Online Simulator for DSB-SC, SSB-SC and Standard AM

Amplitude Modulation & Demodulation (DSB-SC, SSB-SC, and Standard AM)

Modulation Scheme DSB-SC SSB-SC (USB) Standard AM

Msg Freq (fm)

Carrier Freq (fc)

SNR (dB)

Phase Error (φ)

Mode: DSB-SC

Reconstruction Fidelity: 100%

1. Source Signals (Message in Red, Carrier in Blue)

2. Modulated Wave (Transmitted over Noisy Channel)

3. Demodulated Output vs. Original Message

Mathematical Operations & Communication Theory

1. Modulation Stage: The baseband message $m(t)$ is shifted to a higher frequency $f_c$ for efficient transmission. Depending on the scheme, the mathematical model changes:

DSB-SC: s(t) = m(t) · cos(2πfct)
Standard AM: s(t) = [A + m(t)] · cos(2πfct)
SSB-SC: s(t) = m(t)cos(2πfct) ∓ m̂(t)sin(2πfct)

2. Coherent Detection (The Demodulator): To recover the signal, we use a Product Detector. The received signal $r(t)$ is multiplied by a local oscillator $cos(2πfct + φ)$.

v(t) = s(t) · cos(2πfct + φ)

Using trigonometric identities, this generates a baseband component and a high-frequency component at $2f_c$. By passing $v(t)$ through a Low Pass Filter (LPF), we extract the original message.

3. Effect of Phase Error (φ): If the local oscillator is not perfectly synchronized ($φ \neq 0$), the output amplitude is scaled by $cos(φ)$. At $φ = 90^\circ$ (Quadrature Null Effect), the output signal is completely lost in DSB systems.