Front Panel Subgroup; Data Acquisition And Processing Subgroup - Keysight N5221A Service Manual

Theory of Operation
Digital Processing and Digital Control Group Operation

Front Panel Subgroup

The front panel subgroup contains the following assemblies:
• A1 Front Panel Display Board
• A2 USB Board
• A3 Display Assembly
• Keypad Assembly
A1 Front Panel Display Board
The A1 front panel display board detects and decodes user inputs from the keypad assembly and front panel
knob, and transmits them to the A17 CPU board by way of the A14 system motherboard. It also decodes
video data from the video processor on the A17 CPU board and supplies this to the A3 display assembly.
Power from the power bus on the A14 system motherboard is buffered and routed to the keypad assembly
and the A3 display assembly. All data and power signals are routed through a single cable connector to the
A14 system motherboard.
The A1 front panel interface board also includes a speaker that emits the audio signals received from the
A17 CPU board.
A2 USB Board
This board provides four universal serial bus (USB) jacks that are industry standard 4-pin connectors
allowing multiple USB devices to be connected to the analyzer's front panel.
A3 Display Assembly
The A3 display assembly contains an 10-inch LCD with associated drive circuitry and backlight inverter. Two
cables between the A3 display assembly and the A1 front panel display board provide all necessary power
and data for normal operation. The two cables are:
1. A cable to the inverter that supplies buffered power.
2. A cable to the display circuitry that supplies decoded data from the video processor on the A17 CPU
board and the necessary drive circuit power. The video data received from the A17 CPU board includes
the following:
• digital TTL horizontal sync
• digital TTL vertical sync
Keypad Assembly
The keypad assembly provides user interface to the analyzer. The front panel rotary pulse generator (RPG)
knob is not electrically connected to the keypad, but rather provides user inputs directly to the front panel
processor.

Data Acquisition and Processing Subgroup

The data acquisition and processing subgroup contain the following assemblies. See
page 5-27.
5-28
• digital TTL red video
• digital TTL green video
• digital TTL blue video
PNA Series Microwave Network Analyzers
• blanking
• data clock
Figure 5-8 on
Service Guide N5222-90001
N5221A/22A