Telefonaktiebolaget LM Ericsson (publ)
Band reject filters

Abstract:

A method and a band reject filter (BRF) using as acoustic resonators at least one of bulk acoustic wave (BAW) resonators and film bulk acoustic resonators (FBAR) are provided. The BRF includes at least one substrate having at least one of a plurality of capacitors formed thereon, the plurality of capacitors having capacitances selected to achieve a particular band reject response. The BRF also includes at least one die. At least one of a plurality of acoustic wave resonators are formed thereon. The plurality of acoustic wave resonators are one of BAW resonators and FBARs and are designed to have the same resonant frequency. A plurality of conductors between the substrate and the die are positioned to electrically connect the acoustic wave resonators and the capacitors.