Describe data encoding & modulation techniques with figures.

Figure,(a) and (b), shows the encoding and data modulation process. For digital signal, a data source g(t), which may be either digital or analog, is encoded into a signal x(t). The actual form of x(t) depends on the encoding technique and is chosen to optimize use of the transmission medium.

The basis for analog signaling is a continuous constant-frequency signal known as the carrier signal. Data may be modulation. Modulation is the process of encoding source data onto a carrier signal with frequency fc. All modulation techniques involve operation on one or more of the three fundamental frequency domain parameters amplitude, frequency and phase.

The input signal m(t) may be analog or digital and is called the modulating signal or baseband signal. The result of modulating the carrier signal is called the modulated signal s(t).

Figure (b) indicates, s (t) is a band limited signal. The location of the bandwidth on the spectrum is related to fc and is often centered as fc. Again the actual form of the encoding is chosen to optimize some characteristic of the transmission.