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DAZZLER
TM
system manual Part I : installation & operation
7.3
fast high voltage switch or any fast high power equipment, these parts (may) create a lot of
EMI perturbation. They have to be properly shielded, usually they are in metallic housing and
you have to ground them, through their conductive baseplate, or with adhesive copper tape, or
heavy copper braids.
All coaxial cables shall have their BNC or SMB plug externally grounded, either through the
receiving plug/box or with extra copper tape.
7.1.2
Use of EMI ferrites
Protecting the electronics from noise can also be done by inserting ferrite beads right at the
input sockets. Snap-on modules
can be used, such as shown on
Figure 7.1: Snap-on EMI ferrite
7.1.3
Termination of signals
High speed logic signals must be properly terminated to avoid reflections. The input signals to
the Dazzler should come from 50Ω sources via 50Ω cables and be terminated properly with a
50Ω load.
It is often necessary to insert a Tee to observe a signal. To minimize the impedance mis-match,
the impedance of the input fed by the Tee should be high, while the signal is terminated at the
end. Thus the impedance of the Dazzler inputs
trigger
and
aux
is kept high, so as to feed
an oscilloscope input which has an internal 50Ω termination. Do not use a Tee positioned at
the source, this will lead to reflections.
shows three correct wirings.
7.2
USB cable
If the USB cable “sees” too much noise, the communication between laptop and RF generator
will stop erratically
, thus leading the software to declare the unit “off-line”: use the shortest
possible cable, with proper layout and ferrites on both ends.
3
Exemples of such modules: french RS 116-1471, uk RS 222-4343
4
On T1 interfaces the loss of communication due to improper cabling layout accounted for a significant
number of service calls we received ! The T4 interface is more robust.
V3.00 - 8
th
April 2019