This document discusses various electronic communication systems including amplitude modulation (AM) and frequency modulation (FM) transmitters and receivers. It provides block diagrams and circuit implementations of basic AM transmitters using a transistor modulator. It also covers AM receivers using diode and synchronous detectors. For FM it discusses varactor diode modulation, direct and phase locked loop transmitters as well as FM receiver designs using slope detection. Circuit simulations and output waveforms are presented for several of the communication system examples.

1. ELECTRONIC COMMUNICATION
SYSTEMS
Presenter Damion Lawrence, M.Sc., B.Ed

2. A communication system block diagram.

3. Linear addition of two sine waves.

4. AM waveform under varying intelligence signal (ei) conditions.

5. Nonlinear mixing.

6. Percentage modulation determination.

7. Modulation by a band of intelligence
frequencies.

9. Simple transistor modulator.

10. (a) High- and (b) low-level modulation.

11. Simple AM transmitter block
diagram.

12. Class D citizens band transmitter.

13. Signal injection.

14. Signal tracing.

15. Trapezoidal pattern connection scheme and
displays.

16. Comparing input and output signals.

17. The Multisim component view for the
simple transistor amplitude modulator
circuit.

18. The Multisim oscilloscope control panel.

20. Simple radio receiver block diagram.

21. Superheterodyne receiver block diagram.

22. Frequency conversion process.

23. Image frequency not a problem.

24. Troubleshooting a self-excited mixer.

25. Diode detector.

26. An AM diode detector circuit as implemented with
Electronics WorkbenchTM Multisim.

27. Oscilloscope output traces from the diode
detector.

28. A synchronous AM detector circuit as implemented
in Electronics WorkbenchTM Multisim.

29. The waveforms obtained from TP1 and TP2 for the
synchronous AM detector

30. AM broadcast superheterodyne receiver.

31. FM representation.

32. Varactor diode modulator.

33. Crosby direct FM transmitter.

34. PLL FM transmitter block diagram.

35. A frequency-modulation circuit using a voltage-controlled
oscillator, as implemented in an Electronics WorkbenchTM
Multisim circuit.

36. The oscilloscope display of the 10-kHz triangle wave
and the output of the VCO.

37. FM receiver block diagram.

38. Slope detection.

39. Typical FM receiver.

40. An implementation of an FM receiver
using Multisim.

41. The frequency plot of the bandpass filter.