Spread spectrum technique is used to spread a normally narrow band signal over a larger frequency range so that the spreaded signal occupies more bandwidth than the minimum bandwidth necessary to transmit the signal. In this technique, a Pseudo Noise (PN) sequence is used to expand the message signal before transmission. The PN sequence expands the data signal by replacing each data bit with the PN sequence. The uniqueness of the PN sequence secures the information signal from being decoded by other receivers. Figure 1 shows a user selected input sequence, user selected PN sequence and the corresponding spreaded data signal that is transmitted.

Figure 1: 16-bit input signal, 13-bit PN sequence and transmitted data signal

The questions at the end of this experiment instruct students to select different data signals and observe how the spread spectrum technique is implemented on them. Students are encouraged to observe the spreaded signal in both the time and frequency domain and pen their observations.