May 28, 2008
6871620L01-C
3-2
Theory of Operation:
Transceiver Section
3.1
Transceiver Section
The transceiver (XCVR) section performs the transmitter and receiver functions necessary to
translate between voice and data from the VOCON section and the modulated radio-frequency (RF)
carrier at the antenna. The transceiver section contains all the radio’s RF circuits for the following
major components:
• Receiver
• Transmitter
• Frequency Generation Unit (FGU)
illustrates the transceiver board block diagram.
Figure 3-2. RF Transceiver Block Diagram
3.1.1
Connections
This section describes the various connections to and from the transceiver section.
3.1.1.1 Battery Connector M1705
Battery connector M1705 consists of three gold-plated contacts on the printed circuit board that mate
with the battery. Signal descriptions are in
.
Table 3-1. Battery Connector M1705
Pin No.
Signal
Description
1
POS
Battery positive terminal, nominally 7.5 Vdc
2
DATA
Battery status, from battery to VOCON section
3
NEG
Battery negative terminal, tied to PCB GROUND
Harmonic
Filter
Antenna
Switch
Antenna
Matching
Network
50-Ohm
RF Jack
J1704
Power Amp
Q107
Tx Driver
U102
Current
Sense
PCIC
U104
2
nd
Thermal
Cutback
Step
Attenuator
U701
Post-
Selector
Filter
RX LNA
Q430
Mixer
U470
Crystal Filter
FL490
2
nd
LO
Sample
Clk
A-D
VCO Buffer
Tx VCO
Rx VCO
Loop
Filter
FractN
U202
Reference
Oscillator Y200
Tx
Rx
FGU
Tx SSI
from
VOCON
Section
3
3
Rx SSI
to
VOCON
Section
Thermistor
U103
LPF
FL200
DAC
U203
ABACUS III
U500
Pre-
Selector
Filter
-
Current
Sense
PCIC
U104
2
nd
Thermal
Cutback
-
A-D
U302 (VHF)
Rx VCO
Tx
3
Thermistor
U103
ABACUS III
U500
-
To Antenna
Summary of Contents for ASTRO XTSTM 4000
Page 1: ...COLOR CHORDS 7 ASTRO XTSTM 4000 Portable Radio Detailed Service Manual ...
Page 2: ......
Page 16: ...May 28 2008 6871620L01 C xiv Commercial Warranty Notes ...
Page 22: ...May 28 2008 6871620L01 C 1 6 Introduction Notes ...
Page 26: ...May 28 2008 6871620L01 C 2 4 Radio Power Notes ...
Page 56: ...May 28 2008 6871620L01 C 3 30 Theory of Operation Notes ...
Page 100: ...May 28 2008 6871620L01 C 6 8 Troubleshooting Waveforms Notes ...
Page 194: ...May 28 2008 6871620L01 C B 2 Motorola Service Centers Notes ...
Page 204: ...May 28 2008 6871620L01 C Glossary 10 Glossary Notes ...
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