Impedance metasurfaces enable accurate regulation of acoustic fields.However,they can hardly supply a flexible response as such perfect operation is accompanied by stringent requirements on the design of unit cells.Ac...Impedance metasurfaces enable accurate regulation of acoustic fields.However,they can hardly supply a flexible response as such perfect operation is accompanied by stringent requirements on the design of unit cells.Actually,an arbitrary lossless and passive target impedance matrix requires the tuning of 3 independent real parameters.The set composed of a reflection phase,a transmission amplitude,and a transmission phase,enables the representation of an arbitrary impedance matrix,possibly possessing singular elements.In this paper,a mechanism of phase-amplitude-phase modulation(PAP modulation)is developed for the generic design of the unit cells of acoustic impedance metasurfaces.Adjustable acoustic impedance metasurfaces are further available under this framework.An impedance unit with 3 mobile parts is designed based on this idea.The assembled metasurface can handle different incidences for acoustic field manipulation at a given frequency.Beam steering and beam splitting are considered as demonstration examples and are verified by numerical simulation and experiment.PAP modulation enriches the design of acoustic impedance metasurfaces and extends the range of application of impedance theory.展开更多
The resolution of the multistatic passive radar imaging system(MPRIS)is poor due to the narrow bandwidth of the signal transmitted by illuminators of opportunity.Moreover,the inaccuracies caused by the inaccurate trac...The resolution of the multistatic passive radar imaging system(MPRIS)is poor due to the narrow bandwidth of the signal transmitted by illuminators of opportunity.Moreover,the inaccuracies caused by the inaccurate tracking system or the error position measurement of illuminators or receivers can deteriorate the quality of an image.To improve the performance of an MPRIS,an imaging method based on the tomographic imaging principle is presented.Then the compressed sensing technique is extended to the MPRIS to realize high-resolution imaging.Furthermore,a phase correction technique is developed for compensating for phase errors in an MPRIS.Phase errors can be estimated by iteratively solving an equation that is derived by minimizing the mean recovery error of the reconstructed image based on the principle of fixed-point iteration technique.The technique is nonparametric and can be used to estimate phase errors of any form.The effectiveness and convergence of the technique are confirmed by numerical simulations.展开更多
基金supported by the National Natural Science Foundation of China(grant numbers 12072223,12122207,12021002,and 11991032)the EIPHI Graduate School(grant number ANR-17-EURE-0002).
文摘Impedance metasurfaces enable accurate regulation of acoustic fields.However,they can hardly supply a flexible response as such perfect operation is accompanied by stringent requirements on the design of unit cells.Actually,an arbitrary lossless and passive target impedance matrix requires the tuning of 3 independent real parameters.The set composed of a reflection phase,a transmission amplitude,and a transmission phase,enables the representation of an arbitrary impedance matrix,possibly possessing singular elements.In this paper,a mechanism of phase-amplitude-phase modulation(PAP modulation)is developed for the generic design of the unit cells of acoustic impedance metasurfaces.Adjustable acoustic impedance metasurfaces are further available under this framework.An impedance unit with 3 mobile parts is designed based on this idea.The assembled metasurface can handle different incidences for acoustic field manipulation at a given frequency.Beam steering and beam splitting are considered as demonstration examples and are verified by numerical simulation and experiment.PAP modulation enriches the design of acoustic impedance metasurfaces and extends the range of application of impedance theory.
基金Project supported by the National Natural Science Foundation of China(No.61401526)the Innovative Research Team in University,China(No.IRT0954)the Foundation of National Ministries,China(No.9140A07020614DZ01)
文摘The resolution of the multistatic passive radar imaging system(MPRIS)is poor due to the narrow bandwidth of the signal transmitted by illuminators of opportunity.Moreover,the inaccuracies caused by the inaccurate tracking system or the error position measurement of illuminators or receivers can deteriorate the quality of an image.To improve the performance of an MPRIS,an imaging method based on the tomographic imaging principle is presented.Then the compressed sensing technique is extended to the MPRIS to realize high-resolution imaging.Furthermore,a phase correction technique is developed for compensating for phase errors in an MPRIS.Phase errors can be estimated by iteratively solving an equation that is derived by minimizing the mean recovery error of the reconstructed image based on the principle of fixed-point iteration technique.The technique is nonparametric and can be used to estimate phase errors of any form.The effectiveness and convergence of the technique are confirmed by numerical simulations.
