Comparison of LTCC Material Systems through Dielectric and Transmission Characterization for Microwave/Millimeter Wave Applications

摘要

There has been considerable research effort to develop W band millimeter wave automotive-based radar systems. Research has been concentrated around the development of active components and subsystems to meet performance requirements. Sub-system and component level packaging of millimeter wave systems remains the major cost driver. Low temperature co-fired ceramic (LTCC) technology offers very specific advantages both in terms of performance and cost. This is due to advances in ceramic processing, material systems and the availability of the vertical dimension due to its multi-layer structure. This paper presents the evaluation of five LTCC material systems. The focus of this work is to achieve dielectric characterization in the frequency range 10 to 110 GHz, to a level of accuracy acceptable for packaging system design as well as to investigate transmission characteristics of traditional transmission lines fabricated on these substrates. Transmission line resonators are used to do the characterization. Resonators are designed through rigorous, iterative full electromagnetic simulations. A set of microstrip and CPW transmission lines, with varying lengths and launch sections are also designed and fabricated to evaluate the feasibility of low-loss transmission lines on LTCC in millimeter wave frequency ranges. Different types of microstrip to CPW transitions are also designed, fabricated and characterized since transitions are a fundamental building block in package design. All measurements are performed in the 10 to 110 GHz range. The paper reports details of design, simulation and characterization of the above-mentioned test structures as well as dielectric and transmission data.