Keysight Technologies Infiniium MSOV 084A, Руководство по обслуживанию

Страница: 155 / 164

Theory of Operation
7
Infiniium V-Series Oscilloscopes Service Guide 155
SysTrig is the primary output from the trigger system. It is synchronous to the
trigger event and asynchronous to the time base clock, TbClk. Wahoo
synchronizes SysTrig to the timebase clock with low probability of metastability,
producing the TbTrig signal. TbTrig pulses high once immediately after every rising
edge of SysTrig.
Wahoo also produces a trigger signal that is synchronous to RefClk. This signal,
RefTrig, pulses high once immediately after every rising edge of SysTrig. RefTrig
tells the memory controller when a trigger event has occurred. It is important to
note that although DigRun and RefTrig are both synchronous to RefClk, their
phase relationship to RefClk s not important. As long as their phase relationship is
consistent, the memory controller can adjust for it. Finally Wahoo records the
phase relationship between RefTrig and TbTrig, and provides it as the 2-bit digital
value, Nosc. Nosc[0] is driven by the 500 MHz clock and Nosc[1] is driven by the
250 MHz clock.
10 GHz clock generation The fundamental frequency reference of the
oscilloscope's timebase clock is a low-noise precision 10 MHz signal. This 10 MHz
reference can originate from the internal oven-controlled crystal oscillator or from
an external 10 MHz reference signal. Fine frequency adjustment of the internal
crystal oscillator is possible with a DAC line (OSC_FREQ_ADJ). During calibration
you can use a precision 10 MHz source to tune the frequency. A bandpass-filtered,
AC-coupled copy of either the internal 10 MHz reference or a user-selectable
external 10 MHz reference is sent through a cable to a rear-panel BNC connector
for use as a reference source for some other instrument. This connection is a 50
Ohm output designed to drive a single 50 Ohm input. When phase-locking
multiple instruments, the 10 MHz references are usually daisy-chained together.
The following figure shows a block diagram showing clock generation.
The external 10 MHz reference is applied through a rear-panel BNC connector and
runs to the backplane assembly. Users can select between an internal and
external reference through a dialog box in the oscilloscope application. A detector
10 GHz clock generation
10 MHz
OCXO
10 GHz
Sample Clock
10 MHz
Ref In
100 MHz
Elmore
10 GHz
DRO
10 MHz
Ref Out