| 摘要 |
A field disturbance sensor (82) operates with relatively low power, provides an adjustable operating range (83), is not hypersensitive at close range, and allows co-location of multiple sensors. The sensor includes a transmitter that transmits a sequence of transmitted bursts (90) of electromagnetic energy. 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 which receives electromagnetic energy at the transmitter frequency, and includes a mixer which mixes a transmitted burst with reflections of the same transmitted burst to produce an intermediate frequency signal. The mixer mixes the transmitted burst with reflections of the transmitted burst, the burst width defines the sensor range. The burst repetition rate is randomly or pseudorandomly modulated so that bursts have a phase which varies. A second range-defining mode transmits two radio frequency bursts, where the time spacing between the bursts defines the maximum range divided by two.
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