Jin Rencheng

Design and simulation of blue/violet sensitive photodetectors in silicon-on-insulator ∗

According to Lamberts law, a novel structure of photodetectors, namely photodetectors in silicon- on-insulator, is proposed. By choosing a certain thickness value for the SOI layer, the photodetector can absorb blue/violet light effectively and affect the responsivity of the long wavelength in the visible and near-infrared re- gion, making a blue/violet filter unnecessary. The material of the SOI layer is high-resistivity floating-zone silicon which can cause the neutral N type SOI layer to become fully depleted after doping with a P type impurity. This can improve the collection efficiency of short-wavelength photogenerated carriers. The device structure was optimized through numerical simulation, and the results show that the photodiode is a kind of high performance photodetector in the blue/violet region.

A design of efficient transport layer protocol for wireless sensor network gateway

It is necessary that in the small-or-medium-size wireless sensor networks, the networking information of network and monitoring data of sensors should be sent to the remote computers through the gateway to achieve remote monitoring for the target area. Wireless sensor network data characterize strong bursts, instability of traffic and small amount of data in a single packet. Considering these features as well as the bandwidth of wireless network, the paper proposes a Transport Control Protocol (TCP) with an improved Nagle algorithm. The experiments prove that the improved algorithm obviously enhances the utilization of wireless channel and reduces system energy consumption, while it ensures transmission reliability.

A Novel Wireless Sensor Networks Platform for Habitat Surveillance

Wireless sensor networks are more adaptive to habitat surveillance applications than other technique due to high distribution density and self-organization of tiny sensor nodes. This paper introduced a framework of wireless sensor networks combined with GPRS (General Packet Radio Service) for habitat monitoring. Detailed presentation of a novel sensor node making use of ARM technology and IEEE502.15.4 standard was given. This paper concerned on energy management issue, realizing a light-weight and constant duty cycle energy management policy similar to S-MAC (Sensor Medium Access Control). Minimum, maximum and average power consumption of sensor node, under different CPU and VPB frequency, were measured when node was running test program to finish networking and application function. The results help users choosing the most appropriate frequency to optimize power consumption.

The Development of Spectral Responsivity Testing System

The spectral responsivity testing system based on optical fiber transporting light has been designed and developed. The system includes five parts: optical source, monochromator system, darkroom, picoammeter and stepping motor driver. Using the standard photodetector substitution to calibrate the photodetector under testing, with the optical fiber translating monochromatic light, the main technical problem emphasizes on solving the limitation of photodetector’s active area involving in the test of spectral responsivity. The testing result shows that the error is less than 0.46%.