英文资料.doc

武汉纺织大学 2010 届毕业设计( 论文) 1 外文资料 Signals and System Signals are scalar-valued functions ofone or more independent variables. Often for convenience, when the signals are one-dimensional, the independent variable is referred to as“ time ” The independent variable may be continues or discrete. Signals that are continuous in both amplitude and time (often referred to as continuous -time or analog signals) are the monly encountered in signal processing contexts. Discrete-time signals are typically associated with sampling of continuous-time signals. Ina digital implementation of signal processing system, quantization of signal amplitude is also required . Although not precisely Correct in every context, discrete-time signal processing is often referred to as digital signal processing. Discrete-time signals, also referred to as sequences, are denoted by functions whose arguments are integers. For example , x(n) represents a sequence that is defined for integer values ofn and undefined for non-integer value ofn. The notation x(n) refers to the discrete time function xor to the value of function x ata specific value ofn .The distinction between these two will be obvious from the contest . Some sequences and classes of sequences play a particularly important role in discrete-time signal processing .These are summarized below. The unit sample sequence, denoted byδ(n)=1 ,n=0 , δ(n)=0,otherwi