Motorola C1002 Instructions d'exploitation télécharger pdf (Page 57)

100

101

Global Positioning System (GPS) Receiver 6-7

4.0 Global Positioning System (GPS) Receiver

The GPS device is an embedded receiver that provides the location of the subscriber in terms of

latitude, longitude, velocity, direction and altitude.

Figure 6-5: GPS Receiver Block Diagram

The RF signal is received by the antenna and applied to a high-pass filter. The filter consists of C924,

C925, C926, L912 and L913. The filtered RF signal is then applied to a SAW filter, FL8001.

The output of the SAW filter is fed into the LNA (U8001). The LNA biasing is controlled by

SIRF_LNA_EN (pin A4 of the GPS IC, U8000). The LNA input match comprises of C8013, C8014 and

L8001. The LNA output match comprises of L8003 and C8017. After being amplified, the RF signal is

further filtered by a second SAW filter, FL8002.

The output of the second SAW filter is passed to pin P6 of the GPS IC. The input match for pin P6

comprises of C8018, C8019 and L8004. The control and data lines for the GPS IC are GPS_nRESET,

GPS_ON_OFF, GPS_TX, GPS_RX and GPS_BOOT. GPS_nWAKEUP line is fed into the

microcontroller to indicate the state (full power or hibernate state) of the GPS IC so that the

microcontroller will never trigger a GPS_ON_OFF when the GPS IC is in full power state.

A dedicated 32.768kHz quartz crystal oscillator (Y8000) is used to provide RTC clock to the RTC

circuit inside the GPS IC. The second input frequency is a 16.8MHz reference, used by the StarIII to

synthesize the internal LO. This reference will be supplied by a VCTCXO (Y001) located in the

synthesizer block, which will be shared by the Trident.

The GPS IC is powered by 2.8V_DIG_GPS, 2.8V_RF_GPS and 1.2V_GPS_RTC supplied from 3

discrete external regulators (U3701, U3700 & U3006). The input of these regulators is sourced from a

switching regulator (U3020) which regulates the SWB+ to 3.6V.

Section

Digital

Section

TPS79228 TPS79101 LP3990

2.8V

1.2V

LTC1877

3.6V

32.768kHz

XTAL

OMAP

16.8MHz

VCTCXO

FGU

SiRFStarIII

HPF Pre-SAW LNA Post-SAW

Dual band antenna

LNA_EN

LNA_Supply

Battery 7.2V

1 2 ... 52 53 54 55 56 57 58 59 60 61 62 ... 100 101

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Motorola C1002 Instructions d'exploitation Page 57

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