Design of a Si MMIC compatible ferroelectric varactor shunt switch for microwave applications

This paper describes a capacitive shunt switch, based on ferroelectric varactors as a potential replacement for RF MEMS switches for microwave applications. Our implementation is based on a coplanar waveguide (CPW) transmission line shunted by a ferroelectric varactor. The novelty in the implementation comes from the elimination of any moving parts (as in MEMS switches) for switching. The concept of switching ON and OFF is based on the dielectric tunability of the ferroelectric material of barium strontium titanium oxide (BST) thin-films. From electromagnetic simulations performed, the isolation of the switch between 20 and 40 GHz (OFF state S21) is better than 30 dB. The insertion loss of the switch is below 2 dB up to 40 GHz. This paper addresses the design, optimization, electromagnetic simulations, and electrical modeling of the ferroelectric varactor shunt switch with Si MMIC compatible process.