Motorola MOTOTRBO XPR 7550e - FGU (Frequency Generation Unit)

5-2 General Controller Block
1.1 FGU
The synthesizer is powered from 1.8V and 2.8V supplied from CPCAP IC, U3000 as well as 3.6V of
U3270 switching regulator. The synthesizer in turns generates a super-filtered of 3.6V which powers
up the VCO where the output signals of VCO are feedback to RFIC to complete the PLL. The output
of VCO is providing output power level of -4 to 7dBm to ROD_VCO_IN. An external 38.4MHz non-
tunable TCXO is used as the main clock source. The 38.4MHz TCXO output is fed directly to CPCAP
IC via CLK_ROD_19_2MHZ_SHIELD, and being divided down to 19.2MHz by D-type flip flop, U1081
before feeding to FREON IC, U1000 via 19_2MHZ_DIG. The radio uses a 2-port modulation scheme
i.e. through low port and high port modulation at loop filter. This approach was undertaken to obtain
flatter high port modulation sensitivity response across TX frequencies, larger passing margin for
ACP and better modulation flatness across temperature.
For 8/900 MHz band, the synthesizer is powered from 1.8V and 2.8V supplied from CPCAP IC,
U3000. The synthesizer in turn generates a super-filtered of 4.4V via U3250 regulator. which powers
up the VCO where the output signals of VCO are feedback to RFIC to complete the PLL. The output
of VCO is providing output power level of -1.5 to 6dBm to ROD_VCO_IN. An external 19.2MHz non-
tunable TCXO is used as the main clock source. CPCAP uses 19.2MHz from
ROD_19.2MHZ_CLKOUT.The radio uses a 2-port modulation scheme i.e. through low port and high
port modulation at loop filter. This approach was undertaken to obtain flatter high port modulation
sensitivity response across TX frequencies, larger passing margin for ACP and better modulation
flatness across temperature.
Figure 5-2. FGU
RFIC
HP_MOD
CLK_OUT
L - C
Voltag e
Multiplier
Vsf
Vmult2 Vmult1
RX IN
VCO1_EN
VCO2_EN
Loop
Filter
Normal
Adapt
VCO_Vctrl
VCO1
VCO2
*38.4 MHz
REF_IN
VCO_IN
TX OU T
To Controller &
PMIC
LPF
*Note:
For 800/900, 19.2 MHz will be used for REF_IN
For VHF/UHF, 38.4 MHz will be used for REF_IN