To provide antenna structure for an immobilizer capable of securing supply of electromagnetic energy to a portable machine, a communication distance and communication stability even when metal is used for a knob of a switch device.
The switch device 10 has an ignition switch operated in accordance with the operation of the knob 12 and antenna coils 14A, 14B for transmitting electric power signals and request signals. The portable machine 20 transmits an ID code in accordance with the request signals from the switch device 10. The antenna coils 14A, 14B are installed so that each of their centers is positioned in the vicinity of the outer edge part of the metallic knob 12. The antenna coils 14A, 14B are operated at phases reverse to each other, and by composing magnetic fluxes by the respective antenna coils 14A, 14B, magnetic force lines 17 are formed. Since the magnetic force lines 17 do not pass through the knob 12, sufficient magnetic fluxes are applied to the portable machine 20.
SUZUKI TOMOYASU
HANAKI HIDENOBU
| JPH08296354A | 1996-11-12 |
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