ece 2 year

1. Eeng 360 1
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

2. Eeng 360 2
Generalized Transmitters
   
     
     
     
   
Re cos
cos sin
Where
c
j t
c
c c
j t
v t g t e R t t t
v t x t t y t t
g t R t e x t jy t


 
 
  
 
 
 
  
Any type of modulated signal can be represented by
The complex envelope g(t) is a function of the modulating signal m(t)
Transmitter
Modulating
signal
Modulated
signal
Example:
( )
Type of Modulation g(m)
AM : [1 ( )]
PM : p
c
jD m t
c
A m t
A e


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Generalized Transmitters
R(t) and θ(t) are functions of the modulating signal m(t) as given in TABLE 4.1
Two canonical forms for the generalized transmitter:
     
cos c
v t R t t t
 
 
 
 
1. AM- PM Generation Technique: Envelope and phase functions are generated to modulate
the carrier as
Figure 4–27 Generalized transmitter using the AM–PM generation technique.

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Generalized Transmitters
x(t) and y(t) are functions of the modulating signal m(t) as given in TABLE 4.1
      t
t
y
t
t
x
t
v c
c 
 sin
cos 

2. Quadrature Generation Technique: Inphase and quadrature signals are generated to
modulate the carrier as
Fig. 4–28 Generalized transmitter using the quadrature generation technique.

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IQ (In-phase and Quadrature-phase) Detector

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Generalized Receivers
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
Superheterodyne Receiver:
Downconvert RF signal to lower IF frequency
Main amplifixcation takes place at IF
 Two types of receivers:

7. Eeng 360 7
Tuned Radio Frequency (TRF) Receivers
Active
Tuning
Circuit
Detector
Circuit
Local
Oscillator
Bandpass
Filter
Baseband
Audio Amp
 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
(Upconversion/
Downconversion)
Subsequent
Processing
(common)
All
Incoming
Frequencies
Fixed
Intermediate
Frequency
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
fIF fIF
RF Response
IF Response

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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 Frequencies
Image frequency not a problem.
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.