Dual H-and E-field tunable multiferroic bandpass filters with yttrium iron garnet film

A new type of dual magnetically (H-field) and electrically (E-field) tunable bandpass filters (BPF) with an yttrium iron garnet (YIG) film and with a YIG/ PZN-PT (lead zinc niobate-lead titanate) multiferroic heterostructure have been designed, fabricated and characterized. Single-crystal YIG films at their ferromagnetic resonance were adopted as the resonator which was coupled to a T-shaped microstrip coupling structure to form a new bandpass filter design. The operating frequency of the BPF can be tuned via a bias magnetic field, and a large tunability of the operation frequency of 190 MHz ~ 840 MHz with relatively small bias field of 50 ~ 250 Oe, together with a low insertion loss of <; 2 dB. This is equivalent to 12% ~ 54% of the center frequency of the bandpass filter. A clear E-field induced operation frequency shift of 200 MHz, or ~10% was demonstrated on the multiferroics based bandpass filter having a YIG/PZN-PT heterostructure. These demonstrated new multiferroic tunable bandpass filters with dual H- and E-field tunability are very compact and energy efficient, which could have many applications in RF front and other microwave circuits.