Jackson Labs PHASE STATION 53100A, Руководство пользователя

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PhaseStation 53100A User’s Manual V1.04 25-Apr-2022 26
Guidelines for input signal connections
Although the N-F and SMA-F input jacks offer superior mechanical stability, BNC-N coax adapters are
also supplied with the 53100A for operator convenience. Regardless of your choice of coax fittings,
double-shielded cables such as RG223 or RG400 are recommended for low-level measurements that
may be affected by crosstalk and environmental interference.
Use of RG58, RG174 and other common
single-shielded cables can cause artifacts in stability and noise plots , particularly with longer cables.
Input signals should be greater than 0 dBm for best performance -- +5 to +15 dBm is recommended.
While the 53100A is intended for use with sinewave oscillators, it’s possible to measure logic-level clocks
as well if you equip them with suitable matching networks
2
. It’s a good practice to measure an oscillator
with a load that’s similar to what it will encounter in its ultimate application, keeping in mind that most
logic-level sources are not specified to drive 50-ohm loads at all. Overloading of the source, the 53100A,
or both can occur if these devices are connected directly to the instrument’s input jacks. Consult the
manufacturer’s data for the source in question to determine its output impedance and/or current drive
capability.
The required matching network can be as simple as a resistive series termination or voltage divider, but
the 53100A’s own spur performance and broadband noise floor will likely be degraded when measuring
non-sinusoidal sources unless you provide additional bandpass filtering. Careful shielding of matching
networks, buffers, and other interfacing elements is also necessary, since isolation of DUT and reference
signals from stray RF signals (and from each other) is a prerequisite for clean measurements.
Experimentation will likely be required to achieve the desired results with non-sinusoidal signals.
Choosing reference sources
In addition to the host PC and an appropriate power source, measurements made with the 53100A
require either one reference signal to be supplied at the REFERENCE jack or two reference signals
supplied at the CH 1 IN and CH 2 IN jacks.
Virtually all aspects of measurement performance –
accuracy, repeatability, noise floor, spurious responses – depend on your ability to provide the best
reference signal(s) possible.
But what does the “best reference possible” mean? It depends on the goals of your measurement. Very
few reference sources are ideal for both short- and long-term measurements. Typical “house clocks”
that distribute 5 or 10 MHz signals at levels b5 and +15 dBm often work well for ADEV and
other time/frequency measurements, but atomic and GPS standards that are often used as sources for
centralized clock distribution may exhibit more short-term phase noise than an undisciplined crystal
oscillator. Distribution amplifiers can also add substantial noise of their own, as well as phase drift at
longer timescales due to temperature sensitivity.
2
See http://www.wenzel.com/documents/waveform.html for some suggested approaches.