1. •Lecture 3 •Paul Flynn Modulation

2. Frequency Spectrum

3. Long Waves, Medium Waves and Short Waves

4. Modulation of Analog Signals Amplitude Modulation (AM) Frequency Modulation (FM) Phase Modulation (PM)

5. Figure 5.24 Analog-to-analog modulation

6. Types of analog-to-analog modulation

7. Amplitude modulation (AM)

8. Frequency modulation (FM)

9. Phase Modulation (PM)

10. Digital modulation •Three basic methods •– Amplitude shift keying (ASK) •– Frequency shift keying (FSK) •– Phase shift keying (PSK

11. Amplitude shift keying (ASK) •Use different amplitude to represent 0 and 1. •– Simple, low bandwidth – Sensitive to interference. • Multi-path propagation, noise or path loss heavily influence the amplitude. •– A constant amplitude in wireless environment can not be guaranteed. • Used in wired optical communication. •– A light pulse =1, no light =0.

13. Frequency shift keying (FSK) •Binary FSK (BFSK) – One frequency for 0 and one •frequency for 1. – needs larger bandwidth • Avoid discontinuity – Discontinuity creates high •frequencies as side effects. – Continuous phase modulation (CPM) can be used. • Demodulation: – Use two bandpass filters for 2 frequencies.

15. Phase shift keying (PSK) •Use shift in phase to represent data. • Binary PSK (BPSK) – Shift the phase by 180. • Synchronization is important • More resistant to interference • More complex transmitters and receivers.

17. Digitizing Analog Signals 1.Sample 2.Quantize 3.Encode

18. Sampling Analog Signals Original Signal Sample Times Sample Values Reformed Signal

19. Digitizing Analog Signals Original Signal and Samples Actual Sample Values Quantized Sample Values Reconstructed Signal Original Signal

20. Linear Quantizing Actual Sample Values Quantized Sample Values Reconstructed Signal Original Signal

21. Linear Quantizing Linear: quantizing steps for all segments are the same height. SQRSQR 2-42

22. Quantizing Noise TransmitReceive

23. Voice Digitization Process

24. Pulse Code Modulation Waveform-Time Domain-Nondifferential Sample Values Quantized value of each sample is coded

25. Coding How many bits are needed to code this many levels? 111 110 101 100 011 010 001 000 Answer: 3 bits for 8 levels L=2 n

26. Companding or Non-linear Encoding zCompanding = compressing + expanding zWhy companding? zQuantization levels not evenly spaced zReduces overall signal distortion zCan also be done by companding

27. Binary Signaling Encoding Schemes 0 = 1 0 to 1 1 to 0 1=sq sq 1 & 0 c x on 1 chg on 0 alt mark inversion (B8ZS) sq wv 1 inv 2 nd 1 nnnnssssnnnnnnssssnn EIA 232 B8ZsB8Zs

28. 2B1Q (ISDN) EACH LEVEL REPRESENTS TWO BITS 00, 01, 10, AND 11

29. The digital Loop Signal

30. AMI (Alternate Mark Conversion) Violation START OF CONTROL INFO NO MORE THAN 15 0s IN A ROW