This paper discusses the development of a four command BCI system. This system is composed of a wearable electroencephalogram acquisition unit interfaced to a computer by a wireless Bluetooth (BT) connection. The implemented system relies on the steady-state visual evoked potential (SSVEP) protocol applied to a four selection system. In order to achieve the maximum reliability against false positives a five class classifier was used considering the idle state as an independent class. In order to maximize the usability of the system a two channel solution was tested and adopted. The BCI algorithm was based on a supervised multi-class classifier implemented by combining different binary regularized linear discriminant analysis (RLDA) classifiers. The biofeedback was evaluated by combining the resultant time signed distance with quality index related to the number of coherent identification obtained with the one-vs-all approach.

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In this study we explored the possibility to realize a low power device for Cardiac Output continuous monitoring based on impedance cardiography technique. We assessed the possibility to develop a system able to record data allow an intra-subjective analysis based on the daily variations of this measure. The device was able to acquire and to send signals using a wireless Bluetooth transmission. The electronic circuit was designed in order to minimize power consumption, dimension and weight. The reported results were interesting for what concerns the power consumption and then noise level. In this way was obtained a wearable device that will permit to define specific clinical protocols based on continuous monitoring of the Cardiac Output signal.

The here presented work illustrates a novel circuit topology for the conditioning of biomedical signals. The system is composed of an amplification chain and relies on a double feedback path which assures the stability of the system, regardless of the amplification block gain and the order of the low-pass filter settings. During the normal operation, the offset recovery circuit has a linear transfer function, when it detects a saturation of the amplifier, it automatically switches to the fast recovery mode and restores the baseline in few milliseconds. The proposed configuration has been developed in order to make wearable biosignal acquisition devices more robust, simpler and smaller. Thanks to the used AC coupling method, very low high-pass cutoff frequencies, can be achieved even using small valued passive components with advantages in terms of circuit bulkiness. The noise rejection filter between the pre-amplification and the amplification stages eliminates the out-of-band noise before the amplification reducing the possibility of having clipping noise and minimizing the dynamic power consumption. The presented topology is currently used in a prototypal EEG acquisition device in a Brain Computer Interface (BCI) system, and in a commercial polygraph which will be soon certificated for clinical use.