Gps Receiver - LG -P970 Service Manual

3. TECHNICAL BRIEF

3.4 GPS RECEIVER

The Global Positioning System (GPS) is a space-based global navigation satellite system (GNSS) that provides
reliable location and time information in all weather and at all times and anywhere on or near the Earth when
and where there is an unobstructed line of sight to four or more GPS satellites. The GPS Receiver of P970 built-in
BCM4751 is A-GPS chipset is made by BROADCOM that uses a host based integration architecture that splits
processing functions between the GPS core and the CPU on the Host system. The Broadcom BCM4751 is a
single-chip GPS receiver used for tracking and navigation, primarily in mobile devices. It's massively parallel,
hardware correlator architecture provides signal searches, accurate real-time navigation, improved tracking
sensitivity and low average power consumption.
Fig3.7. Block diagram of BCM4751
The BCM4751 supports additional satellite constellations including the Satellite Based Augmentation System
(SBAS) and the Quasi-Zenith Satellite System (QZSS) for Japanese applications, making as many as twelve
additional satellites available for use in navigation.
The BCM4751 GPS receiver offers 65nm CMOS design featuring a highly-integrated RF and baseband processor
with extremely low power consumption. It also claims smallest complete PCB footprint at 30mm2 including
band-pass filter, TCXO and passives.
BCM4751 GPS receiver includes software that meets international standards bodies such as 3GPP, GERAN and
OMA, which promote the delivery of GPS assistance data over cellular networks. Figure shows block diagram of
BCM4751.
The GPS signal is received by the antenna and amplified by an internal LNA. The differential signal coming out of
the LNA is sent to an I/Q mixer, which uses a local Oscillator to directly down-convert the signal to an IF Near
6MHz.
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