Which type of modulation is commonly used in digital cable systems?

Quadrature Amplitude Modulation (QAM) is commonly used in digital cable systems due to its ability to efficiently transmit a significant amount of data over a limited bandwidth. QAM combines two signal sources, which allows it to represent multiple bits of data per symbol. This capability is especially important in cable television systems where high-definition video and numerous channels are transmitted simultaneously.

The efficiency of QAM comes from its ability to modulate both the amplitude and phase of the carrier signal, enabling it to carry more information than other modulation schemes. This characteristic makes QAM particularly well-suited for applications like digital cable, where bandwidth is at a premium, and high data rates are essential.

In contrast, other modulation types have limitations that make them less ideal for this application. Phase Shift Keying is effective for simpler data transmissions where bandwidth may not be as constrained. Frequency Modulation is traditionally used in analog transmissions and may not handle high data rates as efficiently as QAM in a digital context. Amplitude Modulation, while historically significant, is largely outdated for modern digital communication practices, especially for the amount of data required in digital cable systems.