M系列符号を用いたTOF計測のバーニア効果に基づく高分解能化

抄録

In this paper, we propose a high-resolution ranging method for sensor nodes in wireless sensor networks based on RF TOF measurement. Ranging methods using TOF have a high-accuracy because TOF of RF signal is hardly affected by surrounding conditions. However, it is difficult to measure with enough resolution due to its very fast speed. In our laboratory, the principle of vernier caliper, which is called vernier effect, has been used to solve the problem. By using the principle, finer resolution than the periods of measurement clocks can be obtained. As problems of the method, however, it has been reported that the measurement takes too long time and requires additional circuits which lead to higher power consumption and cost. Then, we propose a novel method in this paper for obtaining TOF with just simple calculations and no extra hardware. In this method, the correlation property of M-sequence code is used to achieve accurate and easy measurement. By transmitting and receiving M-sequence code with different clocks and conducting a devised calculation of correlation value, TOF is accurately measured with high-resolution. Also, some experiments were conducted in our research. In the first experiment, we measured the delay time on delay lines. From the result, we found the condition that the measurement results may get worse and the way to achieve enough resolution even in the condition. In the second experiment, the proposed method was applied for laser ranging and it was confirmed that distance can be measured with 3m resolution.