Predicted Ku-Band Attenuation by Twisted Nonshielded Cable and Twisted Shielded, Controlled Impedance Cable

Both the Space Shuttle and the International Space Station utilize Kurtz-under band (Ku-band) systems for communications with the tracking and data relay satellite system. Knowledge of the extent and nature of the field to wire coupling in this operating frequency range is thus necessary to facilitate proper shielding and circuit design for the mitigation of radio-frequency interference with pyrotechnics and other noncommunications-related circuits and subsystems. To that end, this analysis will address the expected common-mode attenuation of twisted nonshielded cable, and twisted shielded, controlled impedance cable, mounted above a conducting ground plane and exposed to Ku-band radiation from nearby communications link antennas. Coupling calculations are performed by treating the cabling as forming a traveling wave antenna above a ground plane. The maximum receiving aperture of this configuration is determined for each cable type, and from this, a maximum coupled power. To facilitate calculation of the maximum receiving aperture, the attenuation constant for each type of cabling is determined from available data, and from treatment of the wiring as either a connected pair or as a single wire above a ground plane. The resulting coupled power at the frequencies of interest for each type of cable is calculated as a final result.