Agilent Technologies 34970A Switch User Manual


 
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.
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.
HI
LO
LO
HI
ShieldTwisted Pair
Recommended Low-Frequency Cable:
Shielded twisted pair
Recommended High-Frequency Cable:
Double-shielded coaxial cable
Shield BraidShield Foil
Center Conductor
PVC Jacket
Chapter 8 Tutorial
System Cabling and Connections
338