CN106777704B - Method and system for predicting electromagnetic coupling degree between antennas on medium coating target - Google Patents
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Abstract
The invention provides a method and a system for predicting the electromagnetic coupling degree between antennas on a medium coating target. The method comprises S1, decomposing the total field of the antenna by electromagnetic wave consistent geometric diffraction method to obtain the diffraction field and the surface wave field generated by the medium, and obtaining the electromagnetic wave reflection characteristic of the medium; and S2, acquiring an electromagnetic wave scattering coefficient between the two ports by using an antenna port network model based on the diffraction field, the surface wave field and the electromagnetic wave reflection characteristics of the medium so as to predict the electromagnetic coupling degree between the antennas on the medium coating target. The invention analyzes the electromagnetic coupling path of the antenna on the coating medium target, reasonably decomposes the total field of the antenna, and utilizes the antenna port network model to qualitatively analyze and quantitatively express the electromagnetic coupling degree under the diffraction field and the surface wave field so as to predict the electromagnetic interference degree between the antennas on the coating medium target.
Description
Technical Field
The invention relates to the field of electromagnetic compatibility, in particular to a method and a system for predicting the electromagnetic coupling degree between antennas on a medium coating target.
Background
Currently, with the development of electronic science and technology, a method of coating a medium is mostly used to reduce the possibility of being tracked. The electromagnetic environment existing in the antenna is complex, and electromagnetic coupling is more likely to occur in a plurality of antennas placed on a medium coating target, so that the analysis of complex coupling paths has certain guiding significance on the electromagnetic compatibility of the antenna.
On an airborne platform, the antenna has the main function of converting an electric signal fed by a transmitter into an electromagnetic wave and radiating the electromagnetic wave into a free space; or weak electromagnetic wave signals in free space are received, converted into electric signals and input into a high-sensitivity airborne receiver. The antenna is mostly concentrated in the limited space of the surface of the airplane, and the coupling interference existing between the antenna and the antenna can affect the normal operation of the antenna. The three elements of electromagnetic compatibility include interference sources, sensitive equipment and coupling channels. Electromagnetic interference is effectively suppressed, and the electromagnetic compatibility of the system can be improved by cutting off any of the three electromagnetic elements.
Electromagnetic compatibility simulation analysis is carried out on electromagnetic interference between antennas, mainly electromagnetic coupling paths are analyzed, and a common method comprises an electromagnetic topology method, namely, the electromagnetic topology theory is utilized to research and analyze the coupling problem of a complex transmission line network, research the electromagnetic pulse propagation and coupling problem and the mutual coupling problem between electronic devices under the condition of multilayer electromagnetic shielding, and the electromagnetic topology is utilized to calculate.
The traditional electromagnetic topological method is difficult to accurately layer the system, the transfer function calculation among all independent units is complex, and the analysis of the electromagnetic coupling among antennas on a medium coating target is less helpful.
Disclosure of Invention
The present invention provides a method and system for predicting the degree of electromagnetic coupling between antennas on a dielectric coated target that overcomes, or at least partially solves, the above-mentioned problems.
According to one aspect of the present invention, there is provided a method of predicting a degree of electromagnetic coupling between antennas on a medium coated object, comprising:
s1, decomposing the total field of the antenna by using an electromagnetic wave consistency geometric diffraction method to obtain a diffraction field and a surface wave field generated by the medium, and acquiring the electromagnetic wave reflection characteristic of the medium;
and S2, acquiring an electromagnetic wave scattering coefficient between the two ports by using an antenna port network model based on the diffraction field, the surface wave field and the electromagnetic wave reflection characteristics of the medium so as to predict the electromagnetic coupling degree between the antennas on the medium coating target.
S1 further includes:
s1.1, decomposing the total field of the antenna into a direct field, a reflected field, a diffraction field and a surface wave field generated by the medium, and shielding the direct field and the reflected field to obtain the diffraction field and the surface wave field;
s1.2, acquiring dielectric loss parameters and magnetic energy loss parameters of the medium by using an electromagnetic model, and acquiring electromagnetic wave reflection characteristic parameters of the medium.
S2 further includes:
s2.1, establishing an antenna port network model by using a microwave network scattering matrix, and acquiring a two-port network model when a receiving port is matched with a load;
and S2.2, acquiring quantitative representation of the electromagnetic wave scattering coefficient and the electromagnetic wave reflection characteristic of the medium according to a coupling degree characterization method of a two-port network based on the diffraction field and the surface wave field.
According to another aspect of the present invention, there is provided a system for predicting a degree of electromagnetic coupling between antennas on a medium coated target, comprising a decomposition obtaining module and a scattering coefficient obtaining module,
the decomposition acquisition module is used for decomposing the total field of the antenna by using an electromagnetic wave consistency geometric diffraction method to obtain a diffraction field and a surface wave field generated by the medium and acquire the electromagnetic wave reflection characteristic of the medium;
and the scattering coefficient obtaining module is used for obtaining the scattering coefficient of the electromagnetic waves between the two ports by utilizing an antenna port network model based on the diffraction field, the surface wave field and the electromagnetic wave reflection characteristics of the medium so as to predict the electromagnetic coupling degree between the antennas on the medium coating target.
The method and the system for predicting the electromagnetic coupling degree between the antennas on the medium coating target analyze the electromagnetic coupling path of the antennas on the medium coating target, and classify a multi-port network formed by the antennas according to three factors of electromagnetic compatibility, namely, a transmitting antenna is used as an electromagnetic interference source, a receiving antenna is used as electromagnetic sensitive equipment, and an electromagnetic energy coupling mode between the antennas is used as an electromagnetic coupling channel. After the antenna platform is coated with the medium, electromagnetic waves enter the surface of the medium to be transmitted and reflected, reflected waves are attenuated by the medium material, the reflection type coupling energy is weakened, and the medium forms a new coupling channel in the transverse direction to form a surface wave field. Based on theoretical analysis and simulation measurement, the total field of the antenna is reasonably decomposed, and the electromagnetic coupling degrees under the diffraction field and the surface wave field are qualitatively analyzed and quantitatively expressed by using an antenna port network model for predicting the electromagnetic interference degree between the antennas on the medium coating target.
Drawings
FIG. 1 is a flow chart of a method of predicting the degree of electromagnetic coupling between antennas on a dielectric coated target in accordance with the present invention;
FIG. 2 is a schematic diagram of an antenna port network model according to the present invention;
FIG. 3 is a schematic diagram of a two-port network transceiver antenna according to the present invention;
FIG. 4 is a schematic diagram of a system for predicting the degree of electromagnetic coupling between antennas on a dielectric coated object in accordance with the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
The dielectric coating target refers to a platform provided with an antenna, and when a dielectric is coated on the antenna platform, the coupling path of electromagnetic waves can be influenced due to the electromagnetic wave characteristics of a dielectric material.
The theoretical basis of the method is as follows: the multi-port network formed by the antennas is classified according to three factors of electromagnetic compatibility, namely, a transmitting antenna is used as an electromagnetic interference source, a receiving antenna is used as an electromagnetic sensitive device, and an electromagnetic energy coupling mode between the antennas is used as an electromagnetic coupling channel. After the antenna platform is coated with the medium, electromagnetic waves enter the surface of the medium to be transmitted and reflected, reflected waves are attenuated by the medium material, the reflection type coupling energy is weakened, and the medium forms a new coupling channel in the transverse direction. By reasonably decomposing the total field of the antenna, the field coupling on the electromagnetic coupling path can be qualitatively and quantitatively analyzed.
The medium coated on the antenna platform mainly acts as an electromagnetic wave propagation medium in an electromagnetic environment, the coupling between the antennas is easy to disturb originally, and the medium on the antenna platform provides a new coupling path for the coupling between the antennas, so that the electromagnetic wave coupling and the coupling path are more complicated.
At the interface between the medium and the air, when the electromagnetic wave radiated by the antenna propagates to the interface, one part is transmitted into the medium, and the other part is reflected. If the medium is a lossy medium, attenuation occurs in both the reflected wave and the transmitted wave and in the surface wave formed inside the medium. The electromagnetic parameters of the medium and the relationship between the frequency of the electromagnetic wave and the geometrical parameters of the medium determine the amplitude and phase variations of the reflected wave and the transmitted wave, and thus determine the reflection coefficient and the transmission coefficient. And the reflection coefficient and the transmission coefficient of the medium are important parameters for determining the electromagnetic coupling degree between the antennae on a medium coating target.
Unless otherwise stated, the meanings of the formulas and the parameters in the formulas have consistency.
As shown in fig. 1, a method for predicting the degree of electromagnetic coupling between antennas on a dielectric coated object, comprising:
s1, decomposing the total field of the antenna by using an electromagnetic wave consistent geometric diffraction method to obtain a diffraction field and a surface wave field generated by the medium, and obtaining the electromagnetic wave reflection characteristic of the medium.
And S2, acquiring an electromagnetic wave scattering coefficient between the two ports by using an antenna port network model based on the diffraction field, the surface wave field and the electromagnetic wave reflection characteristics of the medium so as to predict the electromagnetic coupling degree between the antennas on the medium coating target.
The method for predicting the electromagnetic coupling degree between the antennas on the medium coating target of the invention generates a surface wave field on the basis of the original antenna total field due to the medium coated on the antenna platform, so that the electromagnetic coupling path is more complicated. The total field of the antenna is decomposed by utilizing an electromagnetic wave consistency geometric diffraction method to obtain the electromagnetic coupling path under the diffraction field and the surface wave field analyzed by the method, so that the analysis and the calculation are simplified. By analyzing the electromagnetic coupling degree under the diffraction field and the surface wave field generated by the medium, the difference of the electromagnetic wave scattering coefficients under the conditions of the medium and the medium can be compared, so that the electromagnetic coupling degree between the antennas on the medium coating target can be predicted when the medium exists.
The S1, decomposing the total antenna field by using an electromagnetic wave coherent geometric diffraction method, obtaining a diffraction field and a surface wave field generated by the medium, and obtaining the electromagnetic wave reflection characteristics of the medium, further includes:
s1.1, decomposing the total field of the antenna into a direct field, a reflected field, a diffraction field and a surface wave field generated by the medium, and shielding the direct field and the reflected field to obtain the diffraction field and the surface wave field.
S1.2, acquiring dielectric loss parameters and magnetic energy loss parameters of the medium by using an electromagnetic model, and acquiring electromagnetic wave reflection characteristic parameters of the medium.
In S1.1, the antenna total field is reasonably decomposed by using a consistent geometric diffraction theory of electromagnetic wave propagation, so that the analysis processing process is simplified, and the accuracy of quantitative analysis is improved.
The theory of coherent geometric diffraction mainly includes: the total field of the whole antenna is composed of a direct field, a reflected field, a diffraction field and a surface wave field, so that the coupling path is divided into a direct coupling path, a reflective coupling path, a diffraction coupling path and a surface wave coupling path. Wherein the surface wavefield forms a new coupling channel laterally of the medium.
Firstly, the interference energy of the direct-injection coupling path is calculated according to a Fourier transmission equation, which mainly depends on the distance between the antennas and the gain of the transmitting and receiving antennas, and the calculation formula is as follows:
in the above formula PrFor receiving the power received by the antenna, PtTo transmit power, GrFor receiving antenna gain, GtFor transmit antenna gain, R is the distance between the two antennas.
And then analyzing the reflection type coupling path and the geometric diffraction type coupling path, adopting a classical ray method in a consistency geometric diffraction theory, being simple and easy to calculate, effectively and accurately solving the problems of complex radiation and scattering, overcoming the defect that the geometric diffraction theory on two sides of the geometric shadow boundary fails, and enabling the total field to be continuous everywhere. For the reflected field, when the ray emitted from the electromagnetic wave source point is projected onto the curved surface, the reflected ray is generated on the surface of the curved surface to form the reflected field. When the incident ray is incident to the edge, a diffraction field in the ray base coordinate system is formed at the incident point by taking the edge as an axis.
The analysis and calculation of the electromagnetic coupling path in the case of the total field of the antenna are very complicated, and certain measures can be taken to shield some fields and retain other fields, thus simplifying the whole analysis and calculation process.
The measures adopted by the invention are as follows:
adding an absorption boundary above the transmitting and receiving antenna to separate energy on direct-injection and reflection coupling paths;
or an absorption boundary is added above the transmitting and receiving antenna and in the coating medium to block energy on the direct-injection type, the reflection type and the surface wave type coupling paths.
In the absorption boundary in the above measures, the simulation model can be set as the absorption boundary in the simulation, and the wave-absorbing material can be added in the coating medium in the test.
The invention provides a method for predicting electromagnetic coupling degree between antennas on a medium coating target, which comprises the steps of adding an absorption medium above a transmitting-receiving antenna by considering energy on a surface wave coupling path propagating in a medium, cutting off energy on a direct-injection type coupling path and a reflection type coupling path, leaving a diffraction type coupling path and a surface wave type coupling path, and analyzing the electromagnetic coupling degree under the diffraction type coupling path and the surface wave type coupling path, namely comparing the electromagnetic coupling difference under the condition of the existence/nonexistence of the medium, and further predicting the electromagnetic coupling degree between the antennas on the medium coating target.
In S1.2, when an external alternating electromagnetic field acts on a medium, a potential displacement vector D generated inside the medium and an external alternating electric field have a certain phase difference, so that the dielectric constant of a medium material has a real part and an imaginary part to represent an included angle between the two vectors. Similarly, the magnetic induction B generated inside the dielectric material under the action of the external alternating magnetic field will have a phase difference with the external alternating magnetic field, and its magnetic permeability also takes the form of a complex number, and also has a real part and an imaginary part.
The specific implementation comprises the following steps:
s1.2.1, obtaining dielectric loss parameters of the medium under an external alternating electric field.
The applied alternating electric field is represented by the following formula:
E＝Emejωt
the electrical displacement vector D in the medium can be expressed as:
the complex dielectric constant is the ratio of the electric displacement vector D and the external electric field E, and comprises the following components:
the real part epsilon 'and the imaginary part epsilon' are respectively:
the dielectric loss tangent can be calculated by the following formula:
wherein ε' is the real part of the complex permittivity,. epsilon. "is the imaginary part of the complex permittivity, DmAmplitude of a vector of electric displacement in the medium, EmFor amplitude of applied alternating electric field, deltaeThe phase angle at which the vector of the electric displacement lags behind the applied alternating electric field, epsilon0Is the dielectric constant in air, ejωtIs a complex phase.
Wherein, the imaginary part epsilon 'of the complex dielectric constant influences the dielectric loss in the composite material, and epsilon' is defined as the dielectric loss parameter in the invention.
S1.2.2, acquiring magnetic energy loss parameters of the medium under an external alternating magnetic field;
the applied alternating magnetic field is represented by the following formula:
H＝Hmejωt
the magnetic induction in the medium can be expressed as
The complex permeability is the ratio of the magnetic induction B to the external magnetic field H, and is as follows:
the real part mu 'and the imaginary part mu' of the complex magnetic permeability are respectively:
the magnetic loss tangent is defined as the ratio of the imaginary part and the real part of the complex permeability:
where μ 'is the real part of the complex permeability, μ' is the imaginary part of the complex permeability, BmAmplitude of magnetic induction in a medium, HmFor amplitude of applied alternating magnetic field, deltamThe phase angle at which the magnetic induction lags behind the applied alternating magnetic field, μ0Is the permeability in air, ejωtIs a complex phase.
The imaginary part mu 'of the complex permeability of the composite material influences the magnitude of magnetic energy loss in the composite material, and the definition mu' is a magnetic energy loss parameter in the invention.
S1.2.3, obtaining the electromagnetic wave reflection characteristic parameters of the medium according to the dielectric loss parameters and the magnetic energy loss parameters, including the reflection coefficient Г and the transmission coefficient T.
Order:
V1＝S21+S11
V2＝S21-S11
the sign in the above equation should be chosen to satisfy | Γ | < 1.
The following can be obtained:
thereby obtaining quantitative expressions of a reflection coefficient Г and a transmission coefficient T and the dielectric loss parameter and the magnetic energy loss parameter, whereinr＝μ′+μ″，εrε' + ε ", c is the propagation velocity in vacuum 3.0 x 108W is the angular frequency of the electromagnetic wave and L is the material thickness.
The S2, based on the diffraction field, the surface wave field, and the electromagnetic wave reflection characteristics of the medium, obtaining an electromagnetic wave scattering coefficient between two ports by using an antenna port network model to predict an electromagnetic coupling degree between antennas on the medium coating target, further includes:
s2.1, establishing an antenna port network model by using a microwave network scattering matrix, and acquiring a two-port network model when a receiving port is matched with a load;
and S2.2, acquiring quantitative representation of the electromagnetic wave scattering coefficient and the electromagnetic wave reflection characteristic of the medium according to a coupling degree characterization method of a two-port network based on the diffraction field and the surface wave field.
The specific implementation of S2.1 includes:
s2.1.1, establishing an N-port network model.
And establishing an antenna port network model of the N port by using a microwave network scattering matrix analysis method.
The N port refers to a network with the total number of transmitting antennas and receiving antennas being N, where N is a natural number, and N > is 2.
Suppose Vi +And
incident voltage and incident current of the ith port respectively; vi -And
respectively an exit voltage and an exit current of the ith port; viAnd IiThe port voltage and port current of the ith port, respectively, are:
wherein Z is0iIs the characteristic impedance of the i-th port network.
From the above formula, one can obtain:
to the upper type both sides divided by
The normalized incident and emergent waves are defined as follows:
solving the above equation system can obtain:
establishing a normalized incident wave amplitude aiAnd normalized outgoing wave amplitude biThe scattering matrix of the N-port microwave network can be obtained as follows:
i.e., [ b ] ═ S ] [ a ]
In the above formula, there are
The scattering matrix elements are defined as:
wherein, aiTo normalize the amplitude of the incident wave, biTo normalize the amplitude of the emergent wave, SijI is 1,2, … N, and j is 1,2, … N.
When the incident wave of other ports except j is 0, SijIncident voltage wave a for port jjExciting and measuring the outgoing voltage wave of port ibiTo obtain the final product. SiiIs the scattering coefficient of port i when all other ports are connected to match the load.
S2.1.2, obtaining a two-port network model when N is 2, where the two-port network is a network including a transmitting antenna and a receiving antenna, where the transmitting antenna is a first port and the receiving antenna is a second port.
When N is 2, from the scattering matrix, one can obtain:
b1＝S11a1+S12a2
b2＝S21a1+S22a2
if the transceiving ports are not matched, let the reflection coefficient of the load be gammalI.e. a2＝Γlb2Then the scattering matrix becomes:
b1＝S11a1+S12Γlb2
b2＝S21a1+S22Γlb2
s2.1.3, obtaining a two-port network model when the receiving port matches the load. If the second port and the receiving antenna are load matched, i.e. gammalWhen 0, we can get:
b1＝S11a1
b2＝S21a1
wherein, a1Is the normalized incident wave amplitude of the first port, a2Normalized incident wave amplitude for the second port, b1Normalized emergent wave amplitude of the first port, b2Normalized emergent wave amplitude of the second port, S11Is the scattering coefficient of the first port, S12Is the scattering coefficient from the second port to the first port, S21Is the scattering coefficient from the first port to the second port, S22Is the scattering coefficient of the second port.
The above-mentioned antenna port network model, especially the two-port network model, is established, in order to simplify the analysis, a pair of transceiving antennas is selected from a plurality of antenna ports, and for the selected pair of transceiving antennas, the two-port network model is used to analyze the coupling path and the coupling degree between them.
From the perspective of the antenna, the performance of the antenna after being installed cannot be obviously changed, which is shown in two aspects, namely, if the performance of the antenna is slightly changed, the antenna still can work; secondly, after a plurality of antennas are simultaneously installed on the same antenna platform, no great influence is generated among the antennas, namely, after one receiving antenna receives a working signal, a transmitting signal from another antenna should not be received.
In fact, the above two aspects are not irrelevant, for example, if the performance change after the antenna installation still meets the design index of the antenna, the platform antenna design can be said to be applicable to an airborne platform, but some parameters of the change in the performance may bring a large influence to other antennas. In view of the operating frequency, if the bandwidth of the antenna is widened after installation, the original transmitting antenna will not radiate harmonic waves or interference signals, which may cause accidental transmission after the bandwidth of the antenna is widened, and affect the receiving antenna. Similarly, the frequency band of the receiving antenna is widened, so that the probability and power value of the interference signal received by the receiving antenna are greatly increased. From the perspective of spatial radiation, the antenna has a common electromagnetic compatibility problem after installation, that is, the directional pattern of the antenna is distorted, the directional pattern of the antenna is greatly changed from the directional pattern of the original antenna, and when the installed platform antenna directional pattern still meets the design specification of the antenna, the antenna still has a possibility of generating larger radiation in other unnecessary radiation directions, that is, the side lobe level is increased.
The two-port network model is utilized to analyze the coupling path and the coupling degree between the two transmitting and receiving antennas by selecting a pair of transmitting and receiving antennas based on the reasons.
The specific implementation of S2.2 includes:
s2.2.1, according to the receiving power when the receiving port matches the load and the transmitting power of the transmitting port, the coupling degree between the transmitting and receiving antennas of the two-port network is obtained.
As shown in FIG. 2For a lossless passive network with N ports, the incident power P of the transmitting end is assumedin1 is:
power P emitted from the emitting endoutComprises the following steps:
for a two-port network, a first port represents a transmitting antenna to which signals are transmitted by means of coaxial lines and the like, and the transmitting antenna radiates electromagnetic energy to free space; the second port represents a receiving antenna that receives electromagnetic energy in space and transmits the electromagnetic energy into a receiver.
As shown in fig. 3, when the two-port receive antennas are perfectly matched, their received power can be expressed as follows:
incident power P through the transmitting end in1 and the emergent power P of the transmitting terminaloutSubtracting to obtain the transmitting power of the first port transmitting antenna as follows:
the coupling between the two-port network transceiver antennas can be defined as follows:
if the first port transmitting antenna is also connected to a matched load, i.e. S11If 0, the coupling degree C between the first port transmitting antenna and the second port receiving antenna is the same as
C＝10lg(|S21|2)＝20lg|S21|
The coupling degree C can be used for measuring the electromagnetic compatibility of the antenna and predicting the interference degree among different antennas.
PrFor receiving the power received by the antenna, PinC is the coupling degree between the transmitting and receiving antennas.
S11And S21The scattering coefficient between the transmit and receive antennas of the two-port network.
S2.2.2, obtaining the scattering coefficient S of electromagnetic wave in the diffraction field and the surface wave field generated by the medium according to the reflection coefficient Г and the transmission coefficient T of the medium11S of (A) and (B)21And (4) quantitatively expressing.
By combining theoretical derivation with actual measurement and simulation, the following quantitative results can be obtained:
s2.2.2, the scattering coefficient S between the two-port network receiving and transmitting antenna is given11、S21Relation with the reflection coefficient Г and the transmission coefficient T of the medium, when the reflection coefficient Г and the transmission coefficient T of the medium coated by the antenna platform are obtained through actual measurement or data simulation, S can be obtained through the formula in S2.2.2 in a quantitative mode11And S21Has S11And S21The degree of electromagnetic coupling C between the antennas can be calculated, thereby predicting the degree of electromagnetic coupling between the antennas on the dielectric coated object.
As shown in fig. 4, the present invention further provides a system for predicting the degree of electromagnetic coupling between antennas on a dielectric coated target, comprising a decomposition obtaining module and a scattering coefficient obtaining module,
the decomposition acquisition module is used for decomposing the total field of the antenna by using an electromagnetic wave consistency geometric diffraction method to obtain a diffraction field and a surface wave field generated by the medium and acquire the electromagnetic wave reflection characteristic of the medium;
and the scattering coefficient obtaining module is used for obtaining the scattering coefficient of the electromagnetic waves between the two ports by utilizing an antenna port network model based on the diffraction field, the surface wave field and the electromagnetic wave reflection characteristics of the medium so as to predict the electromagnetic coupling degree between the antennas on the medium coating target.
Compared with the prior art, the method has the advantages that the electromagnetic compatibility analysis is carried out from the angle of the coupling path provided by the medium coated on the antenna platform, and the complex dielectric constant and the complex permeability of the medium are measured by a transmission/reflection method; an electromagnetic analysis model is established, different structural parameters and electromagnetic parameters are set for analysis, and the reflection characteristics of the dielectric material to electromagnetic waves are analyzed in a mode of combining simulation and theoretical analysis.
The method analyzes the reflection field and the diffraction field by using a consistent geometric diffraction method, avoids energy on direct-injection and reflection coupling paths by adopting an actual means, only analyzes the diffraction coupling path with a medium, namely analyzes the diffraction field and a surface wave field, simplifies the process of analysis and calculation, and solves the actual problem that the coupling path is complex and is difficult to analyze the electromagnetic compatibility when the medium is coated on an antenna platform at the present stage.
On the basis of analyzing the antenna electromagnetic compatibility problem, the invention utilizes the correlation theory of the microwave network scattering matrix to equivalently convert the receiving and transmitting antenna into a two-port network, determines a method for representing the interference degree between the antennas by the coupling degree between the antennas, and can be used for the prediction analysis of the coupling degree change between the antennas.
Finally, the method of the present application is only a preferred embodiment and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A method for predicting a degree of electromagnetic coupling between antennas on a dielectric coated object, comprising:
s1, decomposing the total field of the antenna by using an electromagnetic wave consistency geometric diffraction method to obtain a diffraction field and a surface wave field generated by the medium, and acquiring the electromagnetic wave reflection characteristic of the medium;
s2, based on the diffraction field, the surface wave field and the electromagnetic wave reflection characteristics of the medium, obtaining the electromagnetic wave scattering coefficient between two ports by using an antenna port network model to predict the electromagnetic coupling degree between the antennas on the medium coating target; s2 further includes:
s2.1, establishing an antenna port network model by using a microwave network scattering matrix, and acquiring a two-port network model when a receiving port is matched with a load;
and S2.2, acquiring quantitative representation of the electromagnetic wave scattering coefficient and the electromagnetic wave reflection characteristic of the medium according to a coupling degree characterization method of a two-port network based on the diffraction field and the surface wave field.
2. The method of claim 1, wherein S1 further comprises:
s1.1, decomposing the total field of the antenna into a direct field, a reflected field, a diffraction field and a surface wave field generated by the medium, and shielding the direct field and the reflected field to obtain the diffraction field and the surface wave field;
s1.2, acquiring dielectric loss parameters and magnetic energy loss parameters of the medium by using an electromagnetic model, and acquiring electromagnetic wave reflection characteristic parameters of the medium.
3. The method of claim 2, wherein S1.2 further comprises:
s1.2.1, obtaining dielectric loss parameters of the medium under an external alternating electric field;
s1.2.2, acquiring magnetic energy loss parameters of the medium under an external alternating magnetic field;
s1.2.3, obtaining the electromagnetic wave reflection characteristic parameters of the medium according to the dielectric loss parameters and the magnetic energy loss parameters, including the reflection coefficient Г and the transmission coefficient T.
4. The method of claim 3, wherein the dielectric loss parameter is an imaginary part ε "in a complex dielectric constant as follows:
wherein ε' is the real part of the complex permittivity,. epsilon. "is the imaginary part of the complex permittivity, DmAmplitude of a vector of electric displacement in the medium, EmFor amplitude of applied alternating electric field, deltaeThe phase angle at which the vector of the electric displacement lags behind the applied alternating electric field, epsilon0Is the dielectric constant of air.
5. A method as claimed in claim 3, wherein said magnetic energy loss parameter is the imaginary part μ "in complex permeability as follows:
where μ 'is the real part of the complex permeability, μ' is the imaginary part of the complex permeability, BmAmplitude of magnetic induction in a medium, HmFor amplitude of applied alternating magnetic field, deltamThe phase angle at which the magnetic induction lags behind the applied alternating magnetic field, μ0Is the permeability of air.
6. The method of claim 3, wherein said reflection coefficient Г, said transmission coefficient T, said dielectric loss parameter ε "and said magnetic energy loss parameter μ" are related as follows:
wherein, mur＝μ′+μ″，εr-f + f ", f is the real part, u" is the imaginary part, e' is the real part, and e "is the imaginary part; c is the propagation velocity in vacuum 3.0 x 108ω is the angular frequency of the electromagnetic wave and L is the material thickness.
7. The method of claim 1, wherein S2.1 further comprises:
s2.1.1, an N-port network model is established as follows:
i.e., [ b ] ═ S ] [ a ]
Wherein, aiTo normalize the amplitude of the incident wave, biTo normalize the amplitude of the emergent wave, SijIs an element in the scattering matrix, i is 1,2, … N;
s2.1.2, obtaining a two-port network model when N is 2, as follows:
b1＝S11a1+S12a2
b2＝S21a1+S22a2
s2.1.3, obtaining a two-port network model when the receiving port matches the load, as follows:
b1＝S11a1
b2＝S21a1
wherein, a1Is a first portNormalized incident wave amplitude of a2Normalized incident wave amplitude for the second port, b1Normalized emergent wave amplitude of the first port, b2Normalized emergent wave amplitude of the second port, S11Is the scattering coefficient of the first port, S12Is the scattering coefficient from the second port to the first port, S21Is the scattering coefficient from the first port to the second port, S22Is the scattering coefficient of the second port.
8. The method of claim 7, wherein S2.2 further comprises:
s2.2.1, obtaining the coupling degree between the receiving and transmitting antennas of the two-port network according to the receiving power when the receiving port matches the load and the transmitting power of the transmitting port, as follows:
wherein,
Prfor receiving the power received by the antenna, PinC is the coupling degree representation between the receiving antenna and the transmitting antenna;
s2.2.2, obtaining the scattering coefficient S of electromagnetic wave in the diffraction field and the surface wave field generated by the medium according to the reflection coefficient Г and the transmission coefficient T of the medium11S of (A) and (B)21Quantitative representation, as follows:
9. the system for predicting the electromagnetic coupling degree between the antennae on the medium coating target is characterized by comprising a decomposition acquisition module and a scattering coefficient acquisition module,
the decomposition acquisition module is used for decomposing the total field of the antenna by using an electromagnetic wave consistency geometric diffraction method to obtain a diffraction field and a surface wave field generated by the medium and acquire the electromagnetic wave reflection characteristic of the medium;
the scattering coefficient obtaining module is used for obtaining the scattering coefficient of the electromagnetic waves between the two ports by utilizing an antenna port network model based on the diffraction field, the surface wave field and the electromagnetic wave reflection characteristics of the medium so as to predict the electromagnetic coupling degree between the antennas on the medium coating target; the obtain scattering coefficients module is further configured to:
s2.1, establishing an antenna port network model by using a microwave network scattering matrix, and acquiring a two-port network model when a receiving port is matched with a load;
and S2.2, acquiring quantitative representation of the electromagnetic wave scattering coefficient and the electromagnetic wave reflection characteristic of the medium according to a coupling degree characterization method of a two-port network based on the diffraction field and the surface wave field.
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