this work presents a compact wide-range fully integrated sinusoidal signal generator for in vivo Electrochemical Impedance Spectroscopy applications. The circuit is based on a novel architecture combining aspects of direct digital synthesis and interpolation digital to analog conversion. The signal generator demonstrates very precise frequency tuning and high spectral purity, while offering a simple architecture and an uncomplicated clocking scheme. The circuit is fabricated using a 0.5µm sea of transistors CMOS process and occupies 0.32mm2 of active die area. Consuming 110µA at a 3V supply, the circuit covers eight decades of frequency from 1mHz to 100kHz and meets the necessary low energy and high precision requirements for implantable bio-diagnostics.Keywords-impedance spectroscopy; in vivo measurements, DDFS, wide frequency range signal generator, interpolation DAC, SMARTImplant.

Abstract.In this work an Application Specific Integrated Circuit (ASIC) for an implantable electrochemical biosensor system (SMART implant, Stett et al., 2014) is presented. The ASIC drives the measurement electrodes and performs amperometric measurements for determining the oxygen concentration, potentiometric measurements for evaluating the pH-level as well as temperature measurements. A 10-bit pipeline analog to digital (ADC) is used to digitize the acquired analog samples and is implemented as a single stage to reduce power consumption and chip area. For pH measurements, an offset subtraction technique is employed to raise the resolution to 12-bits. Charge integration is utilized for oxygen and temperature measurements with the capability to cover current ranges between 30 nA and 1 µA. In order to achieve good performance over a wide range of supply and process variations, internal reference voltages are generated from a programmable band-gap regulated circuit and biasing currents are supplied from a wide-range bootstrap current reference. To accommodate the limited available electrical power, all components are designed for low power operation. Also a sequential operation approach is applied, in which essential circuit building blocks are time multiplexed between different measurement types. All measurement sequences and parameters are programmable and can be adjusted for different tissues and media. The chip communicates with external unites through a full duplex two-wire Serial Peripheral Interface (SPI), which receives operational instructions and at the same time outputs the internally stored measurement data. The circuit has been fabricated in a standard 0.5-µm CMOS process and operates on a supply as low as 2.7 V. Measurement results show good performance and agree with circuit simulation. It consumes a maximum of 500 µA DC current and is clocked between 500 kHz and

The widespread of embedded computer networks as part of everyday peoples' lives is leading the current research towards smart environments and Ambient Intelligence (AmI). AmI is a new information paradigm where people are empowered through a digital environment that is "aware" of their presence and context and is sensitive, adaptive and responsive to their needs. In this paper, we describe the intelligent Classroom (iClass) which aims to realize the AmI vision in Education in universities and schools. We will describe the architecture employed to build the iClass and we will present three different directions including the utilization of RFID technology, interacting with the user via speech and developing intelligent agents to learn the user behavior and adapt to its change over short and long time intervals.

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