Introduction to Digital Signal ProcessingOverview In the past two decades, the availability on new small, powerful and relatively inexpensive digital computers has increased dramatically, thanks to the applications of digital signal processing. This trend has been reinforced by the concurrent development of efficient numerical procedures for digital signal processing. Now digital signal processing has become a primary application for modern integrated circuit technology with high speed programmable chips capable of performing the operations required. So it is natural to find digital signal processing applied in many diverse areas such as speech signals, seismic signals, radar signal processing, image processing, and many others. Goal of this tutorial: The goal of this tutorial is motivate the reader to acquire techniques and basic concepts needed to investigate one or more of these applications areas through the use of Texas Instruments TMS320C3x DSP starter Kit (DSK). Why digital Systems? Digital signal processing was dependent on the digital computer and the majority of the mathematics or algorithms have thus been developed since 1950. Once these algorithms became established, designers started to look for the computer architectures that would implement them most effectively. The original goal was to proceed simulations that would run in an acceptable time. It is not clear when the idea of using digital computers for real signal processing instead of simulations took hold, but once it did, the objectives changed subtly. The ultimate goal became that the real-time DSP, i.e., the system having to complete all required operations in a time short enough for the process being operated on to continue unaffected. Earlier systems were only able to store the waveform in memory and process it later. Naturally, they could not make discussions based on the data at the time it was changing, hence the term non-real time. However, there are limits to what can be done with DSP systems and sometimes it is even preferable to use analog systems instead. Some advantages of DSP systems: One of the universal uptake of the digital computer is that they are programmable and reprogrammable. Microprocessor technology gives the same advantage to a digital signal processing system. It is possible to design one hardware configuration that can programmed to perform a very wide variety of signal processing tasks simply by loading in different software, For instance, a digital filter may be reprogrammed from low pass to high cases with no change in hardware. In an analog system the whole design would need to be changed. In many cases there is no need to reprogram the system, only to upgrade its operation. Examples might include missile guidance systems, where use in combat circumstances may highlight deficiencies not found in trials. The ability to perform these alterations by the simple replacement of a single memory device is a significant advantage for DSP. To the extent that one can upgrade an analog signal precessing system, it is done by changing component values - generally a soldering iron job. There is a limit to the amount that its function or performance can be changed like this. When we look at the filed performance (i.e. how systems perform in use over a period of time), the situation gets even worse. Components including resistors, capacitors and operational amplifiers all change their characteristics with changes in temperature. This means that an analog circuit may perform quite differently at 0°C than it does at 70°C. Again, digital circuits will show no variation with temperature throughout their guaranteed operating range. A third form of variability that affects analog circuits is component aging. Capacitors in particular are prone to aging of the dielectric material. This will cause a change in impedance and alter the behavior of the circuit. Compensation have to be built into the circuit to allow for component, thermal and aging variations. This can greatly complicate the design process and compromise overall circuit performance. Digital systems are inherently repeatable. If you as five hundred identical digital computers to perform a sequence of sums, they will all provide the same answer, exactly the same answer. If you apply a signal to five hundred analog circuits, built using components of identical specification, you will certainly not get the same output from each circuit. C3x DSK: The 'C3x DSK is a low-cost, simple, high-performance stand-alone application development board that lets you experiment with and use TMS320C3x DSP's for real-time signal processing. The DSK has a TMS320C31 on board to allow full-speed verification of the TMS320C3x code. The DSK also gives you the freedom to build new boards, create your own software on a host PC, download the software to the DSK, and run the software on the DSK board. The TMS320C31 is a 32-bit floating-point processor in 0.6 µm triple-level-metal CMOS technology. The TMS320C31 are part of the TMS320C3x generation of DSP's from Texas Instruments. There are many applications for the TMS320Cx such as MPEG audio codec, LD-CELP vocoders, videophones, voicemail systems, Hi-FI systems, 3-D graphic accelerators, and many others. This tutorial shall provide the reader as well as user of the DSK module the ability to obtain FIR and IIR implementations that would later be used in such applications.
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