| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a method and its sensor for detecting the interruption of microwaves capable of estimating an object, to some degree, intruding between a transmission antenna and a reception antenna, and heightening a function as a sensor for accurately specifying the size of the intruding object. <P>SOLUTION: Oscillation output of a microwave oscillator 1 is transmitted from a transmission antenna 2 and received by a reception antenna 3 opposite to the transmission antenna 2 to detect the size of an object 9 passing in-between. A reception signal received by the reception antenna 3 is mixed by a local oscillator 4 and a mixer 5 to create an intermediate frequency signal. The phase of the intermediate frequency signal is detected by a phase detector 8 with reference to the phase of a reference oscillator 6. A PLL circuit for controlling the local oscillator 4 via a phase comparator 7 in such a way that the frequency of the intermediate frequency signal becomes equal to the frequency of the reference oscillator 6 is formed. <P>COPYRIGHT: (C)2004,JPO</p> |
