Miroslav Husak

NEW ISFET SENSOR INTERFACE CIRCUIT FOR BIOMEDICAL APPLICATIONS

Abstract This article presents a novel architecture of an ISFET sensor interface circuit, monolithically integrated on a 3D MCM, part of a biomedical microsystem. It is a differential configuration with two ISFET devices (one with Si3N4 ion sensitive layer, the other with SiO2 sensitive layer) and realized in a 2.5 μm CMOS technology. The sensor interface is simple, has a current output signal and low silicon area requirements. The circuit architecture provides digital facilities, which makes possible the performance of the configuration been optimized during a calibration step of the system.

Detection of Breathing

Acoustic signals originate by the flow of air through the trachea during breathing. These signals are possible to pick-up by microphone. This paper describes a method of the breathing detection based on the sensing of acoustic signals in trachea. Parameters of the breathing, detection inspiration and expiration and apnoea pause are possible to determine from these signals. This method is simple and easy to use, portable and provides an accurate measurement and seems to be well suited for use as a modern breathing monitor.

One-chip integrated resonance circuit with a capacitive pressure sensor

This paper describes the design, realization and measurement results of an integrated resonance circuit, suggested for pressure measurements. The circuit consists of a variable capacitor and a flat coil, i.e. a passive LC resonator. Changes in capacitance are created by pressure changes. The resonance frequency is changed in the resonance circuit. The circuit as a passive resonance circuit is designed for contactless pressure measurement and wireless information transmission in medical and other applications. The circuit was realized as a monolith integrated sensor on silicon. The dimensions are approximately . Several variants were realized with different layouts and values. The resonance frequency and the frequency dependence of the quality factor Q have been measured.

Thermal microactuators for optical purpose

The core of the project was to design a moveable micromirror array with the most optimal dependence of the optically active area, the deflection angles and the micromirror power consumption. The matrix of 10/spl times/20 micromirrors uses a thermal actuated principle. The micromirror was designed using an industrial 0.8 /spl mu/m double metal CMOS process followed by one single postprocessing step and anisotropic silicon etch. The device consists of one cantilever beam supporting the mirror plate. The beam is a bimorph sandwich of aluminium and silicon dioxide enclosing polysilicon heating resistor. The control electronics contains 20-bit edge-triggered shift register with serial data entry and an output from each of the twenty stages (flip-flop). The output buffer is a driver for the CMOS switch (transfergate) which connects current (Pad Supply for the beam) to the thermal actuator (beam). The ANSYS program was used for the mechanical simulation of thermally actuated micromirror.

Design methodologies for reliability of SSL LED boards

This work presents a comparison of various LED board technologies from thermal, mechanical and reliability point of view provided by an accurate 3-D modelling. LED boards are proposed as a possible technology replacement of FR4 LED boards used in 400 lumen retrofit SSL lamps. Presented design methodology can be used for other high power SSL lamp designs. The performance of new LED board designs were evaluated by numerical modeling. Modeling methodology was proven by measurement on reference FR4 LED board. Thermal performance was compared by extracting of LED boards thermal resistances and thermal stress has been inspected considering the widest temperature operating range according to standards (-40 to +125 C). Thermo-mechanical and reliability analysis have been performed to study parameters of each LED board technology, using thermal boundary conditions extracted from the thermal simulation of a whole LED lamp. Elastic-plastic analysis with temperature dependent stress-strain material properties has been performed. The objective of the work is to optimize not only the thermal management by thermal simulation of LED boards, but also to find potential problems from mechanical failure point of view and to present a methodology to design SSL LED boards for reliability.

NMOS and PMOS Translinear Multiplying Cell for Current-Mode Signal Processing

The paper describes NMOS and PMOS translinear cell which multiplies the current signals and which can be used for the current-mode signal processing. The translinear cell consists of NMOS or PMOS transistors that are treated in the sub-threshold conduction region. In this region the transistors exhibit an exponential dependency of the drain current versus the gate voltage and thus the translinear principle can be used for description of the functionality. Operation region of the cell is limited by the validity of the exponential dependency and also by the transistors leakage currents. Significant error is also induced by the auxiliary current mirrors which are biasing the cells. Channel length modulation effect causes error of the input signals and thus the output signal is affected by the multiplicative error. The paper presents basic idea of the multiplying cell, presents results of simulations in CADENCE and also presents results of measurements on real structure composed using discrete transistors.

Simple wireless A/D converter for isolated systems

Motivation for this paper is to present possible solution for measuring analog values in isolated systems without batteries. It can be suitable for biomedical probes, enclosed systems such as tubes, extreme temperature environments etc. The system is considering no batteries because of their finite lifetime, toxicity or an extreme temperatures environment that is improper for the batteries. System thus must be powered wirelessly and also the information must be transmitted without any wires. It is not necessary a long distance for this powering. Usually it is enough to transfer up to 20 cm. The paper presents basic theory needed for a design of the powering, communication and also the analog to digital converter. The converter is presented consisting of discrete devices and also it is presented scheme for chip realization using the 500 nm CMOS technology.

Fabrication of Diamond Based Quartz Crystal Microbalance Gas Sensor

Synthetic diamond has remarkable properties comparable with natural diamond and hence is a very promising material for many various applications (sensors, heat sink, optical mirrors, cold cathode, tissue engineering, etc.). Nowadays, deposition of diamond films is normally employed in chemical vapor deposition (CVD) usually at high temperatures (800900 °C), what limit its application to high melting substrates. Gravimetric (mass) sensors belong to the major categories of chemical sensors and the most common type of mass sensor is the bulk acoustic quartz crystal microbalance (QCM). This contribution deals with a nanocrystalline diamond (NCD) growth from the H2/CH4/CO2 gas mixture at low temperature (400 °C) by pulsed linear antenna microwave plasma system on 10 MHz circular AT-cut quartz resonators substrate. Gas sensor based on the NCD-coated QCM was developed for detection of ammonia (NH3) at room temperature. Measurements not only confirmed the functionality of this first published NCD-coated QCM sensor, but in addition its sensitivity was twofold to a virgin QCM sensor with a gold active layer.

Respiration monitoring during sleeping

The respiration belongs among basic vital functions and the knowledge of their parameters and quality is necessary in medicine. The research is leading to the methods, which are inconvenienced patients. These methods are important for monitoring respiration towards observation quality sleeping or The Sudden Infant Death Syndrome (SIDS). This paper contains an overview of the methods for the respiration monitoring used not only in practice of medicine but till now developed.

Design and simulation of micromechanical thermal converter for RF power sensor microsystem

Abstract This paper discusses the thermo-mechanical simulations performed with the aim to optimize the temperature distribution of the microwave power sensor (MPS) microsystem keeping the thermal stress as low as possible. The concept of the absorbed power measurement is based on a thermal conversion, where the dissipated or absorbed RF power is converted into the thermal power, inside a thermally isolated system, so-called the micromechanical thermal converter (MTC) device. A new MTC approach uses a GaAs with an active high electron mobility transistor (HEMT) heater. New technology of low stress polyimide has been used for MTC thermal isolation. By means of thermo-mechanical simulations, we propose a GaAs micromechanical thermal converter design and a layout of the active sensor elements (HEMT heater and a temperature sensor TS) placed on the MTC structure. Spatial temperature distribution, thermal time constant, thermal stress and displacement and the power to temperature characteristics are calculated from the heat distribution. These findings are compared with results of thermo-mechanical measurement of real micromachined MTC devices. The 3-D thermal and thermo-mechanical simulations were performed, using the CoventorWare simulator.