromagnetic radiation of ideal antenna, desirable antenna electric performance is decreased.Radome design is the somewhat complex design of structural design and electrical property design combination.

Along with the progress of China's aviation, meteorology and military technology and the development of military situation, the research of carrying out the High Accuracy Radars such as long-range precision tracking instrumentation radar and high-gain aerial has become urgent task with manufacture.And the natural environment of Special geographical position is larger on the impact of equipment, being equipped with radome becomes these radars, the requisite requirement of antenna, and dielectric interlayer formula radome is widely used with its good structural behaviour and electrical property.

Du Yaowei has analyzed the impact of dielectric interlayer formula radome on Antenna Far Field in classical works " radome telecommunications design method " book of publishing for 1993, first the method obtains the transmission coefficient of radome, then obtain the aperture field after covering according to the transmission coefficient of the aperture field of antenna and radome, integration is obtained the far field of covering aft antenna.The deficiency of the method is: the electrical property that there is no to consider to improve by axial defocusing band cover antenna system.

Li Gaosheng uses theory of geometric optics to analyze the impact of axial defocusing on parabolic antenna electrical property in the paper " theory of parabolic antenna feed source axial defocusing and application study " of 2004, first the method has obtained the antenna aperture field under axial defocusing impact, then obtain Antenna Far Field according to integrating the aperture field, but the method does not apply it to in the compensation of covering aft antenna electrical property.

Summary of the invention

The object of the invention is to for above-mentioned the deficiencies in the prior art, a kind of large-scale antenna cover electrical property compensation method based on axial defocusing is provided, to improve the electrical property of band cover antenna system.

For achieving the above object, technical scheme of the present invention comprises the steps:

(1) according to known antenna aperture field calculate the far field F (θ, φ) of antenna, draw far-field pattern T ₁, and from far-field pattern, extract electrical performance indexes, i.e. maximum field strength G ₁, the first from left secondary lobe L ₁with a right secondary lobe R ₁;

(2) calculate the transmission coefficient at each point place on radome by transmission line theory and calculate through the aperture field after radome:

(3), according to the version of the transmission coefficient of radome and antenna, calculate the initial adjustment amount d of antenna axial direction defocusing _f:

For single reflector antenna, its initial adjustment amount is:

wherein Δ η _tthe poor of the phase place maximum of transmission coefficient and minimum value, ξ _maxit is parabola bore subtended angle; If the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ, λ is the wavelength of antenna, wherein f is operating frequency of antenna, and c is the light velocity;

For dijection surface antenna, the calculating of its initial adjustment amount is undertaken by following two kinds of modes:

If adjustment feed, by formula calculate, wherein ξ ' _maxthe subtended angle of feed to subreflector; If the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ.

If adjustment subreflector, by formula calculate, wherein ξ " _maxthe subtended angle of focus to subreflector; If the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ;

(4) the axial defocusing d of calculating antenna _fthe phase difference ψ of the aperture field causing, sees through the aperture field after radome while obtaining axial defocusing:

(5) according to the aperture field seeing through after radome while calculating axial defocusing not, the far field F ' (θ, φ) of band cover antenna, draws far-field pattern T ₂, and from this far-field pattern, extract maximum field strength G ₂, the first from left secondary lobe L ₂, an and right secondary lobe R ₂these electrical performance indexes;

(6) during according to axial defocusing, see through the rear aperture field of radome while calculating axial defocusing, " (θ, φ) draws far-field pattern T to the far field F of band cover antenna ₃, and from this far-field pattern, extract maximum field strength G ₃, the first from left secondary lobe L ₃with a right secondary lobe R ₃these electrical performance indexes;

(7) the far-field pattern T obtaining in contrast step (1), (5), (6) ₁, T ₂, T ₃with corresponding electrical performance indexes, the change amount to antenna electric performance index after calculating covering, and calculate the change amount of after axial defocusing, band being covered to the electrical performance indexes of antenna system;

(8) according to the requirement on electric performance of Antenna Design, judge whether the electrical performance indexes change amount of system meets preset requirement after covering and axial defocusing, if met, export the far-field pattern T obtaining in step (1), (5), (6) ₁, T ₂, T ₃with corresponding electrical performance indexes; Otherwise, to axial defocusing amount d _ffinely tune, and repeating step (4) is to step (8), until result meets the demands.

The present invention is owing to adopting the axial defocusing of feed to compensate the phase distortion of covering aft antenna aperture field, thereby compared with prior art, improved the electrical property of band cover antenna system.

Brief description of the drawings

Fig. 1 is the general flow chart of realizing of the present invention;

Fig. 2 calculates the sub-process figure that sees through the aperture field after radome in the present invention;

Fig. 3 is the variable schematic diagram of single reflector antenna;

Fig. 4 is the variable schematic diagram of dual reflector antenna;

Fig. 5 is the structure chart of dielectric interlayer formula radome;

Fig. 6 is the cross section structure schematic diagram of the C interlayer radome in Fig. 5;

Fig. 7 is the far-field pattern without hooded antenna before and after cover antenna, axial defocusing.

Embodiment

Referring to accompanying drawing, the present invention is described in further detail.

With reference to Fig. 1, concrete steps of the present invention are as follows:

Step 1, calculates Antenna Far Field according to the known aperture field of antenna.

(1a) according to known antenna aperture field distribution calculate the far field F (θ, φ) of antenna:

Wherein, ρ, be taking bore face center as initial point, be based upon the polar coordinates in bore face, θ, φ are the spherical coordinates taking the radome centre of sphere as initial point, λ is the wavelength of antenna, wherein f is operating frequency of antenna, and c is the light velocity, the area that s is integral unit;

(1b) draw far-field pattern T according to gained Antenna Far Field F (θ, φ) ₁, and from this far-field pattern, extract electrical performance indexes, i.e. maximum field strength G ₁, the first from left secondary lobe L ₁with a right secondary lobe R ₁.

Step 2, calculates the aperture field seeing through after radome.

With reference to Fig. 2, being implemented as follows of this step:

(2a) in commercial model analysis software, set up the geometrical model of dielectric interlayer formula radome according to the version of radome, it is λ that the grid length of side is set, and model is carried out to grid division;

(2b), according to the structural parameters of radome and material parameter, calculate the transmission coefficient at each point place on radome by transmission line theory

(2b1), according to the aperture field of the geometry of radome and incident, obtain the incidence angle θ at each point place on radome _mwith polarizing angle φ _m;

On the direction of electromagnetic wave incident ray and radome, the angle of other unit of incidence point place normal direction is incidence angle θ _m, above-mentioned incident ray and other unit's normal have formed plane of incidence, and the polarised direction of electromagnetic wave electric field and the angle of plane of incidence are polarizing angle φ _m;

(2b2) according to the thickness d of covering, relative dielectric constant ε _r, losstangenttanδ, calculate the horizontal polarization component transmission coefficient at each point place on radome with perpendicular polarization component transmission coefficient

${\stackrel{\·}{T}}_H=\frac{2}{\stackrel{\·}{A}+{\stackrel{\·}{B}}_H+{\stackrel{\·}{C}}_H+\stackrel{\·}{D}}=T_H{e}^{-j{\mathrm{\η}}_H}$

${\stackrel{\·}{T}}_V=\frac{2}{\stackrel{\·}{A}+{\stackrel{\·}{B}}_V+{\stackrel{\·}{C}}_V+\stackrel{\·}{D}}=T_V{e}^{-j{\mathrm{\η}}_V}$

Wherein, $\stackrel{\·}{A}=\mathrm{ch}\left(j\stackrel{\·}{V}d\right),$ ${\stackrel{\·}{B}}_H=\frac{{\stackrel{\·}{Z}}_{1H}\mathrm{sh}\left(j\stackrel{\·}{\mathrm{Vd}}\right)}{Z_H},$ ${\stackrel{\·}{B}}_V=\frac{{\stackrel{\·}{Z}}_{1V}\mathrm{sh}\left(j\stackrel{\·}{V}d\right)}{Z_V},$ ${\stackrel{\·}{C}}_H=\frac{Z_H\mathrm{sh}\left(j\stackrel{\·}{V}d\right)}{{\stackrel{\·}{Z}}_{1H}},$

${\stackrel{\·}{C}}_V=\frac{Z_V\mathrm{sh}\left(j\stackrel{\·}{V}d\right)}{{\stackrel{\·}{Z}}_{1V}},$ $\stackrel{\·}{D}=\mathrm{ch}\left(j\stackrel{\·}{V}d\right),$ $\stackrel{\·}{V}=\frac{2\mathrm{\π}}{\mathrm{\λ}}\sqrt{{\stackrel{\·}{\mathrm{\ϵ}}}_r-{\sin }^2{\mathrm{\θ}}_M},$ ${\stackrel{\·}{Z}}_{1H}=\sqrt{{\stackrel{\·}{\mathrm{\ϵ}}}_r\frac{{\sin }^2{\mathrm{\θ}}_M}{{\stackrel{\·}{\mathrm{\ϵ}}}_r}},$

${\stackrel{\·}{Z}}_{1V}=\frac{1}{\sqrt{{\stackrel{\·}{\mathrm{\ϵ}}}_r-{\sin }^2{\mathrm{\θ}}_M}},$ ${\stackrel{\·}{\mathrm{\ϵ}}}_r={\mathrm{\ϵ}}_r(1-j\tan \mathrm{\δ}),$ Z _H=cosθ _M， $Z_V=\frac{1}{{\cos \mathrm{\θ}}_M},$ These parameters are intermediate variable; T _h, T _vbe respectively mould value, η _h, η _vbe respectively phase place;

(2b3) after arbitrary electromagnetic wave incident cover wall, can be decomposed into perpendicular polarization and horizontal polarization wave component, mould value and the phase place of the transmission coefficient of these two components are all inconsistent, therefore line polarization wave will deteriorate to elliptically polarised wave after by radome, according to horizontal polarization component transmission coefficient with perpendicular polarization component transmission coefficient obtain the transmission coefficient of equivalent main pole polarization component:

${\stackrel{\·}{T}}_M=\sqrt{T_H^2{\cos }^4{\mathrm{\φ}}_M+T_V^2{\sin }^4{\mathrm{\φ}}_M+{2T}_H{T}_V\cos ({\mathrm{\η}}_H-{\mathrm{\η}}_V){\cos }^2{\mathrm{\φ}}_M}\•e^{-j({\mathrm{\η}}_H-\mathrm{\α})},$

Wherein, $\mathrm{\α}=\arctan \frac{T_V{\sin }^1{\mathrm{\φ}}_M\sin ({\mathrm{\η}}_H-{\mathrm{\η}}_V)}{T_H{\cos }^2{\mathrm{\φ}}_M+T_V\cos ({\mathrm{\η}}_H-{\mathrm{\η}}_V){\sin }^2{\mathrm{\φ}}_M}$ For intermediate variable;

(2c) will incide aperture field on cover body and be multiplied by the transmission coefficient of its corresponding point position, calculate the aperture field seeing through after radome:

Step 3, the initial adjustment amount of calculating axial defocusing.

Reflector antenna has two types of single reflecting surface, double-reflecting faces, for single reflector antenna, can only realize axial defocusing by adjusting feed, for dual reflector antenna, both can adjust feed, also can adjust subreflector.

For single reflector antenna as shown in Figure 3, its initial adjustment amount is:

wherein Δ η _tthe poor of the phase place maximum of transmission coefficient and minimum value, ξ _maxit is parabola bore subtended angle;

In the present invention, think that axial defocusing only can affect the PHASE DISTRIBUTION of antenna aperture field, can not exert an influence to the amplitude distribution of aperture field, in fact, axial defocusing amount hour, the impact that bore field amplitude is distributed can be ignored, and in the time that axial defocusing amount is greater than 0.1 λ, the impact that axial defocusing distributes on bore field amplitude can not be ignored.Therefore in order to ensure the compensating action of axial defocusing, if the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ;

For dijection surface antenna as shown in Figure 4, the calculating of its initial adjustment amount is undertaken by following two kinds of modes:

If adjustment feed, presses formula calculate, wherein ξ ' _maxthe subtended angle of feed to subreflector; In order to ensure the compensating action of axial defocusing, if the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ.

If adjustment subreflector, presses formula calculate, wherein ξ " _maxthe subtended angle of focus to subreflector; In order to ensure the compensating action of axial defocusing, if the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ;

In the time that the axial defocusing amount of feed and subreflector is identical, the transmission coefficient phase difference that the latter can compensate is much larger than the former, therefore if when transmission coefficient phase difference is larger, can only realize axial defocusing compensation by adjusting subreflector.But it is more convenient sometimes may to adjust feed, when transmission coefficient phase difference hour, also can realize axial defocusing compensation by adjusting feed.In use, according to physical condition choice for use feed axial defocusing or subreflector axial defocusing.

Step 4, sees through the aperture field after radome while calculating axial defocusing.

(4a) calculate according to antenna type the aperture field phase difference that axial defocusing causes:

For single reflector antenna as shown in Figure 3, its axial defocusing d _fthe phase difference ψ of the aperture field causing is:

wherein ξ is focal point to the line of any and the angle of parabolic axis on parabola;

For dijection surface antenna as shown in Figure 4, calculate axial defocusing d _fthe phase difference ψ of the aperture field causing has two kinds of formula:

If adjustment feed, presses formula calculate, wherein ξ ' is feed to the line of any and the angle of subreflector axis on subreflector;

If adjustment subreflector, presses formula calculate, wherein ξ and " be focal point to the line of any and the angle of subreflector axis on subreflector;

(4b) according to the aperture field seeing through after radome aperture field phase difference ψ with axial defocusing causes, sees through the aperture field after radome while calculating axial defocusing:

Step 5, the far field of band cover antenna while calculating axial defocusing not.

(5a) according to the aperture field seeing through after radome the far field F ' (θ, φ) of band cover antenna while calculating axial defocusing not:

(5b) draw far-field pattern T according to gained Antenna Far Field F ' (θ, φ) ₂, and from this far-field pattern, extract maximum field strength G ₂, the first from left secondary lobe L ₂with a right secondary lobe R ₂these electrical performance indexes.

Step 6, the far field of band cover antenna while calculating axial defocusing.

(6a) during according to axial defocusing, see through the rear aperture field of radome the far field F of band cover antenna while calculating axial defocusing " (θ, φ):

(6b) according to gained Antenna Far Field F, " (θ, φ) draws far-field pattern T ₃, and from this far-field pattern, extract maximum field strength G ₃, the first from left secondary lobe L ₃with a right secondary lobe R ₃these electrical performance indexes.

Step 7, contrast is without far-field pattern and the electrical performance indexes of cover antenna, axial defocusing front and back belt cover antenna.

The Antenna Far Field directional diagram T obtaining in contrast step 1, step 5 and step 6 ₁, T ₂, T ₃with corresponding electrical performance indexes, the change amount to antenna electric performance index after calculating covering, and calculate the change amount of after axial defocusing, band being covered to the electrical performance indexes of antenna system:

(7a) the change amount to antenna electric performance index after calculating covering:

After covering, maximum field strength reduces value: Δ G ₁=G ₁-G ₂,

The first from left secondary lobe lift-off value after covering: Δ L ₁=L ₂-L ₁,

Covering rear right one secondary lobe lift-off value: Δ R ₁=R ₂-R ₁,

G in formula ₁, L ₁, R ₁be respectively from far-field pattern T ₁maximum field strength, the first from left secondary lobe and a right secondary lobe of middle extraction, G ₂, L ₂, R ₂be respectively from far-field pattern T ₂maximum field strength, the first from left secondary lobe and a right secondary lobe of middle extraction.

(7b) calculate the change amount of after axial defocusing, band being covered to the electrical performance indexes of antenna system:

After axial defocusing, maximum field strength reduces value: Δ G ₂=G ₂-G ₃,

The first from left secondary lobe lift-off value after axial defocusing: Δ L ₂=L ₃-L ₂,

Axial defocusing rear right one secondary lobe lift-off value: Δ R ₂=R ₃-R ₂,

G in formula ₂, L ₂, R ₂be respectively from far-field pattern T ₂maximum field strength, the first from left secondary lobe and a right secondary lobe of middle extraction, G ₃, L ₃, R ₃be respectively from far-field pattern T ₃maximum field strength, the first from left secondary lobe and a right secondary lobe of middle extraction.

Step 8, judges whether the electrical property of system meets the demands after covering and axial defocusing.

The electrical performance indexes change amount allowing according to antenna, judges whether the electrical performance indexes change amount of system meets preset requirement after covering and axial defocusing, if met, exports the far-field pattern T obtaining in step (1), (5), (6) ₁, T ₂, T ₃with corresponding electrical performance indexes; Otherwise, to axial defocusing amount d _ffinely tune, and repeating step (4) is to step (8), until result meets the demands.

Advantage of the present invention can further illustrate by following emulation experiment:

1. simulation parameter

The 40m dielectric interlayer formula radome of certain ground satellite communication station, structure as shown in Figure 5, adopts C interlayer form, as shown in Figure 6, single-layer skins thickness 0.5mm, single layer core layer thickness 50mm, total covering is that 2mm is thick, total sandwich layer is that 100mm is thick, skin material dielectric constant is 4.2, dielectric loss angle tangent is 0.026, and core material dielectric constant is 1.15, and dielectric loss angle tangent is 0.0098.Consider the impact of fiberglass scrap (bridge), its thickness is 30mm simultaneously, ignores bolt impact.Inside antenna is the dual reflector antenna of 26m bore, and amplification factor M is about 3, and burnt footpath ratio is 0.3, and design aperture field is that constant amplitude homophase distributes.Analysis frequency is 5.7GHz, the antenna placement of looking up to heaven.

2. emulation content and result

Under 5.7GHz frequency, calculate respectively the far field without hooded antenna before and after cover antenna, axial defocusing, to draw far-field pattern and extract electrical performance indexes, as shown in Figure 7, emulated data is as shown in table 1 for simulation result.

In Fig. 7, the far-field pattern that solid line is antenna, circular lines is the far-field pattern of the time band cover antenna without axial defocusing, astroid is the far-field pattern of band cover antenna while having axial defocusing.

The electrical performance indexes of table 1 system

As seen from Table 1, the maximum field strength of covering aft antenna reduces, and minor level raises, and after adopting axial defocusing to compensate, maximum field strength, the minor level of antenna all make moderate progress, and radome diminishes to the adverse effect of antenna electric performance.

Above-mentioned emulated data experiment showed, that the present invention can effectively improve the electrical property of band cover antenna system.

Claims (2)

1. the large-scale antenna cover electrical property compensation method based on axial defocusing, is characterized in that comprising the steps:

(1) according to known antenna aperture field calculate the far field F (θ, φ) of antenna, draw far-field pattern T ₁, and from far-field pattern, extract electrical performance indexes, i.e. maximum field strength G ₁, the first from left secondary lobe L ₁with a right secondary lobe R ₁;

(2) calculate the transmission coefficient at each point place on radome by transmission line theory and calculate through the aperture field after radome:

(3), according to the version of the transmission coefficient of radome and antenna, calculate the initial adjustment amount d of antenna axial direction defocusing _f:

For single reflector antenna, its initial adjustment amount is:

wherein Δ η _tthe poor of the phase place maximum of transmission coefficient and minimum value, ξ _maxit is parabola bore subtended angle; If the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ, λ is the wavelength of antenna, wherein f is operating frequency of antenna, and c is the light velocity;

For dijection surface antenna, the calculating of its initial adjustment amount is undertaken by following two kinds of modes:

If adjustment feed, by formula calculate, wherein ξ ' _maxthe subtended angle of feed to subreflector; If the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ.

If adjustment subreflector, by formula calculate, wherein ξ " _maxthe subtended angle of focus to subreflector; If the d calculating _fbe greater than 0.1 λ, make d _fequal 0.1 λ;

(4) the axial defocusing d of calculating antenna _fthe phase difference ψ of the aperture field causing, sees through the aperture field after radome while obtaining axial defocusing:

(5) according to the aperture field seeing through after radome while calculating axial defocusing not, the far field F ' (θ, φ) of band cover antenna, draws far-field pattern T ₂, and from this far-field pattern, extract maximum field strength G ₂, the first from left secondary lobe L ₂, an and right secondary lobe R ₂these electrical performance indexes;

(6) during according to axial defocusing, see through the rear aperture field of radome while calculating axial defocusing, " (θ, φ) draws far-field pattern T3, and from this far-field pattern, extracts maximum field strength G the far field F of band cover antenna ₃, the first from left secondary lobe L ₃with a right secondary lobe R ₃these electrical performance indexes;

(7) the far-field pattern T obtaining in contrast step (1), (5), (6) ₁, T ₂, T ₃with corresponding electrical performance indexes, the change amount to antenna electric performance index after calculating covering, comprising:

After covering, maximum field strength reduces value: Δ G ₁=G ₁-G ₂,

The first from left secondary lobe lift-off value after covering: Δ L ₁=L ₂-L ₁,

Covering rear right one secondary lobe lift-off value: Δ R ₁=R ₂-R ₁,

Wherein G ₁, L ₁, R ₁be respectively from far-field pattern T ₁maximum field strength, the first from left secondary lobe and a right secondary lobe of middle extraction, G ₂, L ₂, R ₂be respectively from far-field pattern T ₂maximum field strength, the first from left secondary lobe and a right secondary lobe of middle extraction; And the change amount of after calculating axial defocusing, band being covered the electrical performance indexes of antenna system, comprising:

After axial defocusing, maximum field strength reduces value: Δ G ₂=G ₂-G ₃,

The first from left secondary lobe lift-off value after axial defocusing: Δ L ₂=L ₃-L ₂,

Axial defocusing rear right one secondary lobe lift-off value: Δ R ₂=R ₃-R ₂,

Wherein G ₂, L ₂, R ₂be respectively from far-field pattern T ₂maximum field strength, the first from left secondary lobe and a right secondary lobe of middle extraction, G ₃, L ₃, R ₃be respectively from far-field pattern T ₃maximum field strength, the first from left secondary lobe and a right secondary lobe of middle extraction;

(8) according to the requirement on electric performance of Antenna Design, judge whether the electrical performance indexes change amount of system meets preset requirement after covering and axial defocusing, if meet, export the far-field pattern T obtaining in step (1), (5), (6) ₁, T ₂, T ₃with corresponding electrical performance indexes; Otherwise, to axial defocusing amount d _ffinely tune, and repeating step (4) is to step (8), until result meets the demands.

2. the large-scale antenna cover electrical property compensation method based on axial defocusing according to claim 1, is characterized in that the axial defocusing d of the described calculating antenna of step (4) _fthe phase difference ψ of the aperture field causing, is calculated as follows according to antenna type:

For dijection surface antenna, calculate axial defocusing d _fthe phase difference ψ of the aperture field causing has two kinds of formula:

If adjustment feed, by formula calculate, wherein ξ ' is feed to the line of any and the angle of subreflector axis on subreflector;

If adjustment subreflector, by formula calculate, wherein ξ and " be focal point to the line of any and the angle of subreflector axis on subreflector.