Ridge Gap Waveguide Enabled Wireless Power Transfer for Electric Vehicle Applications Walid M. G. Dyab # , Mourad S. Ibrahim # , Ahmed A. Sakr * , Ke Wu $ # Prince Sultan University, Riyadh, KSA * Cairo University, Cairo, Egypt $ Polytechnique Montreal, Quebec, CA {wdyab, mrizk}@psu.edu.sa, ahmed.sakr@analog.com, ke.wu@polymtl.ca Abstract — A technique for wireless power transfer based on a ridge gap waveguide structure is proposed. This technique is named as “Contact-Less Transmission-Line Wireless Power Transfer, CLTL-WPT”. The idea is stemmed from the fact that the ridge gap waveguides are low loss transmission lines which consist of a base and a cover which are not in ohmic contact, thus allowing for an air gap in between. The theoretical efficiency of the proposed wireless power transfer is well compared to the conventional methods. The proposed technique is presented in the context of a high-power wireless charger for electric vehicle applications. An analytical design procedure of the ridge gap waveguide with respect to such an application is shown in details. The presentation is supported with full wave simulations. The main challenges and limitations are addressed. Keywords — Electric vehicle, ridge gap waveguide, wireless power transfer. I. INTRODUCTION A great amount of research efforts is being exerted these days in the field of wireless power transfer (WPT). Those efforts are directed mainly towards enabling wireless charging of various electrical and electronic devices. The applications of such technology penetrate into many different application fields and scenarios, ranging from charging portable electronics to delivering solar power from high altitude generators to ground stations. The distance over which electrical power is to be transferred wirelessly may vary from few millimetres to hundreds of kilometres, depending on applications. The medium through which power is transferred can also vary from simple lossless air to more complex media such as in the case of biomedical implants. However, the main challenge is always related to the efficiency of power transfer. This is due to the loss of electromagnetic power in the wireless medium between the source and the load. There are four main categories of WPT technologies, namely Inductive Power Transfer (IPT), Capacitive Power Transfer (CPT), Near-field methods, and radiative far-field methods [1-6]. All of those methods are found to suffer mainly from the efficiency challenge as mentioned earlier, for distances of few tens of centimetres. The goal of this work is to develop a different category of WPT technology. The proposed technology is called in this work Contact-Less Transmission-Line WPT (CLTL-WPT). This new technology depends on the use of a waveguiding structure capable of delivering power from a source to a load with 100% theoretical efficiency. The waveguiding structure must consist of two separate conductors with no ohmic contact between them. One part of this waveguiding structure is then connected to the main source and the other is connected to the load to which the power should be delivered. It is proposed in this work to use the so-called Ridge Gap Waveguides as the waveguiding structure in this new category of WPT. The Ridge Gap Waveguides (RGW) are a special type of low-loss metallic waveguides which were developed in the first decade of this millennium [7]. RGW consist of a metallic base with two beds of nails enclosing a metallic ridge. This base is then covered by a thin metallic plate. The cover does not touch the base, thereby allowing an air gap in between. This structure is capable of confining electromagnetic fields in the air gap between the ridge and the cover. This waveguiding structure has found applications in the design of microwave devices and millimetre-wave components. Generally, RGW are bulkier than their counterparts represented by conventional metallic rectangular waveguides. However, their superiority comes due to its relatively low loss as compared to the closed guides. Furthermore, the superiority of RGW lies in the total abolishment of the need for good electric contacts between the upper and lower metallic plates used in confining and guiding electromagnetic fields, since the base and the cover must have a gap in between, hence the name of RGW. Generally, RGW are sought to be candidates for high power millimetre-wave applications such as radar and satellite applications. This automatically enforces RGW designers to minimize the overall size of RGW-based devices while maximizing the operation bandwidth. In this research work, the situation is different. The application of interest is to charge, for example an electric vehicle using CLTL-WPT. The RGW is used as a contact-less transmission line. Accordingly, the design constrains mentioned above are well-relaxed. Obviously, the size in an electric vehicle charging system needs not be minimized as compared to radar or satellite applications. Furthermore, the power in WPT to be delivered via the RGW is not modulated to carry any sort of information, i.e. the bandwidth of operation can be minimized without constraint. These design considerations for WPT directly affect the design of RGW-based devices as compared to those procedures found in the literature. The main goal in this paper is to develop the analytical design procedures suitable for this new technology 978-2-87487-059-0 © 2020 EuMA 12 – 14 January 2021, Utrecht, The Netherlands Proceedings of the 50th European Microwave Conference 852 Authorized licensed use limited to: Prince Sultan University. Downloaded on February 04,2021 at 07:01:51 UTC from IEEE Xplore. Restrictions apply.