Jonas Handwerker

A Sub-500 mV Highly Efficient Active Rectifier for Energy Harvesting Applications

This paper presents a highly efficient, ultra-low-voltage active full wave rectifier. A two-stage concept is used including a first passive stage and only one active diode as second stage. A bulk-input comparator working in the subthreshold region is used to drive the switch of the active diode. The voltage drop over the rectifier is some tens of millivolt, which results in voltage and power efficiencies of over 90%. The design was successfully implemented in an 0.35 μm CMOS technology. The measured power consumption of the comparator is 266 nW@500 mV and the minimum operating voltage is 380 mV. Input voltages with frequencies up to 10 kHz can be rectified.

An ultra-low-voltage active rectifier for energy harvesting applications

This paper presents an ultra-low-voltage active rectifier for micro energy harvesting. A two stage concept is used including a first passive stage and an active diode as second stage. A bulk-input comparator design is used which is well suited for low voltage applications. The power consumption is 200 nW and the minimum operation voltage is 350 mV using a 0.35 µm low VTh CMOS technology. The voltage drop over the rectifier is some tens of millivolt which results in voltage and power efficiencies of over 90 %. Input voltages with frequencies in the range of mHz to low kHz can be rectified.

Telemetry for Implantable Medical Devices: Part 1 - Media Properties and Standards

Over the last 50 years, implantable medical devices (IMDs)?such as those listed have become an important tool for medical doctors, researchers in life sciences, and finally mankind to restore lost function, treat disorders, or monitor biological parameters with significant impact on either life quality, health, or the understanding of the body function.

Experimental results on power efficient single-poly floating gate rectifiers

This paper presents measurement results on voltage and power efficient CMOS fully integrated rectifiers. Floating gate (FG) techniques are used to reduce the threshold voltage and thus the voltage drop over the rectifier. A three transistor single-poly FG diode is presented as basic element for half and full wave rectifiers. The rectifiers are implemented using a 0.35 µm high voltage CMOS technology. Measurements show a significantly higher output voltage and efficiency using programmed FG devices compared to non-programmed. Power efficiencies of up to 75 % and 66 % are measured for low and high voltage devices, respectively. The minimum operational input voltage of high voltage rectifiers is drastically reduced.

A low-power high-sensitivity single-chip receiver for NMR microscopy

In this paper, we present a fully-integrated receiver for NMR microscopy applications manufactured in a 0.13μm CMOS technology. The design co-integrates a 10-turn planar detection coil together with a complete quadrature, low-IF downconversion receiver on a single chip, which operates from a single 1.5V supply with a total power dissipation of 18mW. The detectors measured time-domain spin sensitivity is 3×10(13)(1)Hspins/Hz at 7T. Additionally, the paper discusses two important aspects of NMR microscopy using planar detection coils: the link between the detection coils spin sensitivity and the achievable image SNR and the correction of image artifacts induced by the inhomogeneous sensitivity profile of planar detection coils. More specifically, we derive analytical expressions for both the theoretical image SNR as a function of the coils spin sensitivity and the sensitivity correction for a known coil sensitivity profile in CTI MR imaging experiments. Both expressions are validated using measured data in the imaging section of the paper. Thanks to the improved spin sensitivity of the utilized integrated receiver chip compared to a previously presented design, we were able to obtain sensitivity corrected images in a 7T spectroscopy magnet with isotropic resolutions of 9.6μm and 5μm with single-shot SNRs of 37 and 15 in relatively short imaging times of 4.4h and 24h, respectively.

An array of fully-integrated quadrature TX/RX NMR field probes for MRI trajectory mapping

In this paper we present fully-integrated field probes for real-time trajectory mapping during magnetic resonance imaging (MRI) experiments. The field probes co-integrate an NMR microcoil and the required transceiver electronics on a single ASIC manufactured in a 0.13μm CMOS technology. Thanks to an on-chip PLL, power amplifier and low-IF quadrature receiver, all connections to and from the chip carry only low frequency signals allowing for an effective reduction of the magnetic coupling between the field probes and the MRI scanner during imaging. The small form factor and low power consumption of 16.5mW allows for the realization of arrays of field probes, which in contrast to single probes enable the correction of higher order field imperfections. Measured trajectory maps acquired with a prototype array consisting of four probes demonstrate the excellent sensor performance achievable using the proposed approach.

28.2 A 14GHz battery-operated point-of-care ESR spectrometer based on a 0.13µm CMOS ASIC

Thanks to its unique ability to deliver information about the structure, spatial distribution, and even dynamics of paramagnetic species, electron spin resonance (ESR) spectroscopy is one of the most powerful analytical techniques in modern life sciences. Recently, the method has gained significant attention as a tool to study oxidative stress, i.e., a state in which the number of reactive oxygen species (ROS) exceeds the physiological antioxidative potential of the cells, which plays an important role in the development of many chronic diseases as well as acute stress conditions.

A fully-integrated detector for NMR microscopy in 0.13μm CMOS

In this paper, we present a fully integrated receiver for NMR microscopy applications realized in a 0.13 μm CMOS technology. The chip co-integrates a planar detection coil together with a complete low-IF downconversion receiver consisting of a low noise amplifier, a quadrature downconversion mixer, a baseband amplifier stage and line drivers. The chip operates from a single 1.5V supply and consumes about 12mA of current. The active chip area is about 350×450 μm2. The detectors measured input referred voltage noise density at the operating frequency of 300 MHz is 260 pV/√Hz resulting in a measured spin sensitivity of 2×1013 spins/√Hz. Preliminary imaging experiments demonstrate the chips capability of recording micron resolution MR images in imaging times which significantly advance the state-of-the-art.

An Active Transmit/Receive NMR Magnetometer for Field Monitoring in Ultra High Field MRI Scanners.

We present a miniaturized active nuclear magnetic resonance (NMR) magnetometer consisting of a susceptibility matched field probe and a PCB based RF transceiver. Thanks to its transmit-receive (TX/RX) capabilities, the system can be used to monitor the spatio-temporal field evolution during a magnetic resonance imaging (MRI) scan and thereby allows for a correction of gradient field imperfections to improve image quality. The magnetometer can be tuned for magnetic fields ranging from 7 T to 15.5 T and achieves a resolution of 14.8 nT measured in a 9.4 T whole body scanner.

Towards CMOS-based in-vivo NMR spectroscopy and microscopy

In this paper, we discuss the requirements for an NMR setup to allow for combined NMR microscopy and spectroscopy using planar microcoils to study metabolic processes in vivo. Here, NMR is particularly suitable because — unlike most other currently used methods — it can deliver structural information as well as qualitative and quantitative information about the molecules involved in cellular processes. More specifically, based on the reciprocity principle, we derive why previously presented fully-integrated CMOS receivers using on-chip NMR coils in receive-only mode are not suitable for in-vivo spectroscopy applications. As a solution to this problem, we propose the use of fully-integrated transceivers which use their on-chip planar microcoils in TX/RX mode as an ideal tool for combined in-vivo NMR imaging and spectroscopy. Measurements using a planar coil on a thin silicon substrate validate the theoretical analysis.