Transcript EENGR 3810 Chapter 1 - UNT College of Engineering

EENGR 3810 Chapter 1
Introduction to Communication Systems
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Chapter 1 Homework
No Homework for this chapter.
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Communication System History
• 1837 Morse Transmitted What?
– Dots and dashes
• 1876 Bell transmitted voice by what method?
– Telephone
• 1894 Marconi transmitted messages by what method?
– Wireless
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Communication System
• Information Input
– Source: originates the message
• Human voice (Analog signals)
• Computer keyboard (Digital data signals)
– Input transducer
• converts message to electrical waveform
• baseband signal
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Communication System
• Transmitter
– Modulates baseband signal with a Carrier signal
– Transmits modulated signal
• Transmission medium (Channel)
– Wire
– Radio link
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Communication System
• Receiver
– Demodulates baseband signal from modulated signal
– Sends demodulated signal to output transducer
• Output Transducer
– Converts electrical signal to original form
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Frequency Bands.
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Propagation of Radio Frequencies
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Analog Communication Systems
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Amplitude Modulation (AM) Double
Side-band Full Carrier (DSBFC) Signal Generation
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AM DSBFC Transmitter
(AM Transmitters will be covered later. This is an example.)
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AM Superheterodyne Receiver
(AM receivers will be covered later. This is an example.)
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FM with a sinusoidal baseband modulating signal
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FM Transmitter Block Diagram
(FM Transmitters will be covered later. This is an example.)
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FM Receiver Block Diagram
(FM receivers will be covered later. This is an example.)
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Digital Communication Systems
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Digital Communication Systems
• More rugged than analog communication systems
– Avoids accumulation of noise and distortion
– Binary system
• +A/2 and –A/2, where A = signal amplitude
• encoded as rectangular pulses
• Transmitting scheme
– Digitize the signal
– Use pulse-code modulation to transmit digital signals
• takes samples of signals
• quantizes samples
– Regenerative repeater stations along communication path
• cleans out noise and distortion in received signal
• retransmits clean signal
• prevents accumulation of noise and distortion
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PCM Transmission System Block Diagram
(PCM will be covered later.)
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