Eeng 360 1

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• Chapter4
• Transmitters and Receivers
• Generalized Transmitters
• AM PM Generation
• Inphase and Quadrature Generation
• Superheterodyne Receiver
• Frequency Division Multiplexing

Huseyin Bilgekul Eeng360 Communication Systems
I Department of Electrical and Electronic
Engineering Eastern Mediterranean University
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Generalized Transmitters
Modulating signal
Modulated signal
Transmitter
Any type of modulated signal can be represented by
The complex envelope g(t) is a function of the
modulating signal m(t)
Example
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Generalized Transmitters

• Two canonical forms for the generalized
  transmitter

Figure 427 Generalized transmitter using the
AMPM generation technique.
R(t) and ?(t) are functions of the modulating
signal m(t) as given in TABLE 4.1
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Generalized Transmitters
Fig. 428 Generalized transmitter using the
quadrature generation technique.
x(t) and y(t) are functions of the modulating
signal m(t) as given in TABLE 4.1
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IQ (In-phase and Quadrature-phase) Detector
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Generalized Receivers

• Two types of receivers

Tuned Radio Frequency (TRF) Receiver Composed of
RF amplifiers and detectors. No frequency
conversion It is not often used. Difficult to
design tunable RF stages. Difficult to obtain
high gain RF amplifiers
Receivers
Superheterodyne Receiver Downconvert RF signal
to lower IF frequency Main amplifixcation takes
place at IF
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Tuned Radio Frequency (TRF) Receivers

• Composed of RF amplifiers and detectors.
• No frequency conversion. It is not often used.
• Difficult to design tunable RF stages.
• Difficult to obtain high gain RF amplifiers

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Heterodyning
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Superheterodyne Receivers
Superheterodyne Receiver Diagram
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Superheterodyne Receiver

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Superheterodyne Receivers

• The RF and IF frequency responses H1(f) and
  H2(f) are important in providing the required
  reception characteristics.

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Superheterodyne Receivers
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Superheterodyne Receivers
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Superheterodyne Receiver Frequencies

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Superheterodyne Receiver Frequencies

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Frequency Conversion Process
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Image frequency not a problem.
Image Frequencies
Image frequency is also received
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AM Radio Receiver
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Superheterodyne Receiver Typical Signal Levels
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Double-conversion block diagram.