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Cellular field potential includes local field potential (LFP, 0.1Hz∼200Hz) and spike potential (SP, 200Hz∼10kHz). SP signal has been the focus of physiological studies. Recent study shows that the LFP signal plays important roles in modulating many profound cellular mechanisms. Although many bio-signal acquisition circuits have been reported over t...
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... 11-bit SAR ADC is used to quantize the signal from 16 acquisition channels. The sampling clock of every channel has /8 phase shift to enable the multiplexed ADC quantization at 320kS/s. The SAR ADC uses a capacitor array with a bridging capacitor as shown in Fig. 8. This capacitor array needs only 130C 0 to resolve 11 bits. The size of C 0 is found through Monte-Carlo ...
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... The chip is fully verified with biological experiments. A brief description of this work was presented in [32]. This paper includes more analysis, circuit details, and experimental results. ...
The dual-band recording of the local-field potential (LFP, 0.1–200 Hz) and the spike potential (SP, 200 Hz–10 kHz) is important for physiological studies at the cellular level. Recent study shows that the LFP signal plays important roles in modulating many profound cellular mechanisms. Although various bio-signal acquisition circuits have been reported over the years, few designs are applicable to capture both LFP and SP signals. To record both signals accurately, acquisition circuits need low noise and good linearity in both bands. In this paper, we report the design of a dual-band acquisition IC for microelectrode array (MEA) recording. The novel design uses a continuous-time (CT) front-end with chopping to suppress the noise in the LFP band, and a discrete-time (DT) back-end to achieve good linearity. The acquisition channel is fully differential, which leads to a high common-mode rejection ratio (CMRR) and power supply rejection ratio (PSRR) without the 50 Hz injection. The design interfaces the microelectrode with a transistor gate, which has high input impedance. A prototype monolithic acquisition IC is fabricated in a 0.35 $\mu$m CMOS process. It includes 16 channels and an 11 bit successive-approximation (SAR) analog-to-digital converter (ADC). Every channel acquires cellular signals up to 20$~$mV $_{\rm pp}$ with 32.9 nV/Hz $^{0.5}$ and $< 0.1\hbox{\%}$ nonlinearity. The good linearity effectively prevents the aliasing and mixing between the two bands. For LFP signal, the recording noise is 0.9 $\mu$V$_{\rm rms}$. For SP signal, the recording noise is 3.3 $\mu$ V$_{\rm rms}$ . The new design has high input impedance (320 M $\Omega$@1 kHz), high CMRR ( ${>}$ 110 dB) and PSRR ( $>$ 110 dB). The noise-efficiency factor (NEF) of the acquisition channel is 7.6. The IC is experimented to record the field potential from cultured rat cardiomyocytes in-vitro. Overall, the new MEA acquisition channel achieves the state-of-art performance.
With the increasing use of databases, there is an abundant opportunity to investigate new watermarking techniques that cater to the requirements for emerging applications. A major challenge that needs to be tackled is to recover crucial information that may be lost accidentally or due to malicious attacks on a database that represents asset and needs protection. In this paper, we elucidate a scheme for robust watermarking with multiple watermarks that resolve the twin issues of ownership and recovery of information in case of data loss. To resolve ownership conflicts watermark is prepared securely and then embedded into the secretly selected positions of the database. Other watermark encapsulates granular information on user-specified crucial attributes in a manner such that the perturbed or lost data can be regenerated conveniently later. Theoretical analysis proves that the probability of identifying target locations, False hit rate and False miss rate is negligible. We have experimentally verified that the proposed technique is robust enough to extract the watermark accurately even after 100% tuple addition or alteration and after 98% tuple deletion. Experiments on information recovery reveal that successful regeneration of tampered/lost data improves with the increase in the number of candidate attributes for embedding the watermark.
