Cable design and selection must include not only the functional
characteristics of the signal within the wire, but also appropriate methods to
protect the cables from their electromagnetic environment. Cable design,
categorization and separation all work together. In some cases adequate spacing
is not available to provide proper separation. In these instances, the cable
design may require additional shielding to reduce intra-system interference
Several steps should be taken prior to cable design and selection.
(1) First, the electromagnetic environment must be accurately defined to
ensure that adequate protection is provided for each cable. The wire or cable
environment should take into consideration any shielding effectiveness of the
airframe or platform. Details of anticipated inter-system electromagnetic
environments can be obtained from MIL-HDBK-235 or from the customer. If no
details are provided, a worst case estimation should be made.
(2) Second, the sensitivity of the circuits which the Cables interconnect
should be determined.
(3) Next, the protection requirements should be determined for transferring
impedance or coupling loss between the environment and the cables or between the
Where additional protection is required to assure compatible operation,
modifications should be made to the cable selection or routing.