Janez Trontelj

High-performance designs with CMOS analog standard cells

The authors describe an approach to the design of complex analog functions comprising the major functions normally encountered in analog systems using a library of 3-/spl mu/m CMOS analog cells. It is shown that through the use of a fixed-height cell system and a predefined connection system, circuits can be designed that suffer little, if any, area penalty when compared to a full custom layout. In addition, the overall system performance achieved can equal that of some full custom designs.

Humidity sensors printed on recycled paper and cardboard.

Research, design, fabrication and results of various screen printed capacitive humidity sensors is presented in this paper. Two types of capacitive humidity sensors have been designed and fabricated via screen printing on recycled paper and cardboard, obtained from the regional paper and cardboard industry. As printing ink, commercially available silver nanoparticle-based conductive ink was used. A considerable amount of work has been devoted to the humidity measurement methods using paper as a dielectric material. Performances of different structures have been tested in a humidity chamber. Relative humidity in the chamber was varied in the range of 35%–80% relative humidity (RH) at a constant temperature of 23 °C. Parameters of interest were capacitance and conductance of each sensor material, as well as long term behaviour. Process reversibility has also been considered. The results obtained show a mainly logarithmic response of the paper sensors, with the only exception being cardboard-based sensors. Recycled paper-based sensors exhibit a change in value of three orders of magnitude, whereas cardboard-based sensors have a change in value of few 10s over the entire scope of relative humidity range (RH 35%–90%). Two different types of capacitor sensors have been investigated: lateral (comb) type sensors and modified, perforated flat plate type sensors. The objective of the present work was to identify the most important factors affecting the material performances with humidity, and to contribute to the development of a sensor system supported with a Radio Frequency Identification (RFID) chip directly on the material, for use in smart packaging applications. Therefore, the authors built a passive and a battery-supported wireless module based on SL900A smart sensory tags IC to achieve UHF-RFID functionality with data logging capability.

Optimization of integrated magnetic sensor by mixed signal processing

An array of integrated Hall elements is presented to maximize signal to noise ratio and to minimize the offset. Novel magnetic sensor bias circuits and signal amplification circuit suitable for sensor arrays are shown. The positioning of sensor array elements on the ASIC, to precisely determine the spatial distribution of the magnetic field for various physical quantity measurement applications, is discussed. On board sensor calibration together with controlled temperature behavior to compensate for the non-ideal temperature behavior of the applied magnetic field is demonstrated to allow for a robust design suitable for volume ASIC production.

CMOS integrated magnetic field source used as a reference in magnetic field sensors on common substrate

An integrated reference magnetic field generator was introduced for integrated Hall sensors. Its model was presented and analysed. A simple SPICE type design tool was developed. The described structure was designed and the model parameters extracted and verified. Extracted reference voltage is used for compensation of Hall sensitivity temperature, time and mechanical stress dependence compensation and for mass production testing.<<ETX>>

Surface-Functionalized COMB Capacitive Sensors and CMOS Electronics for Vapor Trace Detection of Explosives

In this paper, we present a miniature detection system, which is able to detect and selectively recognize different vapor traces of explosives. It is based on surface-functionalized array of COMB capacitive sensors and extremely low noise integrated electronics. The measurement system is sensitive and selective, consumes minimum amount of energy, is very small and cheap to produce in large quantities, and is insensitive to environmental influences. Owing to extremely low noise electronics and selective modification of COMB capacitor surfaces, it is possible to detect less than 3.5 ppt of TNT in the atmosphere (three TNT molecules in 10+12 molecules of air and 10 times better for RDX) at 25°C in one second using very small volume (few mm3). The measurement system needs only approximately 20 mA current at 5 V supply voltage.

Spectroscopic Terahertz Imaging at Room Temperature Employing Microbolometer Terahertz Sensors and Its Application to the Study of Carcinoma Tissues

A terahertz (THz) imaging system based on narrow band microbolometer sensors (NBMS) and a novel diffractive lens was developed for spectroscopic microscopy applications. The frequency response characteristics of the THz antenna-coupled NBMS were determined employing Fourier transform spectroscopy. The NBMS was found to be a very sensitive frequency selective sensor which was used to develop a compact all-electronic system for multispectral THz measurements. This system was successfully applied for principal components analysis of optically opaque packed samples. A thin diffractive lens with a numerical aperture of 0.62 was proposed for the reduction of system dimensions. The THz imaging system enhanced with novel optics was used to image for the first time non-neoplastic and neoplastic human colon tissues with close to wavelength-limited spatial resolution at 584 GHz frequency. The results demonstrated the new potential of compact RT THz imaging systems in the fields of spectroscopic analysis of materials and medical diagnostics.

Comparison of terahertz technologies for detection and identification of explosives

We present results on the comparison of different THz technologies for the detection and identification of a variety of explosives from our laboratory tests that were carried out in the framework of NATO SET-193 “THz technology for stand-off detection of explosives: from laboratory spectroscopy to detection in the field” under the same controlled conditions. Several laser-pumped pulsed broadband THz time-domain spectroscopy (TDS) systems as well as one electronic frequency-modulated continuous wave (FMCW) device recorded THz spectra in transmission and/or reflection.

A high performance room temperature THz sensor

Resonant THz antenna-coupled micro-bolometers are considered as a potential candidates for room temperature THz imaging, as well as spectroscopic applications. Micromachining technology is found to be well-suitable to fabricate a micro-meter bolometer sensor suitable for MEMS implementation. The sensitivity of the sensor is determined to be up to 1000V/W and the noise equivalent power (NEP) – is down to 5pW /√Hz. The sensor parameters are designed to be easily implemented with a low cost standard preamplifier array which increases the pixel sensitivity to 106V/W without compromising the noise equivalent power.

Micro-machined Millimeter Wave Sensor Array for FM Radar Application

The objective of this work was to create a low cost sensor array that operates at room temperature for millimeter wave applications and could be used for FM radars and various heterodyne receivers. The selected technology was silicon wafer micromachining allowing the creation of microstructures on silicon membranes using different metal layers. The technology used allowed submicron dimensions for a photolithography pattern and thin membranes down to a few micrometers. One of the most critical requirements for the sensor was to achieve a high signal-to-noise ratio and a high bandwidth for a mixed frequency. The sensor is a titanium-based micro-bolometer connected to the micro-antenna which is integrated with the bolometer. The results are very promising. The measured NEP is below 5pW/√Hz and the sensitivity is close to 1000 V/W. In the paper the antenna - bolometer sensor microstructure is analyzed. Theoretical analysis and design guidelines for the bolometer itself are discussed. Simulation results of the bolometer and antenna show very close matching to the measured results. Characterization measurements were performed, and thermal behavior of microbolometer structure was simulated and measured. The measurement results are presented for THz FM radar different targets, and a technology demonstrator is also described.

A Differential Monolithically Integrated Inductive Linear Displacement Measurement Microsystem

An inductive linear displacement measurement microsystem realized as a monolithic Application-Specific Integrated Circuit (ASIC) is presented. The system comprises integrated microtransformers as sensing elements, and analog front-end electronics for signal processing and demodulation, both jointly fabricated in a conventional commercially available four-metal 350-nm CMOS process. The key novelty of the presented system is its full integration, straightforward fabrication, and ease of application, requiring no external light or magnetic field source. Such systems therefore have the possibility of substituting certain conventional position encoder types. The microtransformers are excited by an AC signal in MHz range. The displacement information is modulated into the AC signal by a metal grating scale placed over the microsystem, employing a differential measurement principle. Homodyne mixing is used for the demodulation of the scale displacement information, returned by the ASIC as a DC signal in two quadrature channels allowing the determination of linear position of the target scale. The microsystem design, simulations, and characterization are presented. Various system operating conditions such as frequency, phase, target scale material and distance have been experimentally evaluated. The best results have been achieved at 4 MHz, demonstrating a linear resolution of 20 µm with steel and copper scale, having respective sensitivities of 0.71 V/mm and 0.99 V/mm.