Nelu Blaz

Modeling and Characterization of Frequency and Temperature Variation of Complex Permeability of Ferrite LTCC Material

This paper presents modeling of the complex permeability spectra, fabrication and a wide frequency range characterization of a toroidal LTCC ferrite sample. A commercial ferrite tape ESL 40012 is used, and standard LTCC (Low Temperature Co-flred Ceramic) processing has been applied to the sample fabrication. The characterization was performed using a short coaxial sample holder and a vector network analyzer in the frequency range from 300kHz to 1GHz, at difierent temperatures. Using the model of the complex permeability spectra dispersion parameters of ferrite LTCC material has been determined for various temperatures. Characteristics of test samples are compared with modeled results and commercially available toroid made of similar NiZn ferrite material.

Passive Wireless Sensor for Force Measurements

The goal of this paper is to investigate fabrication and design of a wireless passive sensor, and its application for measuring normal forces. The proposed force sensor consists of a single coil as an essential part, realized in printed circuit board technology, commercially available elastomer, and ferrite core. Measurements are done wirelessly for variable values of applied force by phase-dip technique, using an external coil antenna. By applying force to the sensor, the elastomer deforms and ferrite approaches to the coil, causing changes to the inductance of the coil. As a result, the resonant frequency of the antenna-sensor system shifts toward lower frequencies. The experimental setup is conducted to test and characterize the developed force sensor. A high sensitivity of 311 kHz/N is achieved in the measured force range from 0 to 75 N. The measurement results proved the theoretical and analytical calculations, as well as the electrical simulations.

Ink-jet printed strain sensor on polyimide substrate

This paper describes a method for measuring strain on a specimen with flexible strain sensor. The sensor is made by ink-jet printing of silver ink on polyimide substrate, in that manner providing a combination of electrical conductivity and mechanical flexibility. When a force is applied on the free end of cantilever beam, three different strain gauges are used to measure flex of the beam. The gauge is taped at the fixed end of the beam, on the top side. To determine the strain, it requires accurate measurement of small resistance change, therefore strain gauge is connected to the Source Meter Keithley 2410. This work will consolidate the research on theoretical, technological and experimental aspect of design, development and validation of resistive sensors that are flexible, bendable and stretchable.

Complex Permeability Changes of Ferritic LTCC Samples With Variation of Sintering Temperatures

The complex permeability of commercially available ferrite LTCC (Low Temperature Cofired Ceramics) tapes in dependence of peak sintering temperature have been measured and calculated in the high-frequency range (300 kHz-1.2 GHz). For the first time this dependence is determine at five peak sintering temperatures up to 1300°C. Permeability values have been calculated from S-parameters measured with a vector network analyzer and a short ended coaxial sample holder into which ferritic LTCC toroids have been placed. The toroids were realized by stacking and laminating 62 layers of green tape and then sintered at peak temperatures of 885°C, 1000° C, 1100°C, 1200°C and 1300°C, respectively. Obtained complex permeability values for these toroidal LTCC samples are presented. The maximum real part of permeability values increase up to 930 (at 1100°C firing peak temperature) and show a shift to lower frequency values. At higher sintering temperatures (1200° C and 1300°C) real part of permeability of ferrite samples starts to decrease with further shifting to lower frequency values. In order to determine variation of grain size caused with increasing of sintering temperature and its influence on material complex permeability, an microscopic inspection of samples was performed. Also, using the model of the complex permeability spectra, dispersion parameters of ferrite LTCC material has been determined for various sintering temperatures.

Flexible inkjet printed sensor for liquid level monitoring

In this work a method for liquid level measurement is presented, with a support of experimental results. The presented liquid-level measurement method uses two sensors: level and reference interdigital capacitors. Proposed sensors are fabricated in low-cost inkjet printing technology with nanoparticle silver ink on a Novele™ coated polyethylene terephthalate (PET) substrate. The sensors comprise a two interpenetrating comb electrodes with 1.5 mm width of comb electrode, 1.5 mm spacing between each comb and 15 fingers with length of 135 mm and 8 fingers with length of 19 mm for level and reference sensor, respectively. Capacitance of the level sensor fixed on a test tube increases as the liquid level increases (up to 43.5 mm). The sensor characteristics for three liquids with different permittivity are presented. The reference sensor at the bottom of the tube is completely covered by liquid and its capacitance changes as the permittivity of the liquid changes. Experimental results for three different liquids confirmed simple liquid level measurement method which enables the measurement regardless of the liquid type.

Design and simulation of 13.56 MHz RFID tag in ink-jet printing technology

This paper presents design, modeling and simulation cost-effective RFID (Radio Frequency Identification) tag using ink-jet printing technology. Passive 13.56 MHz RFID tag is based on an inductive-capacitive resonant circuit. Designed RFID tag is part of the ID (Identification) card, which has standard ISO ID1 size (85.60 mm × 53.98 mm). It consists of rectangular spiral planar inductor (antenna) and interdigital capacitor. The modeling and optimization of RFID tag are discussed. At the first step, inductor and capacitor were designed using in-house developed simulation tools AntInd and INDICON, respectively, in order to provide proper electrical characteristics of tag. After that, the designed geometrical structures are modeled and simulated using CST Microwave Studio software. A radiation pattern at operational frequency of 13.56 MHz simulated in CST of the RFID tag insulated in free spaces is presented.

Design of RFID antenna in ink-jet printing technology

In this paper design of 125 kHz RFID antenna is presented. The optimization and improvement of electrical characteristics, including inductance and Q-factor, is also discussed. Designed RFID antenna is part of the ID card, which has standard ISO ID1. It consists of two spiral coils in two layers. Comparison of antenna in flexible and PCB technology is presented. The aim of this work is to introduce novel cost-effective antenna in flexible technology instead of conventional RFID antenna in PCB technology.

Fully inkjet printed CPW meander inductors on PET flexible substrate

This paper presents continued research on CPW (coplanar waveguide) meander inductors. The inductors were made in inkjet printing technology. They were printed on polyethylene terephthalate (PET) based substrate (Novele IJ-220), 140 μm thick. Water-based nanoparticle silver ink (Metalon® JS-B25HV) is used for printing. The fabricated inductors have a great value of quality factor (up to 4.2) and high frequency operating range between 1 GHz ÷ 7 GHz for three turn, and 1 GHz -19 GHz for one turn structure. Those characteristics made them suitable for application in flexible electronics.

Modeling and characterization of LC displacement sensor in PCB technology

This paper presents the development of LC sensor comprised of a movable inductor and a fixed inductor-capacitor resonant circuit, thereby causing the sensor resonant frequency to be displacement dependent. The sensor has been fabricated in PCB (Printed Circuit Board) technology and experimentally characterized. Experimentally obtained results are compared with an electrical model. Good agreement between measured results and parameters estimated by analytical calculations are obtained.

Complex permeability dependence of commercial LTCC ferritic tape on ambient temperature

This paper deals with material characterization of ferrite LTCC (Low Temperature Co-fired Ceramic) and influence of ambient temperature variation to its complex permeability value. Results of the material characterization (chemical analysis, surface roughness) of commercially available ESL 40011 ferrite tape are presented for the first time. In addition, complex permeability dependence on frequency is determined using previously verified measurement method and developed dispersion model. Complex permeability dependence on ambient temperature variation is also measured in the frequency range up to 1 GHz. Presented results show decrease of complex permeability maximum value with temperature increase from 20°C to 120°C. Cut-back of the useful frequency range of the material is also noticeable in the same temperature range.