In this paper theoretical analysis of sound field within a tube with an apcrture on its wall is presented. Equivalent circuit is obtained for calculation of sound waves propagating within the tube. The aperture on tub...In this paper theoretical analysis of sound field within a tube with an apcrture on its wall is presented. Equivalent circuit is obtained for calculation of sound waves propagating within the tube. The aperture on tube wall can be represented by a lumped circuit impedance in the equivalent circuit. The impedance is written in terms of aperture impedance and an inertance due to the disturbance of sound field by the aperture. Expressions for calculation of the impedance are given for a rectangular aperture. The effect of sound source is also discussed.展开更多
Spaceborne Synthetic Aperture Radar(SAR) is a well-established and powerful imaging technology that can provide high-resolution images of the Earth’s surface on a global scale. For future SAR systems, one of the key ...Spaceborne Synthetic Aperture Radar(SAR) is a well-established and powerful imaging technology that can provide high-resolution images of the Earth’s surface on a global scale. For future SAR systems, one of the key capabilities is to acquire images with both high-resolution and wide-swath. In parallel to the evolution of SAR sensors, more precise range models, and effective imaging algorithms are required. Due to the significant azimuth-variance of the echo signal in High-Resolution Wide-Swath(HRWS) SAR, two challenges have been faced in conventional imaging algorithms. The first challenge is constructing a precise range model of the whole scene and the second one is to develop an effective imaging algorithm since existing ones fail to process highresolution and wide azimuth swath SAR data effectively. In this paper, an Advanced High-order Nonlinear Chirp Scaling(A-HNLCS) algorithm for HRWS SAR is proposed. First, a novel Second-Order Equivalent Squint Range Model(SOESRM) is developed to describe the range history of the whole scene, by introducing a quadratic curve to fit the deviation of the azimuth FM rate. Second, a corresponding algorithm is derived, where the azimuth-variance of the echo signal is solved by azimuth equalizing processing and accurate focusing is achieved through a high-order nonlinear chirp scaling algorithm. As a result, the whole scene can be accurately focused through one single imaging processing. Simulations are provided to validate the proposed range model and imaging algorithm.展开更多
文摘In this paper theoretical analysis of sound field within a tube with an apcrture on its wall is presented. Equivalent circuit is obtained for calculation of sound waves propagating within the tube. The aperture on tube wall can be represented by a lumped circuit impedance in the equivalent circuit. The impedance is written in terms of aperture impedance and an inertance due to the disturbance of sound field by the aperture. Expressions for calculation of the impedance are given for a rectangular aperture. The effect of sound source is also discussed.
基金supported by the National Natural Science Foundation of China (No. 61861136008)。
文摘Spaceborne Synthetic Aperture Radar(SAR) is a well-established and powerful imaging technology that can provide high-resolution images of the Earth’s surface on a global scale. For future SAR systems, one of the key capabilities is to acquire images with both high-resolution and wide-swath. In parallel to the evolution of SAR sensors, more precise range models, and effective imaging algorithms are required. Due to the significant azimuth-variance of the echo signal in High-Resolution Wide-Swath(HRWS) SAR, two challenges have been faced in conventional imaging algorithms. The first challenge is constructing a precise range model of the whole scene and the second one is to develop an effective imaging algorithm since existing ones fail to process highresolution and wide azimuth swath SAR data effectively. In this paper, an Advanced High-order Nonlinear Chirp Scaling(A-HNLCS) algorithm for HRWS SAR is proposed. First, a novel Second-Order Equivalent Squint Range Model(SOESRM) is developed to describe the range history of the whole scene, by introducing a quadratic curve to fit the deviation of the azimuth FM rate. Second, a corresponding algorithm is derived, where the azimuth-variance of the echo signal is solved by azimuth equalizing processing and accurate focusing is achieved through a high-order nonlinear chirp scaling algorithm. As a result, the whole scene can be accurately focused through one single imaging processing. Simulations are provided to validate the proposed range model and imaging algorithm.
