3 - 1
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Chapter 3
Basic Modulation Techniques
3 - 2
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Basic Modulation Techniques
Linear Modulation
• DSB
• AM
• SSB
• VSB
Angle Mod.
• PM
• FM
Pulse Mod
• PAM
• PPM
• PDM
3 - 3
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Double-Sideband Modulation
• CoherenceDemodulationis needed
• Costa phase-lock loop
3 - 4
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Amplitude Modulation (AM)
Major advantageover DSB
• Coherent referenceis not needed
• Simple technique(Envelop detection)
Modulation Index
• Distortion
Disagvantages
• Low power efficiency
3 - 5
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Amplitude Modulation (Cont.)
Efficiency
• Signal Power
• Carrier Power
• Total Power
3 - 6
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
AM Demodulation
3 - 7
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Hibert Transform
Baseband Signal
Bandpass signal• Hibert Transfer function
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Generation of Single sideband (SSB)SSB signals
• Upper-sided SSB (USB)
• Lower-sideband SSB (USB)
3 - 9
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Time-Domain SSB signalUSSB
LSSB
3 - 10
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Single sideband Mod. and Demod.
SSB Mod.
• Band Passfilter
• Phase-ShiftModulator
3 - 11
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Superheterodyne Receiver
Mixing
Image freq.
Tuning
• High-side
• Low-side
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
RF Radar Receiver
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Typical Receiver Design
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Angle Modulation
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Performance FM v.s. DSM, SSB, AM
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Angle Mod. Generation
Narrowband AngleModulation
• narrowband and AM
Narrowband-to-widebandConversion
NB anble Mod.
Narrowband-to-wideband
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Spectrum of Angle Modulation
Modulation index
Carson’s rule
Bandwidth
Bessel Function
3 - 19
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Bessel Function
Narrow Band
Wide Band
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Table of Bessel Function
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Spectrum of FM (Examples)
Power spectra
• RX Filter Bandwidth
• Output power of RX filter
Nonlinearity
• nonlinear nature of Anglemodulation
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Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
FM Demodulation
FM Discriminator
• Limiter, Bandpass filter
• Delay and Envelope
• RC network
• Balanced Discriminator
Feedback Demodulation
• Phase-lock loops (PLL)
• Noise performance is gained
• Nonlinear PLL
• Linear PLL
• First-order PLL
• Second-order PLL
• Frequency-Compressive Feedback
• Costas PLL
3 - 23
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
FM Discriminator
3 - 24
Department of Electronical EngineeringFu-Jen Catholic University
Communication Engineering /Basic Modulation Techniques
Sheng-Chou Lin
Feedback Demodulation
Phase-lock loops (PLL)
• Phase Detector
• Loop filter
• Loop Amplifier
• Voltage-Controled Oscillator (VCO)
PLL model
• Nonlinear
• Linear