This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 1 Additively Manufactured Dielectric Waveguides for Advanced Concepts for Millimeter-Wave Interconnects Felix Distler , Mark Sippel, Jan Schür, Gerald Gold , Klaus Helmreich, and Martin Vossiek , Fellow, IEEE Abstract— Technology mega trends, such as autonomous driving, multiple-input multiple-output (MIMO), or multi- gigabit communication, drastically increase the demand for ultra-broadband millimeter-wave (mmW) transmission line technologies. A broadband and robust signal and data transmission between components and modules at low cost is a mandatory requirement to ensure high-performance functionality of advanced communication and radar systems. Dielectric waveguides (DWGs) are a highly suitable technology to meet these requirements due to their outstanding transmission capabilities for mmW signals coupled with their high flexibility, low weight, and low cost. Additive manufacturing (AM) processes based on dielectric materials open up new perspectives for fully automated wiring of mmW modules and systems, and they enable cost-efficient application-specific solutions. In this article, we propose novel printed DWG designs with optimized transmission performance. Measurement results of different DWG designs demonstrate the excellent functionality of the proposed transmission line and interconnection concepts. These results and the shown resiliency and practicality of the presented approaches illustrate attractive opportunities for new interconnect technologies based on new manufacturing processes. Index Terms— Dielectric materials, millimeter-wave (mmW) measurements, transmission line measurements, waveguides (WGs). I. I NTRODUCTION I N RESPONSE to the steadily increasing demands for communication data rates, the associated transmission line technology and network protocol standards are regularly revised. However, not only the data rate and carrier frequency values are steadily increasing but also raising demands with respect to emission standards and concerning cable weight and cost reductions can be noticed. For data-hungry applications such as autonomous driving, massive multiple-input multiple- output (MIMO), and multi-gigabit communication, it is vital to meet these requirements. However, most transmission technologies cannot fully com- ply with these specifications. Coaxial transmission lines and Manuscript received March 13, 2019; revised June 3, 2019; accepted July 23, 2019. (Corresponding author: Felix Distler.) The authors are with the Institute of Microwaves and Photonics, Friedrich- Alexander-Universität Erlangen–Nürnberg, 91058 Erlangen, Germany (e-mail: felix.distler@fau.de; mark.sippel@fau.de; jan.schuer@fau.de; gerald.gold@ fau.de; klaus.helmreich@fau.de; martin.vossiek@fau.de). Color versions of one or more of the figures in this article are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TMTT.2019.2939831 Fig. 1. Schematic of an application-specific wiring process based on AM of DWGs. metallic waveguides (WGs) provide good transmission char- acteristics but are unsuitable for many applications due to their complexity, high weight, and high cost, especially at millimeter-wave (mmW) frequencies. Planar transmission lines and wire bonds show a good transmission behavior at a reasonable cost but are limited to short interconnects only. Optical fiber WGs as well as dielectric WGs (DWGs) have several features that make them an attractive alternative. Consequently, they are in the focus of recent studies [1], [2]. Both optical fibers and DWGs offer an excellent trans- mission behavior, advantageous bending properties, and low weight. With DWG operating at frequencies from several GHz up to THz, insertion loss values smaller than 1 dB/m are feasible. In addition, they can provide reliable high-speed data signal transmission over long distances [3]. Due to the large bandwidth, DWGs are very well suited for broadband data communication as well as for baseband signal or mmW radar signal distribution in advanced radar networks. To increase the transmission performance, many essential aspects of DWGs, such as geometry characteristics [4], [5], shielding struc- tures [6], [7], dispersion reduction [5], [8], and appropriate transition designs [9]–[11], have already been investigated. Although optical fibers are still much more established than DWGs, we think that in the future, DWGs will benefit from the fact that the manufacturing process is much more complex for fiber optics than for DWGs. Based on the thermoplastic material, DWGs can profit strongly from novel additive man- ufacturing (AM) technologies and materials [12], [13], since these techniques allow for simple, cost-effective, flexible and application-specific manufacturing solutions (see Fig. 1). 0018-9480 © 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.