Motorola Confidential Proprietary
V975/V980Theory of Operation
3-6
Draft 1.0
RF GSM Transmitter
BLUE MODULE IC (PRIMSYN GSM_TX)
The PRIMSYN receives SSI TX data at DMCS (digi-
tal input to start Tx modulation), TXCLK (clock for
serial transfer) and SDTX (serial Tx data) from POG.
This data pattern input to a fractional N synthesizer with
a 24-bit resolution. For EGSM the synthesizer output
is 880 – 915MHz, DCS is 1710 – 1785MHz with
GMSK modulation and is directly amplified to the trans-
mitter output.
BLUE MODULE (ALGAE)
TRANSMIT SECTION
An integrated VCO is used for the transmit path. A single
VCO is used for transmit. A low noise floor divide-by-
2 stage drives the high band output. The low band out-
put is driven by a divide-by-4 stage.
Two transmit output stages are provided. Both stages
have integrated output matches in order to reduce the
required number of discrete components. The integrated
matches are implemented as differential to single-ended
transformers.
The transmit signal is fed back to the synthesizer through
a differential output stage that is shared with the re-
ceiver.
/2 /2
/2
/2
RX VCO
TX VC O
RX_TUNE
SYNTH_FDBK
TX_TUNE
TX_OUT_HI
TX_OUT_LO
ALGAE MB
(U900)
Figure 3-8. ALGAE MB (Transceiver)
GMSK
LP
FILTER
TX
SSI
DAC
FracN
PLL
Y500
BDX
BCLKX
DMCS
LP
FILTER
DP
SYNTH_FDBK
RX_TUNE
TX_TUNE
PRIMSYN
(U90 0)
Figure 3-7. PRIMSYN (GSM TX)
RF GSM Transmitter
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