Short-wavelength transmission line with variable characteristic impedance for application to matching components on MMIC

A short-wavelength transmission line with variable characteristic impedance (STLVCI) employing periodically loaded diodes is proposed. Compared with the conventional transmission line, the STLVCI shows a much shorter wavelength, and the characteristic impedance of the VATL is easily controlled by changing only the supplied voltage. Using the STLVCI, a λ/4 impedance transformer has been fabricated on a GaAs MMIC, and its line length is 375 µm, which is 28.3% of that of the conventional impedance transformer. Using the λ/4 impedance transformer, impedance matching could be performed between RF components with various characteristic impedance of 30–100 Ω by adjusting the applied voltage.