Extrusion Freeforming of Millimeter-Wave Electromagnetic Bandgap (EBG) Photonic Crystals

Extrusion freeforming can be used for the rapid prototyping of millimeter-wave electromagnetic bandgap (EBG) structures. In this work, an alumina-polymer paste with a relatively high volatility solvent (propanol) was used and the characteristics of the ceramic paste, particularly the rheological features are described. The advantage of high volatility solvent is that the viscosity and elastic modulus of the paste are increased sharply as the solvent evaporates. Thus, the rigidity of the extruded filament is quickly increased as a small amount of solvent evaporates. Finally, by employing this procedure, different EBG structures such as 2-D, 3-D woodpile and aperiodic structures were fabricated and their bandgaps were measured. The experimental results show that extrusion freeforming is a relatively simple and easy method to fabricate these woodpile structures with a bandgap in the 90-110 GHz region.

Automated Synthesis of Wideband Bandpass Filters Based on Slow-Wave EBG Structures

This paper is focused on the automated synthesis of wideband bandpass filters operating at microwave frequencies and based on electromagnetic bandgap(EBG)structures.The classical counterpart of such filter consists of a combination of transmission line sections and shunt-connected grounded stubs placed at equidistant positions.By replacing the transmission line sections with capacitively-loaded lines(a kind of EBG-based lines)exhibiting the same phase shift at the lower cutoff frequency and the same characteristic(actually Bloch)impedance,filter size is reduced and the spurious pass bands can be efficiently suppressed.In practice,the loading capacitances are implemented by means of patches,in order to achieve a fully planar filter implementation.The presence of the patches reduces the effective phase velocity of the capacitively-loaded lines,thus providing a slow-wave effect useful for filter miniaturization.Moreover,due to periodicity,such EBG-based lines exhibit wide stop bands,which are used for spurious suppression.Even though such EBGbased filters were previously reported by some of the authors,a systematic synthesis method was not applied for filter design.In this paper,the main aim is to demonstrate the potential of aggressive space mapping(ASM)for that purpose,and it will be shown that such filters can be automatically synthesized.