CN104377457B - Method for designing near-field uniform-wave-beam millimeter wave antenna - Google Patents

Abstract

The invention belongs to the technical field of millimeter wave antennas. The problems that near-field wave-beam distribution fluctuation of a millimeter aperture antenna in various application fields is violent and goes against practical application, and an efficient uniform-wave-beam millimeter antenna designing method does not exist at present are solved. By the method for designing the near-field uniform-wave-beam millimeter wave antenna, a millimeter wave antenna with uniform wave beams in a near-field region can be designed step by step. The method for designing the near-field uniform-wave-beam millimeter wave antenna can be widely used for fields with beamforming requirements on near-field wave beam distribution such as millimeter wave plasma heating antennas, millimeter short-range communication, radiofrequency recognition and millimeter wave imaging.

Description

A kind of near-field uniform wave beam millimeter wave antenna method for designing

Technical field

Millimeter wave antenna field of the present invention, specifically refers to a kind of near-field uniform wave beam millimeter wave antenna method for designing.

Background technology

The far-field energy and wave beam distribution character of antenna is only relevant with direction, therefore can describe far field using directional diagram Regularity of energy distribution.But in millimeter wave antenna technical field, it is due to electromagnetic wavelength very short (1mm～10mm), many to apply (such as：Millimeter wave plasma heating, mm-wave imaging/detection, millimeter wave short range communication, RF identification etc.) all concentrate on millimeter The near-field region of wave antenna, due to Fei Nier diffraction overlays, the wave beam and Energy distribution in the near-field region is sufficiently complex, energy Acutely shake with distance change, simply can not be described with directional diagram and design its regularity of distribution.Wish near in above-mentioned application Field millimeter wave wave beam is all more uniform in the range of certain distance, and not yet has a kind of effective method equal to design near field at present The millimeter wave antenna of even wave beam.

The content of the invention

It is an object of the invention to provide a kind of near-field uniform wave beam millimeter wave antenna method for designing, for providing a kind of height Effect, accurate near-field uniform wave beam millimeter wave antenna method for designing, solve the design of current near field shaped-beam millimeter wave antenna A difficult problem.

The present invention for achieving the above object, according to the theoretical formula being derived by, realizes mouth face Electric Field Distribution function to closely Fast transforms between the axis Electric Field Distribution function of field, and then adopt the Converse solved given near field wave beam distribution situation of alternative manner Under the field distribution of corresponding mouth face, adopt quasi-optical method design reflector antenna face type to produce the mouth face point that iteration is comprehensively obtained Cloth, finally produces power density and wave beam radius along the uniform wave beam of lip pencil that distance is basically unchanged in near-field region.

The specific number for setting up near-field uniform wave beam millimeter wave antenna mouth face Electric Field Distribution and near field axis Electric Field Distribution Model and mapping relations between the two are learned, the mapping relations are realized between mouthful face field distribution and the distribution of near field axis back and forth Rapidly and efficiently convert.

The Converse solved method of Antenna aperture field is established based on the mapping relations, can be according to required near field wave beam point The Converse solved mouth face Electric Field Distribution with designing antenna of cloth characteristic.

To solve the mouth face Electric Field Distribution that obtains abstract be to be made up of the quasi-optical ray cluster that gather/defocuses by described, by design instead Penetrate surface antenna face type obtain it is described it is quasi-optical gather/defocus ray cluster, so as to the mouth face Electric Field Distribution described in producing, and then near field Region forms the uniform wave beam of design.

If the near field wave beam for obtaining is less than the desired spatial characteristics of foot, return b is walked and is continued cycling through iteration, otherwise then Exit circulation and complete the Converse solved of Aperture field distribution A (r).

In sum, as a result of above-mentioned technical proposal, the invention has the beneficial effects as follows：By to bore antenna near-field The in-depth analysis of diffraction theory, realize first mouthful face field distribution and near field axis distribution between Fast transforms, and as Basis, gives the Converse solved method in mouth face based on only phase iteration and the mouth face phase place realization side based on poly- scattered angle ray cluster Method, obtains power density and wave beam radius all very using the near-field uniform wave beam millimeter wave antenna that the method is designed near field Uniform millimeter wave wave beam.The method of the present invention can be widely used for designing millimeter wave plasma heating antenna, millimeter wave short range Communication, RF identification and mm-wave imaging etc. are distributed with the field of figuration requirement near field wave beam.

Description of the drawings

Examples of the present invention will be described by way of reference to the accompanying drawings, wherein：

Fig. 1 is circular aperture antennas near field diffraction pattern geometric representation；

Fig. 2 is that axis Electric Field Distribution F (z) mapping relations schematic diagram is arrived in mouthful face Electric Field Distribution f (r)；

Fig. 3 is the Converse solved Aperture distribution flow chart of steps of iteration；

Fig. 4 is the comprehensive mouth face field intensity for obtaining and PHASE DISTRIBUTION；

Fig. 5 is the power density distribution on the axis of near field；

Fig. 6 is that the quasi-optical of special mouth face PHASE DISTRIBUTION realizes principle；

Fig. 7 is given mouth face amplitude distribution；

Fig. 8 is that iteration is inverse solves the mouth face PHASE DISTRIBUTION for obtaining；

Fig. 9 is mouthful corresponding focus position of face different radii and a diapoint position；

Figure 10 is the major and minor face face type that figuration is calculated；

Figure 11 is the near field beam power density scattergram that test is obtained.

Specific embodiment

By the border uniqueness theorem of electromagnetic field, antenna is substantially dependent upon Antenna aperture in the radiation field distribution of free space On distribution, for the circular aperture reflector antenna studied by this problem, the electric field space distribution in its near field domain can be by antenna opening Field integral on footpath is obtained, as shown in figure 1, being represented by with Line Integral：

In formula：R is Near-field observation point position；For the point on mouth face；A is Antenna aperture；E_aFor mouth face Electric Field Distribution.

Round mouth surface antenna mouth face Electric Field Distribution for it is angular it is rotationally symmetrical in the case of, the electricity on our Z axis of concern Field distribution can be reduced to expression formula：

Can see, by (2) although formula can obtain the Electric Field Distribution on axis, meter from the field distribution of mouth face by integration Calculation speed is very slow, and what is more important cannot be obtained on Antenna aperture by desired axis, Electric Field Distribution E (z) is Converse solved Electric Field Distribution E_a(r).Therefore, next section from the integral expression of bore Electric Field Distribution to axis near field distribution, (visit by 2)s The method that rope can realize mutual Fast transforms between Fig. 2 medium calibers distribution f (r) and near field axis Electric Field Distribution F (z).

If the Fast transforms between F (z) and f (r) can be realized, so that it may inversely ask by iteration opposite surface field f (r) Solution.Therefore from formula, (2)s, exploration can be realized mutually quick between Aperture distribution f (r) and near field axis Electric Field Distribution F (z) The method of conversion.Make t=r², then formula (2) be transformed to：

In the region of Z ＞ ＞ r, can be rightItem carries out Taylor expansion and only retains single order item approximately, is expressed as：

Then integral formula (3) abbreviation is：

Make k/2z=p,Then the following expression formula consistent with Fourier transformation form can be obtained by formula (5)：

Round mouth face Electric Field Distribution f is just realized using fast Fourier transform (FFT) by formula (6)_t(t) and near field axis electricity Field distribution F_pMutual Fast transforms between (p).

On the basis of quick mutual conversion of the Aperture distribution near field axis Electric Field Distribution is realized, far field figuration side is used for reference To " Phase Only (only phase) " the Iterative Design method in figure synthesis, with MATLAB language developments, millimeter wave antenna near field is assigned Shape wave beam synthesizer.The PHASE DISTRIBUTION of " Phase Only " iteration integrated approach only opposite surface is optimized, and amplitude distribution Keep fixing, the characteristics of this takes full advantage of reflector antenna phase adjusted and facilitates, reduce the design difficulty of feed, realize stream Journey is as shown in figure 3, specific flow process realizes that step can be expressed as：

A. initial mouth face amplitude distribution | A (r) | and PHASE DISTRIBUTION P are given_A(r)；

B. by formula (6), using FFT by Electric Field Distribution F in Electric Field Distribution A (r) Fast transforms of bore near field axis (z)；

C. F (z) is modified according to desired axis Electric Field Distribution, wherein only changes amplitude | F (z) |, keep F (z) PHASE DISTRIBUTION it is constant；

D. the axis Electric Field Distribution for being obtained by amendmentJing IFFT switch back to corresponding Aperture distribution f (r)_i+1；

E. keep A (r)_i+1Phase invariant, amplitude are changed to initial magnitude distribution | A (r) |；

If the near field wave beam for obtaining is less than the desired spatial characteristics of foot, return b is walked and is continued cycling through iteration, otherwise then Exit circulation and complete the Converse solved of Aperture field distribution A (r).

Using the 95GHz reflector antenna mouths of a diameter of 1.2m of near field shaped-beam mouth face integrated approach opposite surface for proposing Face has carried out mouth face synthesis, and desired target is that the power density holding on axis in 30m～100m distance ranges is for about 2.5mW/cm², given mouth face amplitude distribution drops to the Gauss distribution of -10dB for edge, and irradiation power is 5W, and iteration is obtained Mouth face amplitude and PHASE DISTRIBUTION as shown in figure 4, amplitude distribution is determined by feed, PHASE DISTRIBUTION is obtained by comprehensive Design program, The adjustment of phase place can be realized by the face type of primary reflection surface.

Fig. 5 is the beam power density distribution in the domain of near field on axis, it can be seen that in desired 25m～100m distances In the range of, radiation field axis power density is between 2.5mW/cm²～2.7mW/cm²Between, unevenness is less than 10%.

Additionally, we also pay close attention to the uniformity of wave beam radius distance vertically, uniform wave beam millimeter wave antenna and focusing side The near field power density distribution contrast of formula, it can be seen that the transmitting antenna comprehensively obtained with the comprehensive theory of proposition and method its Beam power density and radius are all very uniform in very large range, compare without focusing or focusing anteena, and the antenna for comprehensively obtaining exists Near field generates the good pencil type beam of beam feature, does not significantly fluctuate or too high power density focus point.

Mouthful face Electric Field Distribution can split-phase bit distribution and amplitude distribution two steps realize that mouth face phase place realizes principle as schemed Shown in 6, according to optical principle, the direction of propagation of quasi-optical ray is the normal orientation of equiphase surface, therefore, specific phase is just distributed Can regard as and be made up of the ray cluster for much focusing on and defocus, just these ray clusters are produced using geometrical optics approach design reflecting surface Expectation PHASE DISTRIBUTION can be formed.

In Fig. 6, poly- (dissipating) focal position of ray is blurted out the different of face radial position and is changed, it is therefore desirable to by reflecting surface Antenna Design is at the different radii of mouth face have different focusing and defocus properties, can obtain mouthful face phase place point by formula (7) Cloth φ (r) and focal position Z_fCorresponding relation：

The control of mouth face amplitude distribution is the θ with ray from feed_sSet out the desired aperture position point r of arrival at angle_aTo realize , according to feed output and the equal principle of mouth face power, θ_sWith r_aRelation should be met：

In formula, f (θ) is feed directional diagram；P (r) is distributed for mouth surface power density；Θ s are cut to feed for subreflector Obtain angle；R_aFor mouth radius surface.

Therefore, to realize that mouthful control of face amplitude is accomplished by first solving r_aWith θ_sCorresponding relation, order：

Then formula (9) abbreviation is：

To formula (10) derivation, can obtain：

According to formula (11) just by given feed directional diagram f (θ) and mouth surface power density distribution P (r), by numerical method Solve differential equation group and obtain θ_sWith r_aRespective function relation r_a(θ_s)。

Specific embodiment

Using method for designing of the present invention, a set of antenna for the research of principle confirmatory experiment is devised, mesh is designed It is designated as：

A. operating frequency:95GHz；

B. bore Ф 300mm；

C. feed-in power:45mW；

D. uniform beam center power density:2.1mW/cm2；

E. the distance range of uniform wave beam:1.2m～4.0m.

Synthesis is carried out to the mouth face of Ф 300mm using near field shaped-beam integrated approach, and integration objective is 1.2m～4.0m Distance range interior axle linear power density is about 2.1mW/cm².Given mouth face amplitude distribution is as shown in fig. 7, mouth face amplitude is throwing Thing type is distributed, and edge illumination is approximately 0.

The mouth face PHASE DISTRIBUTION for obtaining is as shown in Figure 8, it can be seen that be distributed as similar focusing of the phase place in aperture center Distribution, and have periodic ripple at bore edge, intuitively understand it is that wave beam is modulated.Can see, antenna exists Power density concordance good design object is realized in the range of 1.2m～4.1m.

After mouthful face electric field magnitude and PHASE DISTRIBUTION is aware of, extrapolate using the Plane wave spectrum based on 2D-FFT technologies Obtain the wave beam distribution near field, it is seen that the radius of wave beam also keeps basically identical in the target area of 1m～4.0m.Therefore, only Electric field magnitude and PHASE DISTRIBUTION are formed in mouth face by the Shape design of antenna, it is possible near field produce power density and Wave beam radius is all than more uniform pencil type beam.

The corresponding relation of mouthful face PHASE DISTRIBUTION and focal position can be calculated by formula (7), therefore, mouth face different radii Corresponding focus position and diapoint position relationship are as shown in Figure 9.

The figuration calculation procedure of interarea and minor face based on Matlab programming, according to algorithm above obtain it is major and minor The face type in face is as shown in Figure 10.Wherein the feed phase heart is located at zero, minor face centre distance feed 135mm, interarea center Upper inclined 290mm, wave beam exit direction are+Z-direction, test the near field beam power density distribution for measuring as shown in figure 11.

The invention is not limited in aforesaid specific embodiment.The present invention is expanded to and any is disclosed in this manual New feature or any new combination, and the arbitrary new method that discloses or the step of process or any new combination.

Claims (5)

1. a kind of near-field uniform wave beam millimeter wave antenna method for designing, it is characterised in that the method is comprised the following steps：

Set up near-field uniform wave beam millimeter wave antenna mouth face Electric Field Distribution and near field axis Electric Field Distribution mathematical model and both Between mapping relations, the mapping relations realize mouthful face field distribution and near field axis distribution between rapidly and efficiently becoming back and forth Change；

The Converse solved method of Antenna aperture field is established based on the mapping relations, can be special according to required near field wave beam distribution Property Converse solved and designing antenna mouth face Electric Field Distribution；

To solve the mouth face Electric Field Distribution that obtains abstract be to be made up of the quasi-optical ray cluster that gather/defocuses by described, by design reflecting surface The face type of antenna obtain it is described it is quasi-optical gather/defocus ray cluster, so as to the mouth face Electric Field Distribution described in producing, and then near field region Domain forms the uniform wave beam of design；

Mouth face field distribution and near field axis distribution between mapping relations be：

$F_p\left(p\right)=F\left(z\right){\mathrm{ze}}^{jkz}=\underset{0}{\overset{R^2}{\∫}}{f}_t\left(t\right)e^{-jpt}dt,$

Wherein：Z is axial distance, and F (z) is axis Electric Field Distribution, F_p(p) be deformation after axis Electric Field Distribution, f_tT () is mouth Face electric field radial distribution, wherein t=r², r is radial direction radius；

The Converse solved method is concretely comprised the following steps：

Step one, given initial mouth face amplitude distribution | A (r) | and PHASE DISTRIBUTION P_A(r)；

Step 2, by mapping relations, using FFT by the electric field in Electric Field Distribution A (r) Fast transforms of bore near field axis point Cloth F (z)；

Step 3, F (z) is modified according to desired axis Electric Field Distribution, wherein only changes amplitude | F (z) |, keep F (z) PHASE DISTRIBUTION it is constant；

Step 4, the axis Electric Field Distribution obtained by amendmentJing IFFT switch back to corresponding Aperture distribution f (r)_i+1；

Step 5, holding A (r)_i+1Phase invariant, amplitude are changed to initial magnitude distribution | A (r) |；

If step 6, the near field wave beam for obtaining are less than the desired spatial characteristics of foot, return second step and continue cycling through iteration, instead Circulation of then exiting complete the Converse solved of Aperture field distribution A (r).

2. a kind of near-field uniform wave beam millimeter wave antenna method for designing according to claim 1, it is characterised in that the mouth Face Electric Field Distribution is realized by two steps of PHASE DISTRIBUTION and amplitude distribution.

3. a kind of near-field uniform wave beam millimeter wave antenna method for designing according to claim 2, it is characterised in that the phase Bit distribution is made up of the ray cluster for much focusing on and defocus, and the focus point of ray, diapoint position are blurted out face radial position It is different and change.

4. a kind of near-field uniform wave beam millimeter wave antenna method for designing according to claim 3, it is characterised in that the mouth Face PHASE DISTRIBUTION φ (r) and focal position Z_fCorresponding relation be：

$Z_f=\frac{r}{tan\left(arcsin\right(\frac{d\mathrm{\φ}\left(r\right)/k}{dr}))}$

Wherein：φ (r) is mouth face PHASE DISTRIBUTION, and k is wave number, and r is mouth face diameter to radius.

5. a kind of near-field uniform wave beam millimeter wave antenna method for designing according to claim 2, it is characterised in that the width Degree distribution is the θ with ray from feed_sSet out the desired aperture position point r of arrival at angle_aTo realize, the θ_sWith r_aShould meet with Lower relation：

$\frac{{\∫}_0^{{\mathrm{\θ}}_S}\mathrm{\θ}f\left(\mathrm{\θ}\right)d\mathrm{\θ}}{{\∫}_0^{{\mathrm{\Θ}}_S}\mathrm{\θ}f\left(\mathrm{\θ}\right)d\mathrm{\θ}}=\frac{{\∫}_0^{r_a}rP\left(r\right)dr}{{\∫}_0^{R_a}rP\left(r\right)dr}$

In formula, f (θ) is feed directional diagram；P (r) is distributed for mouth surface power density；Θ s are acceptance angle of the subreflector to feed； R_aFor mouth radius surface.