OVERVIEW: Global Positioning System (GPS) Section
1.10.2 GPS Antenna
The GPS antenna is common part of the tri-band antenna common to the iDEN antenna
1.10.3 JANUS IC
The JANUS IC is a multi-purpose IC that host 4 critical parts of the GPS line up.
1.10.3.1 DIPLEXER
This diplexer is used to isolate the GPS signal from the iDEN signal.
1.10.3.2 HIGH PASS FILTER
The high pass filter provides further isolation from the iDEN signal.
1.10.3.3 GPS LNA
GPS LNA is the front end GPS LNA. Expect about 18 dB of gain through this LNA.
1.10.3.4 SAW FILTER
This SAW filter is to enhance the iDEN to GPS isolation and it works as a Balun that converts the
signal ended signal to a differential signal.
1.10.4 GPS Receiver
SLEDGEHAMMER IC is a multi-purpose IC that hosts a number of components in the
GPS lineup. For GPS, the SLEDGEHAMMER IC mainly mixes down the differential RF
signal to differential IF signal and provides the GPS clock to the next stage
1.10.5 GPS Receiver
The ROADRUNNER IC is mainly a DC management IC but also converts the analog
GPS IF signal to digital signal ready to be processed by the ZEUS IC.
1.10.6 GPS Receiver
The ZEUS IC is the main processor for the radio. The ZEUS IC also processes the GPS
signal to calculate the GPS locations and provides the GPS AGC control to the SH IC.
1.10.7 GPS Receiver
A 33.6 MHz clock signal is used by the SH rf circuit as the frequency reference for its
internal local oscillator. This clock is a temperature compensated crystal oscillator whose
frequency accuracy is held to within 0.5 ppm. The high accuracy of the clock frequency
plays a critical role in determining the time it takes to calculate the position coordinates.
1.10.8 GPS Receiver
The baseband digital signals are input to the SiRF processor circuit (integrated in ZEUS)
which in turn computes the position information. Once the position is determined, it is
communicated to the handset microprocessor and displayed on the screen for personal
use or transmitted to the base station for E911 as required
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