Reference Pll (P/O A15); Yto Pll (A7, All, P/O A14, P/O A15); Offset Lock Loop (P/O A15) - HP 8560A Service Manual

YTO
All Spanwidth
20.1 MHz 3.8107 GHz
to
1.01 MHz to 20.0 MHz
100 kHz to 1 MHz
100 Hz to 100 kHz
When the sweep ramp is applied to one of the PLLs, the analyzer must prevent this loop from
trying to compensate for changes in the output frequency. To accomplish this, the analyzer
breaks the PLL by switching the output of the PLL's phase detector to ground.

Reference PLL (P/O A15)

The 600 MHz Reference PLL provides 600 MHz for the second LO, 300 MHz for the
third LO, and the Sampling Oscillator reference. The PLL is locked to a 10 MHz TCXO
(temperature-compensated crystal oscillator) or the optional OCXO (A21 Option 003). (The
PLL can also be locked to an external frequency reference.) The 10 MHz reference also
supplies the reference for the Roller Oscillators, the frequency counter on the A2 Controller
assembly, and the Cal Oscillator on the A4 Log Amplifier/Cal Oscillator assembly.

YTO PLL (A7, All, P/O A14, P/O A15)

The YTO PLL produces the instrument's first LO (3.0 to 6.81 GHz). The oscillator's output
is sampled by the Sampling Oscillator, and the resulting frequency is phase-locked to the
output of the Roller Oscillator PLL.
The A15A2 Sampler mixes the LO signal from the A7 LODA with a harmonic of the
Sampling Oscillator. The mixing product, the Sampler IF, is between 63 and 105.5 MHz
(same frequency range as the Roller Oscillator PLL).

Offset Lock Loop (P/O A15)

The 280 MHz to 298 MHz Sampling Oscillator is used to sample the YTO. By changing the
Offset Lock Loopls programmable dividers, the YTO frequency can be changed.
6-38 General Troubleshooting
To
Sweep Applied
All YTO's main coil
All YTO's FM coil
Roller Oscillator PLL's Main Oscillator
Roller Oscillator PLL's Offset Oscillator