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Signal Conversion Methods - Coggle Diagram
Signal Conversion Methods
Digital to Digital Conversion
Block Coding
Also referred to as mB/nB
It replaces each m bit group with n bits
Line Coding
Unipolar
Unipolar (NRZ)
Has only two levels, +ve and zero or -ve and zero
Level decides bit value
Polar
Polar (NRZ)
Polar NRZ-L
Two levels +ve and -ve, level determines bit value
Polar NRZ-I
Two levels, +ve and -ve
Change or lack of change in level determines bit value
Polar (RZ)
3 levels, +ve, -ve and zero
After each bit, voltage returns to zero
Polar Biphase
Manchester
Combination of NRZ-L and RZ
Differential Manchester
Combination of NRZ-I and RZ
Multilevel
m bits with n combinations are used to represent L levels (2^m)=(L^n)
Eg: 2B/1Q, 8B/6T
Multitransition
In MLT-3, Three levels are used (+ve, -ve and zero)
If the next bit is 0, there is no transition.
If the next bit is 1 and the current level is not 0, the next level is 0.
If the next bit is 1 and the current level is 0, the next level is the opposite of the last nonzero level.
Bipolar
AMI
0 is denoted by resting state and 1 by alternating +ve and -ve levels
Pseudoternary
1 is denoted by resting state and 0 by alternating +ve and -ve levels
Scrambling
Digital to Analog Conversion (DAC)
ASK (Amplitude Shift Keying)
In ASK, amplitude of carrier signal is varied to create signal elements. Frequency and Phase remain unchanged
FSK (Frequency Shift Keying)
In FSK, Frequency of carrier signal is varied to create signal elements. Amplitude and Phase remain unchanged
PSK (Phase Shift Keying)
In PSK, Phase of carrier signal is varied to create signal elements. Frequency and Amplitude remain unchanged
Aspects
Data Element: Smallest piece of information to be exchanged (a bit)
Signal Elements: Shortest unit of signal that is constant
Formula: S=N/r :
S: Signal rate
N: data rate
r: number of data elements per signal element (r=log₂L)
Analog to Digital Conversion (ADC)
Sampling
This process involves taking samples of the analog signal at regular intervals.
Encoding
The quantized samples are then encoded into binary code, typically using techniques like Pulse Code Modulation (PCM), where each sample is represented by a binary number.
Quantization
After sampling, the continuous amplitude of the signal is approximated to a discrete set of levels.
Pulse Code Modulation
The analog signal is sampled.
The sampled signal is quantized.
The quantized values are encoded as streams of bits.
Delta Modulation
Sampling is done at a higher rate compared to PCM.
the difference between successive samples is encoded into n-bit data streams.
the transmitted data is reduced to a 1-bit data stream representing either up (↗) or down (↘).
Analog to Analog Conversion
Amplitude Modulation (AM)
Modulates the amplitude of a carrier signal to encode information.
Phase Modulation (PM)
Modulates the phase of a carrier signal to encode information.
Frequency Modulation (FM)
Modulates the frequency of a carrier signal to encode information.