Agilent Technologies 8564EC, Service Manual

Page: 277 / 512

358 Chapter 7
General Troubleshooting
Block Diagram Description
YTO PLL (A7, A11, part of A14, part of A15)
The YTO PLL produces the 1st LO of the instrument (3.0 to 6.81 GHz).
The YTO output is mixed with a harmonic of the sampling oscillator in
the sampler (A15A2), and the resulting frequency is phase-locked to the
output of the fractional N PLL.
The A15U100 sampler mixes the LO signal from the A7 LOMA with a
harmonic of the sampling oscillator. The mixing product, the sampler
IF, is between 60 and 96 MHz (same frequency range as the fractional
N PLL).
Offset Lock Loop (part of A15)
The 285 MHz to 297.2 MHz sampling oscillator is used to sample the
YTO. By changing the offset lock loop programmable dividers, the YTO
frequency can be changed.
Figure 7-7 Phase Lock Loops