Monolithic crystal filters

Claim 2

A multipole monolithic filter comprising a crystal plate and four pairs of electrodes, the electrodes in each pair being in alignment on opposite sides of said plate so that each pair forms a resonator having a resonance frequency which is a function of the thickness of said plate and with the directions of acoustic coupling between adjacent pairs being at substantially right angles.

Claim 3

A filter as set forth in claim 1 wherein the lines between adjacent resonators form a Z-shape.

Claim 4

A filter as set forth in claim 1 wherein the lines between adjacent resonators form a U-shape.

Claim 5

A multipole monolithic filter comprising a circular AT-cut quartz plate and four pairs of generally sector-shaped electrodes, the electrodes in each pair being in alignment on opposite sides of said plate so that each pair forms a resonator having a resonance frequency which is a function of the thickness of said plate and the mass of the respective electrodes, the spacing between the first and fourth of said resonators being substantially greater than that between other resonator pairs thereby to reduce the acoustic coupling therebetween whereby said first and fourth resonators are acoustically coupled substantially only through said second and third resonators.

Claim 6

A multipole monolithic filter comprising a circular AT-cut quartz plate and four pairs of generally sector-shaped electrodes, the electrodes in each pair being in alignment on opposite sides of said plate so that each pair forms a resonator having a resonance frequency which is a function of the thickness of said plate and the mass of the respective electrodes, the spacing between the first and fourth of said resonators being substantially greater than that between other resonator pairs thereby to reduce the acoustic coupling therebetween whereby said first and fourth resonators are acoustically coupled substantially only through said second and third resonators.

Claim 7

A filter as set forth in claim 4 wherein the directions of acoustic coupling between successive resonators are along lines which are intermediate and substantially different from the X and Z'' axes of said plate.

Claim 8

A filter as set forth in claim 5 wherein said electrodes are substantially right angle sectors and the separation between the First and second resonators is equal to that between the third and fourth electrodes whereby the respective coupling coefficients are substantially equal.

Claim 9

A multipole monolithic filter comprising an AT-cut quartz plate of essentially uniform thickness which, together with a plurality of pairs of electrodes, comprises a plurality of resonators each of which is acoustically coupled to at least one of the other resonators through said quartz plate, each resonator being formed by one pair of electrodes with the electrodes in each pair being in alignment on opposite sides of said plate, the resonant frequency of each resonator being a function of the thickness of the plate and the mass of the respective electrodes, the direction of coupling between acoustically coupled resonators being intermediate and substantially different from the X and Z'' axes of said plate.

Claim 10

A multipole monolithic filter comprising an AT-cut quartz plate of essentially uniform thickness which, together with a plurality of pairs of electrodes, comprises a plurality of resonators each of which is acoustically coupled to at least one of the other resonators through said quartz plate, each resonator being formed by one pair of electrodes with the electrodes in each pair being in alignment on opposite sides of said plate, the resonant frequency of each resonator being a function of the thickness of the plate and the mass of the respective electrodes, the direction of coupling between acoustically coupled resonators being intermediate and substantially different from the X and Z'' axes of said plate.

Claim 11

A multipole monolithic filter comprising an AT-cut quartz plate of essentially uniform thickness which, together with at least three pairs of electrodes, comprises an input resonator, an intermediate resonator which is acoustically coupled to said input resonator through said quartz plate and an output resonator which is acoustically coupled to said intermediate resonator through said quartz plate, each resonator being formed by one pair of electrodes with the electrodes in each pair being in alignment on opposite sides of said plate, the resonant frequency of each resonator being a function of the thickness of the plate and the mass of the respective electrodes, the direction of coupling between acoustically coupled resonators being intermediate and substantially different from the X and Z'' axes of said plate.

Claim 12

A multipole monolithic filter comprising an AT-cut quartz plate of essentially uniform thickness which, together with at least three pairs of electrodes, comprises an input resonator, an intermediate resonator which is acoustically coupled to said input resonator through said quartz plate and an output resonator which is acoustically coupled to said intermediate resonator through said quartz plate, each resonator being formed by one pair of electrodes with the electrodes in each pair being in alignment on opposite sides of said plate, the resonant frequency of each resonator being a function of the thickness of the plate and the mass of the respective electrodes, the direction of coupling between acoustically coupled resonators being intermediate and substantially different from the X and Z'' axes of said plate.

Claim 13

A filter as set forth in claim 8 wherein the direction of acoustic coupling between said input resonator and said intermediate resonator lies in a different quadrant, relative to said X and Z'' axes, than the direction of coupling between said intermediate resonator and said output resonator.