Advertisement
Technical aspects of 125 kHz – magnetic field:
•
virtually no reflections,
•
cubical decrease of field strength → allows good range control,
•
released frequency band (ISM),
•
high penetration,
•
low quiescent current demand due to 125 kHz input stage (SMART KEY FOB),
•
less sensitive for detuning compared to higher frequency.
For the down-link from the SMART KEY FOB to the vehicle, the standard radio frequency
(RF) is used (similar to the classic remote control functions) with FSK modulation.
1.3
System Overview / Block Diagram
L
F
Figure 1: Principle of Communication
ECU sends LF challenge via exterior antenna
ID tag sends identification code to RF receiver
Doors are unlocked automatically
User pulls open the door
Advertisement
