Analog Mode Of Operation; Figure 3-2. Receiver Block Diagram (Uhf1); Figure 3-3. Receiver Block Diagram (Uhf2) - Motorola APX 3000 Basic Service Manual

3-2
3.2

Analog Mode of Operation

This section provides an overview of the analog mode receive and transmit theory of operation.
3.2.1 Receiving
The RF signal is received at the antenna and is routed through the Harmonic Filter, followed by the Antenna
Switch and finally the 15dB Step Attenuator IC. The latter contains a switchable attenuator that is enabled at
predetermined RF power thresholds present at the antenna port. See,
.
Figure 3-5
Antenna
15 dB Step
Switch
Attenuator
DIG_CTRL_ATTH
Diplexer
Antenna
15 dB Step
Switch
Attenuator
DIG_CTRL_ATTH
Diplexer
UHF1 UHF1
To GPS

Figure 3-2. Receiver Block Diagram (UHF1)

UHF2 UHF2
To GPS

Figure 3-3. Receiver Block Diagram (UHF2)

Basic Theory of Operation: Analog Mode of Operation
,
Figure 3-2
IF Filter
Rx LO
2nd
LO
IF Filter
Rx LO
2nd
LO
,
Figure 3-3 Figure 3-4
ABACUS III
Dec.
ΣΔ ADC
SSI
Filter
18Mhz
LO CLK
CLK
Abacus III
ABACUS III
Dec.
ΣΔ ADC
SSI
Filter
18Mhz
LO CLK
CLK
Abacus III
and