I(t)=A e Γ 1 (t t p ) { 1+ ε 1 cos[ 2πf(t t p ) ] } (1a) +B{ 1+ ε 2 cos[ 2πf(t t p ) ] },t t p , I(t)=A e Γ 2 (t t p ) { 1+ ε 1 cos[ 2πf(t t p ) ] } (1b) +B{ 1+ ε 2 cos[ 2πf(t t p ) ] },t> t p ,