Tunable RF filters: Survey and beyond

Without a holistic design and fabrication approach, future wireless communication devices would be extremely large in size to accommodate multiple radio access technologies (RATs) compared to today´s more conventional mono-mode devices. Typically multiple RAT devices will be comprised of multiple RF power amplifiers, low noise amplifiers (LNA), RF band pass filters, modulators and demodulators; one for each wireless technology. Obviously, this will increase the complexity of the circuit design and will cover a large part of the circuit space leading to power hungry devices. Radio frequency microelectromechanical systems (RF-MEMS) can be good candidate for innovative RF front end devices since it is reconfigurable features in nature therefore allowing a reduction in the number of external components in a single device for the use of multiple RATs. This paper discusses the history, state of the art of tunable RF filter and beyond.