In this paper, we demonstrate a novel concept of collision avoidance based on single photon detectors along with time correlated single photon counting techniques, which uses chaotic pulse position modulation for anti-crosstalk considerations. In order to distract the signal from estimated background noise, parameters including pulse rate, discrimination threshold and number of accumulated pulses have been thoroughly analyzed based on the detection requirements, resulting in specified receiver operating characteristics curves. Both simulation and indoor experiments were performed to verify the excellent anti-crosstalk capability of the presented collision avoidance LIDAR despite of ultra-low transmitting power.
Sun sensor is a key device in satellite’s attitude determination system. It acquires satellite’s attitude information by measuring sun light direction. Compared with area array CMOS sun sensor, the linear CMOS sun sensor has the advantages of low power consumption, light weight and relatively simple algorithm. Considering the pixel number, power consumption and efficiency of output, most sun sensors equipped with a single photosensitive unit usually have (±60)x(±60) field of view(FOV). Satellites usually use multiple sun sensors for semi-sphere field of view in total to meet the need of attitude measurement in all directions. Considering the need of large-scale FOV measurement and high integration level, this paper proposes a semi-sphere FOV sun sensor, of which coverage area can be (±90)x(±90) . A prototype has been made and the calibration of key component has been conducted. By integrating four photosensitive units, the semi-sphere FOV sun sensor is achieved, as a result, the demand of high integration can be realized for a micro-satellite device. The photosensitive unit consists of an N-shape slit mask and a linear CMOS image sensor. An N-shape slit model is established to acquire biaxial sun angles from analyzing the shift of 3 peak values from the image of the linear sensor. Embedded system has been designed and developed, in which the MCU control four photosensitive units. Calibration of one photosensitive unit, which is the key step in the process of the whole calibration of semi-sphere FOV sun sensor, has been conducted. As a result of the symmetry of N-shape slit, initial position of the linear image sensor can be fixed. Due to the installation error and machining deviation, centroid algorithm and data gridding technique is adopted to improve the accuracy. Experiments show that the single photosensitive unit can reach an angle accuracy of 0.1625°. Consequently, from the point of significant component in the sun sensor, initial calibration ensures the angle accuracy of semi-sphere FOV sun sensor.
Resilient packet ring (RPR) is a good capacity solution to next generation metropolitan area network (MAN). This paper introduces the back end design of RPR application specific integrated circuit (ASIC) designed independently by Department of Electronic Engineering of Tsinghua University. It draws a back end design flow chart and relates about three key techniques: simultaneous switching output (SSO), design for testability (DFT) and static timing analysis (STA). It makes a brief introduction to each technique. It discusses the ways to avoid SSO problems, to calculate scan chains number, to achieve qualified test pattern fault coverage, and to solve STA violations. In the end, it shows design results and layout figure.