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6
BASEBAND OVERVIEW
6.1 Introduction
The main Baseband circuitry is located with the RF circuits on the Main PCB, while the baseband sub-circuits, comprising keys
and LCD backlights, are located on the Keypad PCB.
A metallised plastic chassis is used to separate the Main and the Keypad PCBs. The continuous chassis design is important
for EMC purposes. When the chassis is sandwiched between the two PCB assemblies, the groundplane of the Keypad PCB
together with the chassis forms an effective shielded enclosure, preventing spurious emissions.
6.2 Functional Description of the PCB
The GD90 baseband is based around a two-chip GSM chipset developed by Texas Instruments. One chip (GEMINI) carries
out signal processing with DSP and CPU, and the other chip (VEGA3) contains the analogue interface chip. The highly
integrated nature of these components means each contain a large number of functions.
DAI RST
SYSTEM
SIMULATOR
DATA
ADAPTER
TESTSET
TEST
MOBILE
SIM
CARD
VIBRATOR
10075-1
MCUK990801G8
Technical Guide
http://cxema.ru
GEMINI
LEAD Megamodule
TEST &
JTAG
EMULATION
TEST &
ROM
CPU
EMULATION
&
CORE
RAM
IRQ
API
nLVA_INT
INTH
APIF
UART
5V
DC/DC
ARM
SIM
CONVERTER
CORE
I/F
+ LEVEL
SHIFTER
I/O
MICROWIRE
MEMORY
I/F
I/F
BUZZER
BACK-
LIGHT
KEYPAD
VOICE
EEPROM
FLASH
SRAM
MEMO
2K*8
1M*16
256K*8
Figure 6.1: Baseband Block Diagram
VEGA
PLL &
BURST
XIO
CLOCKS
STORE
XIO
FILTER
SPI
FILTER
T
TPU
S
P
TDM
TIME-
A
BASE
C
T
TIMER
SLICER
CLKM SLICER
POWER ON/OFF
CONTROL &
POWER SOURCE
FAILURE CIRCUIT
LCD
EXTENDED
OUTPUT
INTER PCB CONNECTOR
Section 6
– 25 –
BASEBAND OVERVIEW
8-Bit
LPF
DIFF
GMSK
I DAC
ENCODE
MOD
8-Bit
LPF
Q DAC
ANTIALIASING
SIGMA-DELTA
FILTER
ANTIALIASING
SIGMA-DELTA
FILTER
APC
(D/A)
INTERNAL REGISTERS
AFC
(D/A)
DAI
SIGMA-DELTA
BPF
LPF
SIGMA-DELTA
BPF
5 INPUT
AGC
TEST
10-BIT A/D
(D/A)
RAPID CHARGE
JTAG
& BATTERY
MONITORING
CIRCUIT
TRICKLE
CHARGE
CIRCUIT
ACCESSORY
CONNECTOR
BATTERY
ULI
ULQ
DLI
DLQ
PARAMP
AFC
SYSTEM
SIMULATOR
Issue A
Revision 0
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