Summary
Highlights
The video introduces the third lab experiment: Frequency Division Multiplexing (FDM) and Demultiplexing. It emphasizes the importance of multiplexing in modern communication. The setup involves two audio frequency (AF) signal generators (AF1 at 1kHz and AF2 at 2kHz) and a clock generator. These signals are fed into Frequency Modulators (FM1 with a 10kHz carrier and FM2 with a 20kHz carrier) before reaching the multiplexer.
Before applying signals to the FM modulators, the video demonstrates how to verify the output of AF1 and AF2 generators using a DSO. The amplitude of these signals can be adjusted based on requirements. The clock signal is also checked to ensure it's functioning correctly, despite some minor noise.
AF1 is applied to FM Modulator 1 and AF2 to FM Modulator 2. The output of FM1 is then checked on the DSO. Adjustments are made to the message signal's amplitude to achieve a clear FM signal, observing variations in frequency. The internal carrier signal of FM1 (without the message signal) is also shown. The same process is repeated for FM Modulator 2 to ensure a clear FM output.
The outputs of the two FM modulators are then fed into the multiplexer, along with the clock pulse. The definition of a multiplexer Selecting one output from N inputs based on selection lines (represented by the clock pulse here) is discussed. FDM is defined as dividing the communication channel into unoverlapped frequency bands, allowing multiple inputs to be transmitted simultaneously to produce a single Frequency Division Multiplexed signal.
The video then moves to demultiplexing, which involves separating a single input into multiple outputs (2^n outputs from one input). Synchronization with the clock pulse is crucial for accurate communication. The output from FM Demodulator 1 (after demultiplexing) is checked, confirming it retrieves the original AF1 message signal. A Phase-Locked Loop (PLL) adjuster is used to control noise and refine the message signal shape. The same procedure is followed for FM Demodulator 2, although some distortion is noted, indicating the potential need for an extra circuit.