Control- And Output-Signals; Receiver; General - Benefon DRAGON TDP70WN Service Manual

5.4.3 Control- and Output-Signals

VTXS
TXAUDIO
13MHz
SCLK
SDATA
SLE
TXINJ
AFC
TXS_REG

5.5 RECEIVER

5.5.1 General

The module contains all FM-receiver functional blocks.
RF-amplifier
1. mixer
1. IF-amplifier
FM IF system
When the RF signal is received it is brought through the duplex filter to the amplifier
stage Q500. The amplified signal is passed through the attenuator to the balanced
mixer.The balanced mixer is made by using discrete components, diode D510 and
RF-transformer M510.
The upper side injection frequency is brought from the synthesizer through a small
resistive attenuator to the mixer. The 78.45 MHz intermediate frequency from the
mixer output is fed through the IF- filter X520 to the FM IF-circuit I550.
RX injection frequency 541.450...545.925MHz
Injection-level/impedance +1 dBm / 50 ohm
The second intermediate-freqency local-oscillator-frequency required by the FM IF-
circuit is generated by multiplying the 13.00 MHz reference-oscillator frequency by
six. The multiplier circuit is made with transistor Q530.
The second intermediate frequency is 450 kHz. The phase-shift required by the
quadrature detector is made with the L550. The detected AF-signal temperature cor-
rection is done in the buffer amplifier stage.
4Z2200GB.fm
Product: TDP70WN /
5.9.2000
TX synthesizer operating voltage (3.0 V)
Transmitter audio signal
13.00 MHz signal to the receiver circuit.
Clock signal for synthesizer control data
Synthesizer control data
ENABLE pulse to the synthesizer
TX synthesizer output to the transmitter (+6 dBm)
AFC control voltage from AF/LOGIC-board
Control line for VTXS-regulator
3SK284
balanced mixer
3SK284
SA 607 includes the following blocks:
2. mixer
IF limiter
quadrature detector
RSSI (received signal strength indicator)
OC2285 Processor/Audio/RF
13