Hybrid integration techniques (HITs) of planar and non-planar structures are discussed for low-cost and high-performance millimeter-wave integrated circuits (ICs) and systems. Current status of this research topic is reviewed with emphasis on various integration/interconnect schemes of planar circuits and non-radiative dielectric (NRD) guides. Co-layered and aperture-coupling arrangements of planar circuits and NRD-guide are presented. Future trend is forecasted with emphasis on single substrate integration of planar and non-planar geometries. Substrate integrated circuits (SICs) are highlighted that can render the non-planar structures in planar form.

Integration and interconnect techniques of planar and non-planar structures for microwave and millimeter-wave circuits - current status and future trend

The design, fabrication and performance of a 60-GHz multi-chip module receiver employing a substrate integrated waveguide filter and antenna are presented. The receiver is integrated onto a single multilayer substrate, fabricated using photoimageable thick-film technology. The module incorporates a GaAs monolithic microwave integrated circuit low-noise amplifier and downconverter, with lumped elements for intermediate frequency (IF) filtering embedded into the substrate. The chip cavities for mounting of the MMICs are photo-imaged as part of the standard process, giving precise dimensional control for short bond-wire lengths. The complete module including integrated antenna measures only 22.5 mm x 5.4 mm x 0.3 mm and works from 58 to 64 GHz.

Design and performance of a 60-GHz multi-chip module receiver employing substrate integrated waveguides

Dielectric rod waveguide antennas of rectangular cross section have a number of advantages over conventional waveguide and horn antennas as an antenna array element. Dielectric rod waveguide antennas have relatively low cost, low losses, a broadband input match and a high packing potential. Additionally the radiation pattern of such antennas is almost frequency independent. In this paper the suitability of Sapphire rod waveguides for an antenna array is studied with simulations and prototype measurements at W band. Strong mutual coupling is observed when the elements are close to each other.

High Permittivity Dielectric Rod Waveguide as an Antenna Array Element for Millimeter Waves

This paper presents the very first investigation of guided-wave properties of a non-radiative dielectric (NRD) guide synthesized on a single substrate for the design of substrate integrated circuits (SICs). The synthesis of the new NRD-guide is made possible by removing part of the substrate or by punching hole or slot arrays that results in two separate lower dielectric-constant regions to which the core NRD strip is bounded. A mode-matching technique is applied to model this guided-wave problem that takes into account various parametric effects of geometry. Propagation constant, leakage loss and modal characteristics are studied for the synthesized NRD-guide structure. The results show that a synthesized NRD-guide can effectively be co-designed with planar circuits based on the same substrate to form a new class of integrated circuits called "substrate integrated circuits" (SICs). This work is useful for the development of low-cost and high-density millimeter-wave ICs.

Guided-wave properties of synthesized nonradiative dielectric waveguide for substrate integrated circuits (SICs)

A variety of transitions between rectangular dielectric waveguides and planar waveguides like microstrip or slotline have been designed to combine the advantages of dielectric wave-guides at millimeterwaves with the excellent hybrid integration capabilities of planar circuits. FDTD field simulations have been applied to analyze and optimize the designed transitions with respect to low insertion and return losses as well as minimized mutual coupling between adjacent transitions. Experimental investigations between 60 and 90 GHz proved the promising results of the simulations with insertion losses between 0.5 and 1.5 dB over the full waveguide band (WR-12). The transitions can well be used for the integration of planar circuits into dielectric waveguides or rod antennas and the designed structures are scalable up to frequencies beyond 100 GHz.

A broadband transition between dielectric and planar waveguides at millimeterwave frequencies

A concept of hybrid integration between planar circuits and a nonradiative dielectric (NRD) waveguide is proposed in this paper with preliminary experiments. This 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. The first is to deposit the NRD-guide on the top of a relatively thin microstrip substrate, thus forming unbalanced NRD-guiding hybrid circuits, while the second is to design CPW circuits directly etched on the ground planes of the NRD-guide. The unbalanced NRD-guide is subject to a certain leakage loss, but at a negligible level, and it may even be suppressed completely in certain circumstances. Such an integration technique is found consistent with the concept of low loss interconnects at millimeter-wave frequencies. In other words, the NRD-guide can be used for viable interconnects of co-layered planar circuits with a simple "put and cover" procedure. Measured results of several co-layered hybrid transitions/baluns indicate that satisfactory transmission properties can readily be achieved. The new building blocks are expected to provide an alternative design approach to three-dimensional multilayered millimeter-wave circuits and systems.

J. Tang

Papers

Co-layered integration and interconnect of planar circuits and nonradiative dielectric (NRD) waveguide