Comtech EF Data SFC4200 - Manual (Page 23)

SFC4200/SFC1275G Synthesized Frequency Downconverter Operation
TM054 - Rev. 4.0 3-7
3.4 AS/3072 Frequency Reference Assembly
The Frequency Reference Assembly provides high-stability, low-noise reference signals to the
synthesizer in the converter system. The assembly also provides a reference output signal and
a means of synchronizing the internal synthesizer to an external 10 MHz source.
Contained within the reference assembly is a 10 MHz SC-cut overtone ovenized frequency
standard. When an external reference is applied to the reference assembly, the internal
oscillator is turned off and the synthesizer attempts to phase-lock to the external 10 MHz.
The RF Signal to the reference assembly includes the following:
EXT REF IN: 10 MHz external reference signal input.
REF-OUT: 10 MHz OXO signal out, or when an external reference
is present, the external reference signal is available for
daisy chaining. In this manner, a single 10 MHz
reference can be supplied to the external reference of
one converter. In turn, the externally supplied 10 MHz
becomes available at the RF Output Port where it can
be supplied to the Reference Input of the next converter.
Int 10 MHz: 10 MHz signal for the synthesizer. Analog & Digital
Signal to the reference assembly includes the following:
Synthesizer Interface: 16-Pin Synthesizer Bus provides control of serial DAC
for the purpose of fine- tuning the 10 MHz Frequency
Reference.
Power Connector: 10-Pin Synthesizer Power Bus provides voltage for
operating the reference assembly.
3.5 AS/3228 Power Supply System
Power for the converter system is derived from a single 75-Watt 15 V switching regulator. With
15 VDC as the secondary voltage for the entire system, it is possible to operate the converter
from a wide range of primary voltages especially DC or battery supplies. In addition, the 15 VDC
can be heavily filtered with a single computer-grade capacitor. This will allow a high degree of
isolation from dirty primary power systems.
3.5.1 AS/3228 Output Board
The other voltages that are required in the system include +9 VDC and +5 VDC. All of these
voltages are filtered but unregulated. The +9 VDC, and –9.5 VDC are all derived from the
+15 VDC supply through DC/DC converters.
Power budgets in the converter are listed in Table 3-7.