Ph.D Thesis

Ph.D StudentSpiegel Solon
SubjectNovel Microwave Elements Design Based on Micromachining
DepartmentDepartment of Quality Assurance and Reliability
Supervisor MR Asher Madjar


Diverse aspects of the design, fabrication and characterization of microwave micro-machined elements are described: silicon finite ground coplanar waveguide transmission line, microwave filters and passive structures, design methodology and characterization of RFMEM switches and a broadband radio front-end for radar and communication systems.

Silicon micro-machined finite ground coplanar waveguide

Modeling of silicon finite ground coplanar waveguide transmission lines is presented. It is shown that the effective substrate conductivity increases in the presence of illumination and in the presence of a passivation layer in the slot regions independently. The strong dependence of the substrate conductivity on illumination suggests that optically controlled attenuators can be implemented with FGCPW transmission lines exhibiting practically no phase change between the different attenuation states.

Flip-Chip Interconnect and Membrane Supported Micro-Machined Microwave Filters

The effect of the bump height on the transition insertion and return losses and on the element values of the equivalent circuit is analyzed. It is shown that the performance of flip-chip transitions is limited by the parasitic capacitance between the bump interconnects and the bump pads. In addition, the fabrication and the results of membrane supported interdigitated millimeter-wave filter are presented. The filter was fabricated on low resistivity silicon substrate, compatible with CMOS technology. The results suggest that low loss microwave structures on CMOS technology can be realized through micromachining techniques by reducing the losses due to the dielectric.

Design Methodology and Characterization of RF Micro-Machined Switches

The design methodology and the analysis of RFMEM switches are presented. The structures of the RFMEM switches investigated are based on the conventional, FGCPW, and the trenched, T-FGCPW, finite ground CPW transmission lines. The results reveal that the equivalent line impedance of T-FGCPW is higher than the FGCPW structure, providing a better compensation to the loading effect of the movable bridge. The presence of the backside ground plane in both structures deteriorates the isolation of both switching structures. Finally, the characterization results of the RFMEM switch are presented.

Novel Broadband Receiver Unit for Wireless Communication and Radar Systems

The last chapter describes novel down-converter architecture for radio receivers and for polarimetric radar systems.  The mixing unit configuration is based on two 900 single balanced mixers, associated in anti-phase, to obtain wide-bandwidth differential IF signals. For analog receivers, the terminals of each of the mixing units are connected to produce single RF and LO signals. This is as opposed to polarimetric systems, where one LO and two RF signals are present. The broadband nature of the differential IF signal suggests that the proposed topology eliminates the need of either passive baluns or active baluns needed to produce 00 and 1800 phase-shifted signals.