| 摘要 |
PROBLEM TO BE SOLVED: To provide a field disturbance sensor, operating with relatively low power, providing an adjustable operating range, not hypersensitive at close range, providing co-location of multiple sensors, and inexpensive to manufacture. SOLUTION: The sensor includes a transmitter 11 that transmits a sequence of bursts 19 of electromagnetic energy. The transmitter frequency is modulated at an intermediate frequency. The sequence of bursts has a burst repetition rate, and each burst has a burst width and comprises a number of cycles at a transmitter frequency. The sensor includes a receiver 21 which receives electromagnetic energy at the transmitter frequency, and includes a mixer 22 which mixes a transmitted burst with reflections of the same transmitted burst to produce an intermediate frequency signal. Circuitry, responsive to the intermediate frequency signal indicates disturbances in the sensor field. The burst repetition rate is randomly or pseudorandomly modulated so that bursts in the sequence of bursts have a phase which varies. COPYRIGHT: (C)2005,JPO&NCIPI
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