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Surface Acoustic Wave Harmonic Response Cancellation Technique

IP.com Disclosure Number: IPCOM000083772D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Moulic, JR: AUTHOR [+2]

Abstract

The use of split-finger electrodes in surface acoustic wave (SAW) devices has proved beneficial in suppressing unwanted electrode reflections. However, the geometry of the electrodes is such as to favor the generation of not only a fundamental response, but a third-harmonic response. This property has allowed SAW devices to operate at much higher frequencies than before.

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Surface Acoustic Wave Harmonic Response Cancellation Technique

The use of split-finger electrodes in surface acoustic wave (SAW) devices has proved beneficial in suppressing unwanted electrode reflections. However, the geometry of the electrodes is such as to favor the generation of not only a fundamental response, but a third-harmonic response. This property has allowed SAW devices to operate at much higher frequencies than before.

In system applications, the higher or lower harmonics may be undesirable to the user and must be removed by filtering schemes external to the SAW device. The present arrangement is an alternative method of removing the undesired responses by modifying the SAW transducer pattern; thus, eliminating the need for further external component filtering.

The technique is to divide either the input or output transducer in half along the acoustic propagation axis, and slide one side a fraction of a wavelength with respect to the other. Thus, the signal received at any point in time by one half of the transducer will cancel with the signal received by the other half. By properly selecting the amount of offset, (see Figs. 2 and 3) either the third harmonic or the fundamental can be removed.

This modification can be made during the original pattern design. Since the cancellation effect is determined by the geometry of the pattern, no external manual tuning is required after fabrication making the technique relatively simple and considerably cheape...