Energy efficiency is of utmost importance in modern applications. Power consumption optimisation could be improved by a comprehensive analytical modeling of the characteristics of critical blocks in a system. Dynamic range (DR) has a strong effect on the power consumption of analog circuits, and is determined by circuit non-linearity and noise level. Noise is well modelled even in deep sub-micron technologies, yet there is a lack of analysis and modeling of the non-linearity. An analytical MOSFET differential pair non-linearity model is presented in this work. The proposed model is universal to a wide range of technologies from long to ultra-deep sub-micron devices, and is valid for all operating regions as it is based on the EKV MOSFET model. Furthermore, a model including drain-voltage-induced non-linearity is also developed, and a concise 3dB input intercept point (IIP3) formula incorporating the drain induced non-linearity in terms of the voltage gain is presented. The proposed models are validated with DC and AC simulations and measurements.

Power consumption is of utmost importance in portable devices as they are operated from a limited energy supply. Wireless radio is one of the most power-hungry blocks in these systems and needs to be activated opportunistically. Radio frequency (RF) spectrum sensing can be performed with a dedicated low power radio to control the main wireless radio. A low power receiver architecture is proposed in this work to monitor the 2.4GHz Industrial, Scientific, and Medical (ISM) band for communication standards such as Wireless Local Area Network (WLAN), Zonal Intercommunication Global-standard (ZigBee), and Bluetooth-Low-Energy (BLE). The whole ISM band is down-converted to zero-intermediate-frequency (ZIF) and a tunable base-band complex band-pass filter (CBPF) is used to scan the spectrum. A widely tunable first order ultra-low-power transconductor-capacitor (Gm-C) CBPF architecture was designed and fabricated in GF 22FDX technology, which occupies 0.0049mm 2 area. A frequency shift of ±60MHz was achieved with 5-40MHz bandwidth range. Power consumption ranges from 6.7$\mu \text{W}$to 99.2$\mu \text{W}$with the best and the worst figure-of-merit of 0.034fJ/pole and 0.082fJ/pole that is the energy consumption per pole normalized by the spurious free dynamic range.

Audio processing had been in demand throughout the electronic era. Recent advances in neural networks increased the demand on audio processing for speech recognition applications. In this work, a rigorous study on the dynamic range and system complexity optimization is presented for a mixed-signal keyword spotting system. The proposed system consists of an analog feature extractor and a neural network based keyword classifier. The results showed that with the proposed method, more than an order of magnitude power saving can be achieved in the analog feature extraction compared to the digital state-of-the-art counterpart.

A glass pill for digestive motility tracking with wireless communication is presented. The pill encapsulates three magnetic transmitter coils with a 125 kHz signal, the circuitry required to control the magnetic coil output and the battery. The system provides real time location of the pill inside the digestive tract of the patient using an external detector housed in a wearable jacket. The custom integrated circuit for this application reduces bill-of-materials (BOM) count and significant reduction in power consumption therefore resulting in further size reduction by adapting a smaller battery package. The outcome of the circuit integration enables the glass pill for pediatric use while providing a total pill diameter of 6 mm. The glass pill system operates continuously for 48 hours with a 1.55 V 8 mAh coin cell battery with an average power consumption of 250 microwatts.

Wireless-powered chips are used in a wide range of applications, including biomedical implants. However, the resonant frequency of the power receiving circuit can be affected not only by process variations, but also by the changing environment. In order to optimize the power transfer and allow the chip to work despite these variations, a fully integrated tuning system is proposed. After having assessed suitable conditions, an on-chip variable capacitance is set to its optimum value using a SAR algorithm maximizing the obtained rectified voltage. The proposed system was implemented in the UMC 0.18 μ m CMOS technology and demonstrated by post-layout simulations. When targeting a reduction of the rectified voltage of at most 5%, the tolerable variation in the receiving coil or its parallel capacitance was increased from ±2.9% to ±11.0%.

This paper presents techniques for increasing communication data rates for OOK modulated signals in the case the carrier frequency is generated by a cross-coupled pair LC oscillator. The proposed circuitry completely turns off the transmitter during the transmission of “0” bit and oscillation occurs only when the data bit is “1” to reduce power consumption. The data bit controls the steady state bias current and the operation of the oscillator. The communication data rate is limited by the turn-on and turn-off time of the LC oscillator. In order to speed up the turn-on time of the oscillator, in addition to bias current, an extra current source is used during the build-up of the oscillator. The decay time of the oscillator when the data is switched from “1” to “0” is accelerated by shortening the inductor connections. The concept is demonstrated through the design of an LC VCO in 0.18 μm CMOS technology. The LC oscillator is designed to oscillate in MedRadio band at 416 MHz frequency. Simulation results show that the proposed architecture shortens the turn-on time from 86.5 ns to 24 ns and the turn-off time from 101 ns to 5.93 ns. With the additional techniques, the maximum achievable communication data rate is increased by more than 6 times.

A full remotely powered system for metabolism monitoring of free-moving mice is presented here. The fully implantable sensing platform hosts two ASICs, one off-the-shelf micro-controller, four biosensors, two other sensors, a coil to receive power, and an antenna to transmit data. Proper enzymes ensure specificity for animal metabolites while Multi-Walled Carbon Nanotubes ensure the due sensitivity. The remote powering is indeed provided by inductive coils located under the floor of the mouse' cage. Two different approaches where investigated to ensure freedom of movement to the animal. The application to studies for personalized medicine is demonstrated by showing continuous monitoring of both glucose and paracetamol.

A charge integrator is an essential building block used in time-based ADCs and sensor readout circuits. In this paper, time-domain noise analysis is used to calculate the effect of all noise sources, including 1/f noise, on the voltage noise variance of the integrator. The results show that for short charge integration intervals, the contribution of 1/f noise sources to the total voltage variance of the integrator is not significant. Different design trade-offs for optimally choosing the capacitance of the integrator and current mirror ratio are discussed. The accuracy of the developed equations is verified by transient noise simulations.

A CMOS integrated RF receiver of a glass pill for tracking motility in the gastrointestinal (GI) tract is presented. The receiver detects a 125 kHz downlink synchronization signal that is sent from an external base station, which is used to trigger the transmission of the 3-axis pill position and also to change the tuning parameters of the receiver system. The incoming downlink RF signal also includes the tuning parameters for the 10-bit resolution adjustable internal ring-oscillator, which generates a 4 MHz clock for providing the 3-axis pill position through the 125 kHz transmitter. The receiver, which is fabricated in UMC 0.18 μm CMOS process is measured using the housing of the glass pill. Experiments show that a maximum operation distance of 80 cm between the base station and the glass pill is achieved. The total power consumption of the integrated solution provides 4.6 times reduction compared to the previous generation tracking pill.

In this work, we present the general concept of an instrumented smart knee prosthesis for in-vivo measurement of forces and kinematics. This system can be used for early monitoring of the patient after implantation and prevent possible damage to the prosthesis. The diagnosis of defects can be done by detecting the load imbalance or abnormal forces and kinematics of the prosthetic knee in function. This work is a step towards the fabrication of an instrumented system for monitoring the function of the knee in daily conditions. Studying the constraints of commercially available prostheses, we designed a minimal sensory system and required electronics to be placed in the polyethylene part of prostheses. Three magnetic sensors and a permanent magnet were chosen and configured to measure the prosthetic knee kinematics. Strain gauges were designed to measure the forces applied to the polyethylene insert. Kinematic and force measurements were validated on a mechanical knee simulator by comparing them to different reference systems. Embedded electronics, including the A/D converters and amplifier were designed to acquire and condition the measurements to wirelessly transmit them to an external unit. By considering the necessary power budget for all components, the optimum coil for remote powering was investigated. The necessary rectifier and voltage doubler for remote powering were also designed. This is the first system capable of internally measuring force and kinematics simultaneously. We propose to package the system in the polyethylene part, bringing versatility to the instrumented system developed, as the polyethylene part can be easily modified for different types of prostheses based on the same principle, without changing the prosthesis design.

Performance of wireless sensor systems are evaluated on the basis of the quality of data communication and efficiency of power transmission. This work presents the design methodology of a miniaturized tag antenna for remote powering of wireless sensor systems at 2.45 GHz ISM band. Accurate simulations of the rectifier input impedance aimed at the maximization of transmitted power are presented. Simulation results combined with simple transmitting antenna scattering parameters and cable loss measurements provide straightforward characterization of the fabricated tag antenna. The experimental measurements on a 12×10mm miniaturized antenna designed with the proposed approach show a gain of -5.9 dB close by 0.8 dB to the simulation results.

An intelligent power feedback design for remotely powered freely moving animal telemetry systems is described. The system uses an optimized wireless power transmission that utilizes multiple transceiver coils. An intelligent mouse cage with controller unit of the feedback system are proposed. System description, experimental setup and measurements of the remotely powered implantable monitoring system are presented.

It is desirable in active medical implants to derive energy from external sources to charge a rechargeable battery. In this paper we have developed a novel system to transfer energy via ultrasound to a deep implanted medical device. Hence, an external base station is designed to transmitt energy and a 64-channel high-voltage driver is proposed for a spherical transducer array. Moreover, a shunt-C class-E power amplifier (PA) is employed as core element for the driver, showing a drain efficiency (DE) of 71% and a power added efficiency (PAE) of 57% including gate-driver switching loss. In addition, a cascaded of two low-drop-out (LDO) regulators is used within the implanted device to reduce rectifier ripple and to set the charge voltage for the micro-energy cell to 4.1 V. The LDOs are implemented in a CMOS 0.18 μm high-voltage (HV) technology and measurement along with simulated results are reported.

Recognizing the importance of interfacing a variety of sensors and networking such sensors around the body area and by cellular services, a Swiss project within the Nano-Tera.ch Initiative is dedicated to developing a platform of circuit technologies for medical data acquisition and communication.

The benefits of adaptive power reconfigurability in WPAN receivers are investigated. The analysis is based on a direct-conversion IEEE 802.15.4 receiver and is focused on the analog baseband block. High-level power models are built for the baseband filter and the ADC which are, then, optimized for minimum total power dissipation to decide on the reconfiguration strategy. The optimum is reached with a first-order filter together with an ADC that is reconfigurable between 21.0 dB and 69.8 dB (corresponds to 3.2-bit and 11.3-bit ENOB). An illustrative operating schedule is derived to evaluate the possible power reduction that can be obtained through adaptive power reconfigurability. In the end, it is found that the average power dissipation can be reduced from 602 μW to 24.1 μW by using a power-reconfigurable ADC, which corresponds to a reduction by a factor of 25 (14 dB).

The design, development, and deployment of Ultra-Wideband (UWB) localization systems involves digital and Radio-Frequency (RF) hardware, embedded software, localization algorithms, security and reliability aspects, electromagnetics, and others. Design and integration decisions affect the performance of an UWB system, in particular the most important metrics: localization accuracy and position update rate. To facilitate further development of UWB localization systems and to analyze some of the major trade-offs we share our experience in deploying the EPFL UWB-Lite test bed (U-Lite). We describe an approach to numerical simulation modeling that can help in the design and evaluation of UWB localization systems. To validate our approach we show experimental results with one transmitter and one receiver. Our UWB test bed includes a mobile robot platform, so we can study and evaluate the UWB performance trade-offs in real-world conditions.

A multiplying D/A converter stage incorporating a novel technique for compensating the residual error due to finite amplifier gain is proposed. The scheme is suitable for deep-submicron CMOS technologies and is advantageous compared to the available correlated double sampling techniques because it neither doubles the size of the sampling capacitance, nor requires processing of the same input signal twice for cancelling the residual error at the virtual ground. The conducted behavioral simulations confirm the efficiency of the proposed technique applied to a pipelined A/D converter.

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.

The design of distributed amplifiers in a CMOS process is investigated. In particular, the impact of parasitic elements from the transistors and from interstage inductors is studied. A methodology for determining an optimum design, including the number of stages, without needing a complete inductor model at the outset, is presented. This proposed methodology reduces the time and complexity of a distributed amplifier design while at the same time allowing the designer to gain more insight into the circuit's behavior.

The unprecedented impact of noise coupling on Mixed-Signal Systems-On-a-Chip (MS-SOC) functionality, brings a new set of challenges for Electronics Design Automation (EDA) tool developers. In this paper, we propose a new approach which combines a thorough physical comprehension of the noise coupling effects with an improved Boundary-Element-Method (BEM) to accelerate the substrate model extraction and to avoid the dense matrix storage. The low computational efforts required, as well as speed and accuracy reached, makes this method a highly promising alternative to verify complex MS-SOCs.

By using the polynomial formalism, the gain-bandwidth restrictions are determined in the case of the single broadband matching of an RLC load when the Chebyshev gain function is used. The roots of polynomial h associated to a global 2-port Q are assumed to be located in the closed right half-plane. A theorem is stated which allows one to determine under which condition an RLC load can be matched by using a Chebyshev gain function. A method is proposed to find automatically the Chebyshev gain function which maximizes the minimum passband gain F/sub m/. For a fixed value of R/sub L/ C/sub L/ /spl omega//sub c/, the curve of the optimal value of F/sub m/, as a function of L'' /spl omega//sub c//R/sub L/, is shown. Finally, the elements of the equalizer are calculated by using the explicit Weinberg relations.

By using the polynomial formalism, the gain-bandwidth restrictions will be established in the case of the double broadband matching of an RL generator impedance and an RLC load. By using an automatic procedure based on the Gauss-Newton algorithm, the optimal equal minima gain function will be determined and compared to the Chebyshev and real frequency solutions. It will be shown how the equal minima method can be extended.>

The objective of this article is the determination of the optimal flat gain level in the case of double broadband matching, through the use of the integral relations. It is shown how these integral relations can be established by using Cauchy's integrals in a way similar to Fano's [1950] and Fielder's [1961] methods, but also involving the polynomial formalism.>