RF Characteristics of a Short Wavelength Comb-Type Capacitive Transmission Line on MMICs

摘要

In this work, the basic characteristics of the comb-type capacitive transmission line (CCTL) structure were investigated for application to the development of miniaturized on-chip passive components. According to the results, the CCTL structure showed short wavelength characteristics, due to its periodically added capacitance. The wavelength of the CCTL structure was only 10 percent of that of a conventional microstrip line on a MMIC. The CCTL structure showed a propagation constant much higher than a conventional microstrip line, due to the slow-wave propagation on a periodic structure. Using the CCTL structure, a highly miniaturized impedance transformer was fabricated on a GaAs MMIC. The impedance transformer showed good RF performances in a broadband from S- to X-Band, and its size was 0.042 mm2, which is 0.95 percent of the size of the transformer fabricated by a conventional microstrip line.