Investigation of new integration and interconnect techniques for three dimensional microwave and millimeter wave integrated circuits

This thesis presents new concept and technology of hybrid integration and interconnects for the applications in microwave and millimeter wave integrated circuits. Guided-wave characteristics of the new hybrid or composite structure, which is surface-mounted on a relatively thin dielectric substrate, are studied numerically and experimentally. It is demonstrated that this type of transmission line can preserve low-loss and almost non-radiating advantages of the conventional NRD (Non-Radiative Dielectric)-guide. New integration and interconnects approach utilizes co-layered arrangement of the two dissimilar structures, which allows the NRD-guide in direct contact with (or surface-mounted on) the planar circuits. Two basic building block schemes are presented that involve microstrip line and coplanar waveguide (CPW) with the NRD-guide. Principal modes generated in the hybrid planar/NRD-guide structure are modeled. Results for transmission and return loss are presented for different transitions. Key technique for suppressing spurious modes is presented with experiments and analysis results. It is simple and very effective in rejecting the spurious modes for performance enhancement of hybrid planar/NRD-guide integrated circuits. Practical examples in the design of millimeter-wave planar/NRD-guide filter are exploited to evaluate features of the proposed technique that yields expected good results. It is found through analysis and experiments that the rejection to all the spurious modes (including TE and LSE modes) can be better than −35 dB for a single microstrip-to-NRD-guide transition over a broadband frequency of interest. General spurious mode-suppressing techniques have also been presented and investigated. For the performance enhanced integrated microstrip-to-surface-mounted NRD-guide transition (NRD-guide surface-mounted on the top of a relatively thin planar substrate), the return loss is better than −20 dB over the frequency band of interest from 27.5 to 28.5 GHz. The worst spurious modes excited in this case are TE₂₀ and LSE₄₀ modes but they are all suppressed to be better than −35 dB over the frequency range. For the performance enhanced integrated CPW-to-surface-mounted NRD-guide transition, all potential spurious modes related to CPW-to-NRD-guide transitions may be suppressed with a simple scheme that involves an integrated mode suppressor. The rejection to all of the spurious modes (including TE and LSE modes) is better than −50 dB for a single transition over a broadband frequency of interest. To facilitate the implementation of the mode suppressor, a compact spurious mode suppressing technique for the design of hybrid planar/NRD-guide integrated transition is then presented and analyzed. A very effective but rather simple scheme of ribbon interconnect is also proposed for co-layer multi-chip module (MCM) of microwave and millimeter-wave circuits.