This document discusses digital modulation techniques used to encode information onto carrier signals for transmission. It explains that modulation involves adding information to a carrier signal by varying the amplitude, frequency, or phase. Specifically, it describes amplitude-shift keying (ASK), which encodes bits as two amplitude levels while keeping frequency constant, as well as frequency-shift keying (FSK) and phase-shift keying (PSK), which encode bits by shifting the frequency or phase of the carrier signal. The document also mentions channel capacity and reasons for choosing different encoding techniques.

1. Digital modulation techniques

2. Modulations systems

3. Channel capacity

4. Reasons for choosing encoding
techniques

5. What is modulation ?
• Modulation = Adding information to a carrier signal
• The sine wave on which the characteristics of the
information signal are modulated is called a carrier signal

6. Analog modulation

7. Digital modulation and
demodulation

8. Signal characteristics that can be
modified
signal x(t) = A cos(2πft + Φ)
• A – amplitude
• f – frequency
• Φ – phase (initial angle of the sinusoidal function at its
origin

9. Modulation

10. Modulation (1)

11. Digital modulation techniques

12. ASK
• ASK On-off keying (Amplitude Shift Keying) –
frequency is kept constant, amplitude has 2 levels (for bit
1 and for bit 0)
The binary sequence 0010110010

13. FSK (Frequency shift keyring)

14. PSK (Phase shift keyring)