| 摘要 |
<p>PURPOSE: To accurately detect objects within a distance range from a short distance to a long distance by resolving such a trouble that noise, especially, such noise that makes detection difficult at short distances, is produced in the low-frequency region of beat signals by transmitting signals circulating to received signals in such a circuit as the circulator, etc., sharing an antenna. CONSTITUTION: Transmission/reception antennas 3A-3D are installed so that beams can overlap each other. At the time of detecting an object at a short distance, beat signals (for example, BB) are obtained by transmitting a beam from one antenna (for example, antenna A) and receiving the bean by means of another antenna (for example, antenna B). At the time of detecting an object at a long distance, the same beam transmitting/receiving means is used. At the time of detecting an object at a short distance, the distance resolution is improved by raising the frequency of the beat signals by making the variation per unit time of the frequency of FM-modulated transmitting signals larger than that at the time of detecting an object at a long distance.</p> |
