Andrea Marić

A Wireless Embedded Resonant Pressure Sensor Fabricated in the Standard LTCC Technology

This paper proposes a fully embedded resonant pressure sensor operating in the MHz range and realized in the standard low-temperature co-fired ceramics (LTCC) technology. Buried sensor design and usage of LTCC materials enable application of this sensor in high-temperature and chemically aggressive environments. Upgraded sensor and sensor-antenna models residing on an analytical concept are used for prediction of the system performance. Also, simulation results show that an increase of Youngs modulus for the LTCC tape diminishes the sensor sensitivity. An experimental setup for wireless data retrieval is designed enabling precise measurement of the influence of pressure variation on the sensors resonant frequency. Experimentally attained results are compared with electrical characteristics determined by analytical calculations as well as those derived from electrical simulations.

Low-Cost CPW Meander Inductors Utilizing Ink-Jet Printing on Flexible Substrate for High-Frequency Applications

This paper describes the design and fabrication of low-cost coplanar waveguide (CPW) miniature meander inductors. Inductors are fabricated on a flexible plastic polyimide foil in ink-jet printed technology with silver nanoparticle ink in a single layer. For the first time, the detailed characterization and simulation of CPW inductors in this technology is reported. The inductors are developed with impressive measured self-resonance frequency up to 18.6 GHz. The 2.107-nH inductor measures only 1 mm × 1.7 mm × 0.075 mm and demonstrates a high level of miniaturization in ink-jet printing technology. The measured response characteristics are in excellent agreement with the predicted simulation response.

Micro force sensor fabricated in the LTCC technology

This paper presents resonant force sensor designed for the operation in the MHz range and for 0 to 6 N load. The LTCC technology is implemented for the sensor fabrication and a wireless readout of the measured data is provided. Used LTCC tape is characterised in order to demonstrate its mechanical and electrical properties at room temperature. Also, theoretical model of the sensor is developed to predict its behaviour. Fabricated sensor performance is experimentally characterised and obtained results are in good agreement with the ones derived from the presented theoretical model.

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.

Material characteristics of the LTCC base material CeramTape GC

This paper provides new material property measurement results of the ceramic film material CERAMTAPE GC (manufactured by CERAMTEC GMBH), a commercially available LTCC (Low Temperature Co-fired Ceramics) tape for electronic and microfluidic applications in harsh environment. Following material properties are presented: x-y-z-shrinkage dependent on the lamination pressure, density, weight loss, surface parameters of the green and co-fired tape, thermal properties, Youngs modulus, permittivity, chemical composition, and bio-compatibility.

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.

Modelling and Characterisation of Fractal Based RF Inductors on Silicon Substrate

This paper offers a new realisation of a lumped element model for the second order Hilbert type fractal inductor on silicon substrate. Modelled elements are derived and analytically determined from the inductors layout specifications and available materials parameters. Based on the presented concept, frequency dependent characteristics for fractals inductance and quality factor (Q-factor) can be anticipated easily and with acceptable tolerances. In order to verify the accuracy of the presented model obtained parameters have been compared with experimentally attained values. Determined model parameters show satisfactory compliance with electrical parameters attained through experimental measurement, for frequencies in lower RF range (up to 10 GHz).

Parameters affecting the sensitivity of LTCC pressure sensors

Purpose – The purpose of this paper is to demonstrate the influence of material properties and fabrication technique on the performance of an embedded pressure sensor. Based on conducted theoretical analysis a suitable material and technological technique that gave the best behavior of designed sensor was chosen for its fabrication. This is verified on the example of a resonant pressure sensor, designed for operation in the MHz range.Design/methodology/approach – A sensor module is fabricated using the low temperature co‐fired ceramics (LTCC) technology and sputtering technique for electrodes deposition. The module comprises an inductor connected with a variable capacitor formed by the sensor membranes in a parallel LC circuit. An extensive parallel analysis of sensors performance for sensors with thick film (screen‐printed) and thin film (sputtered) electrodes is demonstrated. Mechanical and electrical parameters (Youngs modulus and permittivity) of different tape materials that are considered for senso...

Performance improvement of a resonant pressure sensor by means of model based design optimisation

This paper deals with the performance improvement of a resonant pressure sensor designed for MHz range and realised in the LTCC (low temperature co-fired ceramics) technology. A new upgraded and modified sensor model residing on an analytical concept is demonstrated. Based on this model, sensitivity of the sensor could be drastically increased only by a change of the cylindrical cavity radius which is part of the pressure sensitive capacitor radius, but without any modification in the sensor set-up arrangement. Results derived by numerical simulation using the modified sensor model are compared with those attained by the practical measurement.