A3 Digital I.f. Assembly Description - Keysight N8973B Service Manual

Analog/Digital IF Troubleshooting
25 MHz BW IF Section

A3 Digital I.F. Assembly Description

The A3 Digital I.F. has circuitry that is needed to analyze complex
communication signals that can occupy up to 25 MHz of information
bandwidth. It digitizes the final 22.5 MHz I.F. from the A2 Analog I.F. board, by
processing the time domain continuous data into I/Q (in-phase and
quadrature) signals before sending the data to the A4 CPU assembly for further
processing and front panel display.
The Digital I.F. has the following main functions:
— Digitizes the final 22.5 MHz Intermediate Frequency
— 14 bit ADC with a 90 MHz sample rate
— DSP for standard spectrum analysis
— Capture memory for complex signals
— Noise Source Control
— Dither for final I.F.
— Provides the alignment sequence generator for wide band alignments
— Provides wide band Comb Calibration Signal
— Trigger interpolation and associated alignment
260 Keysight NFA Series Noise Figure Analyzers Service Guide