Carrying Data Over an RF Signal
Up to this point in the chapter, only the RF characteristics of wireless signals have been discussed. The RF signals presented have existed only as simple oscillations in the form of a sine wave. The frequency, amplitude, and phase have all been constant. The steady, predictable frequency is important because a receiver needs to tune to a known frequency to find the signal in the first place.
This basic RF signal is called a carrier signal because it is used to carry other useful information. With AM and FM radio signals, the carrier signal also transports audio signals. TV carrier signals have to carry both audio and video. Wireless LAN carrier signals must carry data.
To add data onto the RF signal, the frequency ...
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