NXR-810
23
■
PLL IC (X58-509: IC300)
PLL IC compares the differences in phases of the VCO
oscillation frequency and the VCTCXO reference frequency,
returns the difference to the VCO CV terminal and realizes
the “Phase Locked Loop” for the return control. This allows
the VCO oscillation frequency to accurately match (lock) the
desired frequency.
When the frequency is controlled by the PLL, the fre-
quency convergence time increases as the frequency dif-
ference increases when the set frequency is changed. To
supplement this, the MCU is used before control by the
PLL IC to bring the VCO oscillation frequency close to the
desired frequency. As a result, the VCO CV voltage does not
change and is always stable at approx. 3.0V.
The desired frequency is set for the PLL IC by the MCU
(X53-449: IC20) through the 3-line “SPSD0”, “SPSCLK0”,
“/RXPCS_TR” serial bus. Whether the PLL IC is locked or
not is monitored by the MCU through the “LDR” signal line.
If the VCO is not the desired frequency (unlock), the “LDR”
logic is low.
Fig. 10 Receiver PLL circuit /
图 10 接收机 PLL 电路
Ref 19.2MHz
LDT
SPSCLK0
SPSD0
/RXPCS
Buffer
Q300
RX VCO/PLL
IC300
LPF
RX_CV
LPF
FIN
Loop filter
2-9. AVR circuit
The 13.6V Power Source (+B) is provided through the
Connector (CN701) from the Final unit (X45-393). +B is con-
nected to a FET switch (Q702, Q703) and CN700. Q702
and Q703 are controlled by the “SBC” signal from the MCU
which is in the Control unit (X53-449). If “SBC” logic is
high, Q702 and Q703 turn on. The 13.6V power source (SB)
which is turned on by Q702 and Q703 is provided to the 8V
AVR IC (IC702) and CN700. CN700 is connected to the Con-
trol unit (X53-449) to provide the +B power source and the
SB power source.
IC702 supplies 8V to the VCO, 15V DC/DC converter IC
(IC701), AVR IC (IC700) and FET switches (Q700, Q701).
IC701 is a step-up switching regulator. IC701 regulates 8V
to 15V and supplies the 15V power source to the “assist cir-
cuit” and “front-end BPF tuning circuit”. The FET switches
(Q700, Q701) are controlled by the I/O expander IC (IC805).
When Q700 and Q701 turn on, the 8V power source is pro-
vided to receiver section.
CIRCUIT DESCRIPTION /
电路说明
■ PLL IC(X58-509: IC300)
PLL IC 对比 VCO 震荡频率和 VCTCXO 基准频率的相位差，将
相位差返回 V C O C V 端子，实现返回控制的“锁相环路”
。这
可以使 VCO 震荡频率与所需的频率精确匹配 ( 锁定 )。
频率由 P L L 控制时，频率锁定时间将随着设定频率改变时
频率差的增大而增加。为对此进行补充，在由 PLL IC 控制之
前使用 M C U 以使 V C O 震荡频率接近所需的频率。因此，V C O
CV 的电压不变，始终稳定在约 3.0V。
P L L I C 的 所 需 频 率 由 M C U ( X53-449: I C20) 通 过 3 线 路
“SPSD0”
、
“SPSCLK0”
、
“/RXPCS_TR”串行总线进行设定。PLL
IC 锁定与否由 MCU 通过“LDR”信号线路进行监测。如果 VCO
不是所需的频率 ( 失锁 )，则“LDR”逻辑较低。
2-9. AVR 电路
13.6V 电源 ( + B ) 通过连接器 ( C N701) 从末级单元 ( X45-
393) 提供。+B 连接到 FET 开关 (Q702,Q703) 和 CN700。Q702
和 Q703 由控制单元 ( X53-449) 内来自 M C U 的“S B C”信号控
制。如果“S B C”逻辑高，则 Q702 和 Q703 开启。由 Q702 和
Q703 开启的 13.6V 电源 (SB) 被提供到 8V AVR IC(IC702) 和
C N700。C N700 连接到控制单元 ( X53-449) 以提供 + B 电源和
SB 电源。
I C702 将 8V 提供到 V C O、15V D C / D C 转换器 I C ( I C701)、
AVR IC(IC700) 和 FET 开关 (Q700、Q701)。IC701 是一个升压
型开关稳压器。IC701 将 8V 调节到 15V，
向“辅助电路”和“前
端 B P F 调谐电路”提供 15V 电源。F E T 开关 ( Q700、Q701) 由
I / O 扩展器 I C ( I C805) 控制。当 Q700 和 Q701 开启时，8V 电
源提供到接收机部分。
