1. Amplitude Modulation

2. Basic AM Modulation Amplitude Spectrum Modulation index Carrier
Sideband
Modulation index
0 < m < 1
How to measure?
Modulated carrier vs baseband signal
What happens when m>1?

3. Waveforms
Base Band and Modulation
m = 100%
m = 120%
Math
Real

4. Spectrum
Double Side Band Full Carrier
Spectrum
LSB, USB, Carrier

5. Efficiency Efficiency in Using Bandwidth? Efficiency in Using Power?
Two side bands
Efficiency in Using Power?
Carrier
Side band
Information in side band
Carrier for synchronization

6. Variations of AM Bandwidth Efficiency Power Efficiency Complication
Single Side Band
Vestigial Side Band
Power Efficiency
Reduced Carrier
Suppressed Carrier
Complication
Circuits: generation, tuning, detection
Filter, tone variation, carrier recovery

7. AM Radio Source Carrier Frequency Performance Audio, 20-20 kHz
5 kHz bandwidth
km range
50 µV sensitivity

8. AM Radio

9. Commercial AM Radio
Circuit Diagram

10. Commercial Radio
Circuit Board

11. Block Diagram

12. Crucial Components RF Amplifier Autodyne Oscillator and Mixer
High dynamic range
Autodyne Oscillator and Mixer
Tuning
Loop Antenna
LC resonator
Intermediate Frequency Amplifiers
455 kHz
Tank circuit (double tuner) with flat center band
Diode RF Rectifier
Envelope detection
Automatic Gain Control
Strong vs weak stations
Audio Amplifier
Speaker

13. Heterodyne Incoming RF Local Oscillator Mixer
RF amplifier
Bandpass filter
Local Oscillator
Mixer
Nonlinear device or balanced mixer
Signal proportional to local oscillator strength
Intermediate Frequency (AM at 455 kHz)
No further tuning
EMI from Local Oscillator

14. Detection Baseband Signal Coherent Detection AM modulation
Local oscillator
Mixer
LP filter
AC coupling
High sensitivity for low S/N

15. Envelope Detection Circuit Waveform RF rectifier Filter
RC time constant
Simple for high S/N
Waveform

16. Detection Square Law Detector Modulation Nonlinearity RF filter
Low pass and AC coupling

17. Performance Sensitivity Fidelity or Bandwidth Dynamic Range
Selectivity
Adjacent channel
Image Rejection IF
Spurious Response
Harmonics
Squelch
Noises
Static noise from transmission media
Motor boating noise from drift in frequency

18. Lab and Projects Virtual Laboratory Simple AM Projects Experiments
(Search: FM AM)
Matlab project
Software Radio (
Simple AM Projects
Experiments
Agilent AM modulation
MC1496

19. AM Transmitter
History
Block Diagram
Automatic Level Control
m < 1

20. AM Modulator Balanced Mixer Other Circuit
Base band signal modulates oscillator current

21. Power Amplifier Impedance Matching
Maximize Power to the Load
Impedance
Z = V / I
Change V – I Relation
Transformer
High current, low voltage
Low current, high voltage
RLC Networks
Frequency dependent impedance

22. Impedance Matching MIT Open Courseware
Berkeley RLC Pi and T LC Network Calculator
Role of Antenna
Impedance transformation between circuit and free space

23. Short Wave Radio Terrestrial Coverage, HAM
Regenerative Receiver Project

24. HAM http://www.arrl.org/hamradio.html http://www.qsl.net/dl4yhf/
Spectral analysis of audio signals
Antenna projects
Linux HAM

25. AM Stereo Two Channels Quadrature Amplitude Modulation
L+R
L-R
Quadrature Amplitude Modulation
Sin, Cos: orthogonal
Increase Information Capacity Without Increasing Bandwidth
Motorola CQUAM System
Details
Chip

26. Modern Application of AM
Advanced Television Systems Committee (ATSC)
8-VSB Digital Signaling

27. AM Noise Analysis DSBFC Signal and Noise Coherent Detection
Baseband signal power:
Carrier power:
Noise spectral density:
Double sideband bandwidth:
Total noise power:
Coherent Detection
In phase noise only
S/N

28. AM Noise Analysis Envelope Detection Numerical Analysis
Signal Dominant Regime
Similar to coherent detection
Noise Dominant Regime
Noise large
Signal small with random phase
Numerical Analysis

29. AM Review AM Waveform Modulation Index Limit
Double Sideband, Full Carrier
Detection Circuits
Coherent detection
Envelope detection
Variations
SSB, RC or SC
Vestigial sideband
AM Transmitter
Impedance matching
Efficiency