June 15, 2005
6815854H01-A
3-54
Theory of Operation:
Frequency Generation Unit (FGU)
3.13.3 UHF Range 2 (450–520 MHz) Band
The FGU (
) provides the XTL 1500 radio with a 16.8 MHz reference frequency, receiver
1st local oscillator, and a modulated transmitter RF carrier that is further amplified by the power
amplifier section of the radio.
The FGU consists of the following:
• Reference oscillator (Y5750)
• Low-voltage Fractional-N (LV Frac-N) synthesizer (U5752)
• Three receiver voltage-controlled oscillators (VCOs)
• Two transmitter VCOs
• Three receiver LO amplifiers (Q5904, Q5902 and Q5906)
• Two transmitter injection amplifiers (Q5828, and Q5829)
Figure 3-38. Frequency Generation Unit Block Diagram (UHF Range 2)
Bias 1
3.0V
3.0V
3.0V
3.0V
8.2V
Lock Detect
to Controller
Prescaler Input
Q5755
RF
Feedback
8.2V
Bias 2
9.3V
SFIN
SFBASE
SFOUT
Lock
PREIN
AUX4
AUX3
Mod Out
IADAPT
IOUT
AUX2
AUX1
VMULT4
VMULT3
5.0V
16.8MHz Reference
to Controller and
Receiver Back End
VOLTAGE
MULTIPLIER
D5750 and
D5751
16.8MHz OSC
8.2V
Super Filter
Q5752
U5751
U5752
3.0V
Regulator
U5750
PHASE
DETECTOR BIAS
Q5750 RX and
Q5751 TX
CLOCK
SYN_SEL
DATA
MOD_IN
From
Controller
NC
A
X0
X1
X2
X3
X4
B
C
7.5V
8.2V
Q5706
Q5707
Q5708
Q5709
RX
INJECTION
TX
INJECTION
RX
Injection
TX
Injection
Keyed
9.1V
C5779
C5780
LOOP
FILTER
8.2V SW
8.2V SW
8.2V SW
8.2V SW
Q5825
Q5826
Q5901
Q5903
Q5905
U5753
Q5710
8.2V SW
Содержание XTL 1500
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