This chapter presents a comprehensive analysis of the applications of a low-cost version of additive manufacturing (AM). The technique called Fused Filament Fabrication (FFF), which makes use of plastic as raw material, is explained in the context of its applications to the microwave waveguide engineering field. The main advantages of this technology include the promptness to print models, the variety of feasible geometries, and specially the reduced cost. The main limitations are also explained. Two important applications are considered: (1) rapid prototyping of complex devices and (2) manufacturing of fully functional devices. The former is relevant to get a more realistic perspective of the actual geometry in computer-aided designs, as shown in several examples. It also helps to forecast possible issues in the fabrication process that the computer sometimes fails to detect at the design stage. In the latter case (2), the subsequent and necessary metallization of plastic devices is also addressed. Several examples of state-of-the-art passive waveguide devices are presented, including waveguide filters, a diplexer, a branch-line coupler, a load or horn antennas, which have been printed, metallized, and measured. The results show the potential of three-dimensional (3D) printing and provide a different insight into this innovative technology.
Modern microwave and millimeter-wave systems require high-power amplifiers in very diverse fields such as communications or plasma physics. Although amplification technology has significantly evolved in the last decades, a single module is not enough for achieving the required power level. The solution in this case is the combination of several individual modules with power combiners. In this chapter, this concept is shown with two E-plane radial power combiners, both carrying a high-power signal with the circular waveguide TE01 mode. The first design is a 16-way Ku-band combiner with an excellent experimental performance: return loss better than 30 dB, with a balance for the amplitudes of ±0.15 dB and ±2.5o for the phases, in a 16.7% fractional bandwidth (2 GHz centered at 12 GHz), and efficiency better than 95% in this band. The second design is a 5-way W-band combiner, showing excellent characteristics as well: the experimental prototype has a return loss better than 20 dB, with a balance for the amplitudes of ±0.4 dB and ±3.5o for the phases, in a 12.8% fractional bandwidth (12 GHz centered at 94 GHz), and efficiency better than 85% in this whole band. The experimental results obtained in both designs are the state of the art in the area of radial power combiners.
Part of the book: Electromagnetic Fields and Waves