CN113964549B - Design method and device of space sampling antenna based on interference cancellation - Google Patents
Design method and device of space sampling antenna based on interference cancellation Download PDFInfo
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Abstract
The invention provides a design method and a device of a space sampling antenna based on interference cancellation, belonging to the technical field of anti-interference sampling antennas, wherein the design method comprises the following steps: based on the analytic solution of the surface current distribution of the sampling antenna, the coupling degree between the main antenna and the sampling antenna is obtained by calculating the self-impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna; simultaneously analyzing a format directional diagram, and calculating an interference rejection ratio by a space sampling method; screening out the optimal number of sampling antennas by combining the constraint conditions of array antenna design; the analytical solution acquisition method for the surface current distribution of the sampling antenna comprises the following steps: correcting the dynamic field distribution generated by the current component by adopting the initial current distribution on the sampling antenna; and introducing a distribution parameter mean value which changes along the antenna position to represent the modified dynamic field distribution, and acquiring a single-wire lossy transmission line model equation so as to obtain an analytic solution of the surface current distribution of the sampling antenna. The invention can be used for the optimized design of various anti-interference sampling antennas of line antennas.
Description
Technical Field
The invention belongs to the technical field of anti-interference sampling antennas, and particularly relates to a method and a device for designing a space sampling antenna based on interference cancellation.
Background
The sampling antenna is a miniaturized antenna unit or array which is arranged around a main antenna, samples an interference source in space and is used for self-adaptive adjustment and synthesis cancellation of the interference cancellation device.
In the prior art, the design of the sampling antenna unit and the analysis of the interference cancellation algorithm are usually separated. For example, for radar anti-interference, a sampling antenna in an interference cancellation algorithm usually adopts ideal omnidirectional antenna simulation diagram data array optimization, and obviously, the method is not enough for guiding the actual sampling antenna structure design and only gives an ideal interference suppression condition from the perspective of algorithm optimization; aiming at ultra-short wave anti-interference, simulation directional diagram data of electromagnetic simulation software such as Ansys HFSS, CST Microwave Studio and the like are imported into an optimization algorithm in the prior art, although the method completes antenna design, the interference cancellation algorithm depends on the electromagnetic simulation software, optimization inefficiency is caused, and the characteristics of coupling degree between a main antenna and a sampling antenna, sampling antenna bandwidth and the like are difficult to explain theoretically. No theoretical model for quantitative evaluation of the antenna impedance, gain, pattern, mutual coupling to interference rejection characteristics has been found.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method and a device for designing a space sampling antenna based on interference cancellation, and aims to solve the problem that the prior art cannot comprehensively consider the design and performance characteristics of the sampling antenna in an optimized mode, so that the sampling antenna with the optimal performance meeting the actual requirement is very difficult to design.
In order to achieve the above object, in one aspect, the present invention provides a method for designing a spatial sampling antenna based on interference cancellation, including the following steps:
presetting a plurality of setting methods of the sampling antenna;
for each setting method, based on the analytic solution of the surface current distribution of the sampling antenna, the coupling degree between the main antenna and the sampling antenna is obtained by calculating the self impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna; meanwhile, a format directional diagram is analyzed based on an analytical solution of the surface current distribution of the sampling antenna, and an interference rejection ratio is calculated through a space sampling method;
based on the coupling degree and the interference rejection ratio corresponding to each setting method, screening out the number and the positions of the optimal sampling antennas by combining the constraint conditions of array antenna design, and completing the design of the space sampling antennas;
the method for obtaining the analytic solution of the surface current distribution of the sampling antenna comprises the following steps:
calculating initial current distribution on the sampling antenna according to a single-line lossless transmission line model equation;
modifying the dynamic field distribution generated by the current component in the single-wire lossless transmission line model equation in a mode of dividing the integral part of the dynamic field distribution by the initial current distribution and multiplying the non-integral part by the initial current distribution;
introducing a distribution parameter mean value which changes along the antenna position to represent the modified dynamic field distribution, and combining a Lorentz condition and an electromagnetic field boundary condition to obtain a single-wire lossy transmission line model equation;
and obtaining an analytic solution of the surface current distribution of the sampling antenna by combining a single-line lossy transmission line model equation with the boundary condition of the metal surface electromagnetic field.
The constraint conditions of the array antenna design in the invention comprise the space coverage range of the sampling antenna, the gain of the sampling antenna, the signal characteristics of an interference source, the suitability and the cost of the sampling antenna on an actual ship or vehicle-mounted platform.
Further preferably, the modified dynamic field distribution is:
F z (z)=jωμI(z)·∫0 l {[I(z′)/I(z)]·e jβz-′′/4πz′′}dz′
wherein the content of the first and second substances,jis the number of the imaginary numbers,ωin order to be the angular frequency of the frequency,μin order to have a magnetic permeability,I(z) Representing coordinate axeszIn the form of a function of the current distribution,I(z') denotes coordinatesz' where the numerical value of the current, [ integral ] is the sign of the integral,lfor the length of the dipole antenna to be,βin order to be a free-space propagation constant,z′′=sqrt[(z′-z)2+ρ 2]and isρThe radius of the dipole antenna is shown,dz' means toz' of (a);
further preferably, the single-line lossy transmission line model equation isəV(z)/əz=-jωL′·I(z)+E(z)，əI(z)/əz=-jωC′·V(z)；
Wherein the content of the first and second substances,əthe sign of the partial derivative is such that,V(z) Is the potential of a single line with a lossy transmission line,E(z) The source is represented by a representation of,C′=με/Lis capacitive reactance andεis the dielectric constant;L' is a distribution parameter that varies along the antenna position;μis magnetic permeability.
Further preferably, the method for obtaining the coupling degree between the main antenna and the sampling antenna includes the following steps:
obtaining a far-zone radiation field equation of the sampling antenna based on an analytic solution of the surface current distribution of the sampling antenna;
calculating the self-impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna based on a far-zone radiation field equation of the sampling antenna;
calculating a scattering matrix of the main antenna and the sampling antenna through the self-impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna;
and calculating the coupling degree between the main antenna and the sampling antenna based on the scattering matrixes of the main antenna and the sampling antenna.
Further preferably, the method for obtaining the interference rejection ratio comprises:
obtaining a far-zone radiation field equation of the sampling antenna based on an analytic solution of the surface current distribution of the sampling antenna;
acquiring a directional diagram of the sampling antenna through free space wave impedance, a far-zone radiation field of the sampling antenna and far-field position parameters of the sampling antenna;
acquiring signals received by a main antenna and a sampling antenna based on a sampling antenna directional diagram;
acquiring a space sampling antenna weight by adopting a minimum mean square criterion based on signals received by a main antenna and a sampling antenna;
and calculating the interference rejection ratio by combining the spatial sampling antenna weight and signals received by the main antenna and the sampling antenna.
Preferably, the interference rejection ratio is:
ICR=||S m -W opt S a ||2×||C m +N m ||2/||S m ||2/||C m +N m - W opt (C a +N a ) ||2
wherein | | | purple hair2In order to calculate the sign for the power,C m =c·f m (θ c , φ c )、S m =s·f m (θ s , φ s ) Respectively, interference signals and communication signals received by the main antenna,C a =c·f a (θ c , φ c )、S a =s·f a (θ s , φ s ) Respectively, interference signals and communication signals received by the space sampling array antenna,N m 、N a noise signals received by the main antenna and the sampling antenna respectively; sis a transmitted communication signal;cis a transmitted interference signal; f a (θ s , φ s ) To sample the antenna directionA drawing;f m (θ s , φ s ) Is the main antenna pattern;W opt are the spatially sampled antenna weights.
Further preferably, the method for acquiring the number of sampling antennas comprises:
determining the space coverage range of the sampling antenna according to the incoming wave direction of the interference source;
determining the gain of the sampling antenna according to the directional diagram data of the main antenna, the anti-interference tolerance and the interference sampling method;
according to the design principle of the array antenna, acquiring the relation between the number of sampling antennas and the anti-interference tolerance through the space coverage range, the gain and the signal characteristics of an interference source of the sampling antennas;
and selecting the optimal number of sampling antennas according to the relation between the number of sampling antennas and the anti-induction tolerance by combining the adaptability and the cost of the sampling antennas on the actual ship or vehicle-mounted platform.
In another aspect, the present invention provides an apparatus for designing a spatial sampling antenna based on interference cancellation, including:
the antenna setting module is used for presetting a plurality of setting methods of the sampling antenna;
the performance calculation module is used for acquiring the coupling degree between the main antenna and the sampling antenna by calculating the self-impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna based on the analytic solution of the surface current distribution of the sampling antenna for each setting method; meanwhile, analyzing a format directional diagram based on an analytical solution of the surface current distribution of the sampling antenna, and calculating an interference rejection ratio by a space sampling method;
the antenna design module is used for screening out the number and the positions of the optimal sampling antennas based on the coupling degree and the interference rejection ratio corresponding to each setting method and in combination with the constraint conditions of array antenna design, and completing the design of the space sampling antennas;
the surface current distribution acquisition module is used for acquiring an analytic solution of the surface current distribution of the sampling antenna, and the specific execution method comprises the following steps: calculating initial current distribution on the sampling antenna according to a single-line lossless transmission line model equation; correcting the dynamic field distribution generated by the current component in the single-line lossless transmission line model equation by adopting the initial current distribution on the sampling antenna; introducing a distribution parameter mean value which changes along the antenna position to represent the modified dynamic field distribution, and combining a Lorentz condition and an electromagnetic field boundary condition to obtain a single-wire lossy transmission line model equation; and obtaining an analytic solution of the surface current distribution of the sampling antenna by combining the single-line lossy transmission line model equation with the boundary condition of the metal surface electromagnetic field.
Further preferably, the modified dynamic field distribution is:
F z (z)=jωμI(z)·∫0 l {[I(z′)/I(z)]·e jβz-′′/4πz′′}dz′
wherein the content of the first and second substances,jis an imaginary number;ωis the angular frequency;μis magnetic permeability;I(z) Representing coordinate axeszA current distribution function;I(z') denotes coordinatesz' at the current value; integral sign;lis the dipole antenna length;βis the free space propagation constant;z′′=sqrt[(z′-z)2+ρ 2]and isρRepresents the radius of the dipole antenna;dz' means toz' of (a);
the single-line lossy transmission line model equation is as follows:
əV(z)/əz=-jωL′·I(z)+E(z)，əI(z)/əz=-jωC′·V(z)
wherein the content of the first and second substances,əa partial derivative symbol;V(z) A single line lossy transmission line potential;E(z) Representing a source;C′=με/Lis capacitive reactance andεis the dielectric constant;L' is a distribution parameter that varies along the antenna position.
Further preferably, the interference rejection ratio is:
ICR=||S m -W opt S a ||2×||C m +N m ||2/||S m ||2/||C m +N m - W opt (C a +N a ) ||2
wherein | | | purple hair2In order to calculate the sign for the power,C m =c·f m (θ c , φ c )、S m =s·f m (θ s , φ s ) Respectively, interference signals and communication signals received by the main antenna,C a =c·f a (θ c , φ c )、S a =s·f a (θ s , φ s ) Respectively, interference signals and communication signals received by the space sampling array antenna,N m 、N a noise signals received by the main antenna and the sampling antenna respectively; sandcrespectively a transmitted communication signal and an interference signal; f a (θ s , φ s ) Is a sampled antenna pattern;f m (θ s , φ s ) Is the main antenna pattern;W opt are the spatially sampled antenna weights.
Further preferably, the method for obtaining the coupling degree between the main antenna and the sampling antenna includes the following steps:
obtaining a far-zone radiation field equation of the sampling antenna based on an analytic solution of the surface current distribution of the sampling antenna;
calculating the self-impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna based on a far-zone radiation field equation of the sampling antenna;
calculating a scattering matrix of the main antenna and the sampling antenna through the self-impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna;
and calculating the coupling degree between the main antenna and the sampling antenna based on the scattering matrixes of the main antenna and the sampling antenna.
Preferably, the method for obtaining the interference rejection ratio comprises:
obtaining a far-zone radiation field equation of the sampling antenna based on an analytic solution of the surface current distribution of the sampling antenna;
acquiring a directional diagram of the sampling antenna through free space wave impedance, a far-zone radiation field of the sampling antenna and far-field position parameters of the sampling antenna;
acquiring signals received by a main antenna and a sampling antenna based on a sampling antenna directional diagram;
acquiring a space sampling antenna weight by adopting a minimum mean square criterion according to signals received by a main antenna and a sampling antenna;
and calculating the interference rejection ratio by combining the spatial sampling antenna weight and signals received by the main antenna and the sampling antenna.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
the method corrects the dynamic field distribution generated by the current component in the model equation of the single-line lossless transmission line, and constructs the model equation of the single-line lossy transmission line by combining the Lorentz condition and the boundary condition of the electromagnetic field; based on the basis, the analytic solution of the electromagnetic distribution on the surface of the sampling antenna is accurately obtained by adopting a single-line lossy transmission line model equation, so that the self impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna can be calculated, the distance between the main antenna and the sampling antenna can be optimized, the bandwidth characteristic of the antenna and the coupling degree of the main antenna and the sampling antenna can be theoretically analyzed, and therefore, the commercial electromagnetic software is not needed to be adopted for simulation analysis or test analysis, the analysis efficiency is improved, and the physical concept is clear.
According to the method, the analytic format directional diagram function can be further calculated through analytic solution of the surface current distribution of the sampling antenna, the optimal number of the sampling antennas is obtained through a space sampling method, and the interference suppression ratio is calculated.
The analytic solution analysis of the surface current distribution of the sampling antenna comprises the structural parameters such as the length and the radius of the antenna and the performance parameters such as impedance and gain, and can directly guide the specific design of the sampling antenna.
After the analytical solution of the surface current distribution of the sampling antenna is obtained, the established sampling antenna analysis method has integrity and universality, covers the design of the sampling antenna and the interference cancellation performance analysis, and can be used for the optimal design of various anti-interference sampling antennas of line antennas.
Drawings
Fig. 1 is a schematic diagram of a mutual coupling calculation result of two half-wave antennas according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating cancellation effects of a spatial sampling antenna according to an embodiment of the present invention;
fig. 3 is a flowchart of analyzing the number of antennas for optimal spatial sampling according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In one aspect, the present invention provides a method for designing a space sampling antenna for interference cancellation based on an approximate analysis method, including the following steps:
(1) calculating an analytic solution of the surface current distribution of the sampling antenna by adopting an approximate analytic method based on a single-wire transmission line model so as to accurately and quickly calculate the surface current distribution of the sampling antenna;
the method comprises the following specific steps:
according to the traditional single-wire transmission line model, the current at a certain point on the axis of the wire antenna generates tangential electricity on the surface of the antennaField(s)E s (z) Comprises the following steps:
E s (z)=F z (z)-əV(z)/əz
wherein the content of the first and second substances,əis a symbol of the partial derivative,V(z) Is the potential of a single line with a lossy transmission line,F z (z) Dynamic field distribution generated for current components:
F z (z)=-jωμ·∫0 l [I(z′)·e jβz-′′/4πz′′]dz′
wherein the content of the first and second substances,jis the number of the imaginary numbers,ωin order to be the angular frequency of the frequency,μin order to have a magnetic permeability,I(z') denotes coordinatesz' where the numerical value of the current, [ integral ] is the sign of the integral,lfor the length of the dipole antenna to be,βin order to be a free-space propagation constant,z′′=sqrt[(z′-z)2+ρ 2]and isρThe radius of the dipole antenna is shown,dz' means toz' of (a);zis a certain point on the z-axis;z' is a function integration point on the z-axis;
will flow currentI(z') in current distributionI(z) Is subjected to Euler expansion and can be paired by reasonable mathematical approximationF(z) The simplification is carried out:
F z (z)≈-jωμ·L(z)·I(z)
wherein the content of the first and second substances,L(z) Representing transmission line distributed inductance:
L(z)=μ/(4π)·[2ln(2λ)-2ln(2πρ)-2e 0+Ci(βz)-Ci(βl-βz)]
wherein the content of the first and second substances,e 00.577 is an Euler constant,Ciis a cosine integral function, ln is a logarithm solution sign,λthe wavelength is corresponding to the central frequency of the sampling antenna;
L(z) The average of the integrals is:
L=1/l·∫0 l L(z)·dz=μ/(4π)·{[ln(λ)-ln(2πρ)+0.116+Ci(βl)-[sin(βl)/ (β l)]}
byLSubstitutionF(z) In an approximate expressionL(z) Is obtained byF(z) The partial derivatives are:
əF(z)/əz=-jωμ·L·əI(z)/əz
from the lorentz conditions:
əF z (z)/əz=-ϒ 2 V(z)
wherein the content of the first and second substances,ϒ 2=ω 2 LC，C=με/Lis a capacitor;
then according toF(z) The partial derivative expression of (a) can be given as:
-β 2 V(z)=-jωμ·L·əI(z)/əz
the current partial derivative equation of the traditional single-line lossless transmission line model can be obtained by simplifying the formula:
əI(z)/əz=-jωC·V(z)
according to the boundary condition of the electromagnetic field, the total tangential electric field component of the surface of the antenna is zero; therefore, the method comprises the following steps:
E s (z)+E(z)=F z (z)-əV(z)/əz+E(z)=0
wherein the content of the first and second substances,E(z) Is the incident field tangential component; therefore, the simplified potential partial derivative equation of the traditional single-wire lossless transmission line model is as follows:
əV(z)/əz=-jωL·I(z)+E(z)
due to the fact thatLIs a real number, then-jωL、-jωCThe single-wire transmission line model is a pure imaginary number and respectively represents the distributed inductance and the distributed capacitance of the traditional single-wire transmission line model, so that the single-wire transmission line model is lossless and ignores the ohmic loss on an antenna;
further, to account for losses on the antenna, an initial distribution of current distribution on the antenna is calculated according to a single-wire lossless transmission line model equationI 0(z) Then correcting the dynamic field distribution generated by the current component in the model equation of the single-line lossless transmission lineF z (z)；
F z (z)=jωμI(z)·∫0 l {[I(z′)/I(z)]·e jβz-′′/4πz′′}dz′
Wherein the content of the first and second substances,I(z) Representing coordinateszA current distribution function; at this time, the initial current distribution of the single-wire lossless transmission line model is adoptedI 0(z) Current in the equation aboveI(z) Then, a single-line lossy transmission line model can be established; particular emphasis is given to: current distribution calculated in this stepI(z) Further iterations may be performed until an accurate current distribution is calculated;I(z') denotes coordinatesz' at the current value;
distribution parameters that vary along antenna positionL′(z) Comprises the following steps:
L′(z)=∫0 l {[I(z′)/I(z)]·e jβr-/4πr}dz′
then there are:
F z (z)=jωμL′(z)·I(z)
it is clear that,L′(z) The imaginary part represents radiation loss;
to pairL′(z) By averaging the approximations, a corrected sheet can be obtainedInductive reactance of linear lossy transmission line model equationL′：
L′=1/l·∫0 l L′(z)dz′
By usingLReplacing the lossless inductance in the single-wire lossless transmission line model to obtain a single-wire lossy transmission line model equation:
əV(z)/əz=-jωL′·I(z)+E(z)，əI(z)/əz=-jωC′·V(z)
wherein the content of the first and second substances,əthe sign of the partial derivative is such that,V(z) Is the potential of a single line with a lossy transmission line,E(z) Representing the source (constant when illuminated with a plane wave),C′=με/Lis capacitive reactance andεis a dielectric constant due toL′、C' are complex numbers, so the above formula is a single-line lossy transmission line model equation;
according to the boundary condition of electromagnetic field on metal surfaceI(0)=I(l) =0, whenE(z) When it is planeE(z) Is a constantE 0The current of the modified single-line lossy transmission line equationI(z) The general solution is:
I(z)=A·e rz--B·e rz +r·E 0/Z c
wherein the content of the first and second substances,r=jω·sqrt(L′·C') is the transmission constant of the single-wire lossy transmission line model;Z c =sqrt(L′/C') is the characteristic impedance of the single-wire lossy transmission line model;
A=r·E 0·(1-e rl )/(e rl –e -rl )/Z c
B=r·E 0·(1-e -rl )/(e rl –e -rl )/Z c
obviously, the current distribution on the dipole antenna is in a full analytic form and can be directly used for analytic calculation of a directional diagram, self impedance and mutual impedance;
(2) calculating the self impedance and the mutual impedance of the antenna according to the current distribution on the surface of the antenna, and optimizing the distance between the main antenna and the sampling;
the method comprises the following specific steps:
zcurrent cell ofI(z)dzThe generated far-zone radiation field isdE θ ：
dE θ =30jβsin(θ)/[sqrt(ε)·R]·e jβ R z θ-(-·cos) I(z)dz
Wherein the content of the first and second substances,θfor the antenna pitch angle,Rfor the far field point location, the far field radiation field of the entire sampling antenna is the integral over the entire antenna of the above equation:
E θ =∫0 l dE θ dz=30jβsin(θ)/[sqrt(ε)·R]·e jβR-∫0 l I(z)e jβz θ-·cos dz
modified current for single line lossy transmission line equationsI(z) The general solution is substituted into the formula:
E θ =30jβsin(θ)/[sqrt(ε)·R·Z c ]·e jβR-·[A·(1-e rl jβl θ--cos)/(r+jβcosθ)+B·(1-e rl jβl θ-cos)/(r-jβcosθ)+r·E 0·(1-e jβl θ-cos)/(jβcosθ)]
the self-impedance of the sampling antenna is:
Z 11=-1/(I m1)2·∫0 l [∫0 l (dE θ )dz′]I *(z)dz
wherein the content of the first and second substances,I m1for sampling antinode current of antenna port (usually takingI(z) Maximum of (d) represents conjugation;
R=sqrt(z′2+z 2)；
then sampling the antenna port reflection coefficientS 11Comprises the following steps:
S 11=20×log10[(Z 11-50)/(Z 11+50)]
mutual impedance of main antenna and sampling antennaZ 12Comprises the following steps:
Z 12=-1/(I m1 *·I m2)·∫0 l [∫0 l (dE 12)dz′]I m1 *(z)dz
wherein the content of the first and second substances,I m2is the antinode current of the main antenna port;dE 12a far field radiation field generated for the main antenna current element; at the same time as this is done,Ris modified intoR=sqrt[d 2+(z′- z)2]，dRepresenting the distance between the main antenna and the sampling antenna; from self-impedanceZ 11AndZ 12composed impedance matrix [ Z]Then, the scattering matrix [ S ] of the main antenna and the sampling antenna can be calculated]：
[S]=sqrt{[Y 0]}×{[Z]-[Z 0]}×{[Z]+[Z 0]}-1×sqrt{[Z 0]}
Wherein, the [ alpha ], [ beta ] -aY 0]Is a unit admittance matrix; [ Z ]0]Is a unit impedance matrix; by optimizing the relative position of the main antenna and the sampling antenna, a proper coupling degree is obtained, thereby avoiding larger transmitting powerThe main antenna of the rate affects the performance of the sampling antenna; when present, it is noted thatNWhen there is a sampling antenna, the position information of the sampling antenna can be updated in the above calculation step, and the scattering matrix [ S ]]Has the dimension ofN×N(ii) a The matrix can be further used for the optimal selection of the number of sampling antennas and the coupling degree;
(3) and calculating an analytic format directional diagram function according to the antenna surface current distribution, and separating the interference signal from the communication signal by a space sampling method to obtain a pure interference signal sample for the interference cancellation device, and simultaneously obtaining the optimal number of sampling antennas and calculating the interference rejection ratio of the sampling antennas.
The method comprises the following specific steps:
removing far field position parameters of a sampling antennaRTo obtain the sampled antenna patternf(θ, φ)：
f(θ, φ)=(R·e jβR ·E θ )2/η
Wherein the content of the first and second substances,ηis the free space wave impedance; solving to obtain:
f θ ={30jβsin(θ)/[sqrt(ε)·Z c ]·[A·(1-e rl jβl θ--cos)/(r+jβcosθ)+B·(1-e rl jβl θ-cos)/(r-jβcosθ)+r·E 0·(1-e jβl θ-cos)/(jβcosθ)]}2/η
the signals received by the main antenna and the sampling antenna are respectively as follows:
x m =s·f m (θ s , φ s )+c·f m (θ c , φ c )+n m ，x a =s·f a (θ s , φ s )+c·f a (θ c , φ c )+n a
wherein the content of the first and second substances,f a is a sampled antenna pattern;f m the primary antenna pattern can be calculated by referring to the sampling antenna pattern;s、c、 n m andn a respectively a communication signal, an interference signal, a main antenna noise signal and a sampling antenna noise signal; (θ s , φ s ) And (a)θ c , φ c ) The pitch angle and the azimuth angle are respectively the incoming wave direction of the useful signal and the interference signal;
method for calculating space sampling antenna weight based on least mean square criterionW opt ：
W opt =R aa -1·R am
Wherein the content of the first and second substances,R aa is composed ofx a The covariance matrix of (a);R am is composed ofx m Andx a the covariance matrix of (a);
the ratio of the signal-to-noise ratio before and after suppression is used to define the spatial sampling antenna performance:
ICR=||S m -W opt S a ||2×||C m +N m ||2/||S m ||2/||C m +N m - W opt (C a +N a ) ||2
wherein | | | purple hair2In order to calculate the sign for the power,C m =c·f m (θ c , φ c )、S m =s·f m (θ s , φ s ) Respectively, interference signals and communication signals received by the main antenna,C a =c·f a (θ c , φ c )、S a =s·f a (θ s , φ s ) Respectively, interference signals and communication signals received by the space sampling array antenna,N m 、N a noise signals received by the main antenna and the sampling antenna respectively;sis a transmitted communication signal;cis a transmitted interference signal;
obviously, more sampling antennas can obtain abundant interference signal samples, and the resolution is improved; however, the larger the number of sampling antennas, the larger the number of processing channels of the cancellation device, and the more complex the system; therefore, an optimal sampling antenna number analysis method is provided:
determining the space coverage range of the sampling antenna according to the incoming wave direction of the interference source;
determining the gain of the sampling antenna according to the directional diagram data of the main antenna, the anti-interference tolerance and the interference sampling method;
according to the design principle of the array antenna, the quantitative relation between the number of the sampling antennas and the anti-interference tolerance can be determined through the space coverage range, the gain and the signal characteristics of the interference source of the sampling antennas;
and (3) considering the adaptability, cost and the like of the sampling antennas on the actual ship/vehicle-mounted platform, and selecting the optimal number of the sampling antennas according to the quantitative relation between the number of the sampling antennas and the anti-interference tolerance.
Examples
When main antenna, sample antenna are two parallel and level first oscillators and the second oscillator of symmetry, the current distribution is respectively:
I 1(z 1)=I m1sin[β(l-|z 1|)]，I 2(z 2)=I m2sin[β(l-|z 2|)]
wherein the content of the first and second substances,I m1andI m2the current amplitudes of the first vibrator and the second vibrator are respectively;z 1andz 2respectively showing the positions of the first vibrator and the second vibrator; the second vibrator is coupled with the first vibratordz 1Total induced electric field generatedE θ12(z 1)：
E θ 12(z 1)=j60 I m2/[r 1·sin(d/r)] {cos[βl cos(d/r)]-cos(βl)} e jβr-1
Wherein the content of the first and second substances,dthe distance between the first vibrator and the second vibrator is set;r 1=sqrt(d 2+z 1 2)；
E θ 12(z 1) Component in the first vibrator length directionE z12(z 1) Comprises the following steps:
E z 12(z 1)=-E θ12(z 1) d/r=-j 60 I m2 [sin(d/r)]2/r {cos[βl cos(d/r)] -cos(β l)} e jβr-
will be provided withE z12(z 1) Substituting a mutual impedance calculation formula to obtain the mutual coupling of the second oscillator to the first oscillator; when in used<0.18λThe error of the formula is larger; in fact, with two dipole antenna spacingdReduction of half-wave oscillatorE θ12(z 1) No longer satisfying far field conditions; at the same time, whenz 1Approach toz 2When the temperature of the water is higher than the set temperature,E θ12(z 1) The approximation calculation error of (2) is large.
FIG. 1 shows the mutual coupling calculation results of two half-wave antennas, when the antenna spacing is 0.15m (0.5)λ) The coupling is about-20 dB; spacing 1.5m (20)λ) While, the coupling can be reduced to below-40 dB;
FIG. 2 is a diagram of cancellation effect of 1 main antenna and 3 spatial sampling antennas; the main antenna and the sampling antenna both adopt the structural form of a monopole antenna and are linear arrays (H-plane arrays) which are assisted; the gains of the H surfaces of the main antenna and the sampling antenna are respectively 6dB and 2 dB; sampling antenna spacing of 0.5λThe distance between the main antenna and the nearest sampling antenna is 20λ(ii) a For the pitch angleθ=80 ° azimuthΦ=20 ° and pitch angleθ=90º、ΦCalculating the optimal weight of the sampling antenna by the double interference of =70 degreesW opt =[-0.6902-1.2371j, 0.7198+0.5314j, -0.0297+0.7057j]The null depth of the directional diagrams in the two interference directions can reach-60 dB;
the more the number of sampling antennas is, the more the number of processing channels of the cancellation device is, and the more the system is complex; for this purpose, an optimal sampling antenna number analysis method is proposed, as shown in fig. 3.
In summary, compared with the prior art, the invention has the following advantages: the method corrects the dynamic field distribution generated by the current component in the model equation of the single-line lossless transmission line, and constructs the model equation of the single-line lossy transmission line by combining the Lorentz condition and the boundary condition of the electromagnetic field; based on the basis, the analytic solution of the electromagnetic distribution on the surface of the sampling antenna is obtained by adopting a single-line lossy transmission line model equation, so that the self impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna can be calculated, the distance between the main antenna and the sampling antenna can be optimized, the bandwidth characteristic of the antenna and the coupling degree of the main antenna and the sampling antenna can be analyzed theoretically, and therefore, the commercial electromagnetic software is not needed to be adopted for simulation analysis or test analysis, the analysis efficiency is improved, and the physical concept is clear.
According to the method, the analytic format directional diagram function can be further calculated through analytic solution of the surface current distribution of the sampling antenna, the optimal number of the sampling antennas is obtained through a space sampling method, and the interference suppression ratio is calculated.
The analytic solution analysis of the surface current distribution of the sampling antenna comprises the structural parameters such as the length and the radius of the antenna and the performance parameters such as impedance and gain, and can directly guide the specific design of the sampling antenna.
After the analytical solution of the surface current distribution of the sampling antenna is obtained, the established sampling antenna analysis method has integrity and universality, covers the design of the sampling antenna and the interference cancellation performance analysis, and can be used for the optimal design of various anti-interference sampling antennas of line antennas.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A design method of space sampling antenna based on interference cancellation is characterized by comprising the following steps:
presetting a plurality of setting methods of the sampling antenna; for each setting method, based on the analytic solution of the surface current distribution of the sampling antenna, the coupling degree between the main antenna and the sampling antenna is obtained by calculating the self impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna; meanwhile, analyzing a format directional diagram based on an analytical solution of the surface current distribution of the sampling antenna, and calculating an interference rejection ratio by a space sampling method;
based on the coupling degree and the interference rejection ratio corresponding to each setting method, screening out the number and the positions of the optimal sampling antennas by combining the constraint conditions of array antenna design, and completing the design of the space sampling antennas;
the method for obtaining the analytic solution of the surface current distribution of the sampling antenna comprises the following steps:
calculating initial current distribution on the sampling antenna according to a single-line lossless transmission line model equation;
correcting the dynamic field distribution generated by the current component in the single-line lossless transmission line model equation by adopting the initial current distribution on the sampling antenna;
introducing a distribution parameter mean value which changes along the antenna position to represent the modified dynamic field distribution, and combining a Lorentz condition and an electromagnetic field boundary condition to obtain a single-wire lossy transmission line model equation;
and obtaining an analytic solution of the surface current distribution of the sampling antenna by combining the single-line lossy transmission line model equation with the boundary condition of the metal surface electromagnetic field.
2. The method of claim 1, wherein the modified dynamic field distribution is:F z (z)=jωμI(z)·∫0 l {[I(z′)/I(z)]·e jβz-′′/4πz′′}dz′
wherein the content of the first and second substances,jis an imaginary number;ωis the angular frequency;μis magnetic permeability;I(z) Representing coordinate axeszA current distribution function;I(z') denotes coordinatesz' at the current value; integral sign;lis the dipole antenna length;βis the free space propagation constant;z′′=sqrt[(z′-z)2+ρ 2]and isρRepresents the radius of the dipole antenna;dz' means toz' is integrated.
3. The method of claim 2, wherein the single-line lossy transmission line model equation is:
əV(z)/əz=-jωL′·I(z)+E(z)，əI(z)/əz=-jωC′·V(z)
wherein the content of the first and second substances,əa partial derivative symbol;V(z) A single line lossy transmission line potential;E(z) Representing a source;C′=με/Lis capacitive reactance andεis the dielectric constant;L' is a distribution parameter that varies along the antenna position;μis magnetic permeability.
4. The method of claim 3, wherein the method for obtaining the coupling degree between the main antenna and the sampling antenna comprises the following steps:
obtaining a far-zone radiation field equation of the sampling antenna based on an analytic solution of the surface current distribution of the sampling antenna;
calculating the self-impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna based on a far-zone radiation field equation of the sampling antenna;
calculating a scattering matrix of the main antenna and the sampling antenna according to the self impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna;
and calculating the coupling degree between the main antenna and the sampling antenna based on the scattering matrixes of the main antenna and the sampling antenna.
5. The method of claim 3 or 4, wherein the interference suppression ratio is obtained by:
obtaining a far-zone radiation field equation of the sampling antenna based on an analytic solution of the surface current distribution of the sampling antenna;
acquiring a directional diagram of the sampling antenna through free space wave impedance, a far-zone radiation field of the sampling antenna and far-field position parameters of the sampling antenna;
acquiring signals received by a main antenna and a sampling antenna based on a sampling antenna directional diagram;
acquiring a space sampling antenna weight by adopting a minimum mean square criterion according to signals received by a main antenna and a sampling antenna;
and calculating the interference rejection ratio by combining the spatial sampling antenna weight and signals received by the main antenna and the sampling antenna.
6. The method of claim 5, wherein the interference rejection ratio is:
ICR=||S m -W opt S a ||2×||C m +N m ||2/||S m ||2/||C m +N m - W opt (C a +N a ) ||2
wherein | | | purple hair2In order to calculate the sign for the power,C m =c·f m (θ c , φ c )、S m =s·f m (θ s , φ s ) Respectively, interference signals and communication signals received by the main antenna,C a =c·f a (θ c , φ c )、S a =s·f a (θ s , φ s ) Respectively, interference signals and communication signals received by the space sampling array antenna,N m 、N a noise signals received by the main antenna and the sampling antenna respectively;sis a transmitted communication signal;cis a transmitted interference signal; f a (θ s , φ s ) Is a sampled antenna pattern;f m (θ s , φ s ) Is the main antenna pattern;W opt are the spatially sampled antenna weights.
7. The method of claim 6, wherein the number of sampling antennas is obtained by:
determining the space coverage range of the sampling antenna according to the incoming wave direction of the interference source;
determining the gain of the sampling antenna according to the directional diagram data of the main antenna, the anti-interference tolerance and the interference sampling method;
according to the design principle of the array antenna, acquiring the relation between the number of the sampling antennas and the anti-interference tolerance through the space coverage range, the gain and the signal characteristics of the interference source of the sampling antennas;
and selecting the optimal number of sampling antennas according to the relation between the number of sampling antennas and the anti-induction tolerance by combining the adaptability and the cost of the sampling antennas on the actual ship or vehicle-mounted platform.
8. An apparatus for designing a spatial sampling antenna based on interference cancellation, comprising:
the antenna setting module is used for presetting a plurality of setting methods of the sampling antenna;
the performance calculation module is used for acquiring the coupling degree between the main antenna and the sampling antenna by calculating the self-impedance of the sampling antenna and the mutual impedance of the main antenna and the sampling antenna based on the analytic solution of the surface current distribution of the sampling antenna for each setting method; meanwhile, analyzing a format directional diagram based on an analytical solution of the surface current distribution of the sampling antenna, and calculating an interference rejection ratio by a space sampling method;
the antenna design module is used for screening out the number and the positions of the optimal sampling antennas based on the coupling degree and the interference rejection ratio corresponding to each setting method and in combination with the constraint conditions of array antenna design, and completing the design of the space sampling antennas;
the surface current distribution acquisition module is used for acquiring an analytic solution of the surface current distribution of the sampling antenna, and the specific execution method comprises the following steps: calculating initial current distribution on the sampling antenna according to a single-line lossless transmission line model equation; correcting the dynamic field distribution generated by the current component in the single-line lossless transmission line model equation by adopting the initial current distribution on the sampling antenna; introducing a distribution parameter mean value which changes along the antenna position to represent the modified dynamic field distribution, and combining a Lorentz condition and an electromagnetic field boundary condition to obtain a single-wire lossy transmission line model equation; and obtaining an analytic solution of the surface current distribution of the sampling antenna by combining the single-line lossy transmission line model equation with the boundary condition of the metal surface electromagnetic field.
9. The apparatus for designing a spatial sampling antenna according to claim 8, wherein the modified dynamic field distribution is:F z (z)=jωμI(z)·∫0 l {[I(z′)/I(z)]·e jβz-′′/4πz′′}dz′
wherein the content of the first and second substances,jis an imaginary number;ωis the angular frequency;μis magnetic permeability;I(z) Representing coordinate axeszA current distribution function;I(z') denotes coordinatesz' at the current value; integral sign;lis the dipole antenna length;βis the free space propagation constant;z′′=sqrt[(z′-z)2+ρ 2]and isρRepresents the radius of the dipole antenna;dz' means toz' of (a);
the single-line lossy transmission line model equation is as follows:
əV(z)/əz=-jωL′·I(z)+E(z)，əI(z)/əz=-jωC′·V(z)
wherein the content of the first and second substances,əa partial derivative symbol;V(z) A single line lossy transmission line potential;E(z) Representing a source;C′=με/Lis capacitive reactance andεis the dielectric constant;L' is a distribution parameter that varies along the antenna position.
10. The apparatus of claim 9, wherein the interference rejection ratio is:
ICR=||S m -W opt S a ||2×||C m +N m ||2/||S m ||2/||C m +N m - W opt (C a +N a ) ||2
wherein | | | purple hair2In order to calculate the sign for the power,C m =c·f m (θ c , φ c )、S m =s·f m (θ s , φ s ) Respectively, interference signals and communication signals received by the main antenna,C a =c·f a (θ c , φ c )、S a =s·f a (θ s , φ s ) Respectively, interference signals and communication signals received by the space sampling array antenna,N m 、N a noise signals received by the main antenna and the sampling antenna respectively;sis a transmitted communication signal;cis a transmitted interference signal; f a (θ s , φ s ) Is a sampled antenna pattern;f m (θ s , φ s ) Is the main antenna pattern;W opt are the spatially sampled antenna weights.
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