This paper presents a closed-loop remote powering link for wireless cortical implants. The link operates from a single power supply at the external reader and delivers power to the implant adaptively under changing load conditions. A feedback information is sent from the implant to the external reader about the power consumption in the implant and the external reader adapts the amount of transmitted power depending on this feedback. In addition, an in vitro measurement setup is fabricated in order to characterize the performance of the wireless energy transfer when the implant is immersed into saline solution. The implant is packaged by using biocompatible materials and the operation of the remote powering link is demonstrated in air and in vitro for a wide range of load power delivered from the voltage regulator. The power transfer efficiency of the overall closed-loop remote powering link is measured to be 10.6% in vitro at nominal load power of 10 mW. Finally, the operation of the implant in vitro is demonstrated over a five-week period.

The corrosion and tribocorrosion of tungsten in 0.01 M H(2)SO(4), without and with the presence of lactic acid and phosphoric acid as chelating agents was studied here.The passive behaviour was characterised using potentiostatic polarization and potential step techniques combined with rotating disk electrodes. Surface analysis techniques (XPS, AES) were used to assess surface chemistry. The tribocorrosion of tungsten was investigated using a tribometer equipped with an electrochemical cell operating at applied passive potentials of 0.2V and 1.0V.Under static corrosion conditions chelating agents were found to enhance passive film dissolution and to decrease the passive film thickness. Despite this, the effect of the investigated chelating agents was limited under tribocorrosion conditions. Indeed, only lactic acid at the most anodic potential lead to significant differences in material removal by impeding the formation of protective tungsten oxide tribolayers. The discrepancy on the effect of chelating agents in corrosion and tribocorrosion was explained in terms of the different involved time constants. (C) 2011 Elsevier Ltd. All rights reserved.

This article presents the numerical analysis of temperature elevation in the head due to the operation of a wireless cortical implant. The thermal analyses are done by using a finite-difference time-domain simulation tool and a high-resolution 3-D head phantom with 22 different tissues. The effects of the power dissipation level, size, location, and packaging of the implant on the temperature distribution in the head are investigated by using a generic silicon chip. Furthermore, the distribution of the power consumption in the implant by using multiple integrated circuits is discussed. In order not to exceed the safety precaution limit of 1°C, maximum allowable power dissipation in a chip of size 2 × 2 × 0.5 mm3 is found to be 5.3 mW, whereas it is 9.3 mW for an implant with two chips of the same size separated by 10 mm. Additionally, the thermal analysis of a wireless cortical implant is also done by using a two-body cortical implant prototype. Maximum allowable power consumption for the two-body implant is found as 35 mW, whereas the unibody implant can only dissipate 17.5 mW without exceeding the safety precaution limit. By using the two-body implant, the maximum allowable power consumption in the implant can be increased or the temperature elevation in the tissues can be decreased.

This paper describes a receiver system design for impulse-radio ultra-wideband (IR-UWB) that operates at two carrier frequencies-3.494 and 3.993 GHz-with a 10-Mbps data rate. To reduce the power consumption of the front-end amplifiers, a super-regenerative architecture is used. An integrated circuit, implemented in a CMOS 0.18-μm technology and operating with a 1.5-V power supply, exhibits energy consumption of 0.24 nJ/bit with a measured sensitivity of -66 and -61 dBm at 3.494 and 3.993 GHz, respectively, with a BER of 10-3. Also included on the integrated circuit is an automatic tuning circuit based on a digital phase-locked loop that is used to set the resonant frequency of the super-regenerative block.

Standard voltages used in today's ICs may vary from about 1.3V to more than 100V, depending on the technology and the application. High voltage is therefore a relative notion. High Voltage Devices and Circuits in Standard CMOS Technologies is mainly focused on standard CMOS technologies, where high voltage (HV) is defined as any voltage higher than the nominal (low) voltage, i.e. 5V, 3.3V, or even lower. In this standard CMOS environment, IC designers are more and more frequently confronted with HV problems, particularly at the I/O level of the circuit. In the first group of applications, a large range of industrial or consumer circuits either require HV driving capabilities, or are supposed to work in a high-voltage environment. This includes ultrasonic drivers, flat panel displays, robotics, automotive, etc. On the other hand, in the emerging field of integrated microsystems, MEMS actuators mainly make use of electrostatic forces involving voltages in the typical range of 30 to 60V. Last but not least, with the advent of deep sub-micron and/or low-power technologies, the operating voltage tends towards levels ranging from 1V to 2.5V, while the interface needs to be compatible with higher voltages, such as 5V. For all these categories of applications, it is usually preferable to perform most of the signal processing at low voltage, while the resulting output rises to a higher voltage level. Solving this problem requires some special actions at three levels: technology, circuit design and layout. High Voltage Devices and Circuits in Standard CMOS Technologies addresses these topics in a clear and organized way. The theoretical background is supported by practical information and design examples. It is an invaluable reference for researchers and professionals in both the design and device communities.

This article presents an inductive power link for a cortical implant. The link includes a Class-E power amplifier, an inductive link, a matching network, and a rectifier. The coils of the inductive link are designed and optimized for a distance of 10mm (scalp thickness). The power amplifier is designed in order to allow closed loop power control by controlling the supply voltage. A new packaging topology is proposed in order to position the implant in the skull, without occupying much area, but still obtaining short distance between the remote powering coils. The package is fabricated using biocompatible materials such as PDMS and Parylene-C, and it includes the secondary coil, the matching network, and the rectifier. The power efficiency of the link is characterized for a wide range of load power (1-20mW) and found to be 8.1% for nominal load of 10mW. The matching network improves the power efficiency on the whole range, compared to the link without the matching network.

Radio Frequency IDentification (RFID) stores and retrieves data using devices called RFID tags: objects attached to or incorporated into a product, animal or person which communicate with an RFID reader or interrogator. This book proposes a linear two-port model for an N-stage modified-Greinacher full wave rectifier, predicting the overall conversion efficiency at low power levels where the diodes are operating near their threshold voltage. Included is an experimental procedure to measure how impedance modulation in the tag affects the signal at the reader, and a useful tool for choosing the most appropriate impedances.

The tribocorrosion behavior of tungsten sliding against an alumina ball was evaluated in sulfuric acid under applied electrode potential. Surface chemistry of worn and unworn surfaces was evaluated using XPS and AES. Quasi-potentiostatic polarization curves and potential step measurements were performed under mass transport control to assess relevant corrosion factors. It was found that the tribocorrosion rate of tungsten varies with the applied electrode potential and goes through a maximum for a potential of 0.5V MSE. Different material removal mechanisms were identified. In the wear track, materials deterioration proceeds by cyclic mechanical removal of the passive oxide film followed by anodic oxidation. The removal rate was found to be proportional to the passivation charge density determined in independent electrochemical experiments. At higher potential (1V MSE) a thick WO3 tribolayer forms and by covering the wear track reduces the tribocorrosion damage. Outside the wear track the stirring of the solution induced by the moving alumina ball leads to an enhancement of the dissolution rate of the WO3 passive film and thus to higher material wastage.

This article presents the analysis of the power efficiency of the inductive links used for remote powering of the biomedical implants by considering the effect of the load resistance on the efficiency. The optimum load condition for the inductive links is calculated from the analysis and the coils are optimized accordingly. A remote powering link topology with a matching network between the inductive link and the rectifier has been proposed to operate the inductive link near its optimum load condition to improve overall efficiency. Simulation and measurement results are presented and compared for different configurations. It is shown that, the overall efficiency of the remote powering link can be increased from 9.84% to 20.85% for 6 mW and from 13.16% to 18.85% for 10 mW power delivered to the regulator, respectively.

A model is proposed to describe the fundamental read range limitation due to the local oscillator phase noise in the reader, in IF-based, far-field RFID systems using amplitude-shift keying backscatter modulation. The relation between the system parameters (such as the data transfer rate) and the read range is discussed. The model is validated by measurements done on two different laboratory tag-reader systems.

The impulse radio-ultra wide band (IR-UWB) signalling format has been an attractive mode for wireless communication in wireless sensor node system. The super-regenerative principle can be used for impulse reception for its inherent advantages. The oscillator is the main building block in a super-regenerative based impulse reception system. It is necessary for the oscillator to be tuned to the carrier frequency of the received pulse for achieving maximum sensitivity. In this paper, a multi-band tuning circuitry based on the frequency synthesizer architecture is shown. The oscillator can be tuned to either 3.494 GHz or 3.993 GHz. The circuit is implemented in a CMOS 0.18 mum technology and consumes 8 mA current at 1.5 V supply voltage.

This work presents an investigation of the tribocorrosion of ruthenium in sulphuric acid solutions.

This paper presents a novel architecture for wireless communication systems made up of a base station and a remotely powered transponder. The architecture enables the base station to perform wireless voltage regulation (WVR) of the rectifier's output voltage in the transponder. This new regulation technique can be embedded in any system, provided that the passive transponder uses an IF to transmit data to the base station. The technique relies on a large scale, wireless feedback loop that includes the base station, and the transponder. The overall power efficiency of the system is improved compared to conventional voltage regulation technique. A small-signal model is derived to gain some insight on the dynamics and on the stability of the feedback loop. Measurements were made on an actual system operating in far field at 866.6 MHz. They demonstrate the efficiency improvement related to the use of WVR. The validity of the small-signal model is discussed according to the measurement results.

Suspended Gate (SG) FET valid for entire bias range is proposed. The model is capable of simulating both pull-in and pull-out effects, which are the two important phenomena of this device. A novel hybrid numerical simulation approach combining ANSYS Multiphysics and ISE-DESSIS in a self-consistent system is developed. The model is then validated on this numerical device simulation of SGFET. The model shows excellent performance over the entire drain and gate voltage range. The model has been implemented in Verilog-A code and tested on ELDO and Spectre simulators, which makes it useful for circuit simulations using SGFET devices.

This article presents the design of the inductive links of remotely powered wireless cortical implants for minimum interference from the power link to the data link. This interference is minimized by changing the orientation of the inductors. Different orientation types are investigated and compared. Orthogonally oriented coils with high interference suppression and better reproducibility has been proposed. From the simulations, 29% power efficiency and 46 dB interference suppression is achieved for these coils. The spiral inductors are fabricated on PCBs and results of preliminary measurements are presented. Moreover, a conceptual cortical implant prototype is proposed.

This paper presents the analysis of inductive links for remote powering of implantable devices and a method to improve the power link efficiency by modifying the geometrical parameters of planar spiral inductors. The analysis of the inductive links includes a model for the inductors, which is more accurate for larger bandwidths. The corresponding equations for the power and voltage transfer functions in the inductive links are solved by using MATLABpsilas Symbolic Math Toolbox. These equations are verified in Agilent ADS, and the results perfectly match. Besides the analysis, a method to improve the power efficiency by changing the geometrical parameters of the spiral inductors is proposed.

Low power impulse radio-ultra wide band(IR-UWB) receivers have potential application in the area of wireless sensor networks. In this paper the possibility ofsuperregenerative receivers for pulse detection is demonstrated. The super-regenerative receiver is implemented in a 0.18 mu m CMOS process for a 500 MHz bandwidth (-3 dB) centered at 3.8 GHz. The receiver is operating at 1.5 V and consumes a peak current of 7.5 mA. The receiver shows a 16.5 mV amplitude difference between the presence and absence of a pulse at an average received power of -91.3 dBm at a pulse repetition rate of 1 MHz.

This article presents the numerical analysis of temperature increase in the human head resulting from the power dissipation in a cortical implant. A 3-D head phantom with 22 tissue types and 0.2 mm × 0.2 mm × 2 mm resolution has been used in the simulations. The dependencies of the temperature increase on the power dissipation level, chip size, and location of the implant are investigated. Moreover, distributing power dissipation by using multiple integrated circuits in the implant is discussed. Maximum allowable total power dissipation in a cortical implant of size 2 × 2 mm2 is found to be 4.8 mW, whereas, it is 8.4 mW for an implant with two chips of same size placed 10 mm apart.

The recent increase in the need for energy efficient wireless nodes have led to the study of various low power consumption receiver and transmitter architectures. The super-regenerative receiver architecture is one of the possible candidates for such a low power application. In this paper a detailed study on the noise analysis for such a kind of receiver is carried out. A closed form representation of the output signal to noise ratio for both narrow-band and wide-band communication is derived. The result indicates for a narrow-band communication the output signal to noise ratio cannot be better than a normal tuned amplifier. In the wide-band mode the SNR of super-regenerative receiver in linear regime is similar to a tuned amplifier.