Chapter 5 139
Digital IF Troubleshooting
A3 Digital I.F. Assembly Theory of Operation
Noise Source Voltage Regulator
Various external noise sources can be connected to the rear panel of the
N9000A Signal Analyzer. These noise sources require a very accurate 28 volt
DC power supply.
The 28 volt BNC output connector is used with the 346 series noise sources.
The Smart Noise Source (SNS) interface includes power switching for the
28 volt and 15 volt power supply. In addition, it has buffers to interface to the
SNS I2C bus for control and read back of ENR data automatically. The SNS
connector is used with the SNS series noise sources.
DSP
The signal from the ADC is sent to the Digital Signal Processor.
Digital Bus Common Mode Filtering
The Digital Bus is a real time digital interface. It is sometimes referred to as
Messenger or LVDS. The implementation on the Digital IF is unidirectional,
meaning it can only source data, not receive it. Common mode filtering is
required to translate the digital ground referenced signals to analog ground at
the rear panel.
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