Amplitude modulation (AM) encodes information by varying the amplitude of a carrier wave. In AM, a high amplitude represents a 1 and a low amplitude represents a 0, while the frequency remains unchanged. AM is used in radio transmission where a carrier wave is modulated by an audio signal containing voice information. Frequency modulation (FM) encodes information by varying the frequency of a carrier wave. In FM, different frequencies represent 1s and 0s, while the amplitude stays the same. Phase modulation encodes information by introducing phase shifts of 0 and 90 degrees to the carrier wave, keeping both the frequency and amplitude constant.

1. Modulation
Amplitude Modulation
Presented by- Arun Adhikari

2. Amplitude Modulation (AM)
1
0
1
0
Amp. 1 Amp. 2 Frequency same
1 = Amp. 1
0 = Amp. 2
A B

3. Characteristics of Amplitude
Modulation
• Amplitude of the analog signal is
modulated
• One amplitude represents a 0
• Another amplitude represents a 1
• Frequency remains unchanged in both
cases
• Signals that are modulated at one end
are demodulated at the other end

4. AM and Radio Transmission
Modulated Amplitude
Voice
Carrier
Wave

5. Module
Frequency Modulation

6. Frequency Modulation (FM)
1
0
1
0
Freq. 1 Freq. 2 Amplitude same
1 = Frequency F1
0 = Frequency F2

7. Phase of an Analog Signal
Y
Strength
X
Time Frame
0 90 180 270 360

8. The Concept of Phase Shift
90 degrees phase shift
180 degrees phase shift
0 90
0 180

9. Phase Modulation Technique
1
0
90 Degrees
phase shift
0 Degree
phase shift
In PM, both freq and amp remains same

10. Phase Modulation Technique
1
0
90 Degrees
phase shift
0 Degree
phase shift
In PM, both freq and amp remains same