HYT RPU416A, Руководство пользователя

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4
B
C C
B
ANT
ANTSW
RF
MCF
38.85MHz
CF
450KHz
SYSTEM
AF
SP
X3
multiply
IF
TCXO 12.8MHz
MIC
AMP
MIC PLL
VCO
RX
TX
TX
AMP
PA
AMP
AMP AMP
Fig.1 Frequency configuration
2. Receiver
The receiver is double conversion superheterodyne.
1) Front-end RF amplifier
An incoming signal from the antenna is applied to a Preamplifier (Q203) after passing through a
transmit/receive switch circuit (K102 and D103 are off) and a 3-pole LC filter. After the signal is amplified
(Q203), the signal is filtered by a band pass filter (a3-pole LC filter) to eliminate unwanted signals before it
is passed to the first mixer. The voltages of these diodes are controlled by to track the MPU. (See Fig. 2-b)
B
C C
B
ANT
D102
D103
BPF
Q203
RF AMP
L208-L211
BPF
L214.L203.L204
MCF
XF200
IF AMP
Q201
MIXER
Q202
CF200
IF.MIX
IC200
AF AMP
LPF.HPF
IC300
AF PA AMP
IC302
SP
WIDE/NARROW SW
Q303
X3
multiply
Q1
TCXO
1st Local OSC
(PLL)
TUNE
APC
IC403
MCU
Fig. 2 Receiver section configuration
2) First mixer
The signal from the RF amplifier is heterodyned with the first local oscillator signal from the PLL
frequency synthesizer circuit at the first mixer (Q202) to create a 38.85 MHz first intermediate frequency
(1
st
IF) signal. The first IF signal is then fed through two monolithic crystal filters (MCFs: XF200) to further
remove spurious signals.
3) IF amplifier
The first IF signal is amplified by Q201, and then enters IC 200 (FM processing IC). The signal is
heterodyned again with a second local oscillator signal within IC200 to create a 450kHz second IF