Gps Interface - Nokia RM-555 Service Manual

RM-555
System Module and User Interface

GPS interface

Functional description
The device includes an inbuilt GPS receiver and it works as a stand-alone positioning device.
The GPS solution provides a full GPS HW and SW engine for devices capable of operation in all GPS modes:
• Autonomous (standalone) - no communication with network is required for GPS fix
• MS based - the device receives aiding information from the network and computes fix internally
• MS assisted - the device receives aiding information from the network and computes pseudorange
measurements. The measurements are then sent back to the network for the fix calculation.
At the heart of the GPS solution is GPS5350 GPS receiver IC, which has GPS RF receiver and GPS BB processor
integrated into a single IC. RF section performs down conversion, filtering and IF sampling, whereas BB
section contains an enhanced version of multimode GPS with twelve hardware matched filters, post detection
logic and an ARM controller core.
The features of the GPS solution include:
• 12 channels
• Integrated regulators for RF and BB (including external LNA)
• Direct connection to a battery
• Fast clock calibration through availability of 261MHz clock from RF PLL
• Improved tracking and Hot start (TTFF) reacquisition performance
• Advanced Power Management and Host Wakeup capability.
The I2C interface handles data transfer between GPS and the Rapido. GPS uses the CE RF system clock to
calibrate its own GPS Clk.
GPS has three clock sources:
• 16.368MHz clock from a dedicated TCXO (G6200)
• 38.4MHz reference clock from Ahneus RF ASIC
• 32.768kHz Sleepclk
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