| 摘要 |
PROBLEM TO BE SOLVED: To provide a moving direction detecting radio system which has a simple circuit configuration and high directivities and can securely detect the moving direction, and entry/exiting of a person, a thing, etc. SOLUTION: The system has a transmitter and receivers 14a and 14b which can communicate with each other by radio, and the receivers 14a and 14b each have an antenna array 25 of a plurality of antenna elements 23 and 24. The system has a composite circuit 28 which puts together radio waves received by the antenna elements 23 and 24, a phase shifting circuit 28 connected between one of the antenna elements 23 and 24 and the composite circuit 28, and a receiving circuit 30 which inputs the radio wave composed by the composite circuit 28. Intervals of the plurality of antenna elements 23 and 24 are about 1/4 to 1/6 time as large as the wavelengthλof the received radio waves. The sum of the phase difference between the radio waves shifted in phase by the phase shifting circuit 26 and the phase difference between the received radio waves due to the intervals of the antenna elements 23 and 24 is 2π/3 toπ. The pair of receives 14a and 14b are disposed at an entrance exit 34 while having their directivities in opposite directions. COPYRIGHT: (C)2008,JPO&INPIT
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