1、 1 Baseband Demodulation/Detection In the case of baseband signaling, the received waveforms are already in a pulse-like form. One might ask , why then ,is a demodulator needed to recover the pulse waveforms? The answer is that the arriving baseband pulses are not in the form of ideal pulse shapes,
2、each one occupying its own symbol interval. The filtering to suffer from inter-symbol interference (ISI) and thus appear as an amorphous “smeared” signal, not quite ready for sampling and detection .The goal of the demodulator (receiving filter) is to receiver a baseband pulse with the best possible
3、 signal-to-noise ration (SNR),free of any ISI. Equalization, covered in this chapter, is a technique used to help accomplish this goal. The equalization process is not required for every type of communication channel. However, since equalization embodies a sophisticated set of signal-processing tech
4、niques, making it possible to compensate for channel-induced interference, it is an important area for many systems. The band-pass model of the fourth chapter deals with the detection process, and described in this chapter essentially the same as the baseband model. Before testing, you must first bandpass conversion to the baseband signal. For signal detection in linear systems mathematical expressions do not accept the frequency move, and have the following equivalence theorem (equivalence the
