| 摘要 |
An electromagnetic wave is transmitted from a signal transmission antenna using a signal transmission IC; this electromagnetic wave is received, after having been reflected by a target object, by signal receiving antennas and signal receiving ICs; and the distance to the target object or the azimuth of the target object is detected by a signal processing section. The signal receiving antennas have approximately the same signal receiving characteristics and directivity in approximately the same direction, and are arranged in a row with a predetermined gap between them, thus constituting an antenna array. The levels of the signals received by these signal receiving antennas are detected by a received signal level detection means, and an external objects adhesion detection means decides that some external objects are adhered to the front surface of the signal receiving antennas, if the dispersion, or the level difference, between the levels of these signals received from the antennas is greater than a predetermined value.
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