Compressive Sensing system for recording of ECoG signals in-vivo

considered switch is almost ideal, that is, the close circuit resistance is 1 Ω and the open circuitresistance is 1 TΩ. The control voltages have been chosen as underfor closingthe switch, and overto close it. In this way the uncertain range of control voltageis minimize, but anyway the random binary sequence does not distort. The mixer-integrator hasbeen sketched in Fig.6.2.1.1. A complete multipath acquisition array has been implemented inCadence by considering N = 128 and M = 64. The resulting compressed signal has beencompared in Fig.6.2.1.3 with the one which has resulted in Matlab implementation.As the reconstructed signal is robust in both of the models, the differences regarding thesamples of the compressed signal have to be caused by non-idealities during the sampling andintegrating phases. The compressed signal coming from Cadence is slightly different to the onewhich has been calculated in Matlab, so the reconstruction signal for both of the models iscompared in Fig.6.2.1.4 for LASSO reconstruction method and in Fig.6.2.1.5 for BPDM. InLASSO-based reconstruction (see Eq.15) and in BPDN-based reconstruction(see Eq.14). Both of the values have been chosen as those which have led a better SNRbetween the original signal and the reconstructed one. Hereafter reconstructed signals areincluded for each topology, a comparison between all of them is introduced at 6.2.5 and SNRcomparison is included in 6.2.6.Figure 6.2.1.3. Compressed signals comparison.It is clear that this topology cannot be used for CS purposes on-chip, because in order toincrease the signal swing it is necessary to increase the RC ratio, and so, it becomes a noimplementable design due to area constraints.57