CPW Phase Shifter and Shunt Stub with Air-Bridge Fabricated on Oxidized Porous Silicon(OPS) Substrate

This paper presents a CPW phase shifter and shunt stub with air-bridge on a 10--thick oxidized porous silicon(OPS) substrate using surface micromachining. The line dimensions of the CPW phase shifter was designed with S-W-Sg = 100-30-400 . And the width and length of the air-bridge with "ㄷ“ shape were 100 and 400-460-400 , respectively. In order to achieve low attenuation, stepped air-bridge CPW phase shift was proposed. The insertion loss of the stepped air-bridge CPW phase shift is more improved than that of no stepped air-bridge CPW phase shift. The measured phase characteristic of the fabricated CPW phase shifter is close to 180 over a very broad frequency range of 28 GHz. The measured working frequency of short-end series stub is 28.7 GHz and the return loss is - 20 dB. And the measured working frequency of short-end shunt stub is 28.9 GHz and the return loss is - 23 dB at midband. As a result, the pattering of stub in the center conductor of CPW lines can offer size reduction and lead to high density chip layouts.