Tomas Blecha

Printed passive components for RFID labels

This paper deals with the research and development of printed flexible capacitors and inductors predominantly designed for the construction of RFID labels. These printed RF passive components are required for the construction of fully printed low cost passive RFID labels. The passive components are directly printed on PET substrate by the screen printing technique. The printing process was optimized in order to achieve a high yield and good electrical parameters at the frequency of 13,56 MHz. Electrical parameters of printed capacitors, such as impedance to frequency characteristic, capacity to temperature characteristic, capacity to bias voltage characteristic were measured in detail. The bending tests were also performed for verifying of printed capacitors flexibility. The performance of capacitors was verified in the real sample of resonant circuit at 13,56 MHz.

Implementation of AODV routing protocol in sensor wireless networks

This paper presents an implementation of the Ad hoc On-Demand Distance Vector (AODV) routing protocol in conditions of sensor wireless networks. AODV is a reactive on-demand distance vector protocol and utilizes partially connected mesh network topology. Designed stack is intended for purposes of applications that require quick adaptation to dynamic link conditions. Protocol implementation was primarily focused on embedded systems with constrained memory and computational resources and was intended to be easy portable to other platforms. For testing purposes, designed stack was attached to link layer of SimpliciTI stack and compiled for CC430 microcontroller with on-chip sub-1-GHz RF transceiver supplied by Texas Instruments Company. This work was motivated by the need of a simple implementation of the routing protocol intended for tiny systems and utilizing mesh network topology which will quickly adapt on fast node position changes.

Smart textile-based protective system for firefighters

This paper presents a research focused on a smart textile-based protective system which is intended to bring more safety to firefighters facing hazardous conditions. The system is fully integrated into a firefighter protective suit and it is able to monitor heart rate (HR), to detect movements of a firefighter, to detect toxic and combustible gases in the environment and to measure temperature (T) and relative humidity (RH) inside and outside of the suit. The protective system consists of developed integrated sensor modules, e-textile wiring harnesses, body control unit (BCU), central processing unit (CPU), body area network (BAN) and wide area network (WAN). The measured data are wirelessly transmitted over a wide area network with automatic routing algorithm to the central processing unit, which is checked by a firefighter operation chief, who is kept informed about an actual state of individual fire fighters. In case that some monitored parameter oversteps pre-set threshold values the BCU will automatically inform a fire fighter by means of acoustic alarm about oncoming risk.

Screen printed antennas on textile substrate

This article deals with screen printed antennas on textile substrate that are used for data transmission between intelligent fireman suits. Today the smart textiles are developed in the whole world and research works are focused on integration of electronic devices and systems into textiles. There are different technologies how to do it. Screen printed electronic devices on textile substrates are one of the perspective possibilities how to create electronic devices on textiles. Screen printing technology uses conductive pastes for functional pattern creation. This technology reduces significantly the manufacturing cost, is simple to use and is more and more used in electronics.

Detection of printed circuit board failures based on signal frequency analyses

The inspections of printed circuit boards are necessary carry out because of failures and defects detection. Cracks and change of conductive path width are included to the most frequently defects on printed circuits board where are difficulty detected. These defects can cause change of transmission signal integrity thereby it is necessary their detection. New method for detection of these defects was designed. This method is based on measurement of scattering parameters or spectrum of transmission signal. By evaluation of measurement values the failures and defects can be detected. The results obtained by scattering parameters measuring on conductive path with cracks are presented.

Simulation of reflections caused by microstrip branch lines

The article deals with influences of microstrip branch lines on scattering parameters. The microstrip lines are used for design of high frequency printed circuit boards in many cases. A change of scattering parameters on printed circuit boards is necessary to solve. Especially in design of the printed circuit boards for the high frequency circuits. This paper describes the results of the microstrip long wiring simulation of reflections and its branch lines on substrate

Screen printed chipless RFID tags

Radio Frequency Identification (RFID) is the technology that is used in the daily life. A RFID system consists of RFID tags and readers including many electronic passive and active components. This article deals with design of chipless RFID tags that are screen printed on flexible substrates and do not need any electronic components for their function. There are also presented chipless RFID tag fundamentals and parameters that have an influence on their behavior in the frequency domain. However production of the screen printed chipless RFID tags is cheap and can be used in many applications.

Electrical properties of PEDOT

This article deals with electric properties of metal-organic semiconductor junction. Different types of substrates were used for measurement of electrical parameters of poly(3,4-ethylenedioxythiophene) (PEDOT). On these substrates, the thick layer of PEDOT was created. Current-voltage characteristics were measured to find-out if Schottky barrier on the metal-emiconductor junction is created. Then frequency characteristics were measured to obtain an equivalent circuit of this system.

Detection of gases and vapours concentration from resonance curve of interdigital system

Interdigital structure with thin film sensitive organic layer is the base of many sensors for gases and vapours detection. This structure with sensitive layer has capacitive character where the influence of gas and vapour causes the change of its capacitance and dissipation factor. Resonance circuit, created by interdigital structure and an inductor, is then suitable for gas and vapour concentration detection. This article describes methods of relative humidity detection from the resonance circuit curve and presents many experimental results as well.

High Frequency Behavior of Microstrip Lines on Composite Photopolymer Substrate

Recent trends in PCB design are microvia technologies. Several manufacturing processes are used for microvia technologies. PhotoVia is the method where the photoimageable dielectric materials have to be used. This paper deals with high frequency behavior of microstrip lines created on special photodielectric substrates. Scattering parameters are possible to use to describe high frequency properties of microstrip lines. The results of scattering parameters measurement of microstrip lines on photodielectric substrates are compared with microstrip lines on FR-4 or ARLON ADxxxx substrates.