Motorola pro7100 Manuel de service Page 34
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Noté. / 5. Basé sur avis des utilisateurs
2-20 Theory of Operation
2.5 Transmitter Power Amplifier (PA) 40 W
The radio’s 40W power amplifier (PA) is a four stage amplifier used to amplify the output from the
VCOBIC to the radio transmit level. It consists of the following four stages in the line-up. The first
stage is a LDMOS predriver (U4401) that is controlled by pin 4 of PCIC (U4501) via Q4473
(CNTLVLTG). It is followed by another LDMOS stage (Q4421), an LDMOS stage (Q4431), and a
bipolar final stage (Q4441).
Figure 2-8. UHF Transmitter Block Diagram
Device Q4401 is surface mounted. Q4421, Q4431 and Q4441 are directly attached to the heat sink.
2.5.1 Power Controlled Stage
The first stage (U4401) amplifies the RF signal from the VCO (TXINJ) and controls the output power
of the PA. The output power of the transistor U4401 is controlled by a voltage control line feed from
the PCIC pin4(U4501). The control voltage simultaneously varies the bias of two FET stages within
U4401. This biasing point determines the overall gain of U4401 and therefore its output drive level to
Q4421, which in turn controls the output power of the PA.
In receive mode the voltage control line is at ground level and turns off Q4473 which in turn switches
off the biasing voltage to U4401.
2.5.2 Pre-Driver Stage
The next stage is a 13dB gain LDMOS device (Q4421) which requires a positive gate bias and a
quiescent current flow for proper operation. The voltage of the line PCIC_MOSBIAS_1 is set in
transmit mode by PCIC pin 24 and fed to the gate of Q4421 via the resistive network R4407, R4408,
R4416 and R4415. The bias voltage is tuned in the factory.
PCIC
Pin Diode
Antenna
Switch
RF Jack
Antenna
Harmonic
Filter
Power
Sense
PA -F i na l
Stage
PA
Driver
From VCO
Controlled
Stage
Vcontrol
Bias 1
Bias 2
To Microprocessor
Temperature
Sense
SPI BUS
ASFIC_CMP
PA
PWR
SET
To Microprocessor
- Professional Radio 1
- Computer Software Copyrights 2
- SAFETY INFORMATION 3
- W A R N I N G 4
- C a u t i o n 4
- Safety-3 5
- Safety-4 6
- Relabeling 6
- TABLE OF CONTENTS 7
- Chapter 3 Maintenance 9
- List of Figures 9
- List of Tables 10
- Chapter 1 11
- Introduction 11
- 1.3 Related Documents 12
- 1.4 Technical Support 12
- 1.5 Warranty and Repairs 12
- 1.7 Radio Model Information 14
- Chapter 2 15
- Theory of Operation 15
- 2-2 Theory of Operation 16
- 2.2.2 Automatic On/Off 17
- 2.2.3 Emergency 18
- 2.2.4 Mechanical On/Off 18
- 2.2.5 Ignition 18
- Theory of Operation 2-5 19
- 2.2.8 SBEP Serial Interface 20
- Theory of Operation 2-7 21
- 2-8 Theory of Operation 22
- 2.3.2 Transmit Audio Circuits 23
- 2.3.3 Microphone Input Path 23
- 2-10 Theory of Operation 24
- Theory of Operation 2-11 25
- 2.3.4.2 High Speed Data 26
- 2.3.5 Receive Audio Circuits 27
- 2.3.5.1 Squelch Detect 27
- 2-14 Theory of Operation 28
- 2.3.5.4 Handset Audio 29
- ASFIC_CMP 30
- 2.3.6.3 Voice Storage Option 31
- Theory of Operation 2-19 33
- 2.5.1 Power Controlled Stage 34
- 2.5.2 Pre-Driver Stage 34
- Theory of Operation 2-21 35
- 2.6 Frequency Synthesis 36
- Theory of Operation 2-23 37
- 2-24 Theory of Operation 38
- 2.6.4 Synthesizer Operation 39
- Theory of Operation 2-27 41
- 2.8.1 Power Controlled Stage 42
- 2.8.2 Pre-Driver Stage 42
- 2.8.3 Driver Stage 43
- 2.8.4 Final Stage 43
- 2.8.5 Directional Coupler 43
- 2.8.6 Antenna Switch 43
- 2.8.7 Harmonic Filter 43
- 2.9 Frequency Synthesis 44
- Theory of Operation 2-31 45
- 2.9.4 Synthesizer Operation 47
- 2.10.1 Power Supplies 48
- 2.10.2 Power On/Off 48
- 2.10.3 Microprocessor Circuit 48
- 2.10.4 SBEP Serial Interface 49
- 2.10.5 Keypad Keys 49
- 2.10.8 Speaker 50
- 2.11.1 Power Supplies 51
- 2.11.2 Power On / Off 51
- 2.11.3 Microprocessor Circuit 51
- 2.11.4 SBEP Serial Interface 52
- 2.11.5 Keypad Keys 52
- Theory of Operation 2-39 53
- 2.11.9 Speaker 54
- Chapter 3 55
- Maintenance 55
- Maintenance 3-3 57
- 3-4 Maintenance 58
- Table 3-1 59
- 60
- Maintenance 3-7 61
- 3-8 Maintenance 62
- Mobile Synthesizer Section 63
- 3-10 Maintenance 64
- 3.9 VCO Troubleshooting Chart 65
- 3-12 Maintenance 66
- Chapter 4 67
- 6-LAYER CIRCUIT 68
- COPPER STEPS IN PROPER 68
- LAYER SEQUENCE 68
- BOARD DETAIL VIEWING 68
- ZWG0130113 70
- ZWG0130239 71
- ZWG0130240 72
- ZWG0130136 75
- ZWG0130137 76
- ZWG0130241 77
- ZWG0130242 78
- BACKLIGHT GREEN 79
- U0971 Display Driver 80
- ZWG0130229-A 84
- ZWG0130230 A 85
- ASFIC CMP 86
- ZWG0130231-A 86
- ZWG0130232-A 87
- ZWG0130272 91
- ZWG0130270 92
- ZWG0130271 93
- ZWG0130227P 99
- 3,0 -7,5VDC 100
- (SOURCE) 102
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