Chapter 8 Communication Systems Modulation : The general process of embedding an information -bearing signal into a second signal. Demodulation : Extracting the information-bearing signal. Modulation : Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation (PM) Modulating
The purpose of a receiver is to select a desired group of frequencies from one transmitter, get rid of all unwanted signals and noise, and then demodulate the signal to obtain the modulating infomation. The better the receiver does its job, the closer the demodulated sigmal will resemble the original signal from the transmitter. Regardless of the type of demodula
2.7 A linear system S has the relationship +∞ yn]=]gn-2k] k=-∞0 between its input xn] and outputy[n] g[n]=un]-un-4] (a)x[n]=[n-1]y[n=u[n-2]-u[n-6] (b)x[n=6[n-2]yn=u[n-4]-u[n-8 (c)S is time-varying