| 摘要 |
<p>PURPOSE: To detect the distance to a nearby obstacle highly accurately even when an object reflecting the radio wave strongly is present on the outside of detection range. CONSTITUTION: Two sets of high frequency signal having frequency differencesΔf1 andΔf2, smaller thanΔf1, from a high frequency signal having a constant frequency fc are transmitted simultaneously from a transmitting section and reflected waves from an object are received at a receiving section. Phase comparators 74, 76 detect a phase differenceΔΣ1 of a receiving wave corresponding to a high frequency signal having the frequency differenceΔf1 and a phase differenceΔϕ2 of a receiving wave corresponding to a high frequency signal having the frequency differenceΔf2, respectively. When the phase differenceΔϕ2 is smaller than a threshold value (i.e., when the distance to the obstacle is detected roughly), the precise distance to the obstacle is operated based on the phase differenceΔϕ.</p> |
