Masafumi Asai

Impulse Radio UWB Positioning System

We developed a positioning system using impulse radio UWB. The system consists of tags equipped only with transmitters and nodes provided with both transmitters and receivers. The system calculates the position of the tags using the TDOA method, whereby some nodes receive the UWB pulses sent from a tag. The tag is operated with a coin battery, and sends UWB pulses intermittently. The node sends the receiving time data to a PC via an Ethernet network for position calculation. We developed a time clock correction method, which is also required for the TDOA method. We will further evaluate positioning accuracy etc. in the future

Electron Beam Recorder with Nanometer-Scale Accuracy for 100 Gbit/in2 Density Mastering

An electron beam recorder (EBR) was developed for mastering optical disks with a recording density of 100 Gbit/in2 using a multilevel recording format. In this recording format, a nanometer-scale accuracy of relative pit edge position is required in both radial and tangential directions. To achieve the recording position accuracy, a rotation stage with a noncontact vacuum seal and a correction system for rotation errors were developed. In addition, an active magnetic shield system and a learning compensation for beam displacement were adopted to improve the stability of the beam position. As a result, the ability to record with high accuracy and high resolution was confirmed from experimental results. A fine pit pattern with a minimum pit length of 70 nm was formed precisely. The recording accuracy of the EBR was evaluated to be approximately 2 nm (standard deviation) in both radial and tangential directions. Furthermore, a carrier-to-noise ratio of 64 dB was also obtained by reproducing an etched silicon master with a 240 nm monotone pit pattern.