Strategies for Hybrid Integration and Packaging at Millimeter-Wave and THz Frequencies

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Abstract

In this thesis, the strategies for hybrid integration and packaging at millimeter-wave and terahertz (THz) frequencies are investigated for different applications. The three-dimensional (3D) hybrid integration scheme of a terabit transmitter is introduced. For packaging microwave integrated circuits (MICs) as well as monolithic microwave integrated circuits (MMICs) at millimeter-wave and THz frequencies, rectangular waveguide-to-coplanar waveguide (CPW) transitions are realized by using E-plane probe, wire bonding probe, and wideband patch antenna. The system integration and packaging of a THz photodetector is addressed. As the fundamental research work, planar transmission lines involved in the 3D hybrid integration of the terabit transmitter including CPW, coupled coplanar waveguide (CCPW), coplanar stripline (CPS), and coupled line based on aluminum nitride (AlN) substrate are introduced individually. The transmission line structures, properties, and simulation methods are explained while parasitic effects are also discussed. CPW-to-CPS and CCPW-to-coupled line transitions are developed for guiding single-ended signals and differential signal pairs, respectively. Besides, for suppressing parasitic modes, the coplanar transitions use either wire bonding bridges together with an absorber layer or hollow plated vias going through the AlN substrate. The designed planar transmission lines as well as coplanar transitions are optimized for supporting data transmissions starting from direct current (DC) and at the same time providing large bandwidths. By combining different planar transmission lines as well as coplanar transitions, the interposer for guiding four single-ended signals from the drivers (DRVs) to the Mach-Zehnder modulator (MZM) is formed and the integration scheme of the terabit transmitter is demonstrated. Though rectangular waveguides are widely used as the standard interface for connecting or cascading different components and systems at millimeter-wave and THz frequencies, the MICs and MMICs at such high frequencies still rely on planar transmission lines. Thus, different methods and structures are invented for realizing the transitions between rectangular waveguides and planar transmission lines in particular rectangular waveguide-to-CPW transitions. The development of the packaging strategies is mainly based on the technical innovations of both transition methods and packaging architectures. One of the difficulties for designing rectangular waveguide-to-CPW transitions is to provide a wideband matching with a low insertion loss. In addition, the compatibility for packaging the components and chips as well as the fabrication possibility should also be taken into account. As novel methods, the transitions based on quartz substrate using wire bonding probe and wideband patch antenna are proposed. They are compared with the transitions using E-plane probe. The 3D printing and copper plating processes are evaluated for fabricating the packaging structures at millimeter-wave and THz frequencies. A THz photodetector is implemented by integrating a photoconductor with a feeding network, a bias-tee, and a rectangular waveguide-to-CPW transition. As an electro-optic device used for converting signals from optical domain to electrical domain, the photodetector can be applied on both the transmitter and the receiver sides in THz communication systems. The principal components are designed individually while the chip-level connections and the packaging structures are also described. The assembly structure is demonstrated and the packaging strategy is addressed.
Original languageEnglish
PublisherTechnical University of Denmark
Number of pages146
Publication statusPublished - 2019

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