CN1299160A - Position-phase modulation method for lowering paraxial lobe of millimeter-wave planar diffraction antenna - Google Patents

Abstract

The invention relates to an improvement for the design method of millimetre wave plate antenna so as to resolve the problems of paraxial lobe electrical level increasing of direction figure and noise receiving from the lobes caused by discrete structure. Said inceiving from the lobes caused by discrete structure. Said invention method is to calculate characteristic structure parameters of antenna, lobe position needing to be pressed and pressing quatity; to set estimate functions of characteristic structure size and position; then to do calculation and analyse for the direction figure. Compared with prior art method, it has no energy loss. The gain of antenna is influnced in the minimum limit while the paraxial lobes of millimeter wave plate diffraction antenna are reduced by using the invention method.

Description

The position is the method for modulation reduction millimeter-wave planar diffraction antenna near in sidelobe mutually

The invention belongs to electronics and optical crossover scientific domain, relate to a kind of improvement the millimeter-wave planar antenna design method.

Common millimeter-wave planar diffraction antenna design process is traditional parabolic antenna continuous structure to be carried out discretization according to certain relation handle, and generally is the integral multiple that the position between each endless belt of discrete back is differed 2 π or 2 π.Contribution to each endless belt of far field point antenna on the axis is addition, therefore has the characteristics of gain height, good directionality, and the axial dimension of antenna obtains compression simultaneously.

As attached illustrated in figures 1 and 2, the amplitude limitation of the phase function φ (r) of traditional antenna is promptly formed the phase function φ (r) ' of planar diffraction antenna after ± α/2 scopes.α can get 2l π, and l is the integer more than or equal to 1.As, l=1, α=2 π: during l=2, a=4 π.This moment, theoretical diffraction efficiency all can reach 100%, resulting position phase form and the form equivalence fully mutually of traditional antenna position, thereby the focal position is identical with traditional antenna.The used electromagnetic level of diffraction that different is when l gets different values is time different.It during l=1 one-level; It during l=2 secondary or the like.The position forms a plurality of continuous respectively separately endless belt with three-dimensional relief structures on the surface of planar diffraction antenna in the compression back mutually, and the phase jump point is arranged between the different endless belt.Focal length is the position r of m phase jump point of the planar diffraction antenna of f _mFor: $r_m=\sqrt{2\mathrm{ml\λf}+m^2{l}^2{\mathrm{\λ}}^2}$ λ is an operation wavelength in the formula.L is big more, and the width of each endless belt is also just big more, and the thickness of planar diffraction antenna is also big more simultaneously.Generally get l=1, at this moment the thickness minimum: the thickness that removes sheet base external reflectance formula antenna equals 1/2 of operation wavelength; The thickness of transmission-type antenna equals that λ/(n-1), wherein n is the refractive index of transmission medium.Sometimes l adopts different numerical value in same antenna structure.Promptly get l=1 at interior ring.Arrived outer shroud, unlikely too small for guaranteeing the endless belt width, adopt the phase structure of l＞1.

The limitation of this flat plane antenna is, causes diffraction efficiency to descend owing to introduce discrete topology, and the near in sidelobe level of directional diagram raises.If incident wave is the equally distributed plane wave of the amplitude of normal incidence, antenna efficiency is 100%, ignores to absorb the equal loss, and then diffraction pattern first side-lobe energy on the planar diffraction antenna focal plane accounts for 9.1% of gross energy; Sidelobe level is-16.7dB: diffraction pattern first side-lobe energy on the desirable parabolic antenna focal plane accounts for 7.2% of gross energy; Sidelobe level is-16.9dB.

The objective of the invention is to solve discrete topology causes the near in sidelobe level of directional diagram to raise, cause from these secondary lobes and receive the into problem of noise, provide a kind of position to modulate mutually to each discrete endless belt, influence to Min. the gain of antenna simultaneously, reduce the method for millimeter-wave planar diffraction antenna near in sidelobe.

It is as follows to utilize the present invention to suppress near the method and the step of the secondary lobe of main lobe:

(1), the integral multiple that differs 2 π or 2 π according to the position carries out discretization to the parabolic antenna with continuous phase structure and handles, and tentatively obtains having the parameter of millimeter-wave planar antenna general features structure;

(2), calculate secondary lobe position and the compacting amount that needs are suppressed according to instructions for use;

(3), trace changes feature structural dimension parameter and the position that is obtained by step 1, sets up evaluation function, i.e. analytic expression between compacting amount and the feature structure variable adopts the method for approaching one by one that directional diagram is carried out computational analysis;

(4), after the side lobe levels of calculated direction figure reaches instructions for use, this moment feature structural dimension parameter can reduce millimeter-wave planar antenna near in sidelobe.

As long as we provide needed far-field pattern, perhaps during far field amplitude direction figure, just can calculate a phase modulation parameter in theory.But the actual directional diagram form of being asked can not be arbitrarily.At first the energy of far field construction is a conservation before and after the modulation, and desired directional diagram can not be violated this principle.In addition, the modulation parameter excursion can not be very big.

Good effect of the present invention is the design of the diffraction optics technology being introduced millimeter wave antenna, makes the millimeter wave antenna thin thickness, volume is little and in light weight, keeps simultaneously or improves its some performance, and the outward appearance of complanation makes it to install and adjust very convenient.Make flat plane antenna can adapt to the instructions for use of some particular surroundings.Adopt position phase modulation method to press secondary lobe to compare and do not have energy loss with existing method by control actinal surface field distribution reduction sidelobe level.The present invention selects suitable evaluation function, and contraposition phase modulation parameter is calculated, and searches out best position phase modulation parameter, the position mutually the several side lobe peaks in modulation front and back relatively see attached list 1, as can be seen, first and second secondary lobes of directional diagram are suppressed effectively.Main lobe width slightly increases, and the peak height of main lobe slightly descends, i.e. gain slightly descends.Illustrate to the invention provides the gain that a kind of Min. ground influences antenna, reduce the method for millimeter-wave planar diffraction antenna near in sidelobe simultaneously.

Description of drawings of the present invention;

Fig. 1 is the continuous phase structure of prior art antenna

Fig. 2 is that the prior art discrete processes is the phase structure of planar diffraction antenna

Fig. 3 comparison that to be the present invention distribute mutually with the prior art bits of modulation

Fig. 4 is the comparison of the present invention and prior art directional diagram

Fig. 5 is that focal length of the present invention is the embodiment of the flat plane antenna of infinity

Subordinate list 1 is the comparison of the present invention and the several side lobe peaks of prior art

Subordinate list 2 is variable quantities that modulate mutually the diverse location position of a kind of embodiment of invention

Subordinate list 3 is several main side lobe peak strength values calculated value comparative results before and after modulate mutually an embodiment of the present invention position.

A kind of embodiment of the present invention:

Be that focal length is the flat plane antenna of infinity as shown in Figure 5, it can equivalence be equally spaced diffraction grating.If the diffraction grating unit number is N, grating constant is d, and the width of each unit also is d.Field size on all unit is identical, and the position is also identical mutually.Selecting the center of grating is initial point, and then the greatest irradiation direction is on the vertical centering control separated time of this grating.The unit number N of grating can be an odd number, also can be even number, for general considerations is described, adopts following notation

When very little.At main lobe value normalization far field amplitude E ₀Phasic difference Δ β with the trace modulation _nThe distribution and expression formula be $\mathrm{\Δ}{\mathrm{\β}}_n=\frac{N}{\mathrm{\π}}{\∫}_0^{\mathrm{\π}}\frac{\mathrm{\β}}{\sin \mathrm{\β}}(E_0-E)\sin \mathrm{n\βd\β}---\left(3\right)$ Wherein, $\mathrm{\β}=\frac{\mathrm{\π}}{\mathrm{\λ}}d\sin \mathrm{\θ}----\left(4\right)$

The grating secondary lobe that distributes mutually such as constant amplitude is higher, can force down it with correction pulse at the maximum of secondary lobe, calculates the phase change amount that produces correction pulse by (3) formula then.It is 1,2,3 that the pulse sequence number is counted from initial point ... k, β _kBe the position of k pulse, α _kIntensity for pulse k.Impulse correction this moment item can be write as $E_0-E=\underset{k=1}{\overset{k}{\mathrm{\Σ}}}{a}_k\mathrm{\δ}(\mathrm{\β}-{\mathrm{\β}}_k)---\left(5\right)$ Wherein δ is a unit pulse function.Substitution (3) formula gets $\mathrm{\Δ}{\mathrm{\β}}_n=\frac{N}{\mathrm{\π}}\underset{k=1}{\overset{k}{\mathrm{\Σ}}}{a}_k\frac{{\mathrm{\β}}_k}{\sin {\mathrm{\β}}_k}\sin n{\mathrm{\β}}_k---\left(6\right)$

We are that example is observed the effect that adopts this method pressure secondary lobe with the one-dimensional grating with 10 unit.Distribute the mutually position of grating secondary lobe maximum such as constant amplitude is known.For foregoing one-dimensional grating, the position at the first six place is respectively N β=1.43 π, N β=2.46 π, N β=3.47 π, N β=4.48 π, N β=5.48 π and N β=6.48 π.The size of the maximum side lobe levels of its normalized amplitude is respectively 0.22,0.13,0.09,0.07,0.06 and 0.05.β then ₁=0.143 π, β ₂=0.246 π, β ₃=0.347 π, β ₄=0.448 π, β ₅=0.548 π and β ₆=0.648 π.Require the size of these six secondary lobes of compacting back all to reduce half.Substitution (3) formula has E ₀-E=-0.11 δ (β-0.143 π)+0.07 δ (β-0.2461 π)

-0.05δ(β-0.347π)+0.04δ(β-0.448π)

-0.03 δ (β-0.548 π)+0.02 δ (β-0.648 π) (7) substitution (6) formula gets $\mathrm{\Δ}{\mathrm{\β}}_n=\frac{10}{\mathrm{\π}}\[-0.11\·\frac{0.143\mathrm{\π}}{\sin 0.143\mathrm{\π}}\sin n\·0.143\mathrm{\π}+0.07\·\frac{0.246\mathrm{\π}}{\sin 0.246\mathrm{\π}}\sin n\·0.246\mathrm{\π}$ $-0.05\·\frac{0.347\mathrm{\π}}{\sin 0.347\mathrm{\π}}\sin n\·0.347\mathrm{\π}+0.04\·\frac{0.448\mathrm{\π}}{\sin 0.448\mathrm{\π}}\sin n\·0.448\mathrm{\π}$ $-0.03\·\frac{0.548\mathrm{\π}}{\sin 0.548\mathrm{\π}}\sin n\·0.547\mathrm{\π}+0.02\·\frac{0.648\mathrm{\π}}{\sin 0.648\mathrm{\π}}\sin n\·0.648\mathrm{\π}\]--\left(8\right)$

The Δ β that calculates _nValue is listed in table 2, and table 3 is position comparisons of the several main side lobe peak strength values result of calculations in modulation front and back mutually.

Claims (1)

1, a kind of position is modulated the method that reduces the millimeter-wave planar diffraction antenna near in sidelobe mutually, it is characterized in that:

(1), the integral multiple that differs 2 π or 2 π according to the position carries out discretization to the parabolic antenna with continuous phase structure and handles, and tentatively obtains having the parameter of millimeter-wave planar antenna general features structure;

(2), calculate secondary lobe position and the compacting amount that needs are suppressed according to instructions for use;

(3), trace changes feature structural dimension parameter and the position that is obtained by step 1, sets up evaluation function, i.e. analytic expression between compacting amount and the feature structure variable adopts the method for approaching one by one that directional diagram is carried out computational analysis;

(4), after the side lobe levels of calculated direction figure reaches instructions for use, this moment feature structural dimension parameter can reduce millimeter-wave planar antenna near in sidelobe.