DocID030710 Rev 1 13/31
STA8089G General description
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3 General description
3.1 RF front end
The RF front-end is able to down-convert both the GPS-Galileo signal from 1575.42 MHz to
4.092 MHz (4 Fo, being F0 = 1.023 MHz), the GLONASS signal from 1601.718 MHz to
8.57 MHz and the BeiDou signal from 1561.098 MHz to 10.23 MHz.
It embeds high performance LNA minimizing external component count and a LDO to
supply the internal core facilitating requirements for external power supply. A three bits ADC
converts the IF signals to sign (SIGN) and magnitude (MAG0 and MAG1). They can be
sampled or not by SPI. The magnitude bits are internally integrated in order to control the
variable gain amplifiers. The VGA gain can be also set by the SPI interface.
The RF tuner accepts a wide range of reference clocks (10 to 52 MHz) and can generate
64 Fo sampling clock for the baseband and 192 Fo clock for MCU subsystem.
3.2 GPS/Galileo/GLONASS/BeiDou Base Band (G3BB+)
processor
STA8089G integrates G3BB+ proprietary IP, which is the ST last generation high-sensitivity
Baseband processor fully compliant with GPS, Galileo, GLONASS and BeiDou systems.
The baseband receives, from the embedded RF Front-End, two separate IF signals coded
in sign-magnitude digital format on 3 bits and the related clocks. The Galileo/GPS
(GALGPS) and GLONASS/BeiDou (GNSCOM) signals at the base band inputs are
centered on 4.092 MHz, 8.57 MHz and 10.23 MHz.
The baseband processes the two IF signals performing data codification, sample rate
conversion and final frequency conversion to zero IF before acquisition and tracking
correlations.
The baseband processor has the capability of acquire and track the Galileo, GPS,
GLONASS and BeiDou signals in a simultaneous or single way, or a combination of three,
being GLONASS and BeiDou mutually exclusive. The number of tracking channels to be
used is programmable; the not used tracking channels can be powered down.
A complete multi-OS software library is provided by ST to handle GPS processing,
managing satellite acquisition, tracking, pseudo-range calculation and positioning,
generating the output in the standard NMEA message format or in a ST binary format. The
library includes support of ST self-trained assisted GPS (ST-AGPS), a complete and
scalable solution for assisting GPS start-up with autonomous and server-based ephemeris
prediction and extension.
3.3 MCU Subsystem
The implemented sub-system includes an AHB Lite bus matrix.
An ARM946 core is embedded in the sub-system and masters the AHB bus. The totally
available TCM SRAM is 256 KB. The amount of memory on ITCM and DTCM can be
configured by the ARM946 (see Table 6: TCM Configuration). ITCM can be configured as Ni
x 16 KB; DTCM can be configured as 128 + Nd x 16 KB, where Ni + Nd = 8, Ni 1.
