US 5,334,960 A · Conjugately matched acoustic wave transducers and method

Abstract

A filter device comprises an acoustic wave propagating substrate having an effective coupling coefficient k.sup.2 and having a first filter and a second filter disposed on the acoustic wave propagating substrate. The first filter comprises a first electro-acoustic transducer and a first acousto-electric transducer, both disposed on the acoustic wave propagating substrate. The first acousto-electric transducer comprises N.sub.1 many electrode pairs, wherein N.sub.1 .gtoreq.C/k.sup.2. C is a constant having a value in the range from 1 to 2. The first acousto-electric transducer is acoustically coupled to the first electro-acoustic transducer. The second filter comprises a second electro-acoustic transducer and a second acousto-electric transducer, both disposed on the acoustic wave propagating substrate. The second electro-acoustic transducer is electrically coupled to the first acousto-electric transducer. The second electro-acoustic transducer comprises N.sub.2 many electrode pairs, wherein N.sub.2 <C/k.sup.2. The second acousto-electric transducer is acoustically coupled to the second electro-acoustic transducer.

Claims17

Dependent claims

A method for forming a filter, the method comprising steps of:

(a) providing an acoustic wave propagating substrate having an effective coupling coefficient k.sup.2 ;
(b) disposing a first electro-acoustic transducer on the acoustic wave propagating substrate;
(c) disposing a first acousto-electric transducer having a length M.sub.1 on the acoustic wave propagating substrate, the first acousto-electric transducer having N.sub.1 many electrode pairs therein, wherein N.sub.1 .gtoreq.C/k.sup.2, C being a constant having a value in the range from 1 to 2, the first acousto-electric transducer being acoustically coupled to the first electro-acoustic transducer;
(d) disposing a second acousto-electric transducer on the acoustic wave propagating substrate;
and
(e) disposing a second electro-acoustic transducer having a length M.sub.2 on the acoustic wave propagating substrate, wherein M.sub.2 is more than M.sub.1, the second electro-acoustic transducer being electrically coupled and conjugately impedance matched to the first acousto-electric transducer, the second electro-acoustic transducer having N.sub.2 many electrode pairs therein, wherein N.sub.2 <N.sub.1, the second electro-acoustic transducer being acoustically coupled to the second acousto-electric transducer.

3 more elements

A method for forming a filter, the method comprising steps of:

(a) providing an acoustic wave propagating substrate having an effective coupling coefficient k.sup.2 ;
(b) disposing a first electro-acoustic transducer on the acoustic wave propagating substrate;
(c) disposing a first acousto-electric transducer having a first electrical admittance Y.sub.1 =G.sub.1 +jX.sub.1 on the acoustic wave propagating substrate, wherein G.sub.1 is a first real conductance and X.sub.1 is a first imaginary conductance, the first imaginary conductance X.sub.1 having a negative value over at least a first frequency range, the first acousto-electric transducer having N.sub.1 many electrode pairs therein, wherein N.sub.1 .gtoreq.C/k.sup.2, C being a constant having a value in the range from 1 to 2, the first acousto-electric transducer being acoustically coupled to the first elector-acoustic transducer;
(d) disposing a second acousto-electric transducer on the acoustic wave propagating substrate;
and
(e) disposing a second electro-acoustic transducer having a second electrical admittance Y.sub.2 =G.sub.2 +jX.sub.2 on the acoustic wave propagating substrate, wherein G.sub.2 is a second real conductance and X.sub.2 is a second imaginary conductance, the second imaginary conductance X.sub.2 having a positive value over at least the first frequency range, wherein the first and second real conductances G.sub.1 and G.sub.2 are approximately equal over the first frequency range and wherein magnitudes of the first and second imaginary conductances X.sub.1 and X.sub.2 are approximately equal over the first frequency range, the second electro-acoustic transducer being electrically coupled and conjugately impedance matched to the first acousto-electric transducer, the second electro-acoustic transducer having N.sub.2 many electrode pairs therein, wherein N.sub.2 <N.sub.1, the second electro-acoustic transducer being acoustically coupled to the second acousto-electric transducer.

3 more elements

A filter device comprising:

(a) an acoustic wave propagating substrate having an effective coupling coefficient k.sup.2 ;
(b) a first filter comprising:
(b1) a first electro-acoustic transducer disposed on said acoustic wave propagating substrate, said first electro-acoustic transducer for converting a first electric signal into a first acoustic signal;
and
(b2) a first acousto-electric transducer disposed on said acoustic wave propagating substrate, said first acousto-electric transducer for converting said first acoustic signal into a second electric signal, said first acousto-electric transducer having N.sub.1 many electrode pairs therein, wherein N.sub.1 .gtoreq.C/k.sup.2, C being a constant having a value in a range from 1 to 2, said first acousto-electric transducer being acoustically coupled to said first electro-acoustic transducer, wherein said first acousto-electric transducer has a first electrical admittance Y.sub.1 =G.sub.1 +jX.sub.1, wherein G.sub.1 is a first real conductance and X.sub.1 is a first imaginary conductance, said first imaginary conductance X.sub.1 having a negative value over at least a first frequency range;
and
(c) a second filter comprising:
(c1) a second electro-acoustic transducer disposed on said acoustic wave propagating substrate, said second electro-acoustic transducer being electrically coupled to said first acousto-electric transducer, said second electro-acoustic transducer for converting said second electric signal to a second acoustic signal, said second electro-acoustic transducer having N.sub.2 many electrode pairs therein, wherein N.sub.2 <N.sub.1, wherein said second electro-acoustic transducer has a second electrical admittance Y.sub.2 =G.sub.2 +jX.sub.2, wherein G.sub.2 is a second real conductance and X.sub.2 is a second imaginary conductance, said second imaginary conductance X.sub.2 having a positive value over at least said first frequency range;
and
(c2) a second acousto-electric transducer disposed on said acoustic wave propagating substrate, said second electro-acoustic transducer being acoustically coupled to said second acousto-electric transducer, said second acousto-electric transducer for converting said second acoustic signal to a third electrical signal, said third electrical signal corresponding to a filtered and delayed version of said first electrical signal.

7 more elements

A filter including in combination:

a substrate for propagating acoustic waves;
a first electro-acoustic transducer disposed on said substrate, said first electro-acoustic transducer for generating first acoustic waves in response to a first electrical signal applied to said first electro-acoustic transducer;
a first inductive acoustic transducer disposed on said substrate, said first inductive acoustic transducer acoustically coupled to said first electro-acoustic transducer, said first inductive acoustic transducer having a first electrical admittance Y.sub.1 =G.sub.1 +jX.sub.1, wherein G.sub.1 is a first real conductance and X.sub.1 is a first imaginary conductance, said first imaginary conductance X.sub.1 having a negative value over at least a first frequency range, said first inductive acoustic transducer for generating a second electrical signal in response to said first acoustic waves;
a first capacitive acoustic transducer disposed on said substrate, said first capacitive acoustic transducer electrically coupled to said first inductive acoustic transducer, said first capacitive acoustic transducer having a second electrical admittance Y.sub.2 =G.sub.2 +jX.sub.2, wherein G.sub.2 is a second real conductance and X.sub.2 is a second imaginary conductance, said second imaginary conductance X.sub.2 having a positive value over at least said first frequency range, said first capacitive acoustic transducer for generating second acoustic waves in response to said second electrical signal;
a first acousto-electric transducer disposed on said substrate, said first acousto-electric transducer acoustically coupled to said first capacitive acoustic transducer, said first acousto-electric transducer for generating a third electrical signal in response to said second acoustic waves, said third electrical signal providing a filtered version of said first electrical signal;
wherein said first and second real conductances G.sub.1 and G.sub.2 are approximately equal over said first frequency range;
and
wherein magnitudes of said first and second imaginary conductances X.sub.1 and X.sub.2 are approximately equal over said first frequency range.

5 more elements

A filter device comprising:

(a) an acoustic wave propagating substrate having an effective coupling coefficient k.sup.2 ;
(b) a first filter comprising:
(b1) a first electro-acoustic transducer disposed on said acoustic wave propagating substrate;
and
(b2) a first acousto-electric transducer disposed on said acoustic wave propagating substrate, said first acousto-electric transducer having a first electrical admittance Y.sub.1 =G.sub.1 +jX.sub.1, wherein G.sub.1 is a first real conductance and X.sub.1 is a first imaginary conductance, said first imaginary conductance X.sub.1 having a negative value over at least a first frequency range, said first acousto-electric transducer being acoustically coupled to said first electro-acoustic transducer;
and
(c) a second filter comprising:
(c1) a second acousto-electric transducer disposed on said acoustic wave propagating substrate;
and
(c2) a second electro-acoustic transducer disposed on said acoustic wave propagating substrate, said second electro-acoustic transducer being electrically coupled to said first acousto-electric transducer, said second electro-acoustic transducer having a second electrical admittance Y.sub.2 =G.sub.2 +jX.sub.2, wherein G.sub.2 is a second real conductance and X.sub.2 is a second imaginary conductance, said second imaginary conductance X.sub.2 having a positive value over at least said first frequency range, said second electro-acoustic transducer being acoustically coupled to said second acousto-electric transducer;
and
wherein said first and said second electrical admittances substantially obey a relation:
.vertline.Y.sub.2.sup.* -Y.sub.1 .vertline./.vertline.Y.sub.2.sup.* +Y.sub.1 .vertline.<.delta.,
wherein .delta. is a parameter describing admittance mismatch between said first acousto-electric transducer and said second electro-acoustic transducer.

11 more elements

In a radio frequency apparatus, a filter comprising:

(a) an acoustic wave propagating substrate having an effective coupling coefficient k.sup.2 ;
(b) a first filter comprising:
(b1) a first electro-acoustic transducer disposed on said acoustic wave propagating substrate;
and
(b2) a first acousto-electric transducer disposed on said acoustic wave propagating substrate, said first acousto-electric transducer having N.sub.1 many electrode pairs therein, wherein N.sub.1 .gtoreq.C/k.sup.2, C being a constant having a value in a range from 1 to 2, said first acousto-electric transducer being acoustically coupled to said first electro-acoustic transducer, wherein said first acousto-electric transducer has a first electrical admittance Y.sub.1 =G.sub.1 +jX.sub.1, wherein G.sub.1 is a first real conductance and X.sub.1 is a first imaginary conductance, said first imaginary conductance X.sub.1 having a negative value over at least a first frequency range;
and
(c) a second filter comprising:
(c1) a second acousto-electric transducer disposed on said acoustic wave propagating substrate;
and
(c2) a second electro-acoustic transducer disposed on said acoustic wave propagating substrate, said second electro-acoustic transducer being electrically coupled to said first acousto-electric transducer, said second electro-acoustic transducer having N.sub.2 many electrode pairs therein, wherein N.sub.2 <N.sub.1, said second electro-acoustic transducer being acoustically coupled to said second acousto-electric transducer, wherein said second electro-acoustic transducer has a second electrical admittance Y.sub.2 =G.sub.2 +jX.sub.2, wherein G.sub.2 is a second real conductance and X.sub.2 is a second imaginary conductance, said second imaginary conductance X.sub.2 having a positive value over at least said first frequency range;
wherein said first and second real conductances G.sub.1 and G.sub.2 are approximately equal over said first frequency range;
and
wherein magnitudes of said first and second imaginary conductances X.sub.1 and X.sub.2 are approximately equal over said first frequency range.

10 more elements

Dependencies are inferred from the claim text.

Conjugately matched acoustic wave transducers and method

Life of this patent

Conjugately matched acoustic wave transducers and method

Life of this patent

Abstract

Claims17