# US 7,408,284 B1 · Center chirping within series connected interdigitated transducers

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- Number: US 7,408,284 B1
- Document ID: US7408284B1
- Status: Granted
- Kind: B1
- Application number: 11/431,988
- Filed: 2006-05-11
- Granted: 2008-08-05
- Earliest claimed: 2005-05-24
- Assignees: RF Micro Devices, Inc.
- Inventors: Aleh Loseu; Jayanti Jaganatha Rao
- Web page: https://patentgrep.com/patent/US7408284B1

## CPC

- H03H 9/6406: {Filters characterised by a particular frequency characteristic}
- H03H 9/0038: {the balanced terminals being on the same side of the track}
- H10W 74/00: Encapsulations, e.g. protective coatings
- H10W 90/724: {between a chip and a stacked insulating package substrate, interposer or RDL}
- H10W 90/754: {between a chip and a stacked insulating package substrate, interposer or RDL}
- Y10T 29/42: Piezoelectric device making
- Y10T 29/49005: Acoustic transducer
- Y10T 29/4908: Acoustic transducer
- Y10T 29/49128: Assembling formed circuit to base
- Y10T 29/49155: Manufacturing circuit on or in base
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A SAW architecture is provided with two acoustic reflectors formed on a piezoelectric substrate defining an acoustic cavity between the acoustic reflectors. At least one alpha IDT may be provided, and at least three beta IDTs are provided. These IDTs are placed in acoustic series within the acoustic cavity. The alpha IDT is electrically coupled to a first interface. The beta IDTs are coupled in electrical and acoustic series and associated with a second interface. In certain embodiments, the at least three beta IDTs are adjacent one another, while in other embodiments an additional reflector or an alpha IDT may be placed between two beta IDTs. The beta IDTs include two outer beta IDTs and an inner beta IDT located between the two outer beta IDTs. The inner beta IDT may be chirped in a center portion, wherein the area outside of the center portion is not chirped.

## Claims

### Claim 1

A surface acoustic wave device comprising:
a piezoelectric substrate;
two acoustic reflectors formed on the piezoelectric substrate and defining an acoustic cavity between the acoustic reflectors; and
at least three beta interdigitated transducers (IDTs) formed adjacent one another on the piezoelectric substrate in electrical series with each other and aligned in acoustic series with each other between the acoustic reflectors, such that the at least three beta IDTs comprise at least one inner beta IDT between two outer beta IDTs, a center portion of the at least one inner beta IDT being chirped.

### Claim 2 (depends on 1)

The surface acoustic wave device of claim 1 wherein edge portions of the at least one inner beta IDT are not chirped.

### Claim 3 (depends on 1)

The surface acoustic wave device of claim 1 wherein center portions of the at least two outer beta IDTs are not chirped.

### Claim 4 (depends on 1)

The surface acoustic wave device of claim 1 further comprising at least one alpha IDT formed on the piezoelectric substrate between the acoustic reflectors and coupled in acoustic series with the at least three beta IDTs within the acoustic cavity.

### Claim 5 (depends on 4)

The surface acoustic wave device of claim 4 wherein the at least one alpha IDT comprises at least two alpha IDTs coupled in electrical parallel with each other and aligned in acoustic series with each other.

### Claim 6 (depends on 5)

The surface acoustic wave device of claim 5 wherein the at least one alpha IDT is located in acoustic series with and between two of the at least three beta IDTs.

### Claim 7 (depends on 4)

The surface acoustic wave device of claim 4 wherein the at least one alpha IDT is electrically coupled to a first interface and the at least three beta IDTs are electrically coupled to a second interface.

### Claim 8 (depends on 7)

The surface acoustic wave device of claim 7 wherein the first interface is associated with a first electrical impedance and the second interface is associated with a second electrical impedance, such that an electrical impedance transformation is provided between the first interface and the second interface.

### Claim 9 (depends on 7)

The surface acoustic wave device of claim 7 wherein the at least one alpha IDT and the at least three beta IDTs cooperate to provide a filter response between the first interface and the second interface.

### Claim 10 (depends on 7)

The surface acoustic wave device of claim 7 wherein the first interface is an input and the second interface is an output.

### Claim 11 (depends on 7)

The surface acoustic wave device of claim 7 wherein the first interface is an output and the second interface is an input.

### Claim 12 (depends on 4)

The surface acoustic wave device of claim 4 wherein adjacent edges of the at least one alpha IDT and at least one of the at least three beta IDTs are chirped.