Implementation of Microwave Circuits Using Stereolithography.

In this work, the use of additive manufacturing techniques through stereolithography for the manufacture of high-frequency circuits and devices is presented. Both the resin and the 3D printer used in this research are general-purpose commercial materials, not specifically intended for the implementation of microwave networks. The manufacturing and metallization procedures used to produce substrates for the design of planar microwave circuits are described, introducing the characterization process carried out to determine the electrical properties of the resin used. The ultrasonic techniques that allow the structural analysis of the manufactured substrates are also described. The electrical characterization provides a relative dielectric permittivity of 3.25 and a loss tangent of 0.03 for the resin used. In addition, the structural analysis shows a homogeneity and a finish of the manufactured parts that is not achievable using fused deposition modeling techniques. Finally, as a proof of concept, the design and manufacture of a complex geometry stepped impedance filter on a multi-height substrate using stereolithography techniques is presented, which allows for reducing the size of the traditional implementation of the same filter while maintaining its high-frequency response performance.

Low-Cost Additive Manufacturing Techniques Applied to the Design of Planar Microwave Circuits by Fused Deposition Modeling.

This work presents a study on the implementation and manufacturing of low-cost microwave electronic circuits, made with additive manufacturing techniques using fused deposition modeling (FDM) technology. First, the manufacturing process of substrates with different filaments, using various options offered by additive techniques in the manufacture of 3D printing parts, is described. The implemented substrates are structurally analyzed by ultrasound techniques to verify the correct metallization and fabrication of the substrate, and the characterization of the electrical properties in the microwave frequency range of each filament is performed. Finally, standard and novel microwave filters in microstrip and stripline technology are implemented, making use of the possibilities offered by additive techniques in the manufacturing process. The designed devices were manufactured and measured with good results, which demonstrates the possibility of using low-cost 3D printers in the design process of planar microwave circuits.

Characterization of nanoparticles doped composites using ultrasound.

The aim of this work is the non-destructive automatic mechanical characterization of nanoparticles doped composites using ultrasound in order to understand and control the dispersion of the dopant nanoparticles in the final product. We present a method which is able to measure the elastic constants of composites (Youngs, Bulk, Shear Modulus and Poissons ratio), in addition to other parameters as density, sound velocity and thickness, providing information of the nanoparticles dispersion in the samples. All results are obtained with a single ultrasonic measure at each point of the samples' surface in an immersion setup with both pulse-echo and through-transmission measurements simultaneously, obtaining detailed information for all the samples' surface in a XY scanning. All the analysis is performed automatically, that is, no manual correction or adjustment is needed at any stage of the process. To validate the results, a polyester based resin has been analyzed with different concentrations of graphene nanoparticles as dopant. The method has shown to be very accurate and reliable. The resolution of the values obtained for the elastic constants is limited by the resolution in the velocities measurements, for which we have achieved a resolution in the order of cm/s, thus providing very accurate measurements of the elastic constants.