Acoustically coupled resonators and method of making the same

A method of manufacturing an apparatus, said method comprising:

• etching a cavity within a substrate, the cavity open to a first major surface of the substrate;
• filling said cavity with sacrificial material;
• fabricating a two-stage resonator filter above the cavity;
• and
• removing the sacrificial material from the cavity.

A single-chip duplexer comprising:

• a first two-stage resonator filter configured to pass electrical signal having a frequency within a first range of frequencies, said first two-stage resonator filter including an input resonator, an output resonator, and two floating resonators, each resonator including piezoelectric material;
• a second two-stage resonator filter configured to pass electrical signal having a frequency within a second range of frequencies, said second DMF including an input resonator, an output resonator, and two floating resonators, each resonator including piezoelectric material;
• wherein a lower common piezoelectric layer is shared by said first two-stage resonator filter and by said second two-stage resonator filter;
• and
• wherein an upper common piezoelectric layer is shared by said first two-stage resonator filter and by said second two-stage resonator filter.

An apparatus comprising:

• a two-stage resonator filter connected to two input signal lines and two output signal lines, said two-stage resonator filter comprising:
• a first stage including a first resonator and a second resonator;
• said second resonator acoustically coupled to said first resonator;
• a second stage including a third resonator and a fourth resonator;
• said fourth resonator acoustically coupled to said third resonator;
• a decoupling layer between said first resonator and said second resonator, said decoupling layer extending between said third resonator and said fourth resonator;
• at least one of
• a first shunt resonator across the input signal lines;
• a second shunt resonator across the output signal lines;
• a first series resonator along its input signal lines;
• and
• a second series resonator along its output signal lines.

An apparatus comprising:

• a two-stage resonator filter connected to an input signal line and an output signal line, said two-stage resonator filter comprising:
• a first stage including a first resonator and a second resonator;
• said second resonator acoustically coupled to said first resonator;
• a second stage including a third resonator and a fourth resonator;
• said fourth resonator acoustically coupled to said third resonator;
• a decoupling layer between said first resonator and said second resonator, said decoupling layer extending between said third resonator and said fourth resonator;
• a first bridge capacitor bridging the input signal line and the second resonator;
• and
• a second bridge capacitor bridging the output signal line and the third resonator.

An apparatus comprising:

• a first two-stage resonator filter connected to an input signal line and a first output signal line, said first two-stage resonator filter comprising:
• a first stage including a first resonator and a second resonator;
• said second resonator acoustically coupled to said first resonator;
• a second stage including a third resonator and a fourth resonator;
• said fourth resonator acoustically coupled to said third resonator;
• a decoupling layer between said first resonator and said second resonator, said decoupling layer extending between said third resonator and said fourth resonator;
• a second two-stage resonator filter connected to the input signal line and a second output signal line, said second two-stage resonator filter comprising:
• a first stage including a first resonator and a second resonator;
• said second resonator acoustically coupled to said first resonator;
• a second stage including a third resonator and a fourth resonator;
• said fourth resonator acoustically coupled to said third resonator;
• and
• a decoupling layer between said first resonator and said second resonator, said decoupling layer extending between said third resonator and said fourth resonator;
• and
• wherein both said first two-stage resonator and said second two-stage resonator are connected to the same input signal line.