Correct Answer - Option 4 : 1
1) General equation of SSB modulated wave:
\(s\left( t \right) = \frac{{{A_C}{A_m}}}{2}cos\;2\pi \left( {{f_c} + {f_m}} \right)t\)
2) Output of envelope detector to signal
Acos ωct → A
Application:
Equation of SSB modulated signal
Ac = Am = 1
\(s\left( t \right) = \frac{1}{2}\cos \left( {{\omega _c} \pm {\omega _n}} \right)t\)
the output of envelope detector = ½
The output of the envelope detector is a constant voltage signal
Hence option (d) which represents a constant voltage is correct.