New approach for modelling distributed MEMS transmission lines

The paper presents a new and more accurate model for the distributed MEMS transmission line (DMTL) structures. In this new model, the MEMS bridges that are used as the loading elements of the DMTL structures are represented as low-impedance transmission lines, rather than a lumped CLR circuit. The model also includes LC networks at the transition points from the MEMS bridges to the unloaded parts of the DMTL, which are simply high-impedance transmission lines. These LC networks are employed to model the effects of the impedance discontinuities. The accuracy of the model is verified with simulations and measurements in the range 1-20 GHz on various DMTL structures that are fabricated with an RF MEMS process based on electroforming on a glass substrate. The measurement results of the fabricated devices are in good agreement with the model with an error less than 5%. It is shown that this new model provides better agreement than the conventional method for the DMTL structures with a bridge width larger than 50 μm.