Optimization of a Flexible Printed Cable Broad Side and Edge Coupling

Radio electronic equipment (REE) is disturbed by ultra-wideband (UWB) pulse interference. Such failures may include irreversible failure of some elements, saturation of active elements, and errors in transmitting digital data. To protect against such interference, a modal filtering technique is proposed. Modal filters can be realized at different levels of the structure (as a cable, as a separate protection device, and in the printed circuit board). The amplitude of the UWB interference is thus minimized. They can also be implemented in flexible printed cables (FPCs). These have been widely used in various REEs in recent years. The optimization of a flexible printed cable with broad side and edge coupling is presented in this paper. The study was conducted using real parameters. The polyimide was single-sided and had a total thickness of 80 m. We performed optimization based on three criteria: minimizing pulse amplitudes, maximizing the difference in per-unit-length mode delays, and matching to the 50 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{\Omega}$</tex> path. We have shown how the conductor spacing and width affect the amplitude of the decomposition pulses and the difference of the per-unit-length mode delays. Thus, the optimization achieved a 22.2 times <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\boldsymbol{U}_{\max}=\boldsymbol{0.045}\mathbf{V})$</tex> attenuation of the UWB interference with respect to half of the e.m.f. This study shows that it is possible to attenuate dangerous electromagnetic interference in FPCs with broadside and edge coupling without the use of additional protective devices.