Abstract
The additive manufacturing process of multimaterial extrusion offers performance advantages using functional materials including conductors while making accessible the third dimension in the design of electronics. In this work, we show that the additional geometrical freedom offered by this technique can be exploited for the design and realization of filters made of 3-D resonators that exhibit enhanced characteristics. The coupling properties of 3-D grounded square split ring resonators (SRRs) are initially explored. We demonstrate by simulations and experiments that SRRs with finite height display significantly stronger coupling compared to equivalent thin printed circuit structures. The observed trend can be exploited for designing filters with wider operational bandwidths for a given footprint, or miniaturized layouts and enhanced compatibility with fabrication limits for minimum feature size and spacing without performance degradation. This concept is demonstrated by presenting results of full-wave simulations for sample bandpass filters with identical footprint but formed by coupled 3-D square SRRs of different heights, showing that filters with taller resonators exhibit increasingly wider bandwidths. Two filter prototypes with center frequencies at 1.6 and 2.45 GHz are manufactured by multimaterial 3-D printing. The measured characteristics of these prototypes are found to be in good agreement with numerical simulations taking into account the effect of the lossier metallic and dielectric materials used in 3-D printing and confirm the predicted larger bandwidth of the filters made of 3-D SRRs with marginally higher insertion losses.
Highlights
T HE advancement of additive manufacturing technology has recently produced a new generation of 3-D printing techniques and materials that enable the realization of Manuscript received December 26, 2018; revised March 25, 2019 and June 6, 2019; accepted June 23, 2019
Three simple bandpass filters made of coupled 3-D square split ring resonators (SRRs) of different heights have been developed, using the coupling matrix method [15], to explore the capability offered by height variation in design
This article details our exploration of the potential offered by 3-D printing fabrication for future RF filter design and optimization
Summary
T HE advancement of additive manufacturing technology has recently produced a new generation of 3-D printing techniques and materials that enable the realization of Manuscript received December 26, 2018; revised March 25, 2019 and June 6, 2019; accepted June 23, 2019. The additional geometrical freedom (height) in the design of coupled resonators provided by 3-D printing can be effectively exploited for designing filters with enhanced characteristics, where miniaturization is achieved without sacrificing performance. The V8 silver ink is specified with a conductivity just an order of magnitude lower than that of copper [19], and high enough for high performance antennas and RF devices Another conductive filament for FDM named Electrifi, consisting of a polyester and copper composite, has been recently introduced which has the advantage of being compatible with most of the commercially available desktop filament-based 3-D printers. The filter prototypes presented here have been manufactured using DDM on V8 dual material 3-D printer with one nozzle extruding standard PLA filaments (essentially FDM) and the second extruding V8 silver ink. The fabrication of two different filter prototypes by DDM is described in Section IV, where the measured characteristics of the realized filters are discussed and compared with results of simulation taking into account the effect of the lossy characteristics of metallic and dielectric materials used in DDM
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