Enrico Massoni

Characterization of 3D-printed dielectric substrates with different infill for microwave applications

This paper presents the characterization of a 3D printed material based on Ninjaflex filament, through different techniques: the dielectric properties of the material are preliminary retrieved by a waveguide-based method, where a 3D-printed dielectric sample is inserted into a hollow metallic waveguide: this method allows for an accurate and narrow-band characterization. Subsequently, two microstrip lines with different length, realized on a 3D-printed substrate, are used for the broadband characterization in the frequency band from 2 GHz to 20 GHz. The effect of the infill percentage on the dielectric permittivity and loss tangent of the printed material are rigorously investigated and experimentally demonstrated, showing a large tunability when varying the infill from 25% to 100%. These results pave the road to the implementation of novel microwave components, based on the local variation of the dielectric permittivity, and suggest a technique to effectively reduce dielectric losses.

Modeling and implementation of perforated SIW filters

A novel class of substrate integrated waveguide (SIW) filters is presented in this paper. The filters are based on the perforation of the dielectric substrate, which generates the local modification of the effective dielectric permittivity and, consequently, of the characteristic impedance of the waveguide. In particular, perforations are used to obtain a waveguide section below cutoff in the filter band. The waveguide sections below cutoff are exploited to realize the impedance inverters, which in turn connect resonators obtained by half-wave (not perforated) SIW sections. The impedance inverter has been investigated and a filter has been designed and fabricated to demonstrate the feasibility of the proposed method.

Substrate Integrated Waveguide Filters Based on a Dielectric Layer With Periodic Perforations

This paper presents a novel class of substrate integrated waveguide (SIW) filters, based on periodic perforations of the dielectric layer. The perforations allow to reduce the local effective dielectric permittivity, thus creating waveguide sections below cutoff. This effect is exploited to implement immittance inverters through analytical formulas, providing simple design rules for the direct synthesis of the filters. The proposed solution is demonstrated through the design and testing of several filters with different topologies (including half-mode SIW and folded structures). The comparison with classical iris-type SIW filters demonstrates that the proposed filters exhibit better performance in terms of sensitivity to fabrication inaccuracies and rejection bandwidth, at the cost of a slightly larger size.

3-D Printed Substrate Integrated Slab Waveguide for Single-Mode Bandwidth Enhancement

This letter presents the implementation of a broadband substrate integrated waveguide (SIW) by an additive manufacturing technique. A 3-D printed material based on Ninjaflex filament has been realized by fused deposition modeling. By changing the infill percentage, printed materials with different dielectric properties have been fabricated and experimentally characterized. Two materials obtained from the same filament with different infill percentages have been used for the implementation of a substrate integrated slab waveguide (SISW), which allows increasing the single-mode bandwidth compared with that of a standard SIW. The experimental results for the fundamental and second modes of SIW and SISW show a 50% bandwidth enhancement.