This technical demonstration outlines a methodology for simulating Amplitude Modulation (AM) within the Proteus Design Suite. The procedure utilizes the software’s virtual signal generator, which features integrated modulation functions, to combine a high-frequency carrier wave with a lower-frequency information (modulating) signal. By adjusting the amplitudes of these signals, the simulation provides a visual analysis of the modulation index via a virtual oscilloscope. The demonstration specifically categorizes the resulting waveforms into three distinct states: under-modulation (50%), critical modulation (100%), and over-modulation (>100%), highlighting the envelope distortion and phase inversion associated with exceeding a 1.0 modulation index.
Simulation of Amplitude Modulation in Proteus
0:00 - Component Selection: The simulation requires a carrier signal, an information signal, and a modulator. The Proteus virtual signal generator is selected as the primary instrument because it possesses native modulation functionality.
0:41 - Oscilloscope Configuration: Channel A of the virtual oscilloscope is interfaced with the signal generator’s output to monitor the modulated waveform, while a common ground is established via the terminal section.
1:12 - Carrier Wave Parameters: To optimize computational performance, the carrier frequency is set to 10kHz with an initial peak amplitude of 4V. Oscilloscope settings (volts per division and time base) are calibrated to ensure a stable visualization of the carrier.
2:42 - Information Signal Integration: A secondary sine wave generator provides the information (modulating) signal. Initial parameters are set to a frequency of 50Hz and an amplitude of 2V. This signal is monitored on Channel B for side-by-side comparison.
4:10 - Modulation Index Analysis (50%): With a 2V information signal and a 4V carrier, a modulation index ($m$) of 0.5 is achieved. The oscilloscope confirms that the information signal fits perfectly within the carrier envelope without reaching the zero-crossing point.
5:15 - Critical Modulation (100%): By increasing the information signal amplitude to 4V to match the carrier ($m=1.0$), the simulation demonstrates 100% modulation. The sidebands fully converge at the center axis, representing the theoretical limit for envelope detection without distortion.
6:06 - Over-modulation (>100%): Increasing the information signal to 6V ($m=1.5$) results in over-modulation. This state is characterized by "triplet" forms and inverted envelopes at the carrier’s center, which would cause significant signal clipping and distortion in physical hardware.
7:03 - Future Iterations: The demonstration concludes by suggesting that while a pure sine wave was used for these index calculations, real-world applications involving irregular audio files will be explored in subsequent sessions to observe complex envelope patterns.
Reviewer Recommendation
This topic is best reviewed by Electrical Engineering Educators, Telecommunications Students, and Junior Circuit Designers. The following summary is tailored for this specialized audience:
Technical Summary: AM Index Verification via Proteus CAD
The demonstration validates the mathematical principles of Amplitude Modulation (AM) using the Proteus virtual instrumentation suite. By leveraging the signal generator's modulation input, users can empirically observe the relationship between carrier amplitude ($V_c$) and modulating amplitude ($V_m$). The simulation effectively visualizes the Envelope Detection theory, illustrating how a modulation index $m \le 1$ maintains signal integrity, whereas $m > 1$ introduces phase reversal and envelope distortion. This provides a low-overhead environment for testing modulation depth before moving to physical breadboarding or PCB layout.