Transmitter; General; Function Description; Control- And Output-Signals - Benefon DRAGON TDP70WN Service Manual

5.6 TRANSMITTER

5.6.1 General

Operating voltage
Current consumption
Input level from the synthesizer
Output level to the duplex filter
Frequency range

5.6.2 Function Description

The transmitter unit is comprised of three amplifier stages and two attenuator
stages. The pre-amplifier Q620/Q621 and power module I650 form the transmitter
amplifier chain. The attenuators surrounding the pre-amplifier are included to
enhance the electric separation between the TX synthesizer and the transmitter.
The operational amplifier I640 and transistors Q641 and Q642 serve as a power reg-
ulator circuit, which adjusts the power level so that the voltage from the transmitter
power detector (D660) and the control voltage TXPWR from the audio/processor
unit are equal.
The negative bias voltage for the power amplifier is generated from the 13 MHz
TCXO signal.
I610 amplifies the signal for the switched power supply Q610/D610 and is then regu-
lated by the zenerdiode D611.
I600 serves as voltage regulator for pre-amplifier and for the negative voltage
generetor.
Q631 serves as the ON/OFF switch for the output power.

5.6.3 Control- and Output-Signals

VBAT
TXBIAS
TXPWR
TXINJ
TXDUPLEX
4Z2200GB.fm
Transmitter operating voltage from the
battery-pack (fused)
Power ON/OFF control
Power level control signal from the D/A
converter
RF signal from the TX synthesizer
Transmitter output to the duplex filter
Product: TDP70WN /
5.9.2000
3.5 ... 4.5 v
mid power max. 1.1 A
low power max. 0.45 A
+6 dBm
mid power 33 dBm (2.0W)
low power 24.7 dBm (0.3W)
453.000...457.475 MHz
OC2285 Processor/Audio/RF
0...3V
+6dBm
15