4.1 - 24 THEORY OF OPERATION (TRANSCEIVER)
GPS Sub Module
The MTM800 ENH GPS is based on the Phoenix GAM IC (PGAM), which comprises a custom
mixed mode RF-DSP IC in a single chip FBGA package.
It is a self contained GPS receiver capable of producing a final position including full tracking and
data decode capability.
The GPS signal that applies to the RF cable connector is filtered by two SAW filters FL1 and FL2.
It is amplified by a low noise amplifier (LNA).
The input of the GPS receiver at the RF FME connector is DC coupled.
A voltage regulator on board provides about 20mA at 5V DC voltage to an external antenna low
noise amplifier (LNA).
This phantom voltage is applied to the input by the RF coil L1.
The supply voltages GPS_2V and GPS_3V of the PGAM-IC are derived from two on board voltage
regulators U2 and U3.
A 26MHz TCXO provides the reference clock to the PGAM IC.
Data communication takes place via the serial SPI bus.
Figure 4.1-8 GPS Module Block Diagram
26MHz
TCXO
PGAM-IC
5V Regulator
GPS Antenna
L1
SPI bus
J1
24 p
i
n
connecto
Y1
U4
FL1
FL2
U1
GPS_3V GP
S_2V
3V_DIG
12V
3V DIG
Volt._Reg.
GPS_2V
U2
Volt._Reg.
GPS_3V
U3
Front
End
Filter
LNA
Front
End
Filter
6866539D31.book Page 24 Tuesday, March 20, 2007 6:32 PM
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