Multifunctional Substrates for High-Frequency Applications

Xun Gong, Electrical and Computer Engineering, Purdue University
William J. Chappell, School of Electrical and Computer Engineering, Birck Nanotechnology Center, Purdue University
Linda P. B. Katehi, Electrical and Computer Engineering, Birck Nanotechnology Center, Purdue University

Abstract

A substrate that is designed to suppress parasitic modes while at the same time provides high-Q filtering capability is presented. High-density circuits require the integration of multiple functions in very limited space. More specifically, with the design of three-dimensional (3-D) circuits, parasitic effects caused by the excitation of surface waves result in a serious degradation of performance and impose limitations on circuit density and performance. Herein, an effort is presented to use advanced design concepts to enable embedded functionality within a substrate. The presented substrate geometries can easily be extended to 3-D to allow for the development of system-in-a-package which incorporates a high-Q filter bank to provide effective frequency selectivity. To demonstrate this concept, resonators and filters in LTCC are designed, fabricated and measured. Resonators in LTCC with unloaded Q up to 428 were measured. A narrow-band 2-pole filter is realized to show that a function of a relatively high-Q can be incorporated into the packaging. The 2.28% filter has an insertion loss of 1.7 dB due to the low loss nature of the design. Simulation and measurement of the structures are presented with good agreement achieved.