.
P
ropri
e
ta
ry
dat
a,
c
o
m
p
any
c
onf
ident
ia
l.
A
ll
r
ight
s
res
e
rv
e
d
.
C
onf
ié
à
t
itr
e
de
s
e
c
ret
d'
ent
repr
is
e.
T
ous
dr
oi
ts
rés
e
rv
és
.
C
o
m
u
ni
c
ado
c
o
m
o
segr
edo
em
pr
es
ari
a
l.
R
e
se
rv
ados
t
odos
os
di
re
itos
.
C
onf
idado
co
m
o
s
e
cr
et
o
in
dus
tr
ia
l.
N
o
s
res
e
rv
am
os
t
odos
l
o
s derec
ho
s.
.
W
e
itergabe s
o
w
ie V
er
vi
e
lfäl
tigung di
es
er U
n
te
rl
age,
V
e
r-
w
e
rt
ung und
M
itt
ei
lung
ih
re
s
Inhal
ts
ni
ch
t ges
ta
ttet
, s
o
w
e
it
ni
ch
t
aus
dr
üc
kl
ic
h
z
uges
tand
en.
Z
u
w
ider
handl
ungen
v
e
r-
pf
lic
h
ten z
u
S
chadeners
a
tz
.
A
lle
R
e
ch
te
v
o
rbehal
te
n
,
in
sb
e
-
sondere f
ü
r den F
a
ll der
P
a
tent
ert
e
ilung oder GM
-E
in
tr
agung
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
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
