Fundamentals of Analog and Digital Modulation PPT

1. FREQUENCY MODULATION
Phase
Detector
Low Pass
Filter (LPF)
Voltage
Controlled
Oscillator (VCO)
Ver
fi +fo
fo
Vi
Fi
Input
Signal
Forward path
Feedback path
vo
Output Signal
fo
∆𝑓 =
𝑓𝑚𝑎𝑥 − 𝑓𝑚𝑖𝑛
4
CALCULATION OF MODULATION INDEX OF FM
PLL BLOCK DIAGRAM

2. Nyquist Sampling Theorem
The sampling theorem specifies the minimum-sampling rate at which a continuous-
time signal needs to be uniformly sampled so that the original signal can be
completely recovered or reconstructed by these samples alone.
Sampling theorem:
If a continuous time signal contains no frequency components higher than W Hz,
then it can be completely determined by uniform samples taken at a rate fs samples
per second where fs ≥2 W
FLAT-TOP SAMPLING
NATURAL SAMPLING
INSTANTANEOUS SAMPLING

3. Local
Oscillator
IF
Amplifier
&
Filter
Demodulator
Mixer
RF
Amplifier Audio
Amplifier
AGC
AMPLITUDE MODULATION
AMPLITUDE DEMODULATION/ SUPER HETERODYNE RECEIVER
Modulation Index (𝜇) =
𝐴𝑚
𝐴𝑐
μ =
𝐴𝑚𝑎𝑥 − 𝐴𝑚𝑖𝑛
𝐴𝑚𝑎𝑥 + 𝐴𝑚𝑖𝑛

4. Voltage
Comparator
Unipolar -
Bipolar
Converter
CLK
D f/f
Q
+
-
∫
Analog
Input
Clock Input
Data Output
Integrator
Data Input
Unipolar -
Bipolar
Converter
CLK
D f/f
Q
+
-
∫
Voltage
Comparator
Analog
Input
Clock
Input
Data Output
Integrator
Q0 Q1
Counter
CLK
Control Logic
CLK Input
CLR
DELTA MODULATION (DM)
ADAPTIVE DELTA MODULATION (ADM)
The algorithm to control the logic is
S(k) = S(k-1) d(k) + So d(k-1)

5. Amplitude Shift Keying (ASK)
Y (t)=d(t) A Sin2πf ct
CARRIER
INPUT
OUTPUT
MODULATION
INPUT
CARRIER INPUT
UNIPOLAR DATA STREAM
ASK WAVEFORM
RECTIFIER
DETECTOR LPF
VOLTAGE
COMPATAROR
INPUT ASK
SIGNAL DATA
OUTPUT
BLOCK DIAGRAM OF ASK DEMODULATOR
ASK Applications
 Low-frequency RF applications
 Wireless base stat
BLOCK DIAGRAM OF FSK
MODULATOR
Wave form of Amplitude shift keying

6. Frequency Shift Keying (FSK)
Y (t) =Ad(t) Sin2πf1t +Adn(t) Sin2πf2t
UNIPOLAR DATA
STREAM
Summing
amplifier
CARRIER
INPUT
ASK1
MODULATION
INPUT
CARRIER INPUT
INVERTED DATA
INPUT
ASK2
CARRIER
INPUT
NOT
GATE
ASK1
FSK
ASK2
Modulator1
Modulator2
Block Diagram of Fsk modulator
PLL
DETECTOR LPF
VOLTAGE
COMPATAROR
INPUT FSK
SIGNAL DATA
OUTPUT
BLOCK DIAGRAM OF FSK DEMODULATOR
Wave form of Frequency shift keying
FSK Applications commonly used over telephone lines for caller ID (displaying callers' numbers) and
remote metering applications.

7. Phase Shift Keying (PSK)
The modulated carrier is given by:
Binary 1: S (t) = Ac max. Cos. (2πfct)
Binary 0: S (t) = Ac max. Cos. (2πfct + 180 ο) = - Ac max. Cos.
(2πfct)
UNI PLOAR TO
BIPOLAR
CONVERTER
UNIPOLAR BIT STEAM
CARRIER INPUT
MODULATION INPUT
CARRIER SIGNAL
PSK
OUTPUT
Block Diagram of Psk modulator
PSK
DEMODULATOR LPF
VOLTAGE
COMPARATOR
DIFERENTIAL
BIT
DECODER
PSK
OUTPUT
DEMOD
DATA
Block Diagram of Psk modulator
Wave form of PHASE shift keying
PSK Applications
It is widely used for wireless LANs, RFID and Bluetooth
communication