Agilent Technologies 34972A User Manual page 260

Chapter 7 Tutorial
System Cabling and Connections
Shielding Techniques
Shielding against noise must address both capacitive (electrical) and
inductive (magnetic) coupling. The addition of a grounded shield around
the conductor is highly effective against capacitive coupling. In switching
networks, this shielding often takes the form of coaxial cables and
connectors. For frequencies above 100 MHz, double-shielded coaxial
cable is recommended to maximize shielding effectiveness.
Reducing loop area is the most effective method to shield against
magnetic coupling. Below a few hundred kilohertz, twisted pairs may be
used against magnetic coupling. Use shielded twisted pair for immunity
from magnetic and capacitive pickup. For maximum protection below 1
MHz, make sure that the shield is not one of the signal conductors.
Recommended Low-Frequency Cable:
Shielded twisted pair
LO
HI
Twisted Pair Shield
Separation of High-Level and Low-Level Signals
Signals whose levels exceed a 20-to-1 ratio should be physically
separated as much as possible. The entire signal path should be
examined including cabling and adjacent connections. All unused lines
should be grounded (or tied to LO) and placed between sensitive signal
paths. When making your wiring connections to the screw terminals on
the module, be sure to wire like functions on adjacent channels.
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Recommended High-Frequency Cable:
Double-shielded coaxial cable
HI
LO
Center Conductor
Shield Foil Shield Braid PVC Jacket