提出一种新型磁负超材料单元,通过采用HFSS,Matlab等软件对其电磁特性进行了详细分析和讨论,结果表明其具有较好的磁负特性。根据该磁负超材料在磁负频段谐振产生传输阻带这一特性,设计了一款工作在3 GHz的同轴馈电二单元微带天线阵。...提出一种新型磁负超材料单元,通过采用HFSS,Matlab等软件对其电磁特性进行了详细分析和讨论,结果表明其具有较好的磁负特性。根据该磁负超材料在磁负频段谐振产生传输阻带这一特性,设计了一款工作在3 GHz的同轴馈电二单元微带天线阵。通过在天线阵单元间加载该磁负超材料单元阵列,使天线阵列间互耦有效降低了12.1 d B。天线单元间距仅为λ/10(λ为天线在自由空间工作波长),且天线阵列的远场辐射性能有所提高。因此,所设计的磁负超材料单元在设计紧凑型高性能天线阵列方面具有广阔应用前景。展开更多
设计了一款单馈电的小型圆极化微带天线。在方形贴片上,通过切角和对称开槽的方法,天线获得了良好的右旋圆极化性能,并实现了小型化设计。借助HFSS电磁仿真软件,对天线参数进行了仿真和分析。仿真结果表明,S11<-10 d B的阻抗带宽为82...设计了一款单馈电的小型圆极化微带天线。在方形贴片上,通过切角和对称开槽的方法,天线获得了良好的右旋圆极化性能,并实现了小型化设计。借助HFSS电磁仿真软件,对天线参数进行了仿真和分析。仿真结果表明,S11<-10 d B的阻抗带宽为82 MHz,3 d B圆极化轴比带宽为12 MHz,较好地满足了北斗接收天线的设计要求。该设计具有方法简单、易于实现、成本较低等优点,且具有良好的应用前景。展开更多
Atmospheric electricity is composed of a wide range of electric phenomena in the troposphere, strato- sphere, and even lower ionosphere. Research progress on atmospheric electricity in the past 5 years in China are br...Atmospheric electricity is composed of a wide range of electric phenomena in the troposphere, strato- sphere, and even lower ionosphere. Research progress on atmospheric electricity in the past 5 years in China are briefly reviewed here. This research area has been greatly expanded through rocket-triggered lightning experiments and the increased use of high spatio-temporal resolution techniques for the detection and location of lightning. The main results described in this review are summarized in the following five aspects： （1） processes and parameters inferred from rocket-triggered lightning, （2） lightning physics and ef- fects （observations and theoretical study）, （3） lightning activities associated with different thunderstorms, （4） charge structure of thunderstorms （observations and simulation）, and （5） the VHF/UHF lightning location techniques and discharge channel mapping.展开更多
Besides the electrode-pair antenna,the magnetic antenna is also used for the extremely low frequency （ELF） submarine communication.To receive the weak ELF signals,the structure of a small sized magnetic antenna dete...Besides the electrode-pair antenna,the magnetic antenna is also used for the extremely low frequency （ELF） submarine communication.To receive the weak ELF signals,the structure of a small sized magnetic antenna determines its specific electrical characteristics.The ELF magnetic antenna shows high internal resistance, alternating-current impedance,and a resonance frequency near the operating bandwidth.In accordance with the electrical characteristics of ELF magnetic antenna,a low noise preamplifier and frequency compensation circuit were designed and realized.The preamplifier is a three-stage negative feedback circuit,which is composed of parallel JFET,common-emitter amplifier with a Darlington structure and a common-collector amplifier in push-pull connection.And a frequency compensation circuit is cascaded to compensate the characteristic in low frequency range.In the operating bandwidth f = 30-200 Hz,the circuit has a gain of 39.4 dB.The equivalent input noise is 1.97 nV/Hz^（1/2） and the frequency response keeps flat in operating bandwidth.The proposed preamplifier of the ELF magnetic antenna performs well in receiving ELF signals.展开更多
文摘提出一种新型磁负超材料单元,通过采用HFSS,Matlab等软件对其电磁特性进行了详细分析和讨论,结果表明其具有较好的磁负特性。根据该磁负超材料在磁负频段谐振产生传输阻带这一特性,设计了一款工作在3 GHz的同轴馈电二单元微带天线阵。通过在天线阵单元间加载该磁负超材料单元阵列,使天线阵列间互耦有效降低了12.1 d B。天线单元间距仅为λ/10(λ为天线在自由空间工作波长),且天线阵列的远场辐射性能有所提高。因此,所设计的磁负超材料单元在设计紧凑型高性能天线阵列方面具有广阔应用前景。
文摘设计了一款单馈电的小型圆极化微带天线。在方形贴片上,通过切角和对称开槽的方法,天线获得了良好的右旋圆极化性能,并实现了小型化设计。借助HFSS电磁仿真软件,对天线参数进行了仿真和分析。仿真结果表明,S11<-10 d B的阻抗带宽为82 MHz,3 d B圆极化轴比带宽为12 MHz,较好地满足了北斗接收天线的设计要求。该设计具有方法简单、易于实现、成本较低等优点,且具有良好的应用前景。
基金supported by National Natural Science Foundation of China (Grant No.40930949)the One Hundred Person Project of the Chinese Academy of Sciences
文摘Atmospheric electricity is composed of a wide range of electric phenomena in the troposphere, strato- sphere, and even lower ionosphere. Research progress on atmospheric electricity in the past 5 years in China are briefly reviewed here. This research area has been greatly expanded through rocket-triggered lightning experiments and the increased use of high spatio-temporal resolution techniques for the detection and location of lightning. The main results described in this review are summarized in the following five aspects： （1） processes and parameters inferred from rocket-triggered lightning, （2） lightning physics and ef- fects （observations and theoretical study）, （3） lightning activities associated with different thunderstorms, （4） charge structure of thunderstorms （observations and simulation）, and （5） the VHF/UHF lightning location techniques and discharge channel mapping.
基金Project supported by the Defense Pre-Research Foundation of China(No.51401020503)
文摘Besides the electrode-pair antenna,the magnetic antenna is also used for the extremely low frequency （ELF） submarine communication.To receive the weak ELF signals,the structure of a small sized magnetic antenna determines its specific electrical characteristics.The ELF magnetic antenna shows high internal resistance, alternating-current impedance,and a resonance frequency near the operating bandwidth.In accordance with the electrical characteristics of ELF magnetic antenna,a low noise preamplifier and frequency compensation circuit were designed and realized.The preamplifier is a three-stage negative feedback circuit,which is composed of parallel JFET,common-emitter amplifier with a Darlington structure and a common-collector amplifier in push-pull connection.And a frequency compensation circuit is cascaded to compensate the characteristic in low frequency range.In the operating bandwidth f = 30-200 Hz,the circuit has a gain of 39.4 dB.The equivalent input noise is 1.97 nV/Hz^（1/2） and the frequency response keeps flat in operating bandwidth.The proposed preamplifier of the ELF magnetic antenna performs well in receiving ELF signals.
