LG MG200 Service Manual page 30

3.5.5 Baseband Codec (BBC)
Baseband codec is composed of baseband uplink path (BUL) and baseband downlink path (BDL).
BUL makes GMSK (Gaussian Minimum Shift Keying) modulated signal which has In-phase (I)
component and quadrature (Q) component with burst data from DBB. This modulated signal is
transmitted through RF section via air.
BDL process is opposite procedure of BUL. Namely, it performs GMSK demodulation with input
analog I&Q signal from RF section, and then transmit it to DSP of DBB chip with 270.833kHz data
rate through BSP.
From TSP
Burst
Buffer 1
From BSP
Burst
Buffer 2
Timing
Control
Cosine
Table
GMSK
Modulator
Sine
270 kHz
Table
Figure 15. Baseband codec Block Diagram
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3. H/W CIRCUIT DESCRIPTION
Offset
6-Bit
Register
DAC
10-Bit Low-Pass
Filter
DAC
16 270 kHz
Low-Pass
10-Bit
Filter
DAC
Offset
6-Bit
Register
DAC
BULIP
BULIM
BULQP
BULQM