示例：信号和信号的分类

函数 > 信号处理 > 信号和系统 > 示例：信号和信号的分类

示例：信号和信号的分类

信号是表示物理量或变量的函数或数据集。信号通常包含关于物理现象行为的信息，例如电流通过电阻、声纳声波在水下传播，或地震。在数学上讲，信号代表自变量 t 的函数，t 通常代表时间。因此，信号以 x(t) 表示。

连续时间信号和离散时间信号

如果 t 为连续变量，则信号 x(t) 为连续时间信号。如果 t 为离散变量，即 x(t) 以离散时间定义，则 x(t) 为离散时间信号，通常表示为 x(n)，其中 n 为整数。离散时间信号 x(n) 可表示自变量内在离散的现象，例如股票每天的收盘价；该信号还可通过对连续时间信号 x(t) 在 t = nT 时进行采样而获得，其中 T 为采样周期。

下列示例主要是关于离散时间信号的示例。其中有些示例是常见的离散时间信号。

单位阶梯信号

1. 使用海维赛德阶梯函数定义单位阶梯信号。

海维赛德阶梯函数规定 f(0)=0.5

2. 定义范围并绘制单位阶梯函数图像。

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单位脉冲信号

1. 定义单位脉冲函数。

2. 绘制单位脉冲函数图像。

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3. 设置 k 值以将脉冲向右偏移 k 个样本。

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正弦信号

1. 设置频率。

2. 定义正弦函数。

3. 对正弦函数绘图。

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指数信号

1. 设置 alpha 因子。

2. 定义指数函数。

3. 绘制指数函数图像。

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指数衰减正弦曲线

绘制正弦函数与指数函数相乘所得函数的图像。

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结果生成以指数方式衰减的正弦函数。

模拟信号和数字信号

如果连续时间信号 x(t) 可以取连续时间间隔中的任何值，则 x(t) 被称为模拟信号。如果离散时间信号 x(n) 仅可取有限数目的不同值，则该信号被称为数字信号。要将模拟信号转换为数字信号，需要对模拟信号进行采样和量化。

实信号和复信号

如果信号 x(t) 的值为实数，则其为实信号。同样，如果 x(t) 的值为复数，则其为复信号。使用函数 phase 和 phasecor 操作复信号。

确定信号和随机信号

确定信号是指在任何给定时间都完全指定了值的信号。因此，确定信号可通过已知时间函数 x(t) 来模拟。另一方面，随机信号是指在任何给定时间都可以取随机值的信号。随机信号仅可进行统计性表征。噪声生成器函数 whiten、gaussn 和 onefn 旨在产生由用户定义统计参数所表征的伪随机信号。