chapter 3 basic modulation techniques - fju.edu.t · basic modulation techniques linear modulation...

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Department of Electronical EngineeringFu-Jen Catholic University

Communication Engineering /Basic Modulation Techniques

Sheng-Chou Lin

Chapter 3

Basic Modulation Techniques

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Sheng-Chou Lin

Basic Modulation Techniques

Linear Modulation

• DSB

• AM

• SSB

• VSB

Angle Mod.

• PM

• FM

Pulse Mod

• PAM

• PPM

• PDM

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Double-Sideband Modulation

• CoherenceDemodulationis needed

• Costa phase-lock loop

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Amplitude Modulation (AM)

Major advantageover DSB

• Coherent referenceis not needed

• Simple technique(Envelop detection)

Modulation Index

• Distortion

Disagvantages

• Low power efficiency

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Amplitude Modulation (Cont.)

Efficiency

• Signal Power

• Carrier Power

• Total Power

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AM Demodulation

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Hibert Transform

Baseband Signal

Bandpass signal• Hibert Transfer function

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Generation of Single sideband (SSB)SSB signals

• Upper-sided SSB (USB)

• Lower-sideband SSB (USB)

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Time-Domain SSB signalUSSB

LSSB

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Single sideband Mod. and Demod.

SSB Mod.

• Band Passfilter

• Phase-ShiftModulator

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Superheterodyne Receiver

Mixing

Image freq.

Tuning

• High-side

• Low-side

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RF Radar Receiver

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Typical Receiver Design

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Angle Modulation

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Performance FM v.s. DSM, SSB, AM

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Angle Mod. Generation

Narrowband AngleModulation

• narrowband and AM

Narrowband-to-widebandConversion

NB anble Mod.

Narrowband-to-wideband

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Spectrum of Angle Modulation

Modulation index

Carson’s rule

Bandwidth

Bessel Function

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Bessel Function

Narrow Band

Wide Band

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Table of Bessel Function

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Spectrum of FM (Examples)

Power spectra

• RX Filter Bandwidth

• Output power of RX filter

Nonlinearity

• nonlinear nature of Anglemodulation

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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

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FM Discriminator

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Feedback Demodulation

Phase-lock loops (PLL)

• Phase Detector

• Loop filter

• Loop Amplifier

• Voltage-Controled Oscillator (VCO)

PLL model

• Nonlinear

• Linear

chapter 3 basic modulation techniques - fju.edu.t · basic modulation techniques linear modulation...

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