Wide-band matching of a tunable periodic structure in GaAs technology

Wide-band matching of a tunable 1D periodic microwave structure, designed for fabrication in GaAs technology, is investigated. The two-layer unit cell of the periodic structure consists of a microstrip line loaded by multiple rectangular patches, which can be selectively short-circuited. The wide variation of the position of the bandgap, obtained by electrically controlled switches, induces a large variation of the effective dielectric constant in the considered wide frequency range. This effect is further reflected as a significant variation of the characteristic impedance, and hence a potentially high mismatch loss. A method for wide-band minimization of the mismatch (with respect to a 50 Ω reference impedance), without compromising the performance of the device, is presented.