Proximity detection using DPSK waveform
AssigneeHarris Corporation
InventorsDonald K. Belcher, Albert D. Darby, Jr., Lamar G. McBryde
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Abstract
A method and system for determining whether a transmitting unit is proximate a receiving unit wherein the transmitting unit includes a magnetic field generator for a providing a plurality of time-sequential magnetic fields, each of the sequences being a differential phase shift key (DPSK) modulated code. The magnetic field is transmitted at a relatively interference free frequency of 72 KHz and the DPSK modulation frequency is about 1200 bits per second. Each pair of transmitting and receiving unit uses with a distinguishing code selected from a predetermined group of generally orthogonal codes.
Claims20
A system for determining whether a first device is proximate a second device,
- said first device comprising a magnetic field generator for providing a plurality of time-sequential magnetic fields, said plurality of fields comprising a differential phase shift key (DPSK) modulated code;
- and
- said second device comprising means for determining whether a predetermined number of repetitions of said code have been received within a predetermined period of time.
A method of determining whether a first device is proximate a second device, the method comprising the steps of:
- (a) generating plural time-sequential magnetic fields at the first device;
- (b) differential phase shift key (DPSK) modulating the time-sequential magnetic fields in a code comprising a series of bits;
- (c) transmitting said coded time-sequential magnetic fields from said first device repeatedly;
- and
- (d) determining whether a predetermined number of the coded time-sequential magnetic fields have been received at the second device in a predetermined period of time.
In a method of determining whether a first device is proximate to a second device, the improvement comprising the steps of:
- (a) repeatedly transmitting a multi-bit code via a sequence of differential phase shift key (DPSK) modulated magnetic fields from the first device to the second device;
- and
- (b) determining if less than a predetermined number of repetitions of the code are received at the second device in a predetermined period of time.
Dependencies are inferred from the claim text.