Agilent Technologies 8753ES Option 011 Service Manual page 374

Theory of Operation
Source High Band Operation
7. A synthesized subsweep is generated by A13/A14. The A3 source tracks the
synthesizer. When the source is phase locked to the synthesizer at the start frequency,
the synthesizer starts to sweep. The phase locked loop forces the source to track the
synthesizer, maintaining a constant 1 MHz 1st IF signal.
The full high band sweep is generated in a series of subsweeps, by phase locking the A3
source signal to harmonic multiples of the fractional-N VCO. The 16 to 31 MHz
subsweep is produced by a one half harmonic, using the divide-by-2 circuit on the A14
assembly. At the transitions between subsweeps, the source is pretuned and then
relocks. Table 12-3
and the source output.
Figure 12-5 High Band Operation of the Source
12-20
lists the high band subsweep frequencies from the fractional-N VCO
Chapter 12