| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve detection accuracy of a peak of a correlation value of a code sequence.SOLUTION: A transmission device 10 modulates the same code sequence by using a data code to generate a modulation signal composed of a dummy symbol A, ranging symbol A, ranging symbol B, and dummy symbol B arranged in order on a time axis, and gives off sound of the modulation signal. When a reception device 20 collects the sound of the modulation signal propagated through a medium, a matching filter sequentially calculates a first correlation value by calculating correlation between the modulation signal and code sequence using a predetermined sampling frequency. The reception device 20 multiplies the first correlation value by a second correlation value obtained by giving time delay equal to a symbol period of the ranging symbol A to the first correlation value, suppresses a level of a peak of a correlation value caused by reflection sound and the like low, and emphasise a peak of the correlation value corresponding to a ranging symbol and detects it. The reception device 20 measures propagation time of the modulation signal in the medium on the basis of a result of the detection of the peak of the correlation value, and calculates a distance between the transmission device 10 and reception device 20.</p> |
