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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 - PowerPoint PPT Presentation
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Eeng 360 1
Chapter4
Transmitters and Receivers Generalized Transmitters
AM PM Generation
Inphase and Quadrature Generation
Superheterodyne Receiver
Frequency Division Multiplexing
Huseyin BilgekulEeng360 Communication Systems I
Department of Electrical and Electronic Engineering Eastern Mediterranean University
Eeng 360 2
Generalized Transmitters
Re cos
cos sin
Where
cj tc
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)
TransmitterModulating
signalModulated
signal
Example:
( )
Type of Modulation g(m)
AM : [1 ( )]
PM : p
c
jD m t
c
A m t
A e
Eeng 360 3
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 cv t R t t t
1. AM- PM Generation Technique: Envelope and phase functions are generated to modulate the carrier as
Figure 4–27 Figure 4–27 Generalized transmitter using the AM–PM generation Generalized transmitter using the AM–PM generation technique.technique.
Eeng 360 4
Generalized Transmitters
x(t) and y(t) are functions of the modulating signal m(t) as given in TABLE 4.1
ttyttxtv cc sincos
2. Quadrature Generation Technique: Inphase and quadrature signals are generated to modulate the carrier as
FigFig.. 4–28 4–28 Generalized transmitter using the quadrature generation Generalized transmitter using the quadrature generation technique.technique.
Eeng 360 6
Generalized Receivers
Receivers
Tuned Radio Frequency (TRF) Receiver:Composed of RF amplifiers and detectors. No frequency conversionIt 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 frequencyMain amplifixcation takes place at IF
Two types of receivers:
Eeng 360 7
Tuned Radio Frequency (TRF) Receivers
ActiveTuningCircuit
DetectorCircuit
LocalOscillator
BandpassFilter
BasebandAudio 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
Eeng 360 8
Heterodyning(Upconversion/Downconversion)
SubsequentProcessing(common)
AllIncomingFrequencies
FixedIntermediateFrequency
Heterodyning
Eeng 360 11
Superheterodyne Receivers The RF and IF frequency responses H1(f) and H2(f) are important in providing the required reception characteristics.
Eeng 360 17
Image Frequencies
Image frequency not a problem.Image frequency not a problem.
Image frequency is also receivedImage frequency is also received