An Energy-Efficient Bridge-to-Digital Converter for Implantable Pressure Monitoring Systems

This paper presents an energy-efficient, duty-cycled, and spinning excitation bridge-to-digital converter (BDC) designed for implantable pressure sensing systems. The circuit provides the measure of the pulmonary artery pressure that is particularly relevant for the monitoring of heart failure and pulmonary hypertension patients. The BDC is made of a piezoresistive pressure sensor and a readout integrated circuit (IC) that comprises an instrumentation amplifier (IA) followed by an analog-to-digital converter (ADC). The proposed design spins both the bridge excitation and the ADC’s sampling input voltages simultaneously and exploits duty cycling to reduce the static power consumption of the bridge sensor and IA while cancelling the IA’s offset and 1/f noise at the same time. The readout IC has been designed and fabricated in a standard 180-nm CMOS process and achieves 8.4 effective number of bits (ENOB) at 1 kHz sampling rate while drawing 0.53 µA current from a 1.2 V supply. The BDC, built with the readout IC and a differential pressure sensor having 5 kΩ bridge resistances, achieves 0.44 mmHg resolution in a 270 mmHg pressure range at 1 ms conversion time. The current consumption of the bridge sensor by employing duty cycling is reduced by 99.8% thus becoming 0.39 µA from a 1.2 V supply. The total conversion energy of the pressure sensing system is 1.1 nJ, and achieves a figure-of-merit (FoM) of 3.3 pJ/conversion, which both represent the state of the art

Low Noise Electronics for BASE Collaboration

In my summer student period, I worked within the BASE (Baryon Antibaryon Symmetry Experiment) Collaboration and I developed low noise electronics such as cryogenic low noise amplifier and high voltage filters. In this report, you can find designs and measurements of my projects

Development of Single Sideband Down Converters for Precise Measurements of the Axial Frequency of a Single Trapped Antiproton

The Baryon Antibaryon Symmetry Experiment (BASE) at the antiproton decelerator of CERN, Geneva, Switzerland aims at precise comparisons of the fundamental properties of the antiproton and proton. Such comparisons are interesting because any measured asymmetry between a matter and antimatter-conjugates would hint at physics beyond the Standard Model. In this bachelor's project, a single sideband (SSB) down converter for the measurement of the axial frequency of an antiproton or a proton was developed. The goal is to down-convert the axial frequency into the frequency range of the FFT analyzer and to increase the down-mixed signal to noise ratio of the detection system. In addition, an active feedback cooling system was developed by using this SSB down converter. The temperature of the axial detection system is about 8 Kelvin without feedback. It is demonstrated that the feedback system is capable to decrease the temperature of the detection system and thus that of the particle by about a factor of 3 to 5. This leads to reduction of resonance line widths, faster particle preparation cycles and thus improves measurement precision

Design of a Rad-Hard eFuse Trimming Circuit for Bandgap Voltage Reference for LHC Experiments Upgrades

A precise and stable reference voltage is required to generate a stable output voltage in DC/DC converters. This reference voltage must be independent of temperature, power supply, radiation, intrinsic technology mismatch and process variation. This master's thesis reports the development of a rad-hard bandgap voltage reference with electrical fuse (eFuse) based analog calibration circuit in a commercial 130nm technology. According to the test results, the maximum error in the bandgap voltage (300mV in this application) was reduced from ±30mV to less than ±0.6mV thanks to the eFuse trimming. A temperature, power supply, radiation, mismatch and process-independent reference voltage was generated to provide reference voltage to first (bPOL12V) and second (bPOL2V5) stage DC/DC converters. This circuit will be integrated in bPOL12V and bPOL2V5 converters for high-luminosity LHC upgrades

Serum Ghrelin and Leptin Levels in Patients with Depression and the Effects of Treatment

Objective Ghrelin and leptin, appetite-regulating hormones, play a role in mood regulation. Current data about the relation between leptin/ghrelin and depression are still controversial. This study aimed to investigate serum leptin and ghrelin levels in patients with depression and the effects of treatment on these levels

A CMOS Analog Front-End for Implantable Pulmonary Artery Pressure Monitoring System

This paper presents an energy-efficient analog front-end circuit to monitor the pulmonary artery pressure (PAP) with piezoresistive pressure sensors. A low-power capacitively-coupled instrumentation amplifier (CCIA) is developed in order to boost the amplitude of the bridge sensor to the input range of the analog-to-digital converter (ADC). The 1/f noise and input-referred offset of the amplifier are eliminated by the chopping technique. Simulation results show that this CCIA with chopping technique achieves an input-referred noise density of 38.7 nV/p Hz and an input-referred offset voltage of 4 mu V with a current consumption of 4.28 mu A at 1.8 V voltage supply. This gives a noise-efficiency factor (NEF) of 3.1. Dual supply voltages are used to decrease the power consumption of the bridge sensor. The pressure range is selected to be between 0 and 125 mmHg and the bandwidth of the interface is set from DC to 400 Hz with an RC low pass filter (LPF). This low-noise, low-offset analog front-end circuit achieves an accuracy of 0.125 mmHg

Metastatic cardiac myxoma

A 22-year-old woman who had a history of three cardiac operations and a bilateral femoral embolectomy for recurrent cardiac myxoma and myxoma embolism, respectively, was accepted to our clinic with multiple immobile peripheral masses. One of them was compressing the left common femoral artery. This mass was extirpated. Pathology examination revealed myxoma. Chemotherapy was given to the patient and regression of the masses was observed. (C) 2001 by The Society of Thoracic Surgeons

Anatomical Variations of the Carotid-Vertebral Arteries: "Double-Vessel" Sign on Doppler Ultrasonography

We describe the "double-vessel" sign and its relevance for the diagnosis of carotid and vertebral arterial anatomical variations in a series of four patients with stroke. In these four patients, two arteries could be seen at the expected location of the common carotid artery (CCA), leading to the diagnosis of anatomical variations including separate origin of internal and external carotid artery from the aortic arch on the left side and from the brachiocephalic trunk and the subclavian artery on the right side, early bifurcation of the CCA on both sides, and an aberrant course of the vertebral artery on the left side. The presence of two arteries at the expected location of the CCA should raise the suspicion of carotid or vertebral arterial variations. (C) 2011 Wiley Periodicals, Inc. J Clin Ultrasound 39: 487-492, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jcu.2080

A Capacitively-Coupled Chopper Instrumentation Amplifier for Implantable Bridge Sensor Systems

This paper presents an energy and area efficient capacitively-coupled chopper instrumentation amplifier (CCIA) dedicated to implantable bridge sensor systems. Chopper stabilization is employed to decrease its offset and 1/f noise and the resulting ripple due to the up-modulated offset and 1/f noise is suppressed by a switched-capacitor ripple reduction loop. The gain of the instrumentation amplifier is defined by a programmable capacitive feedback network with a gain range from 40 V/V to 116 V/V, which is suitable for use with bridge sensors having different output voltages. The proposed CCIA has been fabricated in a standard 0.18 mu m CMOS process. It achieves an input noise of 88.2 nV/root Hz, a worst-case input offset of 5 mu V, and an output ripple of less than 185 mu V. The CCIA occupies only 0.17 mm(2) chip area and draws 3.3 mu A current from a 1.2 V supply.SCI-STI-M

An Implantable Inductive Sensor for Direct and Continuous Monitoring of the Pulmonary Artery Cross-Sectional Area

This paper presents a novel method for the measure of the cross-sectional area (CSA) of an artery to be used for the direct and continuous (24/7) monitoring of cardiac output (CO). The method is based on the inductance change of an anchoring loop mounted on a miniaturized system implanted in a section of the pulmonary artery. The inductive sensor comprises an inductive readout circuit and a conductive anchoring loop, which changes its inductance according to the deformation of the artery and can be correlated to the diameter and CSA of the artery section. Direct and periodic measurement of the CSA can improve the accuracy of CO monitoring in heart failure patients. An oscillator-based inductive readout IC was realized in a 180-nm CMOS process and the anchoring loop was implemented by a nitinol wire. The readout IC achieves 0.42 nH inductance resolution in a range from 181 nH to 681 nH and draws 39.7 μA to 51.2 μA current from a 1.2 V supply. The correlation between the artery diameter and loop inductance is demonstrated and the sensor achieves 0.24 mm resolution in a diameter range from 20 mm to 30 mm, a factor of four higher than the lateral resolution of echocardiography.SCI-STI-M