Browse Prior Art Database

Generation of Acoustic Surface Waves in Nonpiezoelectric Materials

IP.com Disclosure Number: IPCOM000083741D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 19K

Publishing Venue

IBM

Related People

Fleming, DJ: AUTHOR [+2]

Abstract

Filters for communications applications may be fabricated by employing acoustic surface waves generated in nonpiezoelectric materials. Such filters have improved characteristics from a reliability, performance and cost stand point relative to analog counterparts.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 74% of the total text.

Page 1 of 2

Generation of Acoustic Surface Waves in Nonpiezoelectric Materials

Filters for communications applications may be fabricated by employing acoustic surface waves generated in nonpiezoelectric materials. Such filters have improved characteristics from a reliability, performance and cost stand point relative to analog counterparts.

A diffused resistor is formed in a silicon or germanium substrate by well- known semiconductor processing steps. Applying an electrical signal to the resistor introduces a localized strain in the substrate by a thermal gradient, due to I/2/R heating of the resistor from the electrical input signal. The strain generates an acoustic surface wave in the substrate. Strain (E) is defined as: E = Delta L over L where; L is the length of the resistor. Delta L is the change in the resistor length due to I/2/R heating.

The strain may be computed as follows after substituting for: . Delta L over L: E = K Delta T over T where; K is the temperature coefficient of expansion of the resistor. T is the temperature of the substrate. Delta T is the change in temperature of the substrate.

The magnitude of strain introduced is extremely geometry dependent, but typically five milliwatts of power will product 0.2 degrees C gradient resulting in a strain of approximately 10/-6/ centimeter/centimeter. Assuming a gage factor of 100 for piezoresistor detectors, an output signal of one millivolt can be expected.

The temperature and strain are proportional to the si...