This paper considers the problem of global stabilization by output feedback for a class of nonlinear systems with uncertain control coefficients and with unmeasured states dependent growth. Mainly due to the uncertain...This paper considers the problem of global stabilization by output feedback for a class of nonlinear systems with uncertain control coefficients and with unmeasured states dependent growth. Mainly due to the uncertain control coefficients, the problem has remained unsolved and its major difficulty stems from the inapplicability of the commonly used high-gain like observer. By introducing an appropriate state transformation and a thoroughly novel observer based on high-gain K-filters, the backstepping design approach is successfully proposed to the output-feedback controller for this class of systems. It is shown that the global asymptotic stability of the closed-loop system can be guaranteed by the appropriate choice of the control parameters.展开更多
设计并制备了一种兼具高增益和低雷达散射截面(radar cross section,RCS)的微带天线,通过给原始微带天线加载双屏频率选择表面(frequency selective surface,FSS)覆层,使其具有宽带的3 d B增益带宽和宽带、宽角度的低RCS特性.该FSS单元...设计并制备了一种兼具高增益和低雷达散射截面(radar cross section,RCS)的微带天线,通过给原始微带天线加载双屏频率选择表面(frequency selective surface,FSS)覆层,使其具有宽带的3 d B增益带宽和宽带、宽角度的低RCS特性.该FSS单元的上层是四个开口处都焊有电阻的金属环结构,下层是中间和四边都开缝的金属贴片结构.上层加载的电阻主要用于吸收雷达入射波,减缩天线RCS;下层的贴片和天线地板构成Fabry-Perot谐振腔,提高天线增益.在5.75—11.37 GHz频带内,S22<-10 d B,S12<-10 d B;在11.21—11.54 GHz频带内,S11反射系数相位曲线斜率为正,幅度模值均在0.86以上.实验结果表明:与原始天线相比,在谐振频点11.73 GHz处,天线增益提高3.4 d B,E,H面的半功率波束宽度分别减小16°和50°;天线的3 d B增益带宽为10.00—12.40 GHz,完全覆盖阻抗带宽.在4.10—11.30 GHz频带内,天线法向RCS均有3 d B以上的减缩,最大减缩23.08 d B;4.95 GHz处的单站RCS在-20°—20°的角域、双站RCS在-37°—37°的角域均有3 d B以上的减缩.实验结果证实了该FSS覆层可用于同时改善天线的辐射和散射性能.展开更多
We report our experimental observation of charge domain oscillation in semi-insulating GaAs photocon-ductive semiconductor switches (PCSSs). The high-gain PCSS is intrinsically a photon-activated charge domain device....We report our experimental observation of charge domain oscillation in semi-insulating GaAs photocon-ductive semiconductor switches (PCSSs). The high-gain PCSS is intrinsically a photon-activated charge domain device. It is the photon-activated carriers that satisfy the requirement of charge domain formation on carrier concentration and device length product of 1012 cm-2. We also show that, because of the repeated process of domain formation, the domain travels with a compromised speed of electron saturation velocity and the speed of light. As a result, the transit time of charge domains in PCSS is much shorter than that of traditional Gunn domains.展开更多
基金the National Natural Science Foundation of China (Grant No.60674036)the Science and Technique Development Plan of Shandong Province (Grant No.2004GG4204014)+2 种基金the Program for New Century Excellent Talents in University of China (Grant No.NCET-07-0513)the Excellent Young and Middle-Aged Scientist Award Grant of Shandong Province of China (Grant No.2007BS01010)the Key Science and Technique Foundation of Ministry of Education (Grant No.108079)
文摘This paper considers the problem of global stabilization by output feedback for a class of nonlinear systems with uncertain control coefficients and with unmeasured states dependent growth. Mainly due to the uncertain control coefficients, the problem has remained unsolved and its major difficulty stems from the inapplicability of the commonly used high-gain like observer. By introducing an appropriate state transformation and a thoroughly novel observer based on high-gain K-filters, the backstepping design approach is successfully proposed to the output-feedback controller for this class of systems. It is shown that the global asymptotic stability of the closed-loop system can be guaranteed by the appropriate choice of the control parameters.
文摘设计并制备了一种兼具高增益和低雷达散射截面(radar cross section,RCS)的微带天线,通过给原始微带天线加载双屏频率选择表面(frequency selective surface,FSS)覆层,使其具有宽带的3 d B增益带宽和宽带、宽角度的低RCS特性.该FSS单元的上层是四个开口处都焊有电阻的金属环结构,下层是中间和四边都开缝的金属贴片结构.上层加载的电阻主要用于吸收雷达入射波,减缩天线RCS;下层的贴片和天线地板构成Fabry-Perot谐振腔,提高天线增益.在5.75—11.37 GHz频带内,S22<-10 d B,S12<-10 d B;在11.21—11.54 GHz频带内,S11反射系数相位曲线斜率为正,幅度模值均在0.86以上.实验结果表明:与原始天线相比,在谐振频点11.73 GHz处,天线增益提高3.4 d B,E,H面的半功率波束宽度分别减小16°和50°;天线的3 d B增益带宽为10.00—12.40 GHz,完全覆盖阻抗带宽.在4.10—11.30 GHz频带内,天线法向RCS均有3 d B以上的减缩,最大减缩23.08 d B;4.95 GHz处的单站RCS在-20°—20°的角域、双站RCS在-37°—37°的角域均有3 d B以上的减缩.实验结果证实了该FSS覆层可用于同时改善天线的辐射和散射性能.
基金This work was supported by the National Natural Sci-ence Foundation of China under Grant No.50077017.
文摘We report our experimental observation of charge domain oscillation in semi-insulating GaAs photocon-ductive semiconductor switches (PCSSs). The high-gain PCSS is intrinsically a photon-activated charge domain device. It is the photon-activated carriers that satisfy the requirement of charge domain formation on carrier concentration and device length product of 1012 cm-2. We also show that, because of the repeated process of domain formation, the domain travels with a compromised speed of electron saturation velocity and the speed of light. As a result, the transit time of charge domains in PCSS is much shorter than that of traditional Gunn domains.
