US Patent 7427946 Object sensing apparatus

While an FM-CW mode for sensing an object, in which a frequency of an electromagnetic wave transmitted from a transmission/reception antenna 6 is continuously modulated, and also, a CW mode for judging an abnormal condition, in which the frequency of the electromagnetic wave to be transmitted from the transmission/reception antenna 6 is not modulated are switched, an abnormal condition judging section judges an abnormal condition when a signal level of a reception signal of the FM-CW mode is smaller than, or equal to a first judging threshold value, and also, a signal level of a reception signal in the CW mode is smaller than, or equal to a second judging threshold value which is higher than the first judging threshold value.