3. Theory of Operation
Functional Block Descriptions
137
Reference Oscillator/RF chain Block
The Reference Oscillator/RF chain Block consists of the A19 reference
oscillator module, A9 frequency multiplier, A5 87 MHz PLL module, A4 digital
synthesizer, A18 9.2 GHz PLL module, and A15 9.2 GHz Microwave
Generator module. It has three inputs:
a. EFC control,
b. I-bus,
c. amplitude modulation program,
and three outputs:
a. 80 MHz 2,
b. Frequency modulated 9.19263177138 GHz microwave probe signal.
A19 is the frequency reference for the RF chain, the output of which drives
A9. A19 is a stable, low-phase noise, ovenized quartz-crystal oscillator with a
nominal output frequency of 10 MHz. An External Frequency Control (EFC)
input allows frequency adjustments over a range of 0.3 ppm, providing servo
loop correction for noise, drift, and aging over several years. A mechanical
trimmer allows larger adjustments. A19 takes about 10 minutes to reach
operating temperature after power on.
A9 multiplies the 10 MHz input to generate four low-noise outputs:
a. an 80 MHz signal sent to A8 1 PPS assembly,
b. an 80 MHz signal sent to A10 output frequency distribution amplifier
module,
c. an 80 MHz signal sent to A5 87 MHz PLL module, and
d. a 320 MHz signal sent to A15 9.2 GHz microwave generator module.
A4 receives command input via its I-bus connection, directing its internal
circuits to generate the appropriate agile sine-wave output centered around
131.77138 kHz. The output is sent to one input of A5.
A5 has two inputs:
a. an 80 MHz signal from A9, and
b. a frequency modulated 131.77138 kHz signal from A4.
These signals are used to create a frequency modulated 87.36822862 MHz
signal sent to one input of the A18 9.2 GHz PLL module.
A18 has two inputs and two outputs. The 87.36822862 MHz signal received
from A5 is phase compared with an 87.36822862 MHz feedback signal from
A15 to generate a tuning-voltage signal routed to one input of A15. Another
output is routed from A18 to A15 that provides +4.5 Vdc power for A15.
A15 has four inputs and two outputs. It uses the 320 MHz signal from A9, the
tuning voltage from A18, the amplitude-modulation program signal from A7,
and +4.5 Vdc power from A18 to create a frequency and amplitude
modulated 9.19263177138 GHz output routed to the cesium beam tube
block.
To Next Page
Loading...
Need help?
General
