The development of ultra-wide band microwave passive components suitable for integration with other active devices to form complete functional modules (e.g. ultra wide band receivers front ends, frequency converters, etc.) is of great interest in many emerging applications in communications, Radar, industrial instrumentation, medical instrumentation, intelligent automobiles and intelligent highways. The Low Temperature Cofired Ceramics (LTCC) process offers the potential for excellent flexible approach to the realization and integration of ultra-wide bandwidth modules consisting of passive microwave devices (such as high quality filters, power dividers, multiplexers, antenna feed elements and phase shifters), having exacting performance, with active devices, in large mass production quantities at very low costs.
The LTCC process implements the microwave circuits in the form of stacking several very thin layers (thickness of .002 to .004 inches) of low to medium relative dielectric constant (2.5 to 7), and depositing metal patterns of any desired shapes on any chosen locations of these layers. Thus most microwave research utilized planar 2-dimensional modeling techniques for the analysis of LTCC circuits. This limited their applicability to the realization of only planar transmission media (such as microstrip, strip line, fin line and coplanar waveguides). The planar structures have high losses due to the narrow line widths and there are limited types of components that can be implemented using them.
Recently concepts for the realization of 3-dimensional LTCC transmission media (such as rectangular waveguides, single and double ridge waveguides) were conceived. These new structures opened the door for the possibility to realize complex 3-dimensional components that offer many performance advantages (such as lower loss, higher quality performance, and integration with active elements in the form of integrated modules) over the 2-dimensional structures. The main concept to construct the 3-dimensional structures is to use planar metalization deposited on the dielectric layers to construct one set of conducting walls, and via fences to constitute the effect of perpendicular walls.
Under this proposal the PI in collaboration with Kyocera America, Inc, will investigate the electromagnetic properties of the 3-D LTCC transmission media, develop tools for their analysis and simulation, and explore the possibilities of employing these tools in the realization of ultra wide band components (such as high quality elliptic function filters, couplers, hybrids, multi-junctions, multiplexers, etc.), verify the developed tools by constructing and testing prototype components. The fundamental technique to be used in analyzing the structures and the discontinuities is the mode matching technique and generalized scattering matrices, due to their conceptual simplicity, accuracy, versatility and fast convergence. The mode matching technique together with the generalized scattering matrices make the optimization of relatively complex components possible and practical, with high degree of precision and reasonable computation times. Kyocera America, Inc. will manufacture some practically challenging test components, designed by the developed tools, using their world class LTCC process. These components will be tested to verify the accuracy and validity of the developed tools.
The modeling, simulation and optimization techniques to be developed in this research will have wide applicability and will be used by researchers in the field to design and investigate many ultra wide band systems. Furthermore, the research will provide fundamental understanding of the bandwidth limitations of LTCC transmission media. Graduate students working on the research will have fundamental training and will be exposed, through the collaboration with Kyocera America, Inc., to the practical aspects of the LTCC manufacturing process and testing. There is a shortage of both undergraduate and graduate microwave engineering students. The research proposed here presents an interesting subject that will attract students to the area of microwaves. Undergraduate students will be involved in senior projects that provide basic training on interesting practical design problems. Preference will be given for the recruitment of minority students. The research results will be published in technical journals and presented at technical conferences.
