Service Manual
8. VHF (136-174 MHz) Information
236
8.3 FGU
The Frequency Generation Unit (FGU) comprises VCO and PLL. It is the core module of the
whole TX-RX system. This circuit provides accurate carrier frequency during transmission,
and stable LO signal during reception. It has a direct influence on the performance of the
system.
TX_VCO
Frequency
Synthesizer
RX_VCO
Ref. Osc
19.2 MHz
MOD-VCO
MOD
2
+Freq
Erro
r
Sh
ift
4CH DAC
4-Pole RC Filter
TX VCO
Amplifier
From OMAP
Reference OSC Signal
CV Buffer
Adapt
SW
Adapt
Control
OP
TX VCO
Buffer
LPF
CV
SW
CV-Read
Control
CV OUT
TX VCO
OUTPUT
OMAP
RX VCO
Amplifier
LPF
RX VCO
Buffer
RX BPF
TX BPF
RX VCO
OUTPUT
Figure 8-4 Diagram of FGU
8.3.1 Working Principle of PLL
The 19.2 MHz frequency generated by the reference crystal oscillator goes to PLL for division,
generating the reference frequency (i.e. step frequency f1). Meanwhile, the frequency
generated by VCO generates another frequency (f2) through the frequency divider in PLL.
Then frequencies f1 and f2 are compared in the phase detector (PD), to generate continuous
pulse current. The current goes to the loop filter for RC integration, and is then converted to
CV voltage. Then the CV voltage is sent to the varactor diode of VCO. It adjusts the output
frequency of VCO directly until the CV voltage becomes constant. Then the PLL is locked,
and the stable frequency output by VCO goes to the TX-RX channel after passing through
two buffer amplifiers.
Содержание RDR9000
Страница 1: ...RDR9000U V Service Manual ...
Страница 45: ...Service Manual 6 UHF1 400 470 MHz Information 35 6 4 PCB View PCB View Main Board Top Layer ...
Страница 46: ...Service Manual 6 UHF1 400 470 MHz Information 36 PCB View Main Board Bottom Layer ...
Страница 48: ...Service Manual 6 UHF1 400 470 MHz Information 38 PCB View Rear Board Top Layer ...
Страница 49: ...Service Manual 6 UHF1 400 470 MHz Information 39 PCB View Rear Board Bottom Layer Figure 6 5 PCB View ...
Страница 146: ...Service Manual 7 UHF3 350 400 MHz Information 136 7 4 PCB View PCB View Main Board Top Layer ...
Страница 147: ...Service Manual 7 UHF3 350 400 MHz Information 137 PCB View Main Board Bottom Layer ...
Страница 148: ...Service Manual 7 UHF3 350 400 MHz Information 138 PCB View Control Head Top Layer PCB View Control Head Bottom Layer ...
Страница 149: ...Service Manual 7 UHF3 350 400 MHz Information 139 PCB View Rear Board Top Layer ...
Страница 150: ...Service Manual 7 UHF3 350 400 MHz Information 140 PCB View Rear Board Bottom Layer Figure 7 5 PCB View ...
Страница 248: ...Service Manual 8 VHF 136 174 MHz Information 238 8 4 PCB View PCB View Main Board Top Layer ...
Страница 249: ...Service Manual 8 VHF 136 174 MHz Information 239 PCB View Main Board Bottom Layer ...
Страница 250: ...Service Manual 8 VHF 136 174 MHz Information 240 PCB View Control Head Top Layer PCB View Control Head Bottom Layer ...
Страница 251: ...Service Manual 8 VHF 136 174 MHz Information 241 PCB View Rear Board Top Layer ...
Страница 252: ...Service Manual 8 VHF 136 174 MHz Information 242 PCB View Rear Board Bottom Layer Figure 8 5 PCB View ...
Страница 346: ...Service Manual 11 Packing Guide 336 11 Packing Guide Figure 11 1Packing Guide ...
Страница 352: ...342 ...