Paul I. Deffenbaugh

Broadband Microwave Frequency Characterization of 3-D Printed Materials

3-D printing allows increased design flexibility in the fabrication of microwave circuits and devices and is reaching a level of maturity that allows for functional parts. Little is known about the RF and microwave properties of the standard materials that have been developed for 3-D printing. This paper measures a wide variety of materials over a broad spectrum of frequencies from 1 MHz to 10 GHz using a variety of well-established measurement methods.

A 2.45 GHz Phased Array Antenna Unit Cell Fabricated Using 3-D Multi-Layer Direct Digital Manufacturing

This paper reports on the design, fabrication and characterization of a 3-D printed RF front end for a 2.45 GHz phased array unit cell. The printed unit cell, which includes a circularly-polarized dipole antenna, a miniaturized capacitive-loaded open-loop resonator filter and a 4-bit phase shifter, is fabricated using a direct digital manufacturing (DDM) approach that integrates fused deposition of thermoplastic substrates with micro-dispensing for deposition of conductive traces. The individual components are combined in a passive phased array antenna unit cell comprised of seven stacked substrate layers with seven conductor layers. The measured return loss of the unit cell is > 12 dB across the 2.45 GHz ISM band and the measured gain is -11 dBi including all components. Experimental and simulation-based characterization is performed to investigate electrical properties of as-printed materials, in particular the inhomogeneity of printed thick-film conductors and substrate surface roughness. The results demonstrate the strong potential for fully-printed RF front ends for light weight, low cost, conformal and readily customized applications.

3D multi-layer additive manufacturing of a 2.45 GHz RF front end

Digital additive manufacturing (AM) is emerging as a promising technology for next-generation RF systems. AM processes that combine multiple materials in a single build and can produce volumetric designs are especially interesting for 3D structural electronics. This paper reports on 3D AM fabricated components for a 2.45 GHz RF front end, specifically a circularly-polarized dipole antenna, a miniaturized capacitive-loaded open-loop resonator filter and a switched-line phase shifter. The printing process integrates fused deposition of thermoplastic substrates with micro-dispensing for deposition of conductive traces. These initial results demonstrate the strong potential for fully-printed RF front ends for light weight, low cost, conformal and readily customized applications.

Multimaterial and Multilayer Direct Digital Manufacturing of 3-D Structural Microwave Electronics

Direct digital manufacturing (DDM) is an emerging technology that is finding its place across a wide array of industries and applications as a cost-effective solution for low volume and mass customizable production. This technology encompasses a class of digital manufacturing techniques which can be combined to enable multimaterial fabrication and postprocessing. One of the promising applications for DDM is structural electronics, where lightweight printed plastics provide mechanical support as a fixture, package, or structural member and also host the electrical interconnects and devices, all in a contiguous fashion. Microwave structural electronics is a specific class of such systems for which the printing resolution as well as electrical and surface properties of the materials are especially important. This paper presents the current state of DDM technology, fundamental research into the electrical and mechanical properties of as-printed structures, and novel 3-D printed structures operating from C-band through Ku-band.

Embedded 6-GHz 3-D Printed Half-Wave Dipole Antenna

In this letter, a three-dimensional packaged half-wave dipole antenna is presented. The design includes a grounded coplanar waveguide (GCPW) balun that is printed on an inclined surface and used to connect the 50-Ω feedline on the lower layer to the dipole on the top layer. For matching purposes, a GCPW quarter-wave transformer is incorporated between the 50-Ω feedline and the balun. The 6-GHz half-wave dipole is approximately λ/4 above the ground plane. Fabrication is done using the direct digital manufacturing technique with an acrylonitrile butadiene styrene substrate (relative permittivity of 2.7 and a loss tangent of 0.008) and Dupont CB028 silver paste. The simulated and measured gains are 4.88 and 4.7 dBi, respectively. Antenna substrate surface roughness is analyzed to explain discrepancies between simulation and measurement results.

Wideband Ku-band antennas using multi-layer direct digital manufacturing

Design and performance of a fully-printed Ku-band aperture coupled patch antenna manufactured by making use of a direct digital manufacturing (DDM) approach that integrates fused deposition of acrylonitrile butadiene styrene (ABS) thermoplastics with in-situ micro-dispensing of conductive silver paste (CB028) is reported. Microstrip line characterizations demonstrate that the microstrip line feed loss of the antenna is minimized by printing ABS in parallel with the line directions. A wideband (20%) performance is achieved by employing a multilayer printing approach. Compared to existing work in literature, the presented antenna stands out as being fully-printed, operating within the Ku-band, and exhibiting high radiation efficiency (6.5 dB gain) with wide bandwidth performance.