66 Keysight FieldFox Handheld Analyzers Service Guide
Theory of Operation
Measurement Group
5-
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.
A5 System Board
The A5 System board controls all of the functions of the analyzer and digitizes
the RF IF signals (NA-R, NA-A, NA-B, and SA IF) from the A4 RF board.
The A6 SOM (System on Module) board is mounted directly on the A5 System
board.
All external connections for the analyzer come through the A5 system board
except for the PORT 2 and PORT 1 ports.
The A5 System board also controls the power switching and power
management.
The instrument model number and serial number are stored on the A5 System
board.
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