Impulse systems do not undergo the multi-path destructive interference that manifests itself as Rayleigh fading prevalent in continuous wave systems, but rather show up as delayed replications of the direct impulse. I...Impulse systems do not undergo the multi-path destructive interference that manifests itself as Rayleigh fading prevalent in continuous wave systems, but rather show up as delayed replications of the direct impulse. In this paper, the model for impulse signals propagation over a plane earth is proposed. The condition for direct pulse and its replication overlapping each other was investigated. The model described here also takes into account the polarization of the transmission signals and the reflection coefficient of the plane, which was always neglected by previous approaches. The simulation result shows that the path loss can be characterized as 3 zones with different path loss exponents as the distance between transmitter and receiver (T-R) increasing.展开更多
Lead iodide single crystal was grown by physical vapor transport method.Two radiation detectors with different configurations were fabricated from the as-grown crystal.The electrical and y-ray response properties at r...Lead iodide single crystal was grown by physical vapor transport method.Two radiation detectors with different configurations were fabricated from the as-grown crystal.The electrical and y-ray response properties at room temperature of the both detectors were investigated.It is found that the dark resistivity of the detectors are respectively 3×10^（10）Ω·cm for bias electric field parallel to crystal c-axis（E//c） and 2×10~8Ω·cm for perpendicular to crystal c-axis（E⊥c）.The energy spectrum response measurement shows that both detectors were sensitive to ^（241） Am 59.5 keVγ-rays,and achieved a good energy resolution of 16.8%for the E⊥c-axis configuration detector with a full width at half maximum of 9.996 keV.展开更多
基金Sponsored by the Key Program of National Natural Science Foundation of China(Grant No60432040)
文摘Impulse systems do not undergo the multi-path destructive interference that manifests itself as Rayleigh fading prevalent in continuous wave systems, but rather show up as delayed replications of the direct impulse. In this paper, the model for impulse signals propagation over a plane earth is proposed. The condition for direct pulse and its replication overlapping each other was investigated. The model described here also takes into account the polarization of the transmission signals and the reflection coefficient of the plane, which was always neglected by previous approaches. The simulation result shows that the path loss can be characterized as 3 zones with different path loss exponents as the distance between transmitter and receiver (T-R) increasing.
基金Project supported by the National Natural Science Foundation of China(No.50902012)the Natural Science Foundation of Sichuan Province,China(No.2009JY0087)
文摘Lead iodide single crystal was grown by physical vapor transport method.Two radiation detectors with different configurations were fabricated from the as-grown crystal.The electrical and y-ray response properties at room temperature of the both detectors were investigated.It is found that the dark resistivity of the detectors are respectively 3×10^（10）Ω·cm for bias electric field parallel to crystal c-axis（E//c） and 2×10~8Ω·cm for perpendicular to crystal c-axis（E⊥c）.The energy spectrum response measurement shows that both detectors were sensitive to ^（241） Am 59.5 keVγ-rays,and achieved a good energy resolution of 16.8%for the E⊥c-axis configuration detector with a full width at half maximum of 9.996 keV.
