Analogue and Digital Signals | 模拟信号与数字信号

📚 Analogue and Digital Signals | 模拟信号与数字信号

In A-Level Physics, analogue and digital signals describe the two main ways in which information can be encoded for transmission, storage and processing. This article explains how each signal type behaves, how conversions between them work, and why modern communication systems prefer digital methods.

在 A-Level 物理中，模拟信号和数字信号描述了信息在传输、存储和处理中的两种主要编码方式。本文将解释两种信号的行为特点、它们之间的转换原理，以及为什么现代通信系统更倾向于数字方法。

1. What Are Analogue Signals? | 什么是模拟信号？

An analogue signal is a continuous signal whose amplitude varies smoothly with time. It can take any value within a given range, so it represents information by directly mirroring the original physical quantity, such as sound pressure or light intensity.

模拟信号是一种连续信号，其幅度随时间平滑变化。它可以取给定范围内的任意数值，因此通过直接反映原始物理量（例如声压或光强）来表示信息。

Typical examples include the voltage produced by a microphone, the oscilloscope trace of a sound wave, vinyl records and analogue radio broadcasts. The exact shape of the waveform is the information itself.

典型例子包括麦克风产生的电压、声波的示波器轨迹、黑胶唱片和模拟无线电广播。波形的精确形状本身就是信息。

Because an analogue signal is continuous in both time and amplitude, any small disturbance or noise added to the waveform changes the received signal and may be impossible to remove completely.

由于模拟信号在时间和幅度上都是连续的，任何叠加在波形上的微小干扰或噪声都会改变接收信号，而且可能无法被完全消除。

2. What Are Digital Signals? | 什么是数字信号？

A digital signal is a discrete signal that switches between a limited set of voltage levels, usually two levels representing binary 0 and binary 1. Information is encoded as a sequence of binary digits, or bits.

数字信号是一种离散信号，它在有限的一组电压电平之间切换，通常用两个电平表示二进制 0 和二进制 1。信息被编码为二进制数字（比特）序列。

Digital signals can be produced by sampling an analogue waveform and converting each sample into a binary number. The original information is therefore represented by numbers rather than by a continuously varying voltage.

数字信号可以通过对模拟波形进行采样并将每个样本转换为二进制数来产生。因此，原始信息用数字表示，而不是用连续变化的电压表示。

Common examples include audio on a CD, data stored on a solid-state drive, mobile phone transmissions and fibre-optic communication. In all these cases, binary digits are used to carry the original information.

常见例子包括 CD 上的音频、固态硬盘中存储的数据、移动电话传输和光纤通信。在所有这些情况下，二进制数字都用于承载原始信息。

3. Comparing Continuous and Discrete Information | 连续信息与离散信息比较

Analogue signals can take any value continuously, while digital signals can only take a finite number of discrete values. This fundamental difference leads to very different behaviour in the presence of noise and during processing.

模拟信号可以连续地取任意值，而数字信号只能取有限个离散值。这一根本差异导致二者在噪声环境和处理过程中的表现截然不同。