Apparatus for treating neurological disorders by electrostimulation and method for processing neural signals collected by the said apparatus
The present disclosure relates to apparatuses and methods for treating neurological disorders by electro-stimulation. In some embodiments, the apparatus includes a stimulation module configured to generate a stimulation signal to be sent to at least one implantable electrode, and an acquisition module configured to acquire a signal measured by the at least one implantable electrode from a patient. The acquisition module may include a front-end block configured to amplify a potential difference of input signals (V 1 a , V 2 a ) received by the acquisition module and to filter a stimulus artifact by cutting off frequencies above a predefined frequency band. The front-end block may include a multi-stage fully-differential switched capacitor circuit configured for discrete-time signal processing.
1. An apparatus comprising:
a stimulation module configured to generate a stimulation signal to be sent to at least one implantable electrode, and
an acquisition module configured to acquire a signal measured by the at least one implantable electrode from a patient,
wherein the acquisition module comprises a front-end block configured to amplify a potential difference of input signals (V 1a , V 2a ) received by the acquisition module and to filter a stimulus artifact by cutting off frequencies above a predefined frequency band; characterized in that the front-end block comprises a multi-stage fully-differential switched capacitor circuit configured for discrete-time signal processing.
2. The apparatus of claim 1 , wherein the front-end block comprises a pre-filter stage and a suppression filter stage positioned downstream from the pre-filter stage.
3. The apparatus of claim 2 , wherein each of the pre-filter stage and the suppression filter stage comprising a fully-differential switched capacitor circuit configured for discrete-time signal processing.
4. The apparatus of claim 3 , wherein the pre-filter stage comprises a first fully-differential low-pass switched capacitor filter, clocked at a first clock frequency.
5. The apparatus of claim 4 , wherein the suppression filter stage comprises a second fully-differential low-pass switched capacitor filter, clocked at a second clock frequency.
6. The apparatus of claim 4 , wherein the fully-differential switched capacitor filter of the pre-filter stage and of the suppression filter stage comprises at least one bilinear switched capacitor integrator.
7. The apparatus of claim 6 , wherein the at least one bilinear switched capacitor integrator is configured to implement correlated double sampling.
8. The apparatus of claim 6 , wherein the at least one bilinear switched capacitor integrator comprises two inputs (V 1a ,V 2a ) which are alternatively connectable to one end of two input capacitors (C 1 , C 2 ), the other end of the two input capacitors (C 1 , C 2 ) being configured to alternatively connect to a reference voltage source (V ref ) or, each respectively, to one of two inputs of an operational amplifier.
9. The apparatus of claim 8 , wherein each input of the operational amplifier being connectable to one respective output of the operational amplifier through interposition of a first (C 3 ,C 5 ) and a second (C 4 ,C 6 ) pair of feedback capacitors, respectively.
10. The apparatus of claim 9 , wherein the feedback capacitor pairs (C 3 ,C 5 ) and (C 4 ,C 6 ,) comprise each a first (C 3 ,C 4 ) and a second (C 5 ,C 6 ) feedback capacitors connected in parallel, and are configured to alternatively connect to the respective input of the operational amplifier .
11. The apparatus of claim 6 , wherein the at least one bilinear switched capacitor integrator comprises two inputs (V 1a ,V 2a ) which are alternatively connectable to one end of two input capacitors (C 1 , C 2 ), the other end of the two input capacitors (C 1 , C 2 ) being configured to alternatively connect to a reference voltage source (V ref ) or, each respectively, to one of two inputs of an operational amplifier, each input of the operational amplifier being connectable to one respective output of the operational amplifier through interposition of a first (C 3 ) and a second (C 4 ) feedback capacitor, respectively.
12. The apparatus of claim 3 , wherein the fully-differential switched capacitor circuit of the pre-filter stage and/or of the suppression filter stage is implemented as ladder filter comprising a plurality of switched capacitor integrators in an active emulation of lossless LC ladder structure.
13. The apparatus of claim 5 , wherein the first fully-differential switched capacitor filter of the pre-filter stage has an order lower than an order of the second fully-differential switched capacitor filter of the suppression filter stage.
14. The apparatus of claim 5 , wherein the first clock frequency of the first fully-differential switched capacitor filter of the pre-filter stage is greater than the second clock frequency of the second fully-differential switched capacitor filter of the suppression filter stage.
15. The apparatus of claim 4 , wherein the first clock frequency is at least 1 KHz.
16. The apparatus of claim 5 , wherein a first cut-off frequency of the first fully-differential switched capacitor filter of the pre-filter stage is greater than a second cut-off frequency of the second fully-differential switched capacitor filter of the suppression filter stage.
17. The apparatus of claim 5 , wherein a first cut-off frequency of the first fully-differential switched capacitor filter of the pre-filter stage is at least 50 Hz and is lower than the second clock frequency.
18. The apparatus of claim 5 , wherein a second cut-off frequency of the second fully-differential switched capacitor filter of the suppression filter stage is in the range of about 35-2000 Hz.
19. The apparatus of claim 1 , wherein the acquisition module further comprises an A/D converter block connected downstream from the front-end block.
20. The apparatus of claim 19 , wherein the A/D converter block optionally comprises a delta-sigma converter.
21. The apparatus of claim 19 , wherein the A/D converter block comprises a fully-differential switched-capacitor circuit.
22. The apparatus of claim 19 , wherein the A/D converter block comprises a first sampling stage, followed by a filter stage configured for removing a quantization noise and a decimation stage.
23. The apparatus of claim 1 , wherein the acquisition module further comprises at least one functional module between:
a first functional module configured for receiving an input synchronization signal coming from the stimulation module for disconnecting or grounding the inputs of the front-end block during stimulus pulses generated by the stimulation module, the first functional module being connected upstream from the front-end block; and/or
a second functional module configured for eliminating high frequencies in a signal produced by the operation of the first functional module; and/or
a third functional module configured for providing high-pass filtering so as to mitigate offset potentials at the at least one implantable electrode.
24. A method comprising:
receiving a signal using at least one implantable electrode;
amplifying and pre-filtering the signal acquired by using a first stage comprising a fully-differential switched capacitor circuit configured for discrete-time signal processing; and
filtering the amplified and pre-filtered signal by cutting off frequencies above a predefined frequency band using a second stage comprising a fully-differential switched capacitor circuit configured for discrete-time signal processing.
25. The method of claim 24 , wherein amplifying the signal or filtering the amplified signal comprises correlated double sampling.
26. The method of claim 24 , wherein amplifying the signal is performed using a first fully-differential switched capacitor filter, clocked at a first clock frequency.
27. The method of claim 26 , wherein the step of filtering the amplified signal is performed using a second fully-differential switched capacitor filter, clocked at a second clock frequency.
28. The method of claim 27 , wherein the first clock frequency is greater than the second clock frequency.
29. The method of claim 27 , wherein a first clock signal at the first clock frequency and/or a second clock signal at the second clock frequency are configured to time an alternative connection and disconnection of second feedback capacitors (C 5 ,C 6 ) of feedback capacitor pairs (C 3 ,C 5 ) and (C 4 ,C 6 ) to the input of an operational amplifier.
30. The method of claim 27 , wherein the first fully-differential switched capacitor filter is a low-pass filter with a first cut-off frequency and the second fully-differential switched capacitor filter is a low-pass filter with a second cut-off frequency smaller than the first cut-off frequency.
31. The method of claim 27 , wherein the first fully-differential switched capacitor filter of the pre-filter stage has an order lower than an order of the second fully-differential switched capacitor filter of the suppression filter stage.
32. The method of claim 25 , wherein the correlated double sampling is implemented using a bilinear switched capacitor integrator, and wherein the bilinear switched capacitor integrator comprises two inputs (V 1a ,V 2a ) which are alternatively connectable to one end of two input capacitors (C 1 , C 2 ), another end of the two input capacitors (C 1 , C 2 ) being configured to alternatively connect to a reference voltage source (V ref ) or, each respectively, to one of two inputs of an operational amplifier.
33. The method of claim 32 , wherein each input of the operational amplifier being connectable to one respective output of the operational amplifier through interposition of a first pair (C 3 ,C 5 ) and a second pair (C 4 ,C 6 ) of feedback capacitors, respectively.
34. The method of claim 33 , wherein the first pair (C 3 ,C 5 ) and the second pair (C 4 ,C 6 ) of feedback capacitors comprise each a first (C 3 ,C 4 ) and a second (C 5 ,C 6 ) feedback capacitors connected in parallel, and are configured to alternatively connect to the respective input of the operational amplifier.