TV signal, over an analog bandpass channel at a modulation and demodulation in communication system pdf frequency, for example over a limited radio frequency band or a cable TV network channel. In music synthesizers, modulation may be used to synthesize waveforms with an extensive overtone spectrum using a small number of oscillators. AM or FM radio wave.
Computers may, however, communicate over a telephone line by means of modems, which are representing the digital bits by tones, called symbols. 00, the second 01, the third 10 and the fourth 11. It can be seen as a two-channel system, each channel using ASK. The resulting signal is equivalent to a combination of PSK and ASK.
Usually, each phase, frequency or amplitude encodes an equal number of bits. For example, with an alphabet consisting of 16 alternative symbols, each symbol represents 4 bits. Thus, the data rate is four times the baud rate. I signal at the x-axis, and the amplitude of the Q signal at the y-axis, for each symbol.