●●●】 ●●●● ●●●● Input signal power:S,=42/2 ●●●● ()=4 ●●●● Output signal cos.1+2 ●●●● ● power: Input narrowband y-6nio=Foy+55rog noise power: =E{x2(t)}=E{y2(t)} Output noise power: The output SNR: So S, No Ni Conclusion:SSB demodulator does not degrade the input SNR 结论：单边带解调器并不恶化输入的信噪比。 15Input signal power: Output signal power: Input narrowband noise power: Output noise power: The output SNR: Conclusion: SSB demodulator does not degrade the input SNR. 结论：单边带解调器并不恶化输入的信噪比。 15 2 / 2 i S A  2 2 0 1 ( ) 22 8 4i A A S S    0 1 ( ) cos 2 2 m A v t t xt    222 2 2 1 1 { ( )} { ( )} { ( )} 2 2 { ( )} { ( )} N En t Ex t Ey t i Ex t Ey t     2 2 0 1 1 {[ ( )] } { ( )} 24 4Ni N E xt E x t   0 0 i i S S N N 