Keysight x-series User Manual

6 Input/Output
6.6 Freq Ref Input
Option Details
Parameter SCPI Notes
Internal
INTernal
When Internal is selected, internal reference signal will be used to synchronize the LO
board
External
EXTernal
When External is selected, external reference signal will be used to synchronize the
LO board. Route the correct reference signal to the specified port before changing
the LO Ref Input to External
For VXT models M9410A/11A, a 4.8 GHz reference signal is required to rout to the
4.8 GHz In port
6.6.5 Ref Lock BW
Lets you adjust the Frequency Reference phase lock bandwidth. This control is
available in some models of the X-Series.
It is possible to improve the phase noise of the instrument by several dB, even tens
of dB, by using an external reference with excellent phase noise. When an external
reference is used the instrument’s close-in phase noise improves to match that of
the reference.
Normally a narrow loop bandwidth is used to phase lock to the external reference.
However, the Ref Lock BW control allows you to choose a wider loop bandwidth to
reduce the phase noise at low offset frequencies, especially 4 to 400 Hz offset. The
Wide setting represents about a 60 Hz loop bandwidth, the Narrow setting about 15
Hz.
When using an external reference with superior phase noise, Keysight recommends
setting the external reference phase-locked-loop bandwidth to Wide to take
advantage of that superior performance.
When using an external reference with inferior phase noise performance, Keysight
recommends setting the bandwidth to Narrow.
In these relationships, inferior and superior phase noise are with respect to −134
dBc/Hz at 30 Hz offset from a 10 MHz reference. Because most reference sources
have phase noise behavior that falls off at a rate of 30 dB/decade, this is usually
equivalent to −120 dBc/Hz at 10 Hz offset.
In instruments with EP1 or EP2, this control only affects the external reference loop
bandwidth. In instruments with EP0, this control also affects the loop bandwidth
used when the Internal reference is selected (reference set manually to Internal or
Pulse, or set to Sense and set by sensing to Internal or Pulse).
Remote Command
[:SENSe]:ROSCillator:BANDwidth WIDE | NARRow
[:SENSe]:ROSCillator:BANDwidth?
Spectrum Analyzer Mode User's &Programmer's Reference 2455

Keysight x-series Specifications

General

Analysis Bandwidth	Up to 1 GHz (depending on model)
Real-Time Bandwidth	Up to 1 GHz (depending on model)
Form Factor	Benchtop
Connectivity	LAN, USB, GPIB
Resolution Bandwidth	1 Hz to 10 MHz (depending on model)