The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed.The spectrum spreads of different orbital angular mom...The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed.The spectrum spreads of different orbital angular momentum(OAM)modes in different non-line-of-sight situations are simulated.The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space.According to the research,the effects about spectrum spreads of higher OAM modes are more obvious.The error in detection is mainly affected by OAM spectrum spreading,which can be reduced by reasonably using different combinations of OAM modes in different practical situations.The above results provide a reference idea for investigating keyhole effect when vortex electromagnetic wave is used to detect accelerations.展开更多
In a quasi-two-dimensional model, the scattering of incident ordinary electromag- netic waves by a dipole-electrostatic drift vortex is studied with first-order Born approximation. The distribution of the scattering c...In a quasi-two-dimensional model, the scattering of incident ordinary electromag- netic waves by a dipole-electrostatic drift vortex is studied with first-order Born approximation. The distribution of the scattering cross-section and total cross-section are evaluated analytically in different approximate conditions, and the physical interpretations are discussed. When the wavelength of incident wave is much longer than the vortex radius （kia〈〈1）, it is found that the angle at which the scattering cross-section reaches its maxim depends significantly on the approximation of the parameters of the vortex used. It is also found that the total scattering cross-section has an affinitive relation with the parameters of the plasma, while it is irrelevant to the frequency of the incident wave in a wide range of parameters of the vortex. In a totally different range of parameters when incident wave is in the radar-frequency range （then kia 〈〈 1, the wavelength of incident wave is much shorter than the vortex radius）, the numerical procedure is conducted with computer in order to obtain the distribution and the total expression of the scattering crosssection. Then it is found that the total scattering cross-section in the low frequency range is much larger than that in high frequency range, so the scattering is more effective in the low frequency range than in high frequency range.展开更多
In this paper,we combine the circular polarization technology and orbital angular momentum(OAM)into the array antenna design for the first time,achieve free switch of the different topological charges in the array by ...In this paper,we combine the circular polarization technology and orbital angular momentum(OAM)into the array antenna design for the first time,achieve free switch of the different topological charges in the array by using high-speed radio frequency(RF)switch technology.We arrange microstrip patch antenna elements equidistantly along the circumference to form eight elements multi-modal OAM vortex electromagnetic wave microstrip array antenna.It can generate elec-tromagnetic waves with dual characteristics of circular polarization and multi-modal vortex OAM(where OAM mode values are l=0,l=±1,l=±2,l=±3).Through simulation,we find mutual coupling between the radiating elements is small relatively,and increasing the number of array elements can not only improve the beam quality,but also generate electromagnetic waves with a higher order of OAM modes.Antenna model can meet the basic demands of ordinary array antenna,and also confirm the practicality of this circular polarized microstrip antenna array model.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11804073 and 61775050).
文摘The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed.The spectrum spreads of different orbital angular momentum(OAM)modes in different non-line-of-sight situations are simulated.The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space.According to the research,the effects about spectrum spreads of higher OAM modes are more obvious.The error in detection is mainly affected by OAM spectrum spreading,which can be reduced by reasonably using different combinations of OAM modes in different practical situations.The above results provide a reference idea for investigating keyhole effect when vortex electromagnetic wave is used to detect accelerations.
基金National Natural Science Foundation of China(Nos,10375063.40336052)
文摘In a quasi-two-dimensional model, the scattering of incident ordinary electromag- netic waves by a dipole-electrostatic drift vortex is studied with first-order Born approximation. The distribution of the scattering cross-section and total cross-section are evaluated analytically in different approximate conditions, and the physical interpretations are discussed. When the wavelength of incident wave is much longer than the vortex radius （kia〈〈1）, it is found that the angle at which the scattering cross-section reaches its maxim depends significantly on the approximation of the parameters of the vortex used. It is also found that the total scattering cross-section has an affinitive relation with the parameters of the plasma, while it is irrelevant to the frequency of the incident wave in a wide range of parameters of the vortex. In a totally different range of parameters when incident wave is in the radar-frequency range （then kia 〈〈 1, the wavelength of incident wave is much shorter than the vortex radius）, the numerical procedure is conducted with computer in order to obtain the distribution and the total expression of the scattering crosssection. Then it is found that the total scattering cross-section in the low frequency range is much larger than that in high frequency range, so the scattering is more effective in the low frequency range than in high frequency range.
基金supported in part by the Nation Natural Science Foundation of China(No.61561039)the Nation Natural Science Foundation of Ningxia Province(No.NZ17041).
文摘In this paper,we combine the circular polarization technology and orbital angular momentum(OAM)into the array antenna design for the first time,achieve free switch of the different topological charges in the array by using high-speed radio frequency(RF)switch technology.We arrange microstrip patch antenna elements equidistantly along the circumference to form eight elements multi-modal OAM vortex electromagnetic wave microstrip array antenna.It can generate elec-tromagnetic waves with dual characteristics of circular polarization and multi-modal vortex OAM(where OAM mode values are l=0,l=±1,l=±2,l=±3).Through simulation,we find mutual coupling between the radiating elements is small relatively,and increasing the number of array elements can not only improve the beam quality,but also generate electromagnetic waves with a higher order of OAM modes.Antenna model can meet the basic demands of ordinary array antenna,and also confirm the practicality of this circular polarized microstrip antenna array model.
