Agilent Technologies FieldFox MW N9913A, Service Manual

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5-16 N9927-90003
Theory of Operation FieldFox Analyzer
Measurement Group
Time Base
The Time Base is an internal TCXO that produces 90 MHz signals for use throughout the analyzer.
A 10 MHz signal at the Ref In/Trig input may be used to provide an external time base. The external time
base function is controlled via the user interface. Refer to the “Frequency Reference Source” section of
the
FieldFox Analyzer User’s Guide (Part Number N9927-90001) for additional information.
The internal 10 MHz frequency reference is available from the Ref/Trig Out connector on the right-side
panel. Use this signal as a common frequency reference when making measurements using external
equipment
Filters, MUX, and ADC’s
The three Filters filter the IF signals in preparation for the ADC. Filter characteristics are fixed (not
programmable).
The ADC’s digitize each of the IF signals received from the A4 RF board. The input to one of the ADC’s
is multiplexed between the NA-A and NA-B input signals.
The 14-bit ADCs sample at a rate of 30 mega samples per second.
Each ADC may be put into a low power mode when not active.
Temperature Sensors
The SB1 Temp Sensor is located on the A4 RF board side of the A5 System board near the headphone
jack (J3).
The SB2 Temp Sensor is on the A4 RF board side of the A5 System board near the edge of the board
against the battery compartment. This temperature sensor is not under a shield.
Audio Output
The speaker is located on the left side panel of the case. Left and right audio signals from the A6 SOM
board go to the headphone jack on the A5 System board. These signals are then combined to create a
single mono signal for the speaker. An amplifier drives the speaker. Plugging in the headphones disables
the speaker output.
LAN Connector
The LAN connector supports the LAN interface on the A6 SOM board. See “LAN Interface” on page
5-30 for more details.
SOM Connector
Refer to “A6 SOM Board” on page 5-17 for information on SOM (System on Module) functions.