3 Baseband Pusle and Digital Signaling.ppt

1Chapter 3BasebandPusle and Digital Signaling2Chapter Objectives?Analog-to-digital signaling(PCM and delta modulation)?Binary and multilevel digitals signals?Spectra and bandwidths of digital signals?Prevention of intersymbol interference?Time division multiplexing?Packet Introduction(main goals)?To study how analog waveforms can be converted to digital waveforms. The most popular technique is called PCM ?To learn how pute the spectrum for digital signals?To examine how to filtering of pulse signals affects out ability to recover the digital information at the receiver(ISI)?To study how we can multiplex data from several digital bit streams into on high-speed digital stream fro transmission over a digital system.(TDM) Pulse Amplitude Modulation?PAM is an engineering term that is used to describe the conversion of the analog signal to a pulse-type signal in which the amplitude of the pulse denotes the analog information?The sampling theorem gives a way to reproduce an analog waveform by using sample values of that waveform and sin(x)/x orthogonal functions?PAM signaling is to provide another waveform that looks like pulses ,yet contains the information that was present in tha analog Pulse Amplitude Modulation?The pulse rate, fs, for PAM is the same as that required by the sampling theorem, namely, fs>=2B, where B is the highest frequency in the analog waveform and 2B is called the Nyquistrate.?Classification : Nature sampling(gating) Instantaneous sampling(Flat-top type) Pulse Amplitude Modulation(Nature sampling or gating)?Definition: if ω(t)is an analog waveform bandlimited to B hertz, the PAM signal that uses natural sampling isωs(t)=ω(t)s(t) Where s(t) is a rectangular wave switching waveform and fs=1/Ts>=2B???∏)1(?∏)(?∏/]-[s(t)∞∞-∞∞-∞∞-????????kksksdktTktkTt???? Pulse Amplitude Modulation(PAM signal with natural sampling)(a) Baseband Analog WaveformS(t) t(b) Switching waveform with Duty