Tuneable RF Filter based on acoustically coupled Ferroelectric Resonators

Abstract

Tuneable filters are a great solution for wireless telecommunications. Micro-actuators resonators are being employed in different configuration in order to provide a much better selectivity. Ferroelectric materials are the main key materials which are being employed as the medium of the resonators and a bias voltage is superimposed with the input signal. The bias voltage varies the main properties of the ferroelectric materials and therefore the impedance profile of the resonator gets shifted into higher frequencies. The drawback associated with homogeneous structure is that resonance frequency has a lower tuneability rate compare to the antiresonance frequency. This is a critical feature since in real tuneable filter the bias voltage increases of the bandwidth rather than shifting the bandpass filter into higher frequencies. Another approach has been proposed in order to overcome this restriction. The new structure contains two distinct ferroelectric layers sandwiched by the electrode. The simulated data exhibits a enhanced tuneability for the resonance frequency. This is a competitive approach for implementation of tuneable filter.