Summary
Highlights
The video introduces the goal of practicing amplitude modulation using Proteus. It highlights the need for a carrier signal, an information signal, and a modulator. The Proteus signal generator can act as a modulator due to its built-in modulation functions. An oscilloscope is used to monitor the waveforms, with Channel A connected to the signal generator's positive output and a ground terminal.
The initial setup shows how the signal generator's output, which will be the carrier wave, looks on the oscilloscope. The frequency is set to 10K, and the amplitude to 4V. The oscilloscope's volts per division (for Channel A) and vertical position are adjusted to get a clear view of the sinusoidal carrier wave.
A second signal generator is introduced to provide the information signal (a sine wave). Its amplitude is set to 2V and frequency to 50Hz. Channel B of the oscilloscope is connected to this information signal to visualize both the carrier (yellow) and information (blue) signals. The carrier signal is shown to be modulated by the information signal, where its amplitude changes based on the information signal's amplitude.
With the carrier at 4V and the information signal at 2V, the demonstration shows a 50% modulation index. The modulated yellow wave clearly shows its amplitude varying according to the blue information signal, which fits perfectly within its envelope. This allows for demodulation to reconstruct the original information.
To achieve 100% modulation, the information signal's amplitude is increased to 4V, matching the carrier's amplitude. The resulting waveform shows complete modulation, where the envelope of the carrier perfectly touches the zero line, indicating full modulation by the information signal without any visible carrier component in the center of the sidebands.
The video then demonstrates over-modulation by increasing the information signal's amplitude to 6V, exceeding the carrier's amplitude. This results in 'triangles' or an inverted waveform appearing in between the modulated signal, which is characteristic of over-modulation (more than 100% modulation index). The video concludes by encouraging users to experiment with different amplitudes and frequencies.