The bandwidth filter 116 includes an input that is connected to the output terminal of the current differential circuit 114 to receive I_FILTER′. The bandwidth filter 116 can be constructed as any variable center frequency bandwidth filter capable of actively varying its center frequency (fo). In at least one embodiment, the controller 106 generates a center frequency control signal indicative of the center frequency (fo), and the bandwidth filter 116 is a digital bandwidth filter that actively varies its center frequency (fo) based on the center frequency control signal output from the controller 106.

The bandwidth filter 116 filters I_FILTER′ according to a bandwidth having a center frequency (fo) that is dynamically (i.e., actively) set according to an estimated rotational speed (ω) of the rotor 103. Thus, the center frequency (fo) of the bandwidth filter 116 is dynamically adjusted or varied as the rotor speed (ω) changes. Accordingly, the bandwidth filter 116 outputs a bandwidth filtered signal (I_BW) as illustrated in FIG. 4. In at least one embodiment, the present rotational speed (ω) of the rotor 103 can be estimated based on the measured voltage of the motor 102 and the measured current of the motor 102. For example, each time the motor 102 is powered, the starting voltage (U_a) and the starting current (I_a) can be measured, and while operating, the motor voltage (U_m) and motor Current (I_m) can also be measured. The measurements can be performed by the controller 106 and/or various sensors installed on the motor 102. The motor internal resistance, i.e.,

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