Heli Jantunen

Heli Jantunen
University of Oulu · Department of Electrical and Information Engineering

About

341
Publications
68,824
Reads
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8,208
Citations
Citations since 2016
115 Research Items
5017 Citations
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800

Publications

Publications (341)
Article
A novel manufacturing method for prestressed piezoelectric unimorphs is introduced and the actuator properties are examined. Prestressed PZT 5A and PZT 5H unimorphs with piezo material thickness of 250 microm and 375 microm were manufactured by using sintering and thermal shrinkage of the prestressing material. The process was carried out by screen...
Article
A miniaturized low-loss Wilkinson power divider was designed and fabricated using standard LTCC technology. Size reduction was implemented by folding the quarter-wave transmission lines into tightly coupled meander lines. Parameters determining the electrical performance of the divider structure were analyzed using both circuit and full-wave electr...
Article
Finland is well known as a high technology country and when it comes to ceramic technology the central or Northern part of the country has long traditions in both research and volume production. Under the global pressure the players in the Oulu and Kemi region have recently joined forces in analysing what technologies are needed and what can be off...
Article
Integration of ferroelectric tunable components into dielectric layers of low temperature co-fired ceramic (LTCC) systems enables the realization of more functional multilayer ceramic modules (MCMs) for telecommunication applications. A composition designed for the low temperature sintering of ferroelectric BST material has been developed based upo...
Article
Optimization of MgTiO3–CaTiO3 based LTCC tapes to be used for microwave purposes was investigated. Three kinds of MgTiO3–CaTiO3 based powders containing B2O3 in different forms, and two different slurry systems (PVB and PM) were prepared for tape casting. The results clearly demonstrated that if the powder contained ‘free’ B2O3, no proper tape coul...
Conference Paper
An enhancement technique of quasi-lumped inductance Q-factor is proposed in order to improve loss performance of LTCC filters. Effectiveness of the technique developed is demonstrated by experimental characteristics of a 3-pole bandpass LTCC filter with reduced in-band insertion loss. Figure of merit of a filter is introduced as a universal charact...
Conference Paper
This paper presents high performance flip-chip and through-substrate via transition designs applicable in millimeter-wave single or multichip module assemblies. Full-wave electromagnetic analysis is performed to achieve an optimized transition topology. Interconnection test structures were fabricated in ceramic substrates and performance was succes...
Conference Paper
Full-text available
In this paper, we propose a new technique, which is capable of yielding high quality circular polarization, with a feeding system that is particularly suitable for incorporating in multilayer microwave circuits. This type of circuit can be fabricated either in thick-film or LTCC, which are attractive because they can provide a combination of high-p...
Article
The poling procedure has always been the key issue in producing piezoelectric actuators with optimised performance. This is also true with the relatively new category of pre-stressed bender actuators, where mechanical bias achieved with a passive layer is introduced in the actuators during manufacturing. Due to these factors, the behaviour of the a...
Article
Low-temperature cofired ceramics (LTCCs) are mainly applied in hybrid microelectronics packaging technology, where the fabrication of metallic conductors on LTCC materials is done using various printing technologies. The conventional process is fast and cost-effective in the case of mass production, but too slow and difficult when repair and/or mod...
Article
Effective permittivity was modeled and measured for composites that consist of up to 35 vol % of titanium dioxide powder dispersed in a continuous epoxy matrix. The study demonstrates a method that enables fast and accurate numerical modeling of the effective permittivity values of ceramic/polymer composites. The model requires electrostatic Monte...
Conference Paper
An original design of passive front-end module for Bluetooth and WLAN applications is proposed. The module consisting of bandpass filter, balun and 10-dB directional coupler is realized as multilayer microwave integrated circuit using low temperature co-fired ceramics.
Article
A low-temperature cofired ceramic (LTCC) composition for radio-frequency purposes was accomplished without prior glass preparation. In this process, the formulation was made by mixing the glass-forming oxides (ZnO, SiO2, and B2O3) with the commercial microwave ceramic MgTiO3–CaTiO3. The sintering, microstructure, and microwave properties were compa...
Article
A family of low-temperature cofired ceramics (LTCC) based on mixtures of a commercial dielectric, MgTiO3–CaTiO3(designated MMT-20) and ZnO, SiO2, and B2O3, has been investigated for microwave applications. The main objective was to optimize the three key properties—relative permittivity (ɛr), dissipation factor (DF), and the temperature dependence...
Article
Ferroelectric films such as Barium Strontium Titanate (BST) films are potential candidates for several microwave applications. In this work, the suitability of fine BST powder prepared by the sol-gel process for tape casting and firing were studied and compared with one commercial BST powder. The particle size of the sol-gel powder was 0.05–0.1 μm....
Article
Tape casting is a feasible method for preparing ceramic tapes with different electrical and magnetic properties for multilayer ceramic devices. This paper describes the tape casting process for several different electroceramic materials (BST, PZT, NZF and ZSB) utilising similar organic additive and solvent systems. The properties of tapes with diff...
Article
A low-temperature cofired ferroelectric ceramic composition for electrically tunable radio frequency devices is introduced. A sintering temperature of 950°C for BaSrTiO3–MgO was obtained following the combined addition of B2O3 and Li2CO3. The effects of these sintering aids on densification, microstructure, and ferroelectric properties were investi...
Conference Paper
This paper presents a novel efficient design approach for faster and more profitable development of highly integrated RF and microwave modules. To demonstrate the feasibility of the proposed design concept, a three-dimensionally (3D) integrated BGA filter module applicable in microwave link communications is designed at K-band. Special emphasis is...
Article
This study considers modeling of macroscopic permittivity of composites that consist of different amounts of TiO2 powder dispersed in a continous epoxy matrix (0-3 composites). The composites researched have no closed form solutions predicting their effective permittivity because the phases used have very different relative permittivity values and...
Article
Low temperature co-fired ceramic (LTCC) technology, widely used in the automotive industry, is now being employed in microwave applications. Several commercial materials with low dielectric losses at microwave frequencies and adequate thermomechanical properties have been introduced. Computer-aided design of three-dimensional circuits has also beco...
Article
Adhesive (>5 MPa) and conductive (ρ~2 μΩ cm) copper films with a thickness of ~200 nm were deposited by chemical means on a recently developed low-k cycloolefin-copolymer (COC). The steps of the metallization procedure (chemical etching, metal seeding and copper plating) were optimized. Raman spectroscopy, SEM and AFM were used in the investigation...
Conference Paper
Full-text available
Designs of a tunable matching network and a tunable phase shifter by LTCC ferroelectric technology are presented. The devices are designed for operation in K frequency band. Test structure measurements are presented along with extracted parameters of used ferroelectrics (dielectric permittivity and tunability). These measured parameters are then us...
Article
Low temperature co-fired ceramics (LTCCs) are mainly applied in hybride microelectronics packaging technology, whereas the fabrication of metallic conductors on LTCC materials is done by various printing technologies. The conventional process is fast and cost-effective in the case of mass-production but too slow and difficult when repair and/or som...
Article
Ferroelectric films based on barium strontium titanates have been widely investigated in microwave devices, such as tunable filters and phase shifters. Recent trends include integration of ferroelectric layers into multilayer dielectric modules by a tape casting procedure. The sintering temperature of BST prepared by the conventional oxide mixing m...
Article
The main objective of this study was to make components from a novel low-loss, low-temperature Co-fired ceramic (LTCC) dielectric, which was also compatible with a high-conductivity silver paste. The multilayer-component fabrication procedure is presented together with a composition for a tape-casting slurry, choice of conductor paste, and LTCC pro...
Article
Mechanical properties and thermal expansivities of two compositionally identical ceramics intended for use in 'low temperature cofired ceramic' (LTCC) technology were investigated. Both were based on a commercial MgCaTiO3 dielectric ceramic with the sintering temperature reduced by addition of ZnO-B2O3-SiO2, either in the glassy state or as separat...
Article
Mixtures of ZnO–SiO2–B2O3/MgTiO3–CaTiO3 (ZSB/MMT-20) and BaO–SiO2–B2O3/MgTiO3–CaTiO3 (BSB/MMT-20) have been investigated as new candidates for LTCC dielectric materials. Two-stage sintering behaviour was observed in both materials, starting at around 600 and 850°C. Nearly full density (97%) was achieved in ZSB/MMT-20 after sintering at 900°C, while...
Article
As a part of the project 'Landsat-studies for Mapping the Variables within Water Areas' this study deals with the classification possibilities of evaluating and mapping depth relations and bottom materials within the barren and clear-watered shores of Lake Yli-Kitka, North-Eastern Finland. It has been discovered that it is possible to distinguish o...
Article
The application of the aquatic area research by computer-assisted Landsat MSS remote sensing is presented. Two lakes in northern Finland were mapped into spectrally identified classes.The open water classes depend mainly on the water quality and depth. The aquatic vegetation classes display the main life-forms (helophyte, nymphaeid, isoetid) and th...
Article
The remote sensing classification procedure applied to the Lake Posionjarvi area in the Kuusamo region of northern Finland is based on spectral reflectances. The aquatic surfaces could be divided into seven classes, which are connected, on the one hand, with water depth, the nature of the bottom and the vegetation, and on the other with water quali...
Article
The water quality data collected on the ground by the Water District Office in Oulu was subjected to statistical analyses together with Landsat data to display a few interactions and the possibilities of exploiting remote sensing methods in water area surveying. Correlations between the Landsat data statistics and some water quality measurements we...
Article
Landsat MSS imagery is employed to assess the aquatic complexes of the regulated Lake Kemijärvi and the adjoining small natural lakes in Northern Finland. Ground data were collected from within the hydrolittoral areas to allow the evaluation and revision of the computer-aided Landsat MSS classification. The major developments reported here are: (1)...
Article
Although large numbers of imageries over planetary surfaces have been aquired by notable space missions over the past twenty years, the versatile technical remote sensing achievements, which have found their long-term and successful applications within the fields of different geosciences, have not been employed in planetology. High resolution image...
Article
Both scientific and technical investigations and the planning of water reservoir areas for different purposes all require accurate base information on water areas in the form of preliminary orientation maps. These are in principle most easily obtained by using the Landsat multispectral scanner (MSS) data in CCT form. Computer-aided analysis such da...
Article
Two bright spots shown by Voyager 2 images on Saturn's north temperate belt are discussed in terms of a simple photometric model in which the brightness differences are caused by obscuring matter above the main cloud layer. In the ultraviolet light, in which scattering by small particles is very effective, the spots are invisible. In the violet lig...
Article
The method for mapping the pixel-scale and larger ruggednesses of the Martian ridged plains within Solis Planum is described by assuming the Lommel-Seeliger's reflection law. This method allows surface tilt angles towards and away from the Sun to be estimated and topographic elevations to be displayed by the aid of monoscopic digital image data. Th...
Article
An inhomogeneous vertical distribution of matter in Saturn''s rings is capable of producing the tilt effect which is observed in ring B. In this model the effective thickness of the rings is 8 to 9 times the radius of the particles.
Article
Full-text available
A composite material made of barium strontium titanate (BST) and thermoplastic polymer (cyclic olefin copolymer, COC) for GHz frequencies was studied in this work. The material's properties were compared with a commercial product. The microstructure exhibited uniform distribution of ceramic particles in the polymer matrix. The composite had relativ...

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Projects

Projects (6)
Project
To fabricate high-performance piezoelectric ceramics at room temperature.
Archived project
Explore the feasibility of using multi-functional sensing components for smart skin.
Project
The objective of this research is to develop novel high-value electronic devices based on green carbon derived from secondary flows of biobased raw materials and contribute to the Finnish bioeconomy and circular economy. This is achieved by interdisciplinary research between materials science and microelectronics. Material research is focusing on development of green carbons and the microelectronic research is dealing with the design, testing and feasibility of the developed nanomaterials in electronic devices such as electromagnetic interference absorbers, electromechanical sensing applications and supercapacitors. The used carbon nanomaterials are made by the carbonization of electrospun lignin nanofibers and biocarbon prepared from pyrolyzed wood both with much lower cost compared to commercial nanocarbon materials such as graphene and carbon nanotubes. The interest to use and develop biobased carbon materials have currently increased due to their great potential in new lightweight nanocomposites and also because of their applicability to wide array of electronic applications due to their nature and low environmental footprint. The proposed work includes study on the biocarbon nanomaterials, and the development of lightweight nanocomposite materials, where the electric functionality will bring added value.