A	Modulus of the analytic signal
a	Scale parameter
$a_i$	Approximation of level i obtained from the discrete wavelet transform
$di$	Detail of level i obtained from the discrete wavelet transform
f	Frequency
$\varphi$	Phase of the analytic signal
$f_1$	Supply frequency
$f_b$	Bandwidth parameter of a wavelet
$f_{B,i}$	Frequency of the fault harmonic related to an inner race cyclic defect
$f_{B,o}$	Frequency of the fault harmonic related to an outer race cyclic defect
$f_{bb}$	Frequency of the fault harmonic related to a bar breakage fault
$f_c$	Central frequency of a wavelet
$f_{ME}$	Frequency of the fault harmonic related to a mixed eccentricity fault
$f_P$	Frequency of the fault harmonic related to load torque pulsation
$f_r$	Rotation frequency of the rotor
$f_s$	Sampling frequency
$f_{tp}$	Frequency of a load torque pulsation
$i_{as}$	Analytic signal obtained from Hilbert transform
$i_{exc}$	Current signal which contains the mixed eccentricity component, obtained through discrete wavelet filtering of tested stator current
$i_{Ls}$	Low sideband component of the stator current
$N_b$	Number of bearing balls
p	Number of pole pairs
$P_x$	Distribution of the energy of a signal x
$R_{IF}$	Correlation parameter
s	Slip, rotor relative speed related to magnetic field speed, in pu
t	Time
$x\left(t\right)$	Generic signal defined in the time domain
$x*$	Conjugate of x
Y	Hilbert transform of a signal
$\psi$	Mother wavelet