Method and relative device for sensing amplitude and phase of an electrical signal

A method of sensing an impedance of an electrically conductive tissue through which an AC stimulation current is forced, comprising:

• taking a first sample of a varying electrical signal representing the impedance based upon an arbitrary initial phase offset and assuming the first sampled value as a real amplitude of a modulating signal and the arbitrary initial phase offset as a real phase;
• taking at least one second sample of the varying electrical signal at a phase offset different from the assumed real phase;
• and
• comparing the at least one second sample with the assumed real amplitude, and updating at each period the assumed real amplitude and assumed real phase such as to correspond either to a maximum or minimum sample corresponding phase offset;
• and
• when the AC stimulation current is forced through a portion of tissue between voltage sensing electrodes, generating the varying electrical signal by
• changing a phase of an AC voltage with respect to the AC stimulation current by the phase offset,
• calculating a product between the AC voltage and a voltage of the voltage sensing electrodes applied on a tissue,
• generating a replica of the product, and
• low-pass filtering the replica.

A device for sensing an impedance of an electrically conductive tissue through which an AC stimulation current is forced providing a modulated electrical signal, the device comprising:

• a sample and hold circuit configured to be controlled by a logic control signal, receive a varying electrical signal representing an impedance for sampling the varying electrical signal when the logic control signal is asserted, and output sampled amplitude values;
• a control unit configured to read the sampled amplitude values and generate logic control signals for
• taking a first sample of the varying electrical signal representing the impedance based upon an arbitrary initial phase offset with respect to a null phase of the AC stimulation current and assuming the first sampled value as a real amplitude of a modulating signal and the arbitrary initial phase offset as a real phase,
• taking at least one second sample of the varying electrical signal at a phase offset different from the assumed real phase, and
• comparing the at least one second sample with the assumed real amplitude, and updating at each period the assumed real amplitude and assumed real phase such as to correspond either to a maximum or minimum sample corresponding phase offset;
• and
• an AC current generator configured to
• supply AC current to electrodes applied to the tissue for forcing the AC stimulation current therethrough, and
• when the AC stimulation current is forced through a portion of tissue between the electrodes, generating the varying electrical signal by changing the phase of an AC voltage with respect to the AC stimulation current by the phase offset,
• calculating a product between the AC voltage and a voltage of the voltage sensing electrodes applied on a tissue, and
• generating a replica of the product, and
• low-pass filtering the replica.

A device for sensing an impedance of an electrically conductive tissue through which an AC stimulation current is forced providing a modulated electrical signal, the device comprising:

• a sample and hold circuit configured to sample a varying electrical signal representing an impedance, and output sampled amplitude values;
• a control unit configured to read the sampled amplitude values and generate logic control signals for
• taking a first sample of the varying electrical signal representing the impedance based upon an arbitrary initial phase offset with respect to a null phase of the AC stimulation current and assuming the first sampled value as a real amplitude of a modulating signal and the arbitrary initial phase offset as a real phase,
• taking at least one second sample of the varying electrical signal at a phase offset different from the assumed real phase, and
• comparing the at least one second sample with the assumed real amplitude, and updating at each period the assumed real amplitude and assumed real phase such as to correspond either to a maximum or minimum sample corresponding phase offset;
• and
• an AC current generator configured to
• supply AC current to electrodes applied to the tissue for forcing the AC stimulation current therethrough, and
• when the AC stimulation current is forced through a portion of tissue between the electrodes, generating the varying electrical signal by changing the phase of an AC voltage with respect to the AC stimulation current by the phase offset,
• calculating a product between the AC voltage and a voltage of the voltage sensing electrodes applied on a tissue, and
• generating a replica of the product, and
• low-pass filtering the replica.