BASEBAND TRANSMISSION TECHNIQUES (FINAL SUBMISSION)

Submitted By: VISHAL MISHRA (111EC0179)

Aim of the experiment:

To design Baseband Transmission techniques namely,

1. NRZ-B Encoding 2. Bipolar Manchester Coding 3. Single-channel 4-bit PCM transmitter and receiver

Software used:

Multisim and OrCAD

Theory:

NRZ-B CODING:

In telecommunication, a non-return-to-zero (NRZ) line code is a binary code in which 1s are represented by one significant condition (usually a positive voltage) and 0s are represented by some other significant condition (usually a negative voltage), with no other neutral or rest condition. The pulses have more energy than a return-to-zero (RZ) code. Unlike RZ, NRZ does not have a rest state. NRZ is not inherently a self-clocking signal, thus some additional synchronization technique (for example a limited constraint, or a parallel synchronization signal) must be used for avoiding bit slip. For a given data signalling rate, i.e., bit rate, the NRZ code requires only half the baseband bandwidth required by the Manchester code (the pass band bandwidth is the same). "One" is represented by one physical level (usually a positive voltage). "Zero" is represented by another level (usually a negative voltage). In clock language, in bipolar NRZ-Level the voltage "swings" from positive to negative on the trailing edge of the previous bit clock cycle. An example of this is RS-232, where "one" is −12 V to −5 V and "zero" is +5 V to +12 V.

MANCHESTER BIPOLAR CODING:

In telecommunication and data storage, Manchester coding (also known as Phase Encoding,

or PE) is a line code in which the encoding of each data bit has at least one transition and

occupies the same time. It therefore has no DC component, and is self-clocking, which means that

it may be inductively or capacitively coupled, and that a clock signal can be recovered from the

encoded data. As a result, electrical connections using a Manchester code are easily galvanically

isolated using a network isolator—a simple one-to-one isolation transformer.

SINGLE CHANNEL 4 BIT PCM TRANSMITTER AND RECEIVER:

This circuit is a PCM system that uses 4 of the 8 bits available. The input signal is a 1Khz sinusoidal

sampled at 8khz, which is the rate used in the public switched telephone network (PSTN), and the

ADC parallel output it's converted to a serial bit stream. To show the recovered signal, a serial to

parallel converter and a DAC is attached to the transmitter. The DAC output is low pass filtered.

Results:

NRZ-B Coding Circuit in OrCAD

NRZ-B Coding Output in OrCAD

Bipolar Manchester Coding Circuit in OrCAD

Bipolar Manchester Coding Output in OrCAD

PCM Coding Circuit in OrCAD

Input Output Signals of DAC in OrCAD

Output of PCM in OrCAD

NRZ-B Coding Circuit in Multisim

NRZ-B Input Signal in Multisim

NRZ-B Output Signal in Multisim

Bipolar Manchester Coding Circuit in Multisim

Bipolar Manchester Input Signal in Multisim

Bipolar Manchester Output Signal in Multisim

Conclusion:

Thus the circuits for generating NRZ-B and Bipolar Manchester coding and Single Channel 4 bit

PCM transmitter and receiver were implemented in Multisim and OrCAD and simulation results

were obtained.