| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To improve a distance resolution of distance measurement using a tone burst at low cost. <P>SOLUTION: The tone burst (magnetic elastic wave) generated by performing amplitude modulation of a reference signal CK is propagated, and orthogonal detection of a detection signal D by the tone burst is performed by an orthogonal detector 25. In an amplitude computing unit 26, the amplitude A<SB>p</SB>of the detection signal D is calculated in each one cycle Tc of the reference signal CK from the results I<SB>p</SB>, Q<SB>p</SB>of the orthogonal detection. In a delay time detector 28, a delay timeτ<SB>d</SB>from a generation timing T1 of the tone burst until a timing T2 when the amplitude A<SB>p</SB>exceeds an amplitude threshold is determined. In a phase computing unit 30, phasesϕ<SB>N, P</SB>of the detection signal D are determined from the results I<SB>p</SB>, Q<SB>p</SB>of the orthogonal detection. In a distance computing unit 31, a propagation distance z is determined by adding the first distance wherein one wavelengthλc of the reference signal CK is used as the resolution based on the delay timeτ<SB>d</SB>to the second distance wherein a distance shorter than the wavelengthλc is expressed highly accurately by a continuous value based on the phasesϕ<SB>N, P</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
