The Scientist and Engineer's Guide to
Digital Signal Processing
By Steven W. Smith, Ph.D.
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Table of contents
- 1: The Breadth and Depth of DSP
- 2: Statistics, Probability and Noise
- 3: ADC and DAC
- 4: DSP Software
- 5: Linear Systems
- 6: Convolution
- 7: Properties of Convolution
- 8: The Discrete Fourier Transform
- 9: Applications of the DFT
- 10: Fourier Transform Properties
- 11: Fourier Transform Pairs
- 12: The Fast Fourier Transform
- 13: Continuous Signal Processing
- 14: Introduction to Digital Filters
- 15: Moving Average Filters
- 16: Windowed-Sinc Filters
- 17: Custom Filters
- 18: FFT Convolution
- 19: Recursive Filters
- 20: Chebyshev Filters
- 21: Filter Comparison
- 22: Audio Processing
- 23: Image Formation & Display
- 24: Linear Image Processing
- 25: Special Imaging Techniques
- 26: Neural Networks (and more!)
- 27: Data Compression
- 28: Digital Signal Processors
- 29: Getting Started with DSPs
- 30: Complex Numbers
- 31: The Complex Fourier Transform
- 32: The Laplace Transform
- 33: The z-Transform
- 34: Explaining Benford's Law
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Chapter 28: Digital Signal Processors
The DSP market is very large and growing rapidly. As shown in Fig.28-14, it will be about 8-10 billion dollars/year at the turn of thecentury, and growing at a rate of 30-40% each year. This is being fueledby the incessant
demand for better and cheaper consumer products, such as: cellulartelephones, multimedia computers, and high-fidelity music reproduction. These high-revenue applications are shaping the field, while lessprofitable areas, such as scientific instrumentation, are just riding thewave of technology.
DSPs can be purchased in three forms, as acore, as aprocessor, and asaboard level product. In DSP, the term "core" refers to the section ofthe processor where the key tasks are carried out, including the dataregisters, multiplier, ALU, address generator, and program sequencer. A completeprocessor requires combining the core with memory andinterfaces to the outside world. While the core and these peripheralsections are designed separately, they will be fabricated on the samepiece of silicon, making theprocessor a single integrated circuit.
Suppose you build cellular telephones and want to include a DSP in thedesign. You will probably want to purchase the DSP as aprocessor, thatis, an integrated circuit ("chip") that contains the core, memory andother internal features. For instance, the SHARC ADSP-21060 comesin a "240 lead Metric PQFP" package, only 35×35×4 mm in size. Toincorporate this IC in your product, you design a printed circuit boardwhere it will be soldered in next to your other electronics. This is themost common way that DSPs are used.
Now, suppose the company you work for manufactures its ownintegrated circuits. In this case, you might not want the entireprocessor,just the design of thecore. After completing the appropriate licensingagreement, you can start making chips that are highly customized toyour particular application. This gives you the flexibility of selectinghow much memory is included, how the chip receives and transmitsdata, how it is packaged, and so on. Custom devices of this type are anincreasingly important segment of the DSP marketplace.
Lastly, there are several dozen companies that will sell you DSPsalready mounted on a printed circuit board. These have such features asextra memory, A/D and D/A converters, EPROM sockets, multipleprocessors on the same board, and so on. While some of these boardsare intended to be used as stand alone computers, most are configuredto be plugged into a host, such as a personal computer. Companies thatmake these types of boards are calledThird Party Developers. The bestway to find them is to ask the manufacturer of the DSP you want to use. Look at the DSP manufacturer's website; if you don't find a list there,send them an e-mail. They will be more than happy to tell you who isusing their products and how to contact them.
The present day Digital Signal Processor market (1998) is dominated byfour companies. Here is a list, and the general scheme they use fornumbering their products:
Keep in mind that the distinction between DSPs and othermicroprocessors is not always a clear line. For instance, look at howIntel describes the MMX technology addition to its Pentium processor:
"Intel engineers have added 57 powerful new instructionsspecifically designed to manipulate and process video, audioand graphical data efficiently. These instructions areoriented to the highly parallel, repetitive sequences oftenfound in multimedia operations."
In the future, we will undoubtedly see more DSP-like functionsmerged into traditional microprocessors and microcontrollers. Theinternet and other multimedia applications are a strong driving force forthese changes. These applications are expanding so rapidly, in twentyyears it is very possible that the Digital Signal Processor maybe the"traditional" microprocessor.
How do you keep up with this rapidly changing field? The best way isto read trade journals that cover the DSP market, such as EDN(Electronic Design News,www.ednmag.com), and ECN (ElectronicComponent News,www.ecnmag.com). These are distributed free, andcontain up-to-date information on what is available and where theindustry is going. Trade journals are a "must-read" for anyone seriousabout the field. You will also want to be on the mailing list of severalDSP manufacturers. This will allow you to receive new productannouncements, pricing information, and special offers (such as freesoftware and low-cost evaluation kits). Some manufacturers alsodistribute periodic newsletters. For instance, Analog Devices publishesAnalog Dialogue four times a year, containing articles and informationon current topics in signal processing. All of these resources, and muchmore, can be contacted over the internet. Start by exploring themanufacturers' websites, and then sending them e-mail requestingspecific information.