atr0603 ATMEL Corporation, atr0603 Datasheet - Page 3

• Manufacturer Part Number: atr0603
• Description: Gps Front-end Ic
• Manufacturer: ATMEL Corporation

3. Functional Description
3.1
3.2
3.3
3.4
3.5
4950B–GPS–11/06
General Description
Startup Logic
TCXO Interface
VCO/PLL
RF Mixer/Image Filter
The ATR0603 GPS receiver IC has been especially designed for GPS applications in both
mobile phone and automotive applications. From this system point of view, it incorporates high-
est isolation between GPS and cellular bands, as well as very low power consumption.
The L1 input signal (f
quency of: f
The digital modulation scheme is bi-phase shift keying (BPSK) with a chip rate of 1.023 Mbps.
As the input signal power at the antenna is approximately –140 dBm, the desired signal is below
the thermal noise floor.
The startup logic ensures reliable operation within the recommended operating conditions. The
external power control signal PU is passed through a Schmitt trigger input to eliminate voltage
ripple and prevent undesired behavior during startup and shutdown.
This block includes a switch to supply external circuits, for example, the TCXO. This switch is
controlled by the power control signal PU.
This receiver is designed for use with an external TCXO. The TCXO output signal is fed to a bal-
anced input buffer.
The recommended reference frequency is: f
Connecting the supply pin of the TCXO to the XSUP pin of ATR0603 allows for a power down of
the TCXO when the ATR0603 is shut off (see
The frequency synthesizer features a balanced VCO and a fully integrated loop filter, thus no
external components are required. The VCO combines very good phase noise behavior and
excellent spurious suppression. The relation between the reference frequency (f
VCO center frequency (f
f
Combined with the antenna, an external LNA provides a first bandpass filtering of the signal. For
the LNA, Atmel
power consumption. The output of the LNA drives a SAW filter, which provides image rejection
for the mixer and the required isolation of all GSM bands. The output of the SAW filter is fed into
a highly linear mixer with high conversion gain and excellent noise performance.
The IF frequency (f
f
VCO
IF
= f
= f
RF
TCXO
– f
VCO
RF
= 1575.42 MHz.
90 = 16.367667 MHz
= 1575.42 MHz – 1473.09003 MHz = 102.32997 MHz.
®
’s ATR0610 is recommended, due to its low noise figure, high linearity and low
IF
) is given by:
RF
) is a direct sequence spread spectrum (DSSS) signal with a center fre-
VCO
) is given by:
90 = 1473.09003 MHz.
TCXO
Section
= 16.367667 MHz.
ATR0603 [Preliminary]
3.2).
TCXO
) and the
3