A full-wave analysis of the electromagnetic problem of a three-dimensional (3-D) antenna radiating through a 3-D dielectric radome is preserued. The problem is formulated using the Poggio-Miller-Chang-Harrington- Wu...A full-wave analysis of the electromagnetic problem of a three-dimensional (3-D) antenna radiating through a 3-D dielectric radome is preserued. The problem is formulated using the Poggio-Miller-Chang-Harrington- Wu(PMCHW) approach for homogeneous dielectric objects and the electric field integral equation for conducting objects. The integral equations are discretized by the method of moment (MoM), in which the conducting and dielectric surface/interfaces are represented by curvilinear triangular patches and the unknown equivalent electric and magnetic currents are expanded using curvilinear RWG basis functions. The resultant matrix equation is then solved by the multilevel fast multipole algorithm (MLFMA) and fast far-field approximation (FAFFA) is used to further accelerate the computation. The radiation patterns of dipole arrays in the presence of radomes are presented. The numerical results demonstrate the accuracy and versatility of this method.展开更多
Some compensation methods have been pro- posed to mitigate the degradation of radiation characteris- tics caused by composite material radomes, however most of them are complex and not applicable for large radomes, fo...Some compensation methods have been pro- posed to mitigate the degradation of radiation characteris- tics caused by composite material radomes, however most of them are complex and not applicable for large radomes, for example, the modification of geometric shape by grinding process. A novel and simple compensation strat- egy based on phase modification is proposed for large reflector antenna-radome systems. Through moving the feed or sub-reflector along axial direction opportunely, the modification of phase distribution in the original aperture of an enclosed reflector antenna can be used to reduce the phase shift caused by composite material radomes. The distortion of far-field pattern can be minimized. The modification formulas are proposed, and the limitation of their application is also discussed. Numerical simulations for a one-piece composite materials sandwich radome and a 40 m multipartite composite materials sandwich radome verify that the novel compensation strategy achieves sat- isfactory compensated results, and improves the distortion of the far-field pattern for the composite material radomes. For one-piece dielectric radome, more than 60% phasedifference caused by radome is reduced. For multipartite radome, the sidelobe level improves about 1.2 dB, the nulling depth improves about 3 dB. The improvement of far-field pattern could be obtained effectively and simply by moving the feed or sub-reflector according to phase shift of the radome.展开更多
In this paper,an in-band and out-of-band microwave wireless power-transmission characteristic analysis of a slot ring radome based on an approximate analytical method is proposed.The main contribution of this paper is...In this paper,an in-band and out-of-band microwave wireless power-transmission characteristic analysis of a slot ring radome based on an approximate analytical method is proposed.The main contribution of this paper is that,in the approximate analysis of the ring radome,a unified expression of the incident field on the radome surface is derived with E-plane and H-plane scanning,and the ring is approximated as 30 segments of straight strips.Solving the corresponding 60×60 linear equations yields the electric current distribution along the ring strip.The magnetic current along the complementary slot ring is obtained by duality.Thanks to the fully analytical format of the current distribution,the microwave wireless power-transmission characteristics are efficiently calculated using Munk’s scheme.An example of a slot ring biplanar symmetric hybrid radome is used to verify the accuracy and efficiency of the proposed scheme.The central processing unit(CPU)time is about 690 s using Ansys HFSS software versus 2.82 s for the proposed method.展开更多
An efficient hybrid method based on the method of moments (MOM) and physical optics (PO) for the analysis of radiation characteristics of an electrically large antenna-radome system is presented. Specifically, MOM...An efficient hybrid method based on the method of moments (MOM) and physical optics (PO) for the analysis of radiation characteristics of an electrically large antenna-radome system is presented. Specifically, MOM is first applied to the antenna to find the current on its surface, and then the equivalent PO currents produced by the antenna radiation are assumed on the radome wall. When the coupling of the PO currents and antenna current is considered, the coupling matrix is divided into a series of partial matrices, in order to deduce the memory requirement and accelerate the evaluation process. Numerical results indicate that the proposed hybrid PO-MOM method is accurate and efficient.展开更多
In this paper, the Geometric Optics (GO) method using the approximate ray paths coupled with the Computer Aided Tri-dimensional Interface Application (CATIA) meshing modeling are implemented to analyze the performance...In this paper, the Geometric Optics (GO) method using the approximate ray paths coupled with the Computer Aided Tri-dimensional Interface Application (CATIA) meshing modeling are implemented to analyze the performance of electric large three-dimensional dielectric radome-enclosed antenna of arbitrary contour shape. The surfaces of the radome are approximated by planar triangular patches, the influences of various number of patches on power transmission coefficient and Insertion Phase Delay (IPD) via an ogive and a conical radome are discussed by the hybrid method. The simulation results indicate that computational error from planar triangular patches can limit in one percent, meeting the engineering application requirements.展开更多
Inorganic coating was fabricated on the surface of the porous Si3N4 ceramic by polymer derived(PD) and spraying technology, via using vinyl-polysilazane(PSN-1) as a preceramic polymer and Si3N4 and lithium alumino...Inorganic coating was fabricated on the surface of the porous Si3N4 ceramic by polymer derived(PD) and spraying technology, via using vinyl-polysilazane(PSN-1) as a preceramic polymer and Si3N4 and lithium aluminosilicate(LAS) powders as fillers. The phase and microstructure of the coatings were analyzed by X-ray diffraction(XRD) analysis and scanning electron microscopy(SEM), respectively. The effect of the coatings on mechanical property and humidity resistance of the porous Si3N4 ceramic was investigated. The experimental results showed that we successfully fabricated the uniform and dense coating which preferably combined with the substrate upon the addition of fillers. The bending strength of the porous Si3N4 ceramic sprayed the coating increased by more than 18%, and the surface hardness increased by 1.7 times. The apparent porosity of the materials reduced by an average of 97.7%, and water absorption was below 0.5%. Therefore, the prepared coating with preferable density had an obviously moisture-proof and enhanced effect on the porous Si3N4 ceramic.展开更多
The feasibility of making two antennas work within a shared aperture conformai to a platform like an aircraft or a missile is investigated. The shared aperture is enclosed by a deep cavity, which is covered by a colum...The feasibility of making two antennas work within a shared aperture conformai to a platform like an aircraft or a missile is investigated. The shared aperture is enclosed by a deep cavity, which is covered by a columniform dielectric radome. A modified quadrifilar helix antenna (QHA) with extended volute arms and a vertical monopole with a ring shaped ground are arranged in this co-aperture for global position system (GPS) orientation and telemetry, respectively. The effects of the cavity on these two antennas and the mutual coupling between these two antennas are studied through large numbers of experiments. The results show that the QHA has a strong influence on the monopole; however, these two antennas of the overall arrangement can perform simultaneously well within the aperture. The QHA has a right hand circular polarization (RHCP) and a broad beam normal to the radome topside, meanwhile the monopole can be used to produce a main lobe in the grazing direction above the aperture in some certain cases of the vertical location of the QHA in the cavity.展开更多
The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show tha...The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.展开更多
The plane wave spectrum surface integration (PWS SI) is a practical and efficient method for antenna radome system analysis, especially for determining the boresight error (BSE) in the system. But it is only used f...The plane wave spectrum surface integration (PWS SI) is a practical and efficient method for antenna radome system analysis, especially for determining the boresight error (BSE) in the system. But it is only used for sum pattern calculation till now, and BSE is calculated by the beam maximum searching method. In this paper, the aperture distribution for difference pattern is formulated as the product of that for sum pattern and a two dimensional periodic window function. A series representation for the spectrum of difference pattern is then obtained according to the convolution theorem. The truncation error of the series has been analyzed by introducing the coverage radius of the spectrum of sum pattern. Based on this representation, the PWS SI technique is extended to difference pattern calculation of radome enclosed antennas. The BSE of a three dimensional multilayered radome, with thickness tapers in all layers, is calculated through the difference pattern null searching. Owing to the steep slope of difference pattern near the nulls, this method for BSE calculation is more stable and reliable than the original beam maximum searching method in PWS SI analysis. The results are compared with those from aperture integration surface integration (AI SI) analysis and the measured ones.展开更多
Electromagnetic transmission and scattering characteristics of radome may conve-niently be analyzed by complex ray paraxial approximation and collective ray methods.As anexample,a 2-D cylindrical single-layered dielec...Electromagnetic transmission and scattering characteristics of radome may conve-niently be analyzed by complex ray paraxial approximation and collective ray methods.As anexample,a 2-D cylindrical single-layered dielectric radome is analyzed and calculated in this in-vestigation,including radome transmission coefficient,radar angular track performance and radarcross section of radomes,as well as the effect of ray parameters and antenna-radome parameterson computation accuracy.It is shown that this method can be used to simplify optimizations formany kinds of radomes.展开更多
An effective broadband modified B Sandwich as radome’s layer structure is profosed. The power transmission coefficient of this sandwich is over 80% under large incident angle range (0°-70°) and broadband (0...An effective broadband modified B Sandwich as radome’s layer structure is profosed. The power transmission coefficient of this sandwich is over 80% under large incident angle range (0°-70°) and broadband (0-40GHz). The difference of insertion phase delay (IPD) between perpendicular polarization and parallel one is very small.展开更多
In this paper, it is offered to use the method of modulated reflection for the measurementof complex transfer factor of a radome wall on various sites of its surface. The circuit of equipmentallowed to carry out of su...In this paper, it is offered to use the method of modulated reflection for the measurementof complex transfer factor of a radome wall on various sites of its surface. The circuit of equipmentallowed to carry out of such measurement is given. The advantage of the given method in comparisonwith measurements on a gleam is shown. The results of the experimental research are given and theestimation of the accuracy of proposed method is considered.展开更多
This paper presents an algorithm for analysis of the dielectric radomes. In this method, the radome is discretized by a regular grid with rooftop basic functions. The Volume Integral Equation (VIE) for 3D dielectric o...This paper presents an algorithm for analysis of the dielectric radomes. In this method, the radome is discretized by a regular grid with rooftop basic functions. The Volume Integral Equation (VIE) for 3D dielectric object is transformed to linear system by Galerkin’s testing formulation. Furthermore, the linear system is presented by Toeplitz matrix which can be solved by the Conjugate Gradient algorithm combined with Fast Fourier Transform (CG-FFT) iteratively. Also, the algorithm requires less computational complexity and memory. This paper simulates the mono-static Radar Cross Section of dielectric radome by the CG-FFT, which was validated against commercial software FEKO.展开更多
Basing on the transformation optics, we propose a kind of transformation method of compressing or stretching. With the method, we propose a design of transparent radome for different structures. The electromagnetic (E...Basing on the transformation optics, we propose a kind of transformation method of compressing or stretching. With the method, we propose a design of transparent radome for different structures. The electromagnetic (EM) waves inside or outside the radome can transmit through the structure without any reflection. Numerical simulations confirm the function of the radome structures.展开更多
An experimental double-layer active frequency-selective surface(AFSS) for stealth radome is proposed. The AFSS is a planar structure which is composed of a fixed frequency-selective surface(FSS), a PIN diodes arra...An experimental double-layer active frequency-selective surface(AFSS) for stealth radome is proposed. The AFSS is a planar structure which is composed of a fixed frequency-selective surface(FSS), a PIN diodes array, and a DC bias network. The AFSS elements incorporating switchable PIN diodes are discussed. By means of controlling the DC bias network, it is possible to switch the frequency response for reflecting and transmitting. Measured and simulated data validate that when the incidence angle varies from 0°to 30° the AFSS produces more than-11.5 dB isolation across6–18 GHz when forward biased. The insertion loss(IL) is less than 0.5 dB across 10–11 GHz when reverse biased.展开更多
In sec.1, we introduce several basic concepts such as random transition function, p-m process and Markov process in random environment and give some examples to construct a random transition function from a non-homoge...In sec.1, we introduce several basic concepts such as random transition function, p-m process and Markov process in random environment and give some examples to construct a random transition function from a non-homogeneous density function. In sec.2, we construct the Markov process in random enviromment and skew product Markov process by p - m process and investigate the properties of Markov process in random environment and the original process and environment process and skew product process. In sec. 3, we give several equivalence theorems on Markov process in random environment.展开更多
基金the National Natural Science Foundation of China (60431010)
文摘A full-wave analysis of the electromagnetic problem of a three-dimensional (3-D) antenna radiating through a 3-D dielectric radome is preserued. The problem is formulated using the Poggio-Miller-Chang-Harrington- Wu(PMCHW) approach for homogeneous dielectric objects and the electric field integral equation for conducting objects. The integral equations are discretized by the method of moment (MoM), in which the conducting and dielectric surface/interfaces are represented by curvilinear triangular patches and the unknown equivalent electric and magnetic currents are expanded using curvilinear RWG basis functions. The resultant matrix equation is then solved by the multilevel fast multipole algorithm (MLFMA) and fast far-field approximation (FAFFA) is used to further accelerate the computation. The radiation patterns of dipole arrays in the presence of radomes are presented. The numerical results demonstrate the accuracy and versatility of this method.
基金Supported by National Natural Science Foundation of China(Grant Nos.51475348,51305322 and 51490660)Open Foundation of State Key Laboratory of Mechanical Transmissions(SKLMT-KFKT-201409)Fundamental Research Funds for the Central Universities of China
文摘Some compensation methods have been pro- posed to mitigate the degradation of radiation characteris- tics caused by composite material radomes, however most of them are complex and not applicable for large radomes, for example, the modification of geometric shape by grinding process. A novel and simple compensation strat- egy based on phase modification is proposed for large reflector antenna-radome systems. Through moving the feed or sub-reflector along axial direction opportunely, the modification of phase distribution in the original aperture of an enclosed reflector antenna can be used to reduce the phase shift caused by composite material radomes. The distortion of far-field pattern can be minimized. The modification formulas are proposed, and the limitation of their application is also discussed. Numerical simulations for a one-piece composite materials sandwich radome and a 40 m multipartite composite materials sandwich radome verify that the novel compensation strategy achieves sat- isfactory compensated results, and improves the distortion of the far-field pattern for the composite material radomes. For one-piece dielectric radome, more than 60% phasedifference caused by radome is reduced. For multipartite radome, the sidelobe level improves about 1.2 dB, the nulling depth improves about 3 dB. The improvement of far-field pattern could be obtained effectively and simply by moving the feed or sub-reflector according to phase shift of the radome.
基金supported in part by the National Key Research and Development Program(2021YFF1500100)Key Basic Research of Basic Strengthening Program of the Science and Technology Commission(2020-JCJQ-ZD-068)。
文摘In this paper,an in-band and out-of-band microwave wireless power-transmission characteristic analysis of a slot ring radome based on an approximate analytical method is proposed.The main contribution of this paper is that,in the approximate analysis of the ring radome,a unified expression of the incident field on the radome surface is derived with E-plane and H-plane scanning,and the ring is approximated as 30 segments of straight strips.Solving the corresponding 60×60 linear equations yields the electric current distribution along the ring strip.The magnetic current along the complementary slot ring is obtained by duality.Thanks to the fully analytical format of the current distribution,the microwave wireless power-transmission characteristics are efficiently calculated using Munk’s scheme.An example of a slot ring biplanar symmetric hybrid radome is used to verify the accuracy and efficiency of the proposed scheme.The central processing unit(CPU)time is about 690 s using Ansys HFSS software versus 2.82 s for the proposed method.
基金the National Natural Science Foundation of China (60471040)
文摘An efficient hybrid method based on the method of moments (MOM) and physical optics (PO) for the analysis of radiation characteristics of an electrically large antenna-radome system is presented. Specifically, MOM is first applied to the antenna to find the current on its surface, and then the equivalent PO currents produced by the antenna radiation are assumed on the radome wall. When the coupling of the PO currents and antenna current is considered, the coupling matrix is divided into a series of partial matrices, in order to deduce the memory requirement and accelerate the evaluation process. Numerical results indicate that the proposed hybrid PO-MOM method is accurate and efficient.
基金Supported by the National Natural Science Foundation of China (No. 61172024)
文摘In this paper, the Geometric Optics (GO) method using the approximate ray paths coupled with the Computer Aided Tri-dimensional Interface Application (CATIA) meshing modeling are implemented to analyze the performance of electric large three-dimensional dielectric radome-enclosed antenna of arbitrary contour shape. The surfaces of the radome are approximated by planar triangular patches, the influences of various number of patches on power transmission coefficient and Insertion Phase Delay (IPD) via an ogive and a conical radome are discussed by the hybrid method. The simulation results indicate that computational error from planar triangular patches can limit in one percent, meeting the engineering application requirements.
文摘Inorganic coating was fabricated on the surface of the porous Si3N4 ceramic by polymer derived(PD) and spraying technology, via using vinyl-polysilazane(PSN-1) as a preceramic polymer and Si3N4 and lithium aluminosilicate(LAS) powders as fillers. The phase and microstructure of the coatings were analyzed by X-ray diffraction(XRD) analysis and scanning electron microscopy(SEM), respectively. The effect of the coatings on mechanical property and humidity resistance of the porous Si3N4 ceramic was investigated. The experimental results showed that we successfully fabricated the uniform and dense coating which preferably combined with the substrate upon the addition of fillers. The bending strength of the porous Si3N4 ceramic sprayed the coating increased by more than 18%, and the surface hardness increased by 1.7 times. The apparent porosity of the materials reduced by an average of 97.7%, and water absorption was below 0.5%. Therefore, the prepared coating with preferable density had an obviously moisture-proof and enhanced effect on the porous Si3N4 ceramic.
文摘The feasibility of making two antennas work within a shared aperture conformai to a platform like an aircraft or a missile is investigated. The shared aperture is enclosed by a deep cavity, which is covered by a columniform dielectric radome. A modified quadrifilar helix antenna (QHA) with extended volute arms and a vertical monopole with a ring shaped ground are arranged in this co-aperture for global position system (GPS) orientation and telemetry, respectively. The effects of the cavity on these two antennas and the mutual coupling between these two antennas are studied through large numbers of experiments. The results show that the QHA has a strong influence on the monopole; however, these two antennas of the overall arrangement can perform simultaneously well within the aperture. The QHA has a right hand circular polarization (RHCP) and a broad beam normal to the radome topside, meanwhile the monopole can be used to produce a main lobe in the grazing direction above the aperture in some certain cases of the vertical location of the QHA in the cavity.
基金Project supported by the Major Research Plan of the National Natural Science Foundation of China (Grant No. 90305026)
文摘The transmission properties of compound frequency selective structures with dielectric slab and air gaps were investigated by computation and experimentation. Mechanism analyses were also carried out. Results show that the air gaps have a distinct influence on the transmission properties. Resonant frequency of the structure would increase rapidly when the air gap appears. After the gap gets larger to a specific value, generally 1/5 wavelength corresponding to the resonant frequency, the transmission properties would change periodically with the gap thickness. The change of transmission properties in one period has a close relationship with the dielectric thickness. These results provide a new method for designing a bandpass radome of large incidence angle and low loss with the concept of stealth shield radome.
文摘The plane wave spectrum surface integration (PWS SI) is a practical and efficient method for antenna radome system analysis, especially for determining the boresight error (BSE) in the system. But it is only used for sum pattern calculation till now, and BSE is calculated by the beam maximum searching method. In this paper, the aperture distribution for difference pattern is formulated as the product of that for sum pattern and a two dimensional periodic window function. A series representation for the spectrum of difference pattern is then obtained according to the convolution theorem. The truncation error of the series has been analyzed by introducing the coverage radius of the spectrum of sum pattern. Based on this representation, the PWS SI technique is extended to difference pattern calculation of radome enclosed antennas. The BSE of a three dimensional multilayered radome, with thickness tapers in all layers, is calculated through the difference pattern null searching. Owing to the steep slope of difference pattern near the nulls, this method for BSE calculation is more stable and reliable than the original beam maximum searching method in PWS SI analysis. The results are compared with those from aperture integration surface integration (AI SI) analysis and the measured ones.
基金This work is supported by Chinese Research Institute of Electronic Science Nanchang Aerocraft Company.
文摘Electromagnetic transmission and scattering characteristics of radome may conve-niently be analyzed by complex ray paraxial approximation and collective ray methods.As anexample,a 2-D cylindrical single-layered dielectric radome is analyzed and calculated in this in-vestigation,including radome transmission coefficient,radar angular track performance and radarcross section of radomes,as well as the effect of ray parameters and antenna-radome parameterson computation accuracy.It is shown that this method can be used to simplify optimizations formany kinds of radomes.
文摘An effective broadband modified B Sandwich as radome’s layer structure is profosed. The power transmission coefficient of this sandwich is over 80% under large incident angle range (0°-70°) and broadband (0-40GHz). The difference of insertion phase delay (IPD) between perpendicular polarization and parallel one is very small.
文摘In this paper, it is offered to use the method of modulated reflection for the measurementof complex transfer factor of a radome wall on various sites of its surface. The circuit of equipmentallowed to carry out of such measurement is given. The advantage of the given method in comparisonwith measurements on a gleam is shown. The results of the experimental research are given and theestimation of the accuracy of proposed method is considered.
文摘This paper presents an algorithm for analysis of the dielectric radomes. In this method, the radome is discretized by a regular grid with rooftop basic functions. The Volume Integral Equation (VIE) for 3D dielectric object is transformed to linear system by Galerkin’s testing formulation. Furthermore, the linear system is presented by Toeplitz matrix which can be solved by the Conjugate Gradient algorithm combined with Fast Fourier Transform (CG-FFT) iteratively. Also, the algorithm requires less computational complexity and memory. This paper simulates the mono-static Radar Cross Section of dielectric radome by the CG-FFT, which was validated against commercial software FEKO.
文摘Basing on the transformation optics, we propose a kind of transformation method of compressing or stretching. With the method, we propose a design of transparent radome for different structures. The electromagnetic (EM) waves inside or outside the radome can transmit through the structure without any reflection. Numerical simulations confirm the function of the radome structures.
基金Project supported by the National Basic Resarch Program of China(Grant No.2014CB339800)the National Natural Science Foundation of China(Grant No.11173015)
文摘An experimental double-layer active frequency-selective surface(AFSS) for stealth radome is proposed. The AFSS is a planar structure which is composed of a fixed frequency-selective surface(FSS), a PIN diodes array, and a DC bias network. The AFSS elements incorporating switchable PIN diodes are discussed. By means of controlling the DC bias network, it is possible to switch the frequency response for reflecting and transmitting. Measured and simulated data validate that when the incidence angle varies from 0°to 30° the AFSS produces more than-11.5 dB isolation across6–18 GHz when forward biased. The insertion loss(IL) is less than 0.5 dB across 10–11 GHz when reverse biased.
基金This work was supported by the National Natural Science Foundation of China(Grant No.10371092)Foundation of Wuhan University.
文摘In sec.1, we introduce several basic concepts such as random transition function, p-m process and Markov process in random environment and give some examples to construct a random transition function from a non-homogeneous density function. In sec.2, we construct the Markov process in random enviromment and skew product Markov process by p - m process and investigate the properties of Markov process in random environment and the original process and environment process and skew product process. In sec. 3, we give several equivalence theorems on Markov process in random environment.