Bulk acoustic wave resonator with two piezoelectric layers as balun in filters and duplexers

Claim 2

A bulk acoustic wave device having a signal input port, a first signal output port, a second signal output port and a device ground, said device having a resonant frequency and an acoustic wavelength characteristic of the resonant frequency, said device comprising: a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes; and a dielectric layer, wherein the first resonator and the second resonator are arranged in a stack with the dielectric layer disposed between the second electrode and the third electrode, and wherein the first electrode is coupled to the signal input port, the second electrode is electrically connected to the device ground, the third electrode is coupled to the first signal output port, and the fourth electrode is coupled to the second signal output port.

Claim 3

An acoustic wave apparatus formed on a substrate having an upper surface, said apparatus having a device ground, a signal input, a first signal output, a second signal output and a device ground, said structure comprising: a first bulk acoustic wave device; and a second bulk acoustic wave device coupled to the first bulk acoustic wave device, wherein the first bulk acoustic wave device comprising: a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; and a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes, wherein the first resonator and the second resonator are arranged in a stack with a first dielectric layer disposed between the second and third electrode for electrically insulating the second electrode from the third electrode, and the second bulk acoustic wave device comprising: a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; and a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes, wherein the first resonator and the second resonator are arranged in a stack with a first dielectric layer disposed between the second and third electrode for electrically insulating the second electrode from the third electrode, and wherein the fourth electrode of the first bulk acoustic wave device is coupled to the first signal output of the structure, the fourth electrode of the second bulk acoustic wave device is coupled to the second signal output of the structure, the first electrode of the first bulk acoustic wave device is coupled to the signal input of the structure and is electrically connected to the second electrode of the second bulk acoustic wave device, and the second electrode and the third electrode of the first bulk acoustic wave device are electrically connected to the device ground and the first electrode of the second bulk acoustic wave device.

Claim 4

An acoustic wave apparatus formed on a substrate having an upper surface, said apparatus having a device ground, a signal input, a first signal output, a second signal output and a device ground, said structure comprising: a first bulk acoustic wave device; and a second bulk acoustic wave device coupled to the first bulk acoustic wave device, wherein the first bulk acoustic wave device comprising: a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; and a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes, wherein the first resonator and the second resonator are arranged in a stack with a first dielectric layer disposed between the second and third electrode for electrically insulating the second electrode from the third electrode, and the second bulk acoustic wave device comprising: a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; and a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes, wherein the first resonator and the second resonator are arranged in a stack with a first dielectric layer disposed between the second and third electrode for electrically insulating the second electrode from the third electrode, and wherein the fourth electrode of the first bulk acoustic wave device is coupled to the first signal output of the structure, the fourth electrode of the second bulk acoustic wave device is coupled to the second signal output of the structure, the first electrode of the first bulk acoustic wave device is coupled to the signal input of the structure and is electrically connected to the second electrode of the second bulk acoustic wave device, and the second electrode and the third electrode of the first bulk acoustic wave device are electrically connected to the device ground and the first electrode of the second bulk acoustic wave device.

Claim 5

A duplexer comprising: an antenna port; a first transceiver port; a second transceiver port; a device ground; a first balun coupled between the antenna port and the first transceiver port; a second balun coupled between the antenna port and the second transceiver port; and a phase shifting means coupled between the first balun and the second balun at the antenna port, wherein each of the baluns has at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the antenna port, and the first and second signal output ends of each balun are connected to each of the first and second transceiver ports.

Claim 6

A duplexer comprising: an antenna port; a first transceiver port; a second transceiver port; a device ground; a first balun coupled between the antenna port and the first transceiver port; a second balun coupled between the antenna port and the second transceiver port; and a phase shifting means coupled between the first balun and the second balun at the antenna port, wherein each of the baluns has at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the antenna port, and the first and second signal output ends of each balun are connected to each of the first and second transceiver ports.

Claim 7

A bulk acoustic device having a resonant frequency and an acoustic wavelength characteristic of the resonant frequency, said device comprising: a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes; and an electrically insulating layer, wherein the first resonator and the second resonator are arranged in a stack with the electrically insulating layer disposed between the second electrode and the third electrode, wherein the device has a signal input port, a first signal output port, a second signal output port and a device ground, and wherein the first electrode is coupled to the signal input port, the second electrode is electrically connected to the device ground, the third electrode is coupled to the first signal output port, and the fourth electrode is coupled to the second signal output port.

Claim 8

A bulk acoustic device having a resonant frequency and an acoustic wavelength characteristic of the resonant frequency, said device comprising: a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes; and an electrically insulating layer, wherein the first resonator and the second resonator are arranged in a stack with the electrically insulating layer disposed between the second electrode and the third electrode, wherein the device has a signal input port, a first signal output port, a second signal output port and a device ground, and wherein the first electrode is coupled to the signal input port, the second electrode is electrically connected to the device ground, the third electrode is coupled to the first signal output port, and the fourth electrode is coupled to the second signal output port.

Claim 9

The bulk acoustic wave device of claim 4 , further comprising a capacitive element coupled between the fourth electrode and the device ground for adjusting the parasitic capacitance therebetween.

Claim 10

The bulk acoustic wave device of claim 4 , further comprising an inductance element coupled between the first and second signal output ports for impedance matching and bandwidth widening.

Claim 11

The bulk acoustic wave device of claim 4 , further comprising an inductance element coupled between the signal input port and the device ground for impedance matching and bandwidth widening.

Claim 12

A duplexer comprising: an antenna port; a first transceiver port; a second transceiver port; a device ground; a balun coupled between the antenna port and the first transceiver port; a bulk acoustic wave filter having a first filter end coupled to the second transceiver port, and a second filter end coupled to the antenna port; and a phase shifting means coupled between the balun and bulk acoustic wave filter at the antenna port for matching the balun and the bulk acoustic wave filter, wherein the balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the antenna port, and the first and second signal output ends are connected to the first transceiver port.

Claim 13

A duplexer comprising: an antenna port; a first transceiver port; a second transceiver port; a device ground; a balun coupled between the antenna port and the first transceiver port; a bulk acoustic wave filter having a first filter end coupled to the second transceiver port, and a second filter end coupled to the antenna port; and a phase shifting means coupled between the balun and bulk acoustic wave filter at the antenna port for matching the balun and the bulk acoustic wave filter, wherein the balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the antenna port, and the first and second signal output ends are connected to the first transceiver port.

Claim 14

The duplexer of claim 8 , wherein the bulk acoustic wave filter comprises at least one lattice filter including two series elements and two shunt elements connected to the series elements in a cross-connection fashion.

Claim 15

The duplexer of claim 9 , further comprising a further balun coupled between the bulk acoustic wave filter and the antenna port, wherein the further balun has at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the antenna port via the phase shifting means, and the first and second signal output ends are connected to the second filter end of the bulk acoustic wave filter.

Claim 16

The duplexer of claim 8 , wherein the bulk acoustic wave filter comprises at least one ladder filter including a series element having a first end connected to the first filter end, and a second end coupled to the antenna port via the phase shifter, and a shunt element having a first end connected to the second end of the series element, and a second end connected to the device ground.

Claim 17

The duplexer of claim 11 , further comprising a further balun coupled between the bulk acoustic wave filter and the second transceiver port, wherein the further balun has at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the first filter end of the bulk acoustic wave filter, and the first and second signal output ends are connected to the second transceiver port.

Claim 18

A bulk acoustic wave filter having a signal input terminal, a first signal output terminal, a second signal output terminal and a device ground, said bulk acoustic wave filter comprising: a balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the first signal output end is coupled to the first signal output terminal, the second signal output end is coupled to the second signal output terminal; and at least one acoustic filter segment having a series element having a first end and a second end, and a shunt element having a first end and a second end, wherein the first end of the series element is connected to the signal input end of the balun, the second end of the series element is connected to the signal input terminal, the first end of the shunt element is connected to the second end of the series element, and the second end of the shunt element is connected to the device ground.

Claim 19

A bulk acoustic wave filter having a signal input terminal, a first signal output terminal, a second signal output terminal and a device ground, said bulk acoustic wave filter comprising: a balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the first signal output end is coupled to the first signal output terminal, the second signal output end is coupled to the second signal output terminal; and at least one acoustic filter segment having a series element having a first end and a second end, and a shunt element having a first end and a second end, wherein the first end of the series element is connected to the signal input end of the balun, the second end of the series element is connected to the signal input terminal, the first end of the shunt element is connected to the second end of the series element, and the second end of the shunt element is connected to the device ground.

Claim 20

The bulk acoustic wave filter of claim 13 , wherein the first resonator of the balun comprises a first electrode connected to the signal input end, a second electrode connected to the device ground, and a first piezoelectric layer disposed between the first and second electrodes, and the second resonator of the balun comprises a third electrode connected to the first signal output end, a fourth electrode connected to the second signal output end, and a second piezoelectric layer disposed between the third and fourth electrodes, and wherein the balun further comprises a dielectric layer disposed between the second electrode of the first resonator and the third electrode of the second resonator.

Claim 21

A bulk acoustic wave device structure formed on a substrate having an upper section, said structure comprising: a first electrode provided on the upper section; a first piezoelectric layer provided on top of at least part of the first electrode; a second electrode provided on top of at least part of the first piezoelectric layer, wherein the first electrode, the first piezoelectric layer and the second electrode have an overlapping area for forming a first acoustic resonator; a dielectric layer disposed on top of at least part of the second electrode; a third electrode disposed on top of at least part of the dielectric layer such that the third electrode and the second electrode are electrically insulated by the dielectric layer; a second piezoelectric layer provided on top of at least part of the third electrode, and a fourth electrode provided on top of at least part of the second piezoelectric layer, wherein the third electrode, the second piezoelectric layer and the fourth electrode have a further overlapping area for forming a second resonator, wherein the structure has a signal input port, a first signal output port, a second signal output port and a device ground, and wherein the first electrode is coupled to the signal input port, the second electrode is electrically connected to the device ground, the third electrode is coupled to the first signal output port, and the fourth electrode is coupled to the second signal output port.

Claim 22

A bulk acoustic wave device structure formed on a substrate having an upper section, said structure comprising: a first electrode provided on the upper section; a first piezoelectric layer provided on top of at least part of the first electrode; a second electrode provided on top of at least part of the first piezoelectric layer, wherein the first electrode, the first piezoelectric layer and the second electrode have an overlapping area for forming a first acoustic resonator; a dielectric layer disposed on top of at least part of the second electrode; a third electrode disposed on top of at least part of the dielectric layer such that the third electrode and the second electrode are electrically insulated by the dielectric layer; a second piezoelectric layer provided on top of at least part of the third electrode, and a fourth electrode provided on top of at least part of the second piezoelectric layer, wherein the third electrode, the second piezoelectric layer and the fourth electrode have a further overlapping area for forming a second resonator, wherein the structure has a signal input port, a first signal output port, a second signal output port and a device ground, and wherein the first electrode is coupled to the signal input port, the second electrode is electrically connected to the device ground, the third electrode is coupled to the first signal output port, and the fourth electrode is coupled to the second signal output port.

Claim 23

The bulk acoustic wave device of claim 15 , further comprising a capacitive element coupled between the fourth electrode and the device ground for adjusting the parasitic capacitance therebetween.

Claim 24

The bulk acoustic wave device of claim 16 , wherein the first acoustic resonator and the second acoustic resonator have a further overlapping area for defining an active area of the bulk acoustic wave device structure, and wherein the second electrode has an extended portion located outside the active area, the fourth electrode has a further extended portion located outside the active area, wherein the extended portion and the further extended portion have yet another overlapping area for forming said capacitive element.

Claim 25

The bulk acoustic wave device of claim 15 , further comprising an inductance element coupled between the first and second signal output ports for impedance matching and bandwidth widening.

Claim 26

The bulk acoustic wave device of claim 15 , further comprising an inductance element coupled between the signal input port and the device ground for impedance matching and bandwidth widening.

Claim 27

The bulk acoustic wave device structure of claim 15 , further having an acoustic mirror structure provided between part of the first electrode and the upper section of the substrate.

Claim 28

A bulk acoustic wave filter having a signal input terminal, a first signal output terminal, a second signal output terminal and a device ground, said bulk acoustic wave filter comprising: at least one acoustic filter segment having a first terminal coupled to the first signal output terminal, a second terminal coupled to the second signal output terminal, a third terminal, a fourth terminal, a first series element having a first end connected to the first terminal and a second end connected to the third terminal, a second series element having a first end connected to the second terminal and a second end connected to the fourth terminal, a first shunt element having a first end connected to the third terminal and a second end connected to the second terminal, and a second shunt element having a first end connected to the first terminal and a second end connected to the fourth terminal; and a balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is coupled to the signal input terminal, the first signal output end is connected to the fourth terminal of the acoustic filter segment, and the second signal output end is connected to the third terminal of the acoustic filter segment.

Claim 29

A bulk acoustic wave filter having a signal input terminal, a first signal output terminal, a second signal output terminal and a device ground, said bulk acoustic wave filter comprising: at least one acoustic filter segment having a first terminal coupled to the first signal output terminal, a second terminal coupled to the second signal output terminal, a third terminal, a fourth terminal, a first series element having a first end connected to the first terminal and a second end connected to the third terminal, a second series element having a first end connected to the second terminal and a second end connected to the fourth terminal, a first shunt element having a first end connected to the third terminal and a second end connected to the second terminal, and a second shunt element having a first end connected to the first terminal and a second end connected to the fourth terminal; and a balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is coupled to the signal input terminal, the first signal output end is connected to the fourth terminal of the acoustic filter segment, and the second signal output end is connected to the third terminal of the acoustic filter segment.

Claim 30

The bulk acoustic wave filter of claim 21 , wherein the first resonator of the balun comprises a first electrode connected to the signal input end, a second electrode connected to the device ground, and a first piezoelectric layer disposed between the first and second electrodes, and the second resonator of the balun comprises a third electrode connected to the first signal output end, a fourth electrode connected to the second signal output end, and a second piezoelectric layer disposed between the third and fourth electrodes, and wherein the balun further comprises a dielectric layer disposed between the second electrode of the first resonator and the third electrode of the second resonator.

Claim 31

The bulk acoustic wave filter of claim 21 , wherein each of the first and second series elements has a first active area and each of the first and second shunt elements has a second active area different from the first active area in size.

Claim 32

The bulk acoustic wave filter of claim 23 , wherein the first active area is greater than the second active area.

Claim 33

The bulk acoustic wave filter of claim 23 , wherein the ratio of the first active area to the second active area is substantially equal to 1.2.

Claim 34

A duplexer comprising: a first port; a second port; a third port; a device ground; a lattice bulk acoustic wave filter, disposed between the first port and the second port, said lattice bulk acoustic wave filter having a first end coupled to the first port, and a second end; a balun coupled between the second port and the second end of the lattice filter; a further bulk acoustic wave filter having a first end coupled to the third port, and a second end coupled to the second port; and a phase shifting means coupled between the lattice bulk acoustic wave filter and the further bulk acoustic wave filter for matching the lattice bulk acoustic wave filter and the further bulk acoustic wave filter, wherein the balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the second port, and the first and second signal output ends are connected to the second end of the lattice bulk acoustic wave filter.

Claim 35

A duplexer comprising: a first port; a second port; a third port; a device ground; a lattice bulk acoustic wave filter, disposed between the first port and the second port, said lattice bulk acoustic wave filter having a first end coupled to the first port, and a second end; a balun coupled between the second port and the second end of the lattice filter; a further bulk acoustic wave filter having a first end coupled to the third port, and a second end coupled to the second port; and a phase shifting means coupled between the lattice bulk acoustic wave filter and the further bulk acoustic wave filter for matching the lattice bulk acoustic wave filter and the further bulk acoustic wave filter, wherein the balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the second port, and the first and second signal output ends are connected to the second end of the lattice bulk acoustic wave filter.

Claim 36

The duplexer of claim 26 , wherein the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness, the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness, the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the first thickness, and the second resonator of the balun includes a piezolectic layer having a fourth thickness substantially equal to the second thickness.

Claim 37

The duplexer of claim 27 , wherein the first thickness is greater than the second thickness.

Claim 38

The duplexer of claim 27 , wherein the first thickness is smaller than the second thickness.

Claim 39

The duplexer of claim 26 , further comprising a further balun coupled between the phase shifting means and the further bulk acoustic wave filter, wherein said further balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the phase shifting means and the signal output ends are connected to the second end of the further bulk acoustic wave filter.

Claim 40

The duplexer of claim 30 , wherein the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness, the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness, the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the first thickness, the second resonator of the balun includes a piezoelectric layer having a fourth thickness substantially equal to the second thickness, the first resonator of the further balun includes a piezoelectric layer having a fifth thickness substantially equal to the third thickness, and the second resonator of the further balun includes a piezoelectric layer having a sixth thickness substantially equal to the fourth thickness.

Claim 41

The duplexer of claim 31 , wherein the first thickness is greater than the second thickness.

Claim 42

The duplexer of claim 31 , wherein the first thickness is smaller than the second thickness.

Claim 43

The duplexer of claim 30 , wherein the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness, the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness, the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the second thickness, the second resonator of the balun includes a piezoelectric layer having a fourth thickness substantially equal to the first thickness, the first resonator of the further balun includes a piezoelectric layer having a fifth thickness substantially equal to the third thickness, and the second resonator of the further balun includes a piezoelectric layer having a sixth thickness substantially equal to the fourth thickness.

Claim 44

The duplexer of claim 34 , wherein the first thickness is greater than the second thickness.

Claim 45

The duplexer of claim 34 , wherein the first thickness is smaller than the second thickness.

Claim 46

The duplexer of claim 26 , wherein the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness, the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness, the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the second thickness, and the second resonator of the balun includes a piezolectic layer having a fourth thickness substantially equal to the first thickness.

Claim 47

The duplexer of claim 37 , wherein the first thickness is smaller than the second thickness.

Claim 48

The duplexer of claim 37 , wherein the first thickness is greater than the second thickness.

Claim 49

The duplexer of claim 26 , wherein the further bulk acoustic wave filter comprises a further lattice bulk acoustic wave filter.

Claim 50

The duplexer of claim 26 , wherein the further bulk acoustic wave filter comprises a ladder bulk acoustic wave filter.

Claim 51

The duplexer of claim 41 , further comprising a further balun disposed between the ladder bulk acoustic wave filter and the third port, wherein said further balun having at least two resonators in a stacked-up configuration including a first resonator coupled between a signal input end and the device ground, and a second resonator coupled between a first signal end and a second signal end, wherein the signal input end is connected to the first end of the ladder bulk acoustic device, and the signal output ends are connected to the third port.

Claim 52

The duplexer of claim 42 , wherein the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness, the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness, the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the second thickness, the second resonator of the balun includes a piezoelectric layer having a fourth thickness substantially equal to the first thickness, the first resonator of the further balun includes a piezoelectric layer having a fifth thickness substantially equal to the third thickness, and the second resonator of the further balun includes a piezoelectric layer having a sixth thickness substantially equal to the fourth thickness.

Claim 53

The duplexer of claim 43 , wherein the first thickness is greater than the second thickness.

Claim 54

The duplexer of claim 43 , wherein the first thickness is smaller than the second thickness.

Claim 55

The duplexer of claim 42 , wherein the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness, the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness, the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the first thickness, the second resonator of the balun includes a piezoelectric layer having a fourth thickness substantially equal to the second thickness, the first resonator of the further balun includes a piezoelectric layer having a fifth thickness substantially equal to the third thickness, and the second resonator of the further balun includes a piezoelectric layer having a sixth thickness substantially equal to the fourth thickness.

Claim 56

The duplexer of claim 46 , the first thickness is greater than the second thickness.

Claim 57

The duplexer of claim 46 , wherein the first thickness is smaller than the second thickness.