Monolithic implementation of coaxial line using BCB- or air-filled cavity for high isolation

Abstract

In this these, BCB coaxial line and rectangular air coaxial line for high isolation are described. In the chapter 2, The BCB coaxial line has good performance for signal isolation because its closed structure. The measured isolation level is below -60dB(2mm coupling length, 200um distance), and less than -0.08dB/mm attenuation level to 20GHz frequency range. In chapter 3, the air rectangular coaxial line is developed. The air coaxial line has also high isolation performance and additionally low loss attenuation property because of its air dielectric material. The attenuation of the air coaxial line is less than 0.07dB/mm to 38GHz frequency range. The isolation is below -52dB(2mm coupling length, 60um coupling distance). To fabricate the air coaxial line, air multi-layer process is developed. The key process step of the air multi-layer, is using patterned Au seed metal as plating seed metal. Pattern seed metal can prevent plating metal attack during removing seed metal process. Because the pattern seed process, it is possible to develop air multi-layer process. In the chapter 4, some other transmission line and device such as buried microstrip line, air gap coplanar waveguide, air strip line and air gap inductors, are described. The attenuation of the air coplanar waveguide, BMSL, and strip line are 0.07, 0.08, 0.18 respectively, due to air dielectric material. The elevated inductor has very high Q factor. Some inductor has above 130 maximum Q factor, and high resonance frequency property because it use loss less dielectric material. Recently, the development of next-generation digital wireless communication system is placing increasing demands on circuit interconnection techniques for high frequency operation and high isolation performance. So the monolithic integrated coaxial line is good solution to meet these demands.