Transceiver Section; Figure 3-2. Rf Transceiver Block Diagram; Table 3-1. Battery Connector M1705 - Motorola ASTRO XTSTM 4000 Detailed Service Manual

3-2
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)
Figure 3-2 illustrates the transceiver board block diagram.
To Antenna
Antenna RF Jack
J1704
Matching
Network
50-Ohm -
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
Pin No.
1
2
3
May 28, 2008
Thermistor Thermistor
Tx Tx
U103 U103
PCIC PCIC
U104 U104
Power Amp
Q107
Harmonic Antenna
Filter Switch
Step Pre- -
Attenuator Selector
Rx
U701 Filter

Figure 3-2. RF Transceiver Block Diagram

Table

Table 3-1. Battery Connector M1705

Signal Description
POS Battery positive terminal, nominally 7.5 Vdc
DATA Battery status, from battery to VOCON section
NEG Battery negative terminal, tied to PCB GROUND
Theory of Operation: Transceiver Section
FGU
Current Current
Sense Sense
VCO Buffer
2 2 nd nd Thermal Thermal
U302 (VHF)
Tx VCO
Cutback Cutback
Rx VCO Rx VCO
Tx Driver
U102
RX LNA Post- - Mixer Crystal Filter
Q430 Selector U470 FL490
Filter
3-1.
LPF DAC
3
FL200 U203
Tx SSI
from
A-D A-D
VOCON
FractN
Reference
Section
U202
Oscillator Y200
Loop
Filter
3 3
ABACUS III ABACUS III Rx SSI
U500 U500
to
VOCON
Section
Sample
2 nd LO
Clk
6871620L01-C