Monolithic crystal filter with auxiliary filter shorting tabs

Claim 2

A monolithic crystal filter comprising, in combination, a piezoelectric crystal body member sandwiched between at least three spaced electrode pairs, means shorting a first one of said pairs, said shorting means comprising an auxiliary filter tuned to a passband having a center frequency that differs from the center frequency of the passband of said monolithic crystal filter, said auxiliary filter including an auxiliary pair of electrodes sandwiching said body member to form an auxiliary monolithic crystal filter, said auxiliary pair of electrodes being mass loaded to reflect energy back into the trapped energy zone of the resonator formed by said first one of said pairs, whereby energy dissipation in said shorting means is avoided and overall filter efficiency is enhanced.

Claim 3

Apparatus in accordance with claim 1 wherein said monolithic crystal filter is of the thickness-shear type and wherein said auxiliary filter is of the thickness-twist type.

Claim 4

Apparatus in accordance with claim 1 wherein the electrodes of said first pair are in substantial alignment on opposite sides of said body, said auxiliary pair of electrodes being non-aligned, one positioned between one of said first pair and one boundary of said body and the other between the other of said first pair and an opposite boundary of said body, said shorting means including first thin film conducting means connecting each of said first pair of electrodes to the adjacent one of said auxiliary pair of electrodes and second thin film conducting means extending between each of said auxiliary pair of electrodes and the adjacent one of said boundaries, said shorting means further including first means connecting said second thin film conducting means to each other.

Claim 5

Apparatus in accordance with claim 3 wherein said auxiliary electrodes are substantially thicker than said first one of said pairs.

Claim 6

Apparatus in accordance with claim 3 including means connecting said first connecting means to a reference potential.

Claim 7

A monolithic crystal filter comprising, in combination, a piezoelectric crystal body member sandwiched between input and output electrode pairs and between a plurality of intermediate electrode pairs, respective means shorting each of said intermediate electrode pairs, each of said respective shorting means comprising a respective auxiliary filter tuned to a passband having a center frequency that differs from the center frequency of the passband of said monolithic crystal filter, each of said auxiliary filters including a respective auxiliary pair of electrodes sandwiching said body member to form a respective auxiliary monolithic crystal filter, each of said auxiliary pair of electrodes being mass loaded to reflect energy back into the trapped energy zone of the resonator formed by the corresponding one of said plurality of intermediate electrode pairs, whereby energy dissipation is avoided and overall filter efficiency is enhanced.

Claim 8

A monolithic crystal filter comprising, in combination, a piezoelectric crystal body member sandwiched between input and output electrode pairs and between a plurality of intermediate electrode pairs, respective means shorting each of said intermediate electrode pairs, each of said respective shorting means comprising a respective auxiliary filter tuned to a passband having a center frequency that differs from the center frequency of the passband of said monolithic crystal filter, each of said auxiliary filters including a respective auxiliary pair of electrodes sandwiching said body member to form a respective auxiliary monolithic crystal filter, each of said auxiliary pair of electrodes being mass loaded to reflect energy back into the trapped energy zone of the resonator formed by the corresponding one of said plurality of intermediate electrode pairs, whereby energy dissipation is avoided and overall filter efficiency is enhanced.

Claim 9

Apparatus in accordance with claim 6 wherein each of said auxiliary filters comprises a composite of different mass loaded regions each in conductive contact with at least one adjacent one of said regions and each of the electrodes of said intermediate pairs being in conductive contact with a respective one of said regions.

Claim 10

Apparatus in accordance with claim 7 wherein each composite of said regions comprises first and second auxiliary electrodes each spaced Between a respective one of the electrodes of one of said intermediate electrode pairs and a respective boundary portion of said crystal body, first conducting means connecting each of said auxiliary electrodes to a corresponding one of said intermediate electrodes, second conducting means between each of said auxiliary electrodes and a respective one of said boundary portions, and third conducting means connecting said second conducting means.

Claim 11

Apparatus in accordance with claim 8 wherein said first and second conducting means comprises thin film portions exceeded substantially in thickness by said electrodes.

Claim 12

Apparatus in accordance with claim 9 wherein the thickness of said auxiliary electrodes exceeds the thickness of said intermediate electrode pairs.