The Field Programmable Microwave Substrate

This thesis describes a research project to create a programmable microwave circuit having a similar level of programmability as that of a field programmable gate array (FPGA). The result of the thesis is the realization of the first ever practical low-loss programmable microwave waveguides. Since waveguides are a key component in any microwave circuit, this allows for the realization of a broad range of microwave functions with a single circuit. The programmable waveguides are implemented in what is referred to as a field programmable microwave substrate. The programmable substrate is implemented using metamaterials between two parallel metal plates. Between the metal plates are electrically small unit cells that consist of metal structuring that connects with active components not contained between the metal plates (i.e. above or below the metal plates). Each of these unit cells can be programmed to have a range of positive dielectric constants or a negative dielectric constant. Programming a positive dielectric constant core and negative dielectric constant sidewall yields a structure that can be described using the slab waveguide equations. This allows for waveguides to be dynamically programmed within the field programmable microwave substrate.The theory required to design low-loss metamaterials is presented and used to realize two prototype circuits. The first implementation is on an FR4 substrate and is used to demonstrate low-loss waveguides, amplifiers and oscillators from 0.9-3 GHz. The other field programmable microwave substrate is implemented in low temperature co-fired ceramic and uses custom designed CMOS chips. This version is used to demonstrate miniaturization. The losses of the waveguides are high, but this is mainly due to manufacturing capabilities of the process used. Low-loss small field programmable microwave substrates should be possible to implement with the use of higher performance components and more sophisticated manufacturing processes.