A basic study on RF characteristics of inverted comb-type capacitive transmission line structure on MMIC

In this work, the inverted comb-type capacitive transmission line (ICCTL) structure on GaAs monolithic microwave integrated circuit (MMIC) was proposed and its RF characteristics were investigated for application to a development of miniaturized on-chip passive components. According to the results, the ICCTL structure showed short wavelength characteristic due to an enhancement of its periodic capacitance. Concretely, the wavelength of the ICCTL structure was only 11.85% of conventional microstrip line on MMIC. The insertion loss of the ICCTL with a length of λ/8 was less than 0.36 dB up to 6 GHz, which was comparable to conventional microstrip line. Attenuation constant α and propagation constant β were also extracted using transmission line theory. According to the results, the ICCTL structure showed attenuation constant α lower than 1.06 Np/mm up to 10 GHz, and propagation constant β of 0.254 ~ 4.14 rad/mm from 0.5 to 10 GHz.