Digital-To-Digital Conversion LINE CODING: data element signal element
Digital-To-Digital ConversionLINE CODING: data element signal element
DATA RATE AND SIGNAL RATE The data rate is measured in bps (bits/sec). The data rate is also called bit rate. The signal rate is measured in baud. The signal rate is also called pulse rate, modulation rate, or baud rate.
Unipolar Scheme
Polar Scheme
Return to Zero (RZ)
BIPHASE Manchester and Differential Manchester
BIPOLAR SCHEMES (MULTILEVEL BINARY)(i)AMI (alternate mark inversion)
(ii)Pseudoternary
MULTILEVEL SCHEMES2B1Q (Two binary, one Quaternary)Transition Table
Previous level=positive Previous level=negativeNext bits Next level Next level
00 +1 -101 +3 -310 -1 +111 -3 +3
ANALOG TO DIGITAL CONVERSIONPulse Code Modulation (PCM)
1.Sampling:
2. Quantization:
3. Encoding:For example, if a sample has quantization code of 2, then it is encoded as 010, similarly, 5 is encoded as 101, and so on. The bit rate will be
SNRdB = 6.02nb + 1.76 dB
DIGITAL-TO-ANALOG CONVERSION
An analog signal carries 4 bits per signal element. If 1000 signal elements are sent per second, find the bit rate.
Amplitude Shift Keying (ASK)
Implementation
Frequency Shift Keying (FSK)
Implementation
Phase Shift Keying
Implementation
Quadrature PSK (QPSK)
Constellation Diagram
Quadrature Amplitude Modulation (QAM)
ANALOG-TO-ANALOG CONVERSION
Amplitude Modulation:
Frequency Modulation:
Phase Modulation: