Multiport Technology: The New Rise of an Old Concept

Modern society has shown a large demand for ubiquitous and wireless connectivity, information transmission with high data rates, and precise sensors for any kind of physical dimension. Nevertheless, the frequency spectrum is limited and bandwidth restricted by regulatory issues. Over the last few years, a continuous rise in operating frequency linked to rising bandwidth has been observed. For short-range operation, the license-free industrial, scientific, and medical (ISM) bands beyond 100 GHz are becoming more a focus for practical applications. At the same time, microwave monolithic integrated circuit (MMIC) processes must keep up with this rise in operating frequency, requiring high investment costs in new MMIC technology. Initially, before the cost of this technology becomes reasonable, alternative hybrid circuit concepts are needed as a door opener for mass-market applications. For this purpose, an old frontend concept is getting increased support, leading to a constant growth of an originally small, but worldwide, community: multiport technology. This article provides an overview of the basics, possible applications, and specific calibration procedures for the six-port circuit, which is the most common multiport implementation of this promising architecture.