数字滤波器简介外文翻译(编辑修改稿)

数字滤波器简介外文翻译(编辑修改稿)内容摘要：

r a given requirement. At all stages, the signal being filtered is an electrical voltage or current which is the direct analogue of the physical quantity (. a sound or video signal or transducer output) involved. A digital filter uses a digital processor to perform numerical calculations on sampled values of the signal. The processor may be a generalpurpose puter such as a PC, or a specialised DSP (Digital Signal Processor) chip. The analog input signal must first be sampled and digitised using an ADC (analog to digital converter). The resulting binary numbers, representing successive sampled values of the input signal, are transferred to the processor, which carries out numerical calculations on them. These calculations typically involve multiplying the input values by constants and adding the products together. If necessary, the results of these calculations,which now represent sampled values of the filtered signal, are output through a DAC (digital to analog converter) to convert the signal back to analog form. Note that in a digital filter, the signal is represented by a sequence of numbers, rather than a voltage or current. The following diagram shows the basic setup of such a system. Advantages of using digital filters The following list gives some of the main advantages of digital over analog filters. 1. A digital filter is programmable, . its operation is determined by a program stored in the processor39。 s memory. This means the digital filter can easily be changed without affecting the circuitry (hardware). An analog filter can only be changed by redesigning the filter circuit. 2. Digital filters are easily designed, tested and implemented on a generalpurpose puter or workstation. 3. The characteristics of analog filter circuits (particularly those containing active ponents) are subject to drift and are dependent on temperature. Digital filters do not suffer from these problems, and so are extremely stable with respect both to time and temperature. 4. Unlike their an。