M. Komulainen

University of Oulu, Oulu, Oulu, Finland

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Publications (21)11.31 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the designs as well as modeled and measured characteristics of two miniaturized 3-dB directional couplers for wireless applications at 2.45 GHz that provide 90° and 180° phase differences between the output signals. The 90° directional coupler was designed as a branch-line coupler with one pair of quarter-wavelength transmission line sections replaced by artificial transmission lines with positive frequency dispersion and another pair of transmission lines replaced by metamaterial transmission lines with negative dispersion. The 180° directional coupler was designed on the basis of the 90° directional coupler by connecting an additional 90° phase shifting network to one of its outputs. Both directional couplers were implemented as fullyintegrated quasi-lumped-element structures in multilayer LTCC packages, fabricated, and experimentally investigated.
    Journal of Electromagnetic Waves and Applications 04/2012; 25(2):169-175. · 1.40 Impact Factor
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    ABSTRACT: In this paper, the high-frequency behavior of ball grid array solder interconnections during thermal cycling tests (TCTs) was investigated. This interconnection type was used in ceramic antenna modules that were attached to printed wiring boards thermo-mechanically equivalent to commonly used FR-4 material. The tests were carried out in a TCT chamber operating in the 0-100 °C range. To observe TCT-induced failures in the in- terconnections, scattering parameter measurements (return loss) were performed both during the TCT and at room temperature during cycling breaks. These measurement data were contrasted with imaging results obtained with scanning acoustic microscopy (SAM), and scanning electron microscopy (SEM) was used to verify the failure mechanisms in the interconnections. The results indicate that degradation of interconnection(s) can be seen both during cycling and in room-temperature measurements in a wide frequency band. The degradation was seen best in deteriorating out-of-band characteristics of the antennas. Measurements dur- ing cycling gave a more comprehensive picture of the assemblies' electrical response to fractures in interconnections than did off-cycle measurements. SAM imaging showed indications of cracking much earlier than they were observed in S-parameter measurements. SEM results suggested that the main failure mechanism was cracking in solder.
    IEEE Transactions on Components, Packaging, and Manufacturing Technology 09/2011; 1(9). · 1.26 Impact Factor
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    ABSTRACT: The feasibility of using a capacitive sensor to sense the proximity of an external load, especially a finger, to a mobile terminal antenna was experimentally studied using a PIFA-type antenna as one of the sensor's electrodes. It was found that with the proposed arrangement it is possible to detect objects with permittivity close to that of body tissue or the conductivity level of aluminium and the size of a human finger at distances up to 15 mm.
    Progress In Electromagnetics Research Letters 01/2010; 15:13-18.
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    ABSTRACT: A tunable microwave phase shifter composed of a low-sintering-temperature, screen-printable barium strontium titanate (BST) film and silver metallization was fabricated on an alumina substrate and co-fired at 900 °C for 3 h. The dielectric properties of the films were characterized in a frequency range of 0.8–8 GHz using scattering parameter measurements and a quasi-static coplanar waveguide transmission line model. The temperature dependency of the films was measured through capacitance measurements in a frequency range of 0.5–2.5 GHz. The figure of merit (phase shift/dB of insertion loss) of the phase shifter was found to be 14.6 at 3 GHz with an applied bias field strength of 2.5 V/μm. The performance of the phase shifter is briefly discussed and compared with other phase shifters fabricated by direct screen-printing of BST films.
    Journal of the European Ceramic Society. 01/2010;
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    ABSTRACT: A method for measuring user-induced load on a triple-band GSM PIFA antenna is presented. The capacitance, total efficiency and matching of the antenna were measured in terms of the increased load of a phantom hand. Up to 10% tuning of the centre frequency occurred, with from 52 to 15% decreased total efficiency owing to the undesired hand grip. The comparable capacitance increased proportionally from 3.83 to 4.45 pF, allowing evaluation of the magnitude of the load.
    Electronics Letters 11/2009; · 1.04 Impact Factor
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    ABSTRACT: The dielectric properties of low-sintering-temperature (LTCC) Barium Strontium Titanate (BST) thick film paste at high frequencies (0.8–5 GHz) are briefly presented. The utility of the BST paste was demonstrated by tuning the resonance frequency of a ceramic PIFA for mobile terminals operating at 2 GHz. The frequency tuning achieved can be used to compensate frequency detuning caused by the proximity of the user to the antenna. The impact of tuning on the antenna's total efficiency and radiation pattern was experimentally studied through a comparison with the performance of a reference antenna not incorporating the varactor.
    Ferroelectrics 01/2009; 388(1):10-16. · 0.42 Impact Factor
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    ABSTRACT: A novel method is presented for electrically tuning the frequency of a planar inverted-F antenna (PIFA). A tuning circuit, comprising an RF switch and discrete passive components, has been completely integrated into the antenna element, which is thus free of dc wires. The proposed tuning method has been demonstrated with a dual-band PIFA capable of operating in four frequency bands. The antenna covers the GSM850, GSM900, GSM1800, PCS1900 and UMTS frequency ranges with over 40% total efficiency. The impact of the tuning circuit on the antenna's efficiency and radiation pattern have been experimentally studied through comparison with the performance of a reference antenna not incorporating the tuning circuit. The proposed frequency tuning concept can be extended to more complex PIFA structures as well as other types of antennas to give enhanced electrical performance.
    IEEE Transactions on Antennas and Propagation 05/2008; · 2.33 Impact Factor
  • M. Komulainen, H. Jantunen
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    ABSTRACT: This paper describes the implementation of a dual-band planar inverted-F antenna that is electrically switched to operate in eight frequency bands. The eight bands are achieved by combining two frequency tuning concepts studied in our previous works. The complete tuning circuitry, consisting of three RF PIN diode switches and four passive components, is implemented without increasing the overall volume of the antenna. The antenna covers the 750-1080 MHz band with 25% and the 1560-2270 MHz band with 50% total efficiency margins.
    Antennas and Propagation Conference, 2008. LAPC 2008. Loughborough; 04/2008
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    ABSTRACT: This paper presents high-performance flip-chip, through-substrate via and board-level BGA transition designs applicable in microwave and millimeter-wave multichip module (MCM) assemblies. Full-wave electromagnetic analysis was performed to achieve optimized transition structures. Interconnection test structures were fabricated in ceramic substrates and their performance was validated using on-wafer scattering parameter measurements. Both the flip-chip transition and the through-substrate via transition with a height of 800 mum exhibited return losses better than 25 dB and 20 dB, respectively, with low transmission losses up to 50 GHz. Furthermore, the wideband board-level BGA transition with a standoff height of 500 showed low insertion loss (< 0.5 dB) over a wide frequency range, from direct current (dc) up to 32.5 GHz.
    IEEE Transactions on Advanced Packaging 03/2008; · 1.12 Impact Factor
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    ABSTRACT: A method for manufacturing embedded variable capacitors (varactors) inside a low-temperature cofired ceramic substrate is presented. A varactor is fabricated by filling a via hole with ferroelectric barium strontium titanate paste. The measured capacitance of the varactor changed from 1.47 to 0.97 pF and the Q factor from 18.2 to 31.5 at 1 GHz when the bias voltage was increased from 0 to 200 V.
    Electronics Letters 02/2008; · 1.04 Impact Factor
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    ABSTRACT: This investigation is one of the first steps toward the realization of low-cost, mass-producible, tunable antenna applications utilizing an integrated ferroelectric-thick film made of bariumstrontiumtitanate material. The dielectric properties of the electric-field-adjustable fired BST thick film are presented in the frequency range of 16 GHz. The key advantages of the material are high tunability (25% with 2.5 V/mum), compatibility with silver electrodes, and the ability to produce film thicknesses down to 25 mum. The utilization of the material is demonstrated by tuning the operating frequency of a folded slot antenna with an integrated variable capacitor. In addition, the impact of tuning on the antenna's total efficiency and radiation pattern is experimentally studied through a comparison with the performance of a reference antenna not incorporating the varactor.
    IEEE Antennas and Wireless Propagation Letters 02/2008; · 1.67 Impact Factor
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    ABSTRACT: This paper describes the design, modeling and implementation of a compact surface-mountable LTCC-BGA antenna package for use in X-band wireless communication. A stacked patch microstrip antenna is embedded on the top side of the LTCC package, while the electromagnetically shielded bottom side is used for RF signal routing. A broadband vertical BGA-via transition path, starting from an organic motherboard (PCB) and ending at the antenna, was designed for frequencies up to 15 GHz. The complete BGA antenna package with dimensions of 12 mm x 12 mm x 1.4 mm was mounted on the PCB using standard surface-mounted device (SMD) assembly processes. The measured antenna characteristics of the package assembly showed a 10-dB impedance bandwidth of 5.8 % and a maximum gain of 4 dBi at 10 GHz. Moreover, an accurate circuit model for the BGA package was developed for use in efficient co-design of RF transceiver systems. Finally, the thermal fatigue reliability of the reflow soldered BGA assemblies was tested under harsh cycling conditions (−40 °C – +125 °C).
    01/2008;
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    ABSTRACT: A frequency tunable planar monopole antenna for mobile terminal applications is presented. The operating frequency of the antenna is electrically switched from the DCS (1710-1880 MHz) to the WLAN (2400-2484 MHz) bands. This is done by using a RF pin diode switch situated in the middle of the antenna. The size of the antenna is 14 x 15 mm<sup>2</sup>, and it covers both bands with over 60 % total antenna efficiency margin. The impact of tuning on the resonant frequency of the antennas, total antenna efficiency and radiation pattern are experimentally studied and compared with reference antennas that have no tuning circuit.
    Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on; 12/2007
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    ABSTRACT: The main purpose of this paper is to present a method for electrically reconfiguring the operating frequency of a planar monopole antenna. In this method a tuning circuit composed of a RF PIN diode switch and two discrete passive components is built inside the antenna structure. This allows a DC control voltage to be brought to the diode switch along with the RF signal. Thus, this method of tuning does not require separate DC wiring, unlike commonly used structures proposed by Zachou et al. The method presented is demonstrated with a dual-band monopole antenna applicable in a mobile handset. The antenna has the capability of switching the lower band between the GSM850 and GSM900 frequency ranges with only a minor impact on the upper band. The upper band covers the frequency ranges of the GSM1800 and DCS 1900 telecommunication standards. Along with the antenna structure, the measured return loss and far-field gain are presented and discussed.
    Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
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    A.D. Abeygunasekera, C.E. Free, M. Komulainen
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    ABSTRACT: In this paper, a radiation enhancement method using low dielectric constant material is demonstrated. Excellent return loss and improved radiation efficiency was obtained from the novel multilayer design structure. The proposed structure is suitable for compact multilayer microwave structures.
    Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
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    ABSTRACT: In this paper a frequency-tunable inverted F-antenna (IFA) for DVB-H reception is presented. The antenna is suitable for small mobile devices (40 mm times 90 mm times 10 mm). The operating frequency of the antenna is tuned with a varactor component. The varactor loads the IFA element and thus enables it to resonate at different frequencies. This kind of tunable narrowband antenna is suitable for DVB-H reception, since one channel in a bandwidth of 8 MHz is received at a time. The antenna presented in this paper can be compared with a frequency- tunable IFA of Ying (2005), presented in a recently published patent. This proves the potential of this kind of DVB-H antenna solution in commercial applications. A special advantage of the proposed antenna is that, since it can be located in a vertical position on the long side of the ground plane, as opposed to the work of Ying (2005), GSM antennas can be located in their optimal position at the upper part of the device.
    Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
  • M. Komulainen, M. Berg, H. Jantunen, E. Salonen
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    ABSTRACT: A compact varactor-tuned meander line monopole antenna for DVB-H signal reception is presented. The operating frequency of the antenna is continuously tuned over the frequency range of the DVB-H standard 470-702 MHz. The antenna has an omnidirectional radiation pattern and covers the frequency range with requisite impedance bandwidth and gain level. The antenna element occupies a very small volume (0.7 cm<sup>3</sup> ) and can be used in 40 x 100 x 10 mm devices.
    Electronics Letters 02/2007; · 1.04 Impact Factor
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    ABSTRACT: One of the major challenges for next-generation, highly integrated, wireless system-on-packages (SOPs) is to integrate the antenna into the package. Due to the inherent narrow bandwidth of planar antennas on LTCC substrates that have moderate relative permittivities in the range 5–20, techniques for improving the bandwidth have to be considered in order to meet the requirements of wideband telecommunication standards. This paper presents a study of laser-micromachined air cavities embedded into an LTCC substrate, and their application in improving the bandwidth of an aperture coupled microstrip patch antenna operating at around 10 GHz. Furthermore, the effects of the air cavity on the size, gain, and radiation efficiency of the antenna are presented and discussed.
    Journal of the European Ceramic Society. 01/2007;
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    ABSTRACT: In this paper, two approaches for frequency reconfigurable planar inverted F-antennas (PIFAs) are proposed and experimentally studied. In the first PIFA, an electrically-controlled frequency shift is achieved with a tuning circuit designed for the grounded PCB beside the antenna, while in the second PIFA the tuning circuit is integrated directly into the antenna with no separate DC wiring. The measured return losses, radiation patterns and total efficiencies of the antennas are presented and briefly discussed.
    Antennas and Propagation, 2006. EuCAP 2006. First European Conference on; 12/2006
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    ABSTRACT: In this paper, a frequency reconfigurable annular slot antenna is presented. The tuning system, which consists of diode switch, is located in the microstrip feed. Different bias voltages are supplied over the diode switch to change the length of the feed and thus two different resonance modes are generated for the antenna. The frequency reconfigurable antenna and two reference antennas are fabricated and measured. Experimental results showed a frequency shift of 43 % from 1.63 GHz to 2.34 GHz. Only a small effect by the tuning system on the impedance bandwidth of the proposed antenna compared to the reference antennas is observed. According to the measurement, the proposed tuning method also enabled the antenna to radiate with an acceptable level of efficiency.
    Antennas and Propagation, 2006. EuCAP 2006. First European Conference on; 12/2006