Empirical Model and Experimental Validation of Meshed Ground Impact on RF Performance of Flexible Microstrip Lines for Bending Applications

Abstract

Meshing of conventional printed circuit board (PCB) grounds refers to a process in which certain ground planes appear as copper lattices; regular openings are placed at regular intervals. The need for ground meshing for rigid PCBs has become minor with the development of micro-etching approaches. However, for flexible hybrid electronics (FHEs), meshed grounds could offer some benefits, such as being unsusceptible to bending and conserving material and time. In this article, we study how meshed ground planes affect the radio frequency (RF) performance of straight microstrip lines. Simulations show meshed grounds with more than 50% filling produce good RF performance. When the filling percentage of the meshed grounds is less than 50%, ripples in the insertion loss start to appear. To confirm the simulation results, dispensing and aerosol jet printing (AJP) systems were used to fabricate silver ink microstrip lines on PET substrates with different meshed ground patterns. The experimental measurement confirmed the simulation results. Bend testing was carried out to investigate the impact of mesh grounds on the RF performance of the microstrip lines after bending. The results demonstrate that the less-filled meshed ground samples are less susceptible to bending. As an extension of the work, we developed an empirical model to modify the microstrip line’s width to smoothen the insertion loss ripples while maintaining the bending superiority. To experimentally validate the model, predictions from this empirical model were used to fabricate and measure some samples.