Gps Sub Module - Motorola MTM800 User Manual

4.1 - 24

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.
GPS_3V GPS_2V
PG AM-IC
26 MHz
TCXO
Y1
3V_DIG
Front
End
Filter
FL2
U4
GPS _2V
Volt._Reg.
U2
Figure 4.1-8 GPS Module Block Diagram
Front
End
Filter
LNA FL1
GPS_3V
5V Regulator
V o lt._Reg.
U1
U3
THEORY OF OPERATION (TRANSCEIVER)
GPS Anten na
L1
J1
12V
24 pin
3V DIG
connector
SPI bus