Periodically structured thin-film cables

Periodic structuring of the ground plane is presented as a method of adjusting the properties of thin-film microstrip cables. Such cables may be useful as interconnects when flexibility is required and space is at a premium. Simple analytic models are presented and verified by numerical simulation. Prototype cables are fabricated in 2 m lengths of copper-clad polyimide. The effect of dimensions on characteristic impedance, cut-off frequency and propagation loss is investigated, and it is shown that impedance close to 50 may be combined with low loss, using feature sizes compatible with flexible printed circuit board (PCB) fabrication.