Agilent Technologies 85032B/E 50 Specifiche Pagina 223

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Theory of Operation 8712ET/ES and 8714ET/ES
System Theory RF Network Analyzers
6-8 Service Guide
3.5" Internal Disk Drive Assembly (A8)
The 3.5" disk drive is referred to by the analyzer as the internal disk. It accepts double
density or high density 3.5" disks. It can read from either LIF or DOS format disks, but can
only write to DOS disks. The analyzer can format disks only in DOS format (the LIF
format is not supported).
Source Group
The source group consists of the A3 fractional-N/reference assembly and the A4 source
assembly. The source assembly theory is split into 8712ET/ES and 8714ET/ES
descriptions.
Firmware on the CPU controls the operation of the source and the fractional-N board
including:
the frequency of the signal output of the source board and fractional-N board
the frequency translation in the source board
Fractional-N/Reference Assembly (A3)
The fractional-N/reference assembly provides signals to the A4 source board and various
reference signals used throughout the analyzer. The fractional-N circuit, which is part of
the phase-locked loop, generates a 30 to 60 MHz synthesized signal that is applied to the
A4 source assembly. The reference circuitry generates three reference signals. It uses
either the internal 10 MHz crystal oscillator or an external 10 MHz reference signal to
generate the 10 MHz signal and the two 5 MHz signals. The 10 MHz signal is used by the
A4 source assembly. One 5 MHz signal is used in the fractional-N VCO phase lock loop.
The other 5 MHz signal goes to the backplane, where it is routed to the CPU (A2) and
receiver (A5) assemblies for use in signal processing.
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