Hybrid connection of RF MEMS and SMT components in an impedance tuner

This paper presents a systematic construction of a model for a hybrid connected RF MEMS and SMT components in a reconfigurable impedance tuner. The double stub hybrid impedance tuner which employs a high number of MEMS switches is selected to demonstrate the feasibility of the connections. In the hybrid tuner, MEMS switches are actuated with DC bias signals, where SMT resistors de-couple RF from the DC lines. The hybrid tuner is realized in two steps, where the MEMS impedance tuner is fabricated on a glass substrate using an in-house surface micromachining process, and the SMT resistors are mounted on the glass substrate following the MEMS fabrication. The parasitics introduced by the SMT resistors and their connections in the hybrid tuner are modeled in 1-20 GHz band. The constructed model is used to simulate the hybrid impedance tuner, which is capable of matching 2(10) points on the Smith Chart, covering a wide impedance range 1.5-393 Omega in the real and -210 to 220 Omega in the imaginary parts at 18 GHz. The hybrid impedance tuner is measured for 25 switch combinations to verify the model in which a good agreement is obtained. The comparison of the simulation and measurement results show that the constructed model is successful in terms of handling parasitics of a hybrid structure up to 20 GHz where the parasitics vitally affect the device performance. (C) 2010 Elsevier GmbH. All rights reserved.