Service Guide N5227-90001 5-33
PNA Series Microwave Network Analyzers Theory of Operation
N5227A Digital Processing and Digital Control Group Operation
Front Panel Subgroup
The front panel subgroup contains the following assemblies:
• A1 Front Panel Interface Board
• A2 USB Board
• A3 Display Assembly
• Keypad Assembly
A1 Front Panel Interface Board
The A1 front panel interface board detects and decodes user inputs from the keypad assembly and front
panel knob, and transmits them to the A21 CPU board by way of the A18 system motherboard. It also
decodes video data from the video processor on the A21 CPU board and supplies this to the A3 display
assembly. Power from the power bus on the A18 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 A18 system motherboard.
The A1 front panel interface board also includes a speaker that emits the audio signals received from the
A21 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 a 10-inch LCD with associated drive circuitry and backlight inverter. Two
cables between the A3 display assembly and the A1 front panel interface 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 A21 CPU
board and the necessary drive circuit power. The video data received from the A21 CPU board includes
the following:
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 Figure 5-9 on
page 5-32.
• digital TTL horizontal sync • digital TTL red video • blanking
• digital TTL vertical sync • digital TTL green video • data clock
• digital TTL blue video
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