Agilent Technologies FieldFox MW N9913A, Service Manual, Page: 62 / 156

5-12 N9927-90003
Theory of Operation FieldFox Analyzer
Measurement Group
Power Management Circuitry
The circuitry on the A4 RF board has five special sections that may be powered down for the purpose of
power management. These sections may be selectively powered down (via “load switching”) when not
required for the current operating mode of the analyzer.
The sections that may be selectively powered down are:
• Source—most of the source synthesizer circuitry
• LO—most of the LO synthesizer circuitry
• SA—most of the first, second, and third converter circuitry
• Reflectometer—put into a low power state
• High-Band Pre-amp—high band section of the pre-amp turned off
The load switching for the Source and LO sections is accomplished on the A5 System board via the
Analog Linear Regulators and Load Switching circuitry.
The load switching for the Reflectometer and High-Band Preamp is accomplished on the A4 RF board.
Other Circuitry
The FPGA (Field Programmable Gate Array) communicates with the FPGA on the A5 System board via
FPGA Serial Bus. It provides the digital control for the functions on the A4 RF board. It also reads the
VCO unlock signals.
RF Serial Bus allows the System Monitor on the A5 System board to read a temperature sensor and the
ID EPROM for the A4 RF board.