Time Division Multiplexing and Demultiplexing using Emona trainer 101 #Digital communication lab

The video introduces Time Division Multiplexing (TDM) and Demultiplexing. It distinguishes between multiplexing, where multiple signals are combined into one for transmission over a single channel, and multiple access, where multiple signals access the same channel without combining, using techniques like frequency, time, or code.

The speaker presents the block diagram for the TDM experiment. Two sine wave signals (1 kHz and 2 kHz) are used as inputs to a TDM encoder. The encoded signal is then passed to a TDM decoder, followed by a low-pass filter to reconstruct the original signals. The Emona Trainer 101 kit is used, which has two input channels, but more can be simulated in software like MATLAB.

Since a 1 kHz sine wave is not directly available from the master signal on the trainer kit, it is generated using a Voltage Controlled Oscillator (VCO). The frequency of this generated sine wave is then adjusted and measured using an oscilloscope to achieve approximately 1 kHz.

The 1 kHz sine wave from the VCO and a 2 kHz sine wave from the master signal are fed into the TDM encoder. A 100 kHz clock frequency is used. The output of the TDM multiplexer, which is a combined signal of both inputs, is shown on the oscilloscope. This combined signal exhibits some distortion due to the addition of the two input signals.

The first output signal from the TDM decoder (corresponding to the 1 kHz input) is passed through a low-pass filter. The reconstructed signal and the original 1 kHz signal are displayed on the oscilloscope. The frequency of the reconstructed signal is measured, showing an accurate reconstruction of the 1 kHz input.

Next, the second output signal from the TDM decoder (corresponding to the 2 kHz input) is connected to the low-pass filter. The reconstructed 2 kHz signal and the original 2 kHz signal are observed and measured on the oscilloscope, confirming accurate reconstruction.

The experiment successfully demonstrates time division multiplexing where two signals are combined, transmitted over a single channel, and then accurately reconstructed. The speaker reiterates the difference between multiplexing (combining and transmitting) and multiple access (dividing a single channel based on frequency, time, or code). In TDM, signals are combined and extracted from different output ports.