Hewlettpackard Journal
Technical In formation from the Laboratories of Hewlett-Packard Company
Contents:
Surface-Acoustic-Wave Delay Lines and Transversal Filters, by Waguih S. Ishak. H. Edward
Karrer, and William R. Shreve Generating and detecting minute ripples on the surface of a solid provides a way fo delay and/or filter electronic signals in a small space.
Surface-Acoustic-Wave Resonators, by Peter S. Cross and Scott S. Elliott By reflecting acoustic waves back and forth on the surface of a crystal one can obtain resonant devices for frequencies in the UHF range.
S AWR Fabrication, by Robert C. Bray and Yen C. Chu The process used to make surface-acoustic-wave resonators is similar in many ways to the processes used to make integrated circuits
280-MHz Production SAWR, by Marek E. Mierzwinski and Mark E. Terr/en It's the first SAW component designed for use in an HP instrument.
Physical Sensors using SAW Devices, by J. Fleming Dias Novel force and pressure transducers sense the effects of mechanical stress on surface wave velocity and resonant frequency.
Proximity Effect Correction by Means of Processing: Theory and Applications, by Paul
Rissman and Michael P. C. Watts Electron beam lithography can produce extremely fine geometries if electron scattering in target materials is kept under control.
Monte Carlo Simulations for Electron Beam Exposures, by Armand P. Neukermans and
Steven G. Eaton A computer model of electron scattering aids research into this effect. 1981 Index
In this Issue:
Most of this issue is about SAWs—not the cutting kind, with teeth, but surface acoustic waves. These are like the waves or ripples that radiate outwards from the spot where a pebble is dropped into a pond. Instead of water, the surface acoustic waves described in this issue propagate on the surface of a solid, such as a piece of quartz. Of course, the atoms in the solid don't move as much as the water molecules do; one can't even see these SAWs. But it turns out that by guiding and controlling these waves, it's possible to create electronic components that perform useful functions and have advantages over other ways of performing the same functions. SAW devices include delay lines, filters, resonators, sensors for temperature, pressure, force, or displacement, and various exotic processing devices such as correlators and convolvers. The waves are called acoustic not because you can hear them but because they are vibrational rather than electromagnetic waves. Their operating frequencies are by no means limited to audible frequencies. Some SAW devices operate in the gigahertz range and find applications in sophisticated radar systems.
The articles in this issue represent both an introduction to SAW devices and a discussion of the work being done on them at Hewlett-Packard. Delay lines and filters are described in the article on page 3. resonators on page 9 and sensors on page 18. The article on page 11 discusses how SAW resonators are made (many integrated circuit processing techniques are used) and the article on page 15 tells about the first SAW device used in an HP instrument, a 280-megahertz SAW resonator (pictured on this month's cover) that replaces a quartz crystal resonator in the 8558B and 8568A Spectrum Analyzers. Associate editor Ken Shaw had a good time editing these articles because he wrote his doctoral thesis many years ago on SAW devices. He's working on another article on SAW signal processing for an upcoming issue.
Among the integrated circuit techniques sometimes used in making SAWs is electron beam lithography. Our May 1981 issue was all about this technology and HP's high-speed electron beam lithography system. A fact of life in electron beam lithography is that electrons scatter when they hit a solid target, so when you try to expose very fine lines (less than a micrometre wide) very close together on a layer of electron-sensitive material, the contour of a given line may be affected by the presence of nearby lines. This is called proximity effect. On pages 21 and 24, four Hewlett-Packard scientists report on research into methods of controlling this effect.
December is our annual index issue. You'll find this year's index on pages 28-32.
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