The objective of this PhD research was to design and implement novel microfluidic radio-frequency (RF) structures on multilayer organic substrates for cooling and tuning purposes. The different designs were implemented to target applications up to C-band (4 GHz – 8 GHz) frequencies. The system-on-package (SoP) solution adopted throughout this work is well adapted for such designs where there is a need to integrate the functionality of different sub-components into a single hybrid fully packaged system. The first part of the thesis is dedicated to the study of a specific liquid cooling scheme using integrated microchannels on organics placed beneath different types of heat sources. A 1 W gallium nitride (GaN) die was cooled using this method and an analysis is presented regarding the cases where the coolant is static or dynamic inside the microchannel. The second part of the thesis deals with microfluidically reconfigurable microstrip RF circuits, mainly bandpass filters and power amplifiers (PAs). The microfluidic tuning technique is based on the change in the effective dielectric constant that the RF signal “sees” when traveling above two microchannels with different fluids. This technique was used to shift the frequency response of an L-band microstrip bandpass filter by replacing DI water with acetone inside a 60 mil micro-machined cavity. This technique was also used to design reconfigurable matching networks which constitute the main part of the proposed tunable GaN-based PA for S- and C-band applications. The final part of the thesis expands the previous results by combining both cooling and tuning in a single RF design. To prove the concept, cooling and tuning microchannels were integrated into a single package to cool a GaN-based PA and tune its frequency response at the same time from 2.4 GHz to 5.8 GHz and vice versa.

This thesis concerns the introduction and development in our laboratory of a multilayer ceramic technology, called LTCC, for RF and microwave packaging. LTCC stands for Low Temperature Co-fired Ceramics. As can be understood from its name, the low temperature means that the LTCC circuit is fired below 1000 °C that allows the use of high conductivity materials such as gold and silver. The thesis work starts after the bibliographic study of RF packaging technology, with the choice of LTCC substrate and conductor materials necessary to implement LTCC technology in our laboratory. Then, the LTCC manufacturing process is put in place and validated in order to produce operational LTCC circuits. This process includes the cut of LTCC layers, via hole and cavity creation, via fill for vertical interconnecting, screen printing for horizontal patterns, stacking, lamination and finally the firing to obtain a 3D circuit. Most encountered technological problems are resolved and the fabrication steps are validated. LTCC DESIGN RULES that contain all dimensional values required for future RF packaging designers at the laboratory is elaborated. Next, after the successful establishment of LTCC technology, it is qualified up to 40 GHz using simple RF structures such as transmission lines and planar resonators. Then, a multilayer LTCC package for an MMIC oscillator functioning in the frequency band between 10.6 and 12.6 GHz is proposed, fabricated and finally measured.

The objective of this research is to explore the possibilities of developing transmit/receive (T/R) modules using silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) BiCMOS technology to integrate with organic liquid crystal polymer (LCP) packages for the next-generation phased-array radar system. The T/R module requirements are low power, compact, lightweight, low cost, high performance, and high reliability. All these requirements have provided a very strong motivation for developing fully monolithic T/R modules. SiGe HBT BiCMOS technology is an excellent candidate to integrate all the RF circuit blocks on the T/R module into a single die and thus, reducing the overall cost and size of the phase-array radar system. In addition, this research also investigates the effects and the modeling issues of LCP package on the SiGe circuits at X-band.