Digital Transmission Through Bandlimited Channels -The Power Spectrum of Digital PAM Signal -Characterization of Bandlimited Channels and Channel Distortion Characterization of Intersymbol Interface -Communication System Design for Bandlimited Channels Linear Equalizer
Digital Transmission Through Bandlimited Channels ◼The Power Spectrum of Digital PAM Signal ◼Characterization of Bandlimited Channels and Channel Distortion ◼Characterization of Intersymbol Interface ◼Communication System Design for Bandlimited Channels ◼Linear Equalizer
Power spectrum of Digital PAM signal The power spectrum of PAM is function of Power spectrum of information ■Spectrum of pulse g()t If information is uncorrelated Then power spectrum of PAM is dependent only on the spectrum of g(t) We have to consider the spectrum of g(t)if channel is bandlimited
Power spectrum of Digital PAM signal ◼ The power spectrum of PAM is function of ◼ Power spectrum of information ◼ Spectrum of pulse g(t) ◼ If information is uncorrelated ◼ Then power spectrum of PAM is dependent only on the spectrum of g(t) ◼ We have to consider the spectrum of g(t) if channel is bandlimited
Characterization of Bandlimited Channel and Channel Distortion Communication channel can be modeled as s Bandlimited Linear Filter Amplitude response Phase response Distortion caused by channel Amplitude distortion Delay distortion ISI(Inter Symbol Interference)caused by delay At Radio channel lonospheric/Tropospheric/multipath
Characterization of Bandlimited Channel and Channel Distortion ◼ Communication channel can be modeled as ◼ Bandlimited Linear Filter ◼ Amplitude response ◼ Phase response ◼ Distortion caused by channel ◼ Amplitude distortion ◼ Delay distortion ◼ ISI(Inter Symbol Interference) caused by delay ◼ At Radio channel ◼ Ionospheric/Tropospheric/multipath
Characterization of ISl The amount of ISl and noise in digital communication system can be viewed on an oscilloscope Eye pattern Large ISI close the eye Small ISI open the eye
Characterization of ISI ◼ The amount of ISI and noise in digital communication system can be viewed on an oscilloscope ◼ Eye pattern ◼ Large ISI close the eye ◼ Small ISI open the eye
Communication system design for Bandlimited Channel Two approaches Design is based on transmitter and receiver filter that result in zero ISI Design is based on transmitter and receiver filter that has predetermined amount of ISl Controlled amount of ISI
Communication system design for Bandlimited Channel ◼ Two approaches ◼ Design is based on transmitter and receiver filter that result in zero ISI ◼ Design is based on transmitter and receiver filter that has predetermined amount of ISI ◼ Controlled amount of ISI