Pressure sensor using elements operating with acoustic surface waves (saw elements)

• US 6,003,378 A
• Filed: 09/12/1997
• Issued: 12/21/1999
• Est. Priority Date: 09/13/1996
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Scherr, Holger, Scholl, Gerd
• Primary Examiner(s): OEN, WILLIAM L
• Application Number:
  US08/928,928
• Time in Patent Office: 830 Days
• Field of Search: 73/703, 73/723, 310/313 B, 310/313 D, 310/313 A
• US Class Current: 73/703
• CPC Class Codes: G01L 9/0025 with acoustic surface waves

Abstract

A pressure sensor with a reflective acoustic surface wave (SAW) delay line fashioned on a pressure-sensing membrane having at least three reflectors wherein the delay line extends over both an expanding region and a compressing region of the pressure-sensing membrane.

Claims

1. A pressure sensor, comprising:

a pressure-sensing membrane having an expanding region and a compressing region;

a reflective acoustic surface wave delay line on the pressure-sensing membrane, the delay line extending over both the expanding region and the compressing region and being the only delay line of the pressure sensor;

a first reflector arranged in the expanding region of the pressure-sensing membrane;

a second reflector arranged in the compressing region of the pressure-sensing membrane; and

a third reflector arranged between the first reflector and the second reflector.

2. A pressure sensor as claimed in claim 1, further comprising:

a piezoelectric substrate as the pressure-sensing membrane.

3. A pressure sensor as claimed in claim 1, wherein the third reflector is arranged in a neutral transition region between the expanding region and the compressing region of the pressure-sensing membrane.

4. A pressure sensor as claimed in claim 1, further comprising:

a fourth reflector arranged closely to one of the at least three reflectors on the delay line wherein, given maximum pressure, a phase displacement of at most 360°

occurs between acoustic surface waves reflected at the fourth reflector and the one of the at least three reflectors.

5. A pressure sensor as claimed in claim 1, further comprising:

a fourth reflector arranged approximately in the center between two of the at least three reflectors.

6. A pressure sensor as claimed in claim 1, wherein the at least three reflectors on the delay line are arranged in a single acoustic track on the pressure-sensing membrane.

7. A pressure sensor as claimed in claim 1, wherein the at least three reflectors on the delay line are arranged in at least two acoustic tracks on the pressure-sensing membrane, the at least two acoustic tracks coupled with a diverter.

8. A pressure sensor as claimed in claim 1, further comprising:

an input/output interdigital converter on the delay line, the converter coupled to an antenna that receives an interrogation signal via radio and radiates a response signal thereto.