Analog vs. Digital Transmission - IDC-Online（模拟与数字传输IDC-Online）.pdf

Analog vs. Digital Transmission There are three predominant methods of encoding a transmission signal. Amplitude modulation(AM), and frequency modulation(FM) are both analog modulation schemes. The third method is digital modulation. The Table 1 outlines the basic characteristics of the three modulation schemes. Table 1 - Comparison of AM, FM, and Digital Encoding Techniques Parameter AM FM Digital Signal-to- Moderate- Low-to-Moderate High Noise Ratio High Performance Sensitive Tolerant Invariant vs.Attenuation Transmitter Moderate-High Moderate High Cost Moderate- Receiver Cost Moderate High High Receiver Gain Not Not Often Required Adjustment Required Required No No Adjustments Installation Adjustments Adjustments Requires Required Required Multichannel Require Fewer Good Capabilities High LinearityOptics Channels Performance Moderate Excellent Excellent Over Time Environmental Moderate Excellent Excellent Factors AM, FM, and digital modulation are described in detail in other sections of this web site. One key difference between analog and digital transmission involves the bandwidth, or transmission capacity required for both schemes. Analog signals require much less bandwidth, only about 4.5 MHz with