Patent ID: 7058529

Claim:
A microwave sensor system comprising: a plurality of sensors each having a different phase that transmit microwaves toward a detection area and that receive microwaves reflected from the detection area; a determination unit that determines whether or not the microwaves have been received by the sensors; and a measurement unit that computes the respective phase differences of the microwaves received by the a plurality of sensors when the determination unit has verified reception of the microwaves and computes the distance from the sensors to a target serving as a detection target within the detection area, the measurement unit measuring detection error on the basis of the computed phase difference, the computed distance and a preset frequency difference, wherein the measurement by the measurement unit includes detection error resulting from the presence of moisture such as rainfall in the air between the sensors and the target, detection error that the system has, and detection error obtained by adding these detection errors together, wherein the detection error resulting from moisture sharply increases as the preset frequency difference becomes larger and the detection error that the system has sharply decreases as the preset frequency difference becomes larger, wherein using the preset frequency difference as a parameter, a range in which a range where the rate of variability of the value of the detection error resulting from moisture with respect to the preset frequency difference is low overlaps with a range where the rate of variability of the value of the detection error that the system has is low is set as the range of the added detection error, and wherein the value of the added detection error becomes lower than the value of the detection error that the system has.