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NXR-810
22
2-8. Receiver PLL circuit (SUB unit)
■
VCO
RX VCO circuit consists of two VCOs (VCO A X58-
509: Q352, VCO B X58-509: Q353). Those VCOs gener-
ate a 1st local signal. For the VCO oscillation frequency,
the 1st local signal is 341.95 to 411.95MHz. (VCO A:
341.95~376.95MHz, VCO B: 376.95~411.95MHz)
Those VCO oscillation frequency is determined by two
systems of voltage control terminals “CV” and “RXASSIST”.
The voltage control terminals, “CV” and “RXASSIST”,
are controlled by the PLL IC (X58-509: IC300) and the MCU
(X53-449: IC20) and the output frequency changes continu-
ously according to the applied voltage.
Fig. 8 IF circuit /
图 8 中频电路
SW
450kHz
RSSI
CN802
AGC
58.05MHz
IF IC
IC403
IC405
SW
IC406
CF402
CF403
CF401
SW
IC408
SW
IC407
CF400
RSSI
IF2
AGC
IF1
2nd Lo
57.6MHz
IF AMP
IC404
IF AMP
IC400
MCF
XF300
IF AGC AMP
Q300
IF POST AMP
Q301
Diff AMP
IC401(B/2)
AMP
IC409(A/2,B/2)
Buffer
IC401(A/2)
Buffer
IC402
Fig. 9 Receiver VCO circuit /
图 9 接收机 VCO 电路
D355
D352
D358
D359
SW
Q350
Q351
RXVCOA/B
RX_CV
RXASSIST
80C
VO
VCO_A
Q352
Buffer
Q354
D357
D353
D360
D361
VCO_B
Q353
CIRCUIT DESCRIPTION /
电路说明
2-8. 接收机 PLL 电路 (SUB 单元 )
■ VCO
RX VCO 电路由两个 VCO(VCO A X58-509:Q352,VCO B X58-
509:Q353) 组成。这些 VCO 生成第 1 本地信号。对于 VCO 振荡
频率,第 1 本地信号为 341.95 到 411.95MHz。(VCO A:341.95
~ 376.95MHz,VCO B:376.95 ~ 411.95MHz)
这些 V C O 振荡频率由电压控制端子的两个系统 :“C V”和
“RXASSIST”决定。
电 压 控 制 端 子“C V” 和“R X A S S I S T” 由 P L L I C ( X58-
509:IC300) 和 MCU(X53-449:IC20) 控制,并根据施加的电压
连续输出频率变化。