BASEBAND TRANSMISSION IN DIGITAL COMMUNICATION

1. CONTENTs
PART-II:
1. Baseband Signal Receiver, ISI, Eye Patterns
2. Probability of error, Optimum Receiver
3. Coherent Reception

2. The transmitted signal is limited to a range from –B Hz to +B
Hz that means they are centered around zero.
f
|X(f)|
B
-B f
|X(f)|
fc
-fc
• Example baseband channels includes,
- copper cable, magnetic disk, CD-(ROM).
• Signal containing a band of frequencies not centered around zero,
simply a Band pass filtered signal is called bandpass signal.
Baseband signals Bandpass signals
0 0
Baseband Transmission
Low freq signals High freq signals

3. Baseband Transmission
24/03/2025 3
What is Baseband Signal?
What is Baseband transmission?
What are Its Limitations?
Solutions limitations.

4. Baseband Transmission Model
24/03/2025 4
 
( ) k b
k
x t A g t kT

 
 

 
( ) ( ) k b
k
y t x t A g t kT
 


 
  

1
0
k
k
k
a if b
A
a if b
 


 

Where,
• If i=k then ISI becomes zero, this is the condition for zero ISI.
t= kTb

5. Intersymbol interference
24/03/2025 5
Intersymbol interference (ISI) is a form of distortion of a
signal in which one symbol interferes with subsequent symbols.

6. Eye Pattern Diagrams
24/03/2025 6

7. Probability of Error (Pe)
24/03/2025 7
• Noise interference leads to make wrong decision at the receiver and
to overcome this we calculate probability of error Pe at the receiver.
Where P0, P1 are probabilities of binary input signal.
and PE0, PE1 are probability of false alarm and missed detection.
But
Pe depends on SNR

8. Baseband Signal Receiver
24/03/2025 8
A simple and basic detector for the detection of digital signals is nothing but a
Integrator & dump filter also called baseband signal receiver.

9. Baseband Signal Receiver
24/03/2025 9
SNR, Probability of error (Pe) Calculation:

10. Optimum Receiver
24/03/2025 10
• Let us assume that the received signal is a binary waveform of
Polar NRZ signal,
for binary ‘1’; s1(t) = +A for one bit period ‘T”
for binary ‘0’; s2(t) = - A for one bit period ‘T”
• Thus input signal will be either s1(t) or s2(t) depending upon the
polarity of the NRZ signal.