Agilent Technologies FieldFox MW N9913A, Service Manual

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N9927-90003 5-19
FieldFox Analyzer Theory of Operation
Grounding and Power
Power Control and Management
Power States
The On/Off Button is used to switch between On, Off, and Standby power states:
Off Only the System Monitor and battery control circuits are powered up (if power is available from
the battery or external power).
If the battery is charging, the LED below the On/Off Button slowly flashes orange with increasing
intensity, otherwise this LED is off.
Some battery power is required in the “Off” state. A fully charged battery will discharge completely
in four to six weeks when left in the analyzer.
On This is normal operation. The On/Off Button LED is steadily lit green.
Standby Only the digital power supplies are on. The CPU is in a low power state, maintaining RAM
content. The On/Off Button LED flashes yellow briefly every two seconds.
During normal operation, unexpectedly disconnecting power to the analyzer (such as removing the main
battery when the analyzer is not connected to external power) should not cause any problems. Simply
re-apply power. No firmware problems are expected. Of course, this does not apply during a firmware
upgrade.
Smart Power Management
The analyzer uses extensive “load switching” to minimize power dissipation. This is termed Smart
Power Management (SPM). There are two motivations for power management:
• to extend battery run time
• to prevent overheating.
Sections of the circuitry are selectively powered down via “load switching”, depending on the operating
mode of the analyzer. Five different sections of the circuitry on the A4 RF board may be controlled via
“load switching”. These sections are as follows:
• Source—switched off during SA mode, switched off between sweeps during CAT or NA modes.
• LO—switched off when data is not being taken by receivers.
• SA—switched off when in one port CAT or NA modes, on all the time in two port mode.
• Reflectometer—switched to low power through state when RF OUT port receivers are inactive.
• High-Band Pre-amp—switched off when not required.
On the A5 System board, each of the ADC’s may be individually switched to a low power mode when
not active.
Load switching is generally transparent to the user. One obvious exception is the that the source turns off
during “retrace” in the CAT and NA modes.