Digital Signal Processing (5)

　　数字信号处理技术及其应用，目前正以惊人的速度向前发展着。随着大规模集成电路的出现和由此而来的数字部件的成本下降、体积缩小和运算速度提高，数字信号处理应用的种类也在日益增长。目前已制成多种专用数字滤波器，取样率可高达兆赫。高速专用快速傅里叶变换(FFT)处理器已有商品出售。简单的数字滤波器已制成集成电路片。目前几乎所有的语音带宽压缩系统的讨论都倾向于全数字化，因为目前它是最实际可行的方法。数字处理器已成为许多现代化雷达和声纳系统的不可缺少的部分。除了专用数字信号处理硬件发展之处，还出现了可编程序的数字信号处理专用计算机，这种计算机的构造特别适于解决信号处理问题。它们目前正应用于实时信号的处理以及直接导致专用数字硬件发展的实时仿真。

　　数字信号处理的重要性仍在不断提高，毫无停滞的迹象。的确，这一学科将来的发展可能比刚才介绍的发展过程更加引人注目。数字信号处理技术的冲击无疑会促使某些应用部门发生革命性的进展。最明显的例子就是电信部门，由于使用数字方法，在实现交换系统和传输系统时，使经济基础性和灵活性显著提高。

　　The techniques and applications of digital signal processing are expanding at a tremendous rate. With the advent of large scale integration and the resulting reduction in cost and size of digital components, together with increasing speed, the class of applications of digital signal processing techniques is growing. Special purpose digital filters can now be implemented at sampling rates in the megahertz range. Special purpose processors for implementing the fast Fourier transform at high data rates are commercially available. Simple digital filters have been integrated on circuit chips. Almost all current discussions of speech bandwidth compression systems are directed toward all digital implementation because these are now the most practical. Digital processors also form an integral part of many modern radar and sonar systems. In addition to the development of special purpose digital signal processing hardware, there are available special programmable digital signal processing computers whose architecture is matched to signal processing problems. Such computers are finding application in real-time signal processing as well as for real-time simulations directed toward the development of special purpose digital hardware.

　　The importance of digital processing appears to be increasing with no visible sign of saturation. Indeed, the future development of the field is likely to be even more dramatic than the course of development that we have just described. The impact of digital signal processing techniques will undoubtedly promote revolutionary advances in some fields of application. A notable example is in the area of telephony, where digital techniques promise dramatically increased economy and flexibility in implementing switching and transmission systems.（游米儿）