LG MG220 Service Manual page 17

3. H/W Circuit Description
3.2.2. Synthesizer
The Aero II transceiver integrates two complete PLLs including VCOs, varactors, resonators, loop
filters, reference and VCO dividers, and phase detectors. The RF PLL uses two multiplexed VCOs.
The RF1 VCO is used for receive mode, and the RF2 VCO is used for transmit mode. The IF PLL is
used only during transmit mode. All VCO tuning inductors are also integrated. The IF and RF output
frequencies are set by programming the N-Divider registers, NRF1, NRF2 and NIF. Programming the
N-Divider register for either RF1 or RF2 automatically selects the proper VCO.
Transmit modes should always use f∅ = 200kHz. The IF and RF output frequencies are set by
programmi ng the N-Divider registers and also programmed via 3-wire interface with external system
controler.
X500
VC-TCXO
Baseband
Baseband
(TI)
(TI)
U100
U100
IOTA
IOTA
+
+
U101
U101
Calypso-
Calypso-
26MHz
1,2
1,2
XTAL1
XOUT
XEN
PDIB
Power
Power
PDN control
control
PDRB
SDIO
Serial
Serial
SCLK
I/O
I/O
SEN
SDOSEL[4:0]
Figure 2. Synthesizer Block
- 16 -
65,130
65,130
DET
DET
Self
Self
Tune
Tune
RF PLL
Self
Self
Tune
Tune
DET
DET
IF PLL
U501/Si4210
RF1
RF2
To Rx/Tx
N [15:0]
RF1
1/N
1/N
N [15:0]
RF2
1/N
1/N
N [15:0]
IF
To Tx