Development of non-conventional microwave devices based on substrate-integrated technology for advanced applications

Abstract

Introduction 1.1 Motivation and Interest of the TopicThere has been a rapid transformation in communication systems in recent years, with a particular impact on satellite communications. The high demand for data throughput, bandwidth and ubiquitous connectivity is pushing microwave technology to its limits. This change is particularly evident in the space industry, where the business focus has shifted from large Geostationary Earth Orbit (GEO) satellites to constellations of numerous satellites operating in Low Earth Orbit (LEO). The concept of large LEO constellations is reminiscent of the ambitious global phone connectivity projects of the 1990s that include Iridium, Globalstar, and Odyssey. Most of these systems were ultimately cancelled due to their high costs or technological limitations, which led the new LEO systems to focus on reducing the cost per bit.In this evolving scenario, the feasibility of these new satellite systems heavily relies on the reduction of production, launching, and operation costs. Microwave devices used in these space communications systems must not only exhibit high performance and adaptability but also undergo a drastic reduction in weight, size, and price. These factors are crucial for the success and sustainability of the new generation of space communication systems, as highlighted by studies on large LEO constellations and industry reports [1,2].Different solutions can be applied to improve the performance and reduce the production cost and weight of the Radio Frequency (RF) front-ends. One notable solution is the Substrate Integrated Circuit (SIC) technology, which emerged in the late 1990s to address similar demands of the industry [3,4]. The SIC technology involves the integration of different waveguide topologies within a substrate stack-up, combining the benefits of planar transmission lines (e.g., microstrip, coplanar, and stripline) and non-planar technologies (e.g.,• Geostationary Earth Orbit (GEO) satellites orbit the Earth at an altitude of approximately 36 000 km [11]. At this altitude, satellites travel at the same rate as the Earth's rotation, making them appear stationary in the sky. This characteristic eliminates the need for complex tracking systems in the ground segment and enables near-continental coverage. A single GEO satellite can provide coverage from around 20 degrees north to 20 degrees south latitude [9]. Moreover, due to its high altitude, only three equally spaced GEO satellites are required to achieve quasi-global coverage. These characteristics make the GEO systems particularly suitable for broadcasting communications Substrate integrated technologiesThe integration of planar and non-planar circuits is a critical aspect of microwave and millimetre wave front-ends. Planar transmission lines (i.e., microstrip, coplanar waveguide, Empty Substrate Integrated Coaxial Line (ESICL) and Ridge Empty Substrate Integrated Waveguide (RESIW) that integrate coaxial lines and ridge waveguides in planar substrates.The significant interest in this technology has als...