Continental Automotive Systems Corporation QEFGE04 Manual De Usuario
Editor :
DM.Son
Document name
Project code
Version:
1.0
Dec. 18. 2017
ECO / DF No.
Identification No. : Document No.
File:
Page 4 / 6
.
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The functions of the SMART KEY system have to be provided in a clearly defined and
limited range. For the up-link from the vehicle to the SMART KEY FOB, a magnetic field
with a frequency of 125 kHz and ASK modulation is used. Inductive antennas in and at
the vehicle radiate the electromagnetic energy.
Technical aspects of 125 kHz – magnetic field:
virtually no reflections,
cubical decrease of field strength allows good range control,
released frequency band (ISM),
high
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.
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
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
L
F
F