Campbell Surface Acoustic Wave Devices and Their Signal Processing Applications

1. Auflage 2012
ISBN: 978-0-323-14866-5
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 484 Seiten

Surface Acoustic Wave Devices and Their Signal Processing Applications is a textbook that combines experiment and theory in assessing the signal processing applications of surface acoustic wave (SAW) devices. The operating principles of SAW devices are described from a circuit design viewpoint. This book is comprised of 18 chapters and begins with a historical background on surface acoustic waves and a discussion on the merits of SAW devices as well as their applications. The next chapter introduces the reader to the basics of acoustic waves and piezoelectricity, together with the effect of acoustic bulk waves on the performance of SAW filters. The principles of linear phase SAW filter design and equivalent circuit models for a SAW filter are then described. The remaining chapters focus on trade-offs in linear phase SAW filter design; compensation for second-order effects; harmonic SAW delay lines for gigahertz frequencies; and coding techniques using linear SAW transducers. The final chapter highlights Some other significant alternative design techniques and applications for SAW devices. This monograph will be suitable for engineering or physics students as well as engineers, scientists, and technical staff in industry who seek further information on SAW-based circuits, systems, and applications.

Autoren/Hrsg.

Campbell, Colin

Leseproben

1

Introduction

Publisher Summary

This chapter outlines the operating principles of surface acoustic wave (SAW) devices from the viewpoint of a circuit design. Devices and systems based on SAW technology have several excellent features when compared to competing technologies. SAW devices can generally be designed to provide quite complex signal processing functions within a single package. SAW devices can be mass produced using semiconductor micro-fabrication techniques. As these can be implemented in small, rugged, light, and power-efficient modules, these devices are finding ever-increasing application in mobile and space-borne communications systems. Though SAW devices are analog devices, they can be employed in many digital communications systems. Moreover, SAW filters can be made to operate very efficiently at high-harmonic modes. The signal processing and frequency response characteristics of a SAW device on a piezoelectric substrate are primarily governed by the geometry of the metal-film interdigital transducers (IDTs) deposited on the substrate. The transducers and device structures can be grouped into four general categories. The first three categories relate to the SAW devices on piezoelectric substrates where the signal levels are small enough for the acoustoelectric interactions to be considered linear. The fourth category relates to the SAW devices that utilize the weak nonlinear response of the piezoelectric under high signal level excitation.

1.1 Historical Background

Surface acoustic waves can be generated at the free surface of an elastic solid. This phenomenon has been exploited for electronic analog signal processing over the past 20 years, with the development of a host of devices and systems for consumer, commercial and military applications running at a multimillion dollar annual rate. While this is a comparatively new electronic technology, it has its roots in scientific findings that date back over the past 100 years. Indeed, a mathematical discussion on the propagation of surface acoustic waves at the free surface of a homogeneous isotropic elastic solid was first reported by Lord Rayleigh in an address to the London Mathematical Society on 12 November 1855 [1]. His paper begins with the statement “… It is proposed to investigate the behaviour of waves upon the plane free surface of an infinite homogeneous isotropic elastic solid, their character being such that the disturbance is confined to a superficial region, of thickness comparable with the wavelength…” It concludes with the observation “… it is not improbable that the surface waves investigated play an important part in earthquakes, and in the collision of elastic solids. Diverging in two dimensions only, they must acquire at a great distance from the source a continually increasing preponderance …” The presence of these surface acoustic waves (also known as Rayleigh waves) in earthquake shocks was later verified using seismograph recording techniques.

It was not until 1965, however, that the phenomenon of surface acoustic wave (SAW) propagation was first exploited for its applications to electronic devices. This was with the invention of the (IDT) by White and Voltmer at the University of California [2] as a most efficient technique for the generation and detection of SAW waves on a piezoelectric surface. Before this major discovery, applications of acoustic wave processes to solid-state electronic device technology had been principally restricted to piezoelectric transducers employing acoustic wave phenomena (such as “conventional” quartz crystals for oscillator circuit design). The advent of the IDT opened up the gateway to a new and most versatile approach to the design of analog electrical filters operating at selected frequencies in the range from about 10 MHz to 1 GHz or above. This immediately generated two major electrical engineering product design challenges, with quite divergent thrusts. At one end of the scale, in the high-volume, low-cost TV component market, the challenge related to whether or not mass-produced SAW filters could be competitive in price and performance with inductance-capacitance (LC) filters currently employed in the intermediate-frequency (IF) circuit stages. At the opposite extreme, relating to low-volume, high-cost components for radar signal-processing, maximum emphasis was given to the efficient implementation of SAW pulse compression filters with very large compression gains. Between these extremes, a wide range of other SAW device configurations and applications started to receive intensive research scrutiny.

Initially, principal research activities in North America in the late 1960s relating to SAW device applications were limited to a few centers such as at Stanford University, Texas Instruments Inc., Hughes Aircraft Company and Lincoln Laboratory of the Massachusetts Institute of Technology. At the same time in England, the Royal Radar Establishment was actively involved in radar systems implementation of this technology. Only a few more years passed, however, before a host of other research laboratories in industry, government and universities around the world became involved in SAW device research.

The extent of this rapid expansion of SAW device research activity can perhaps be highlighted by a listing of of the participating laboratories publishing research papers on SAW devices within a 10-year period following White and Voltmer’s introduction of the interdigital transducer. By that time published research papers from industrial and government laboratories in North America included (in alphabetical order) those from Air Force Cambridge Research Laboratories, Anderson Laboratories Inc., Bell Laboratories, Hazeltine Corporation, Hughes Aircraft Company, Lincoln Laboratory at the Massachusetts Institute of Technology, Magnavox Company, Motorola Inc., Naval Undersea Center, Raytheon Research

Division, Rockwell International, Sperry Research Center, Tektronix Inc., Texas Instrument Inc., Westinghouse Electric Corporation and Zenith Radio Corporation. Universities in North America also publishing SAW research papers within this period included those of California, Carnegie-Mellon, McGill, Northwestern, Illinois, Pennsylvania, Purdue, Rensselaer Polytechnic, Stanford and Toronto.

In Britain, leading laboratories involved in SAW research at an early date included The General Electric Company, Mullard Research Laboratories, The Plessey Company, The Royal Radar Establishment (now the Royal Signals and Radar Establishment) and Standard Telecommunications Laboratories Limited, together with the University of Edinburgh, Queen Mary College and University College, London. In Norway, pioneering contributions to SAW research were emanating from the Norwegian Institute of Technology. In France, SAW research was well under way at centers such as Thomson-CSF and Centre National d’Etudes des Telecommunications, while in West Germany research activities were reported by the Institut fur Angewandte Festkorper-Physik. In Italy, SAW signal processing studies were conducted at the Istituto di Ricerca sulle Onde Elettromagnetiche CNR in Florence. Japanese laboratories with early publications of SAW research activities included Matsushita Research Institute, Tokyo Institute of Technology, Nippon Electric Company and Tohoku University.

This intensive research activity had rapid results in terms of applications to the consumer, commercial and military markets. In 1977, Wiliamson [3] listed 45 different types of SAW devices that had received development effort by that date, with varying degrees of success, including 10 major devices with exceptional performance that had already received widespread application. Developmental successes continued so that by 1985 (only 20 years after the introduction of the IDT), Hartmann [4] listed nine major consumer applications, nine major commercial applications and 18 major military applications of the technology.

1.2 Merits of Saw Devices

As noted by Hartmann in a review paper on the systems impact of modern SAW device technology [4], many SAW-based devices and systems have several excellent features when compared to competing technologies. These include the following:

1. SAW devices can generally be designed to provide quite complex signal processing functions within a single package containing but a single piezoelectric substrate with superimposed thin-film input and output interdigital transducers. Thus, for example, SAW bandpass filters with outstanding response characteristics can now be routinely designed to achieve responses that would require several hundred inductors and capacitors in conventional LC-filter designs.

2. SAW devices can be mass produced using semiconductor microfabrication techniques. As a result, they can be made to be cost competitive in mass-volume applications, with some products selling for less than $1.00.

3. SAW devices can have outstanding reproducibility in performance, from device to device. This is especially desirable for the design and implementation of channelized receivers for spectral analyses of signals in electronic support measures (ESM). Indeed, the practical implementation of such channelized receivers has only been made possible since the arrival of SAW devices.

4. Since they can often be implemented in...