Preface: digital signal processing and digital filter design

Digital signal processing (DSP) has existed as long as quantitative calculations have been systematically applied to data in Science, SocialScience, and Technology. The set of activities started out as a collection of ideas and techniques in very different applications. Around1965, when the fast Fourier transform (FFT) was rediscovered, DSP was extracted from its applications and became a single academic andprofessional discipline to be developed as far as possible.

One of the earliest books on DSP was by Gold and Rader [link] , written in 1968, although there had been earlier books on sampled data control andtime series analysis, and chapters in books on computer applications. In the late 60's and early 70's there was an explosion of activity in boththe theory and application of DSP. As the area was beginning to mature, two very important books on DSP were published in 1975, one by Oppenheimand Schafer [link] and the other by Rabiner and Gold [link] . These three books dominated the early courses in universities and self study in industry.

The early applications of DSP were in the defense, oil, and medical industries. They were the ones who needed and could afford theexpensive but higher quality processing that digital techniques offered over analog signal processing. However, as the theorydeveloped more efficient algorithms, as computers became more powerful and cheaper, and finally, as DSP chips became commodityitems (e.g. the Texas Instruments TMS-320 series) DSP moved into a variety of commercial applications and the current digitization ofcommunications began. The applications are now everywhere. They are tele-communications, seismic signal processing, radar and sonarsignal processing, speech and music signal processing, image and picture processing, entertainment signal processing, financial datasignal processing, medical signal processing, nondestructive testing, factory floor monitoring, simulation, visualization,virtual reality, robotics, and control. DSP chips are found in virtually all cell phones, digital cameras, high-end stereo systems,MP3 players, DVD players, cars, toys, the “Segway", and many other digital systems.

In a modern curriculum, DSP has moved from a specialized graduate course down to a general undergraduate course, and, in somecases, to the introductory freshman or sophomore EE course [link] . An exciting project is experimenting with teaching DSP in high schools andin colleges to non-technical majors [link] .

Our reason for writing this book and adding to the already long list of DSP books is to cover the new results in digital filter design that have becomeavailable in the last 10 to 20 years and to make these results available on line in Connexions as well as print. Digital filters are important parts ofa large number of systems and processes. In many cases, the use of modern optimal design methods allows the use of a less expensive DSP chip for aparticular application or obtaining higher performance with existing hardware. The book should be useful in an introductory course if the students havehad a course on discrete-time systems. It can be used in a second DSP course on filter design or used for self-study or reference in industry.