Reminder on complex numbers
Form of a complex number
A complex number I can be written in different forms:

in Cartesian form:
I = Ir + j Ii
where:
Ir : real part of I
Ii : imaginary part of I
j: pure imaginary number with j² = –1

in Polar form (or exponential form):
$I=Imod{e}^{j\varphi}$
where:
I mod : modulus of I
ϕ : argument of I (or phase)
j: pure imaginary number with j² = –1
Conjugate of a complex number
The conjugate of I is defined by:
I* = Ir – j Ii
Modulus of a complex number
The modulus of I is defined by: