A3 Digital If Assembly Description - Keysight n9020a Service Manual

Analog/Digital IF Troubleshooting
40 MHz BW IF Section

A3 Digital IF Assembly Description

The A3 Digital I.F. has circuitry that is needed to analyze complex
communication signals that can occupy up to 40 MHz of information
bandwidth. This assembly has two inputs:
1. The final 22.5 MHz I.F. from the A2 Analog I.F. for IF bandwidth paths up
to 25 MHz wide. This input is used for swept and FFT spectrum analysis.
2. The 250 MHz IF from the A15 Front End Control Assembly for IF
bandwid th of 40 MHz. If Option B85, B1A, or B1X is also installed, the 250
MHz IF will be routed to A3 via W53, A25, and W52.
Each input has a separate ADC that processes 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 22.5 MHz and the 250 MHz IF signals
— 16 bit ADC with a 100 MHz sample rate to digitize the 22.5 MHz IF
— 12 bit ADC with a 200 MHz sample rate to digitize the 250 MHz IF
— 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
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