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L T R A V I E W
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E R V I C E
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A N U A L
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H E O R Y
Voltage Controlled Crystal Oscillator
•
Colpitts oscillator operating at the fifth overtone.
•
Frequency is pulled by modulating the voltage on two variactor
diodes in series with the crystal.
First and Second Frequency Doublers
-
The transistor in each stage generates the second harmonic
of the input frequency.
-
The filter following each transistor filters all frequencies
except the second harmonic of the input frequency.
The two cascaded stages multiply the VCXO’s frequency by a factor
of four.
Transmitter RF PCBA Block Diagrams (91341, 91343, 91347)
Figure 3-6 91341/91343/91347 narrowband/wideband transmitter -
top level
RF Module
Digital Module
ECG Interface
ECG Power
L
e
a
d
F
a
u
lt L
o
g
ic
In
te
rfa
c
e
SPO2 Interface
Vcc
R
e
co
rd
S
w
it
ch
SynLD
SynClk
SynData
SynLE
TxMod
VCC3V3
Antenna
Low Battery
LED
+
2
.5
V Vr
e
f
Le
ad
I
L
ead
I
I
Le
ad I
II
AU
X
Le
ad
I
V
GN
D
+5
V
Sp
ar
e
Record
SPO2T1 Timing
SPO2T2 Timing
SPO2
BT1
VCC5V5
RA ON
RL ON
CH ON
LL ON
LA ON
Pacer Flag
2 -
8p
in
D
ip -
S
wi
tc
he
s
Dip-Switch Bus
BT
1
GN
D
Battery
Connector
Lead Fault Control
Pu
ls
e
RA
RL
CH
LL
LA
LowBatt
LED
Lo
w
B
at
t