Browsing by Author "Ala-Laurinaho, Juha"
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Item 5G antenna challenges and opportunities(2019-08-01) Viikari, Ville; Luomaniemi, Rasmus; Ala-Laurinaho, Juha; Kurvinen, Joni; Kahkonen, Henri; Lehtovuori, Anu; Leino, Mikko; Department of Electronics and Nanoengineering; Ville Viikari GroupAntenna is one of the most important single part of a wireless communications system and significantly affects the total energy consumption. Current mobile antennas can be inefficient in both converting radio energy to radiating waves and also focusing the radiated waves. The upcoming 5G introduces additional challenges to antennas but could also provide opportunities to use RF energy more efficiently. This paper discusses 5G antenna challenges and presents two potential antenna solutions for 5G mobile devices and one for mm-wave access points.Item 650 GHz imaging as alignment verification for millimeter wave corneal reflectometry(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-03-01) Hu, Yong; Baggio, Mariangela; Dabironezare, Shahab; Tamminen, Aleksi; Toy, Brandon; Ala-Laurinaho, Juha; Brown, Elliot; Llombart, Nuria; Deng, Sophie; Wallace, Vincent; Taylor, Zachary; Department of Electronics and Nanoengineering; Zachary Taylor Group; Ville Viikari Group; University of California, Los Angeles; Delft University of Technology; Wright State University; University of Western AustraliaA system concept for online alignment verification of millimeter-wave, corneal reflectometry is presented. The system utilizes beam scanning to generate magnitude-only reflectivity maps of the cornea at 650 GHz and compares these images to a precomputed/measured template map to confirm/reject sufficient alignment. A system utilizing five off-axis parabolic mirrors, a thin film beam splitter, and two-axis galvanometric mirror was designed, simulated, and evaluated with geometric and physical optics. Simulation results informed the construction of a demonstrator system which was tested with a reference reflector. Similarity metrics computed with the aligned template and 26 misaligned positions, distributed on a 0.5 mm x 0.5 mm x 0.5 mm mesh, demonstrated sufficient misalignment detection sensitivity in 23 out of 26 positions. The results show that positional accuracy on the order of 0.5 mm is possible using 0.462 mm wavelength radiation due to the perturbation of coupling efficiency via beam distortion and beam walk-off.Item Antenna Array Based on 3D-printed Plastic BoR Elements Coated with Conductive Paint(2023) Kuosmanen, Matti; Ala-Laurinaho, Juha; Holopainen, Jari; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari GroupThe body-of-revolution (BoR) Vivaldi arrays are usually all-metal, including both antenna elements and the antenna base. However, despite the robustness and low losses of the all-metal designs, they are often heavy and expensive. In this paper, we investigate 3D-printed, dual-polarized BoR antenna elements operating at 2±6 GHz. By 3D printing the antenna elements from plastic, we can make them less expensive, hollow, and thus lightweight. The elements are made conductive by painting them with silver paint. The performance of the antenna array is evaluated with simulations and measurements. Due to the relatively low conductivity of the paint, resistive losses of the array are higher than those of the all-metal counterparts. Nevertheless, the measured total efficiency of the array is still high, 95% at the highest, which confirms the applicability of the proposed manufacturing technique. Furthermore, we compare the proposed design to a previously published inverted BoR antenna array.Item Antenna measurements at millimeter wavelengths - Overview(2018-01-01) Räisänen, Antti V.; Zheng, Jianfang; Ala-Laurinaho, Juha; Viikari, Ville; Department of Electronics and Nanoengineering; Zachary Taylor Group; Ville Viikari GroupTesting of electrically large antennas as well as that of electrically small integrated antennas at millimeter wavelengths is very challenging. In this overview we discuss the physical and technical challenges and limitations in testing of the various kinds of mm-wave antennas.Item Antennivahvistuksen määrittäminen lähikenttämittauksissa(2017-12-04) Pälli, Samu-Ville; Ala-Laurinaho, Juha; Sähkötekniikan korkeakoulu; Turunen, MarkusItem Beam Optimization for 28 GHz Phased Array Utilizing Measurement Data(2020-03) Leino, Mikko K.; Bergman, Jan; Ala-Laurinaho, Juha; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari GroupThis paper presents beam optimization methods for a phased array operating at 28GHz. The phase of each antenna element is controlled with an element-specific 5-bit phase shifter. The amplitude of each element varies with the chosen phase shift state due to the antenna design. Each individual element is measured and based on the measurement data, the beam optimization for the maximum gain is done. The optimization increases the measured gain compared to the nominal case by 1.3dB at broadside. Furthermore, the element amplitude variation allows optimization for the lower side lobes to be done by finding the correctly weighted amplitudes. Taylor distribution is used for this optimization and the side-lobe level decreases 2.4dB for the broadside beam.Item Beam steerable 26 – 30 GHz antenna for a fifth generation cellular base station(2016-06-13) Montoya Moreno, Resti; Ala-Laurinaho, Juha; Sähkötekniikan korkeakoulu; Viikari, VilleItem Beam-Reconfigurable Antenna Based on Vector Modulator and Rotman Lens on LTCC(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2021) Karki, Sabin Kumar; Varonen, Mikko; Kaunisto, Mikko; Rantala, Arto; Lahti, Markku; Lamminen, Antti; Holmberg, Jan; Kantanen, Mikko; Ala-Laurinaho, Juha; Viikari, Ville; Ville Viikari Group; VTT Technical Research Centre of Finland; Department of Electronics and NanoengineeringA beam-switching array is designed using a $4\times 6$ Rotman lens as a beam-forming network to switch the beam towards -30°, -10°, 10°, and 30°. Six substrate integrated waveguide fed $1\times 4$ microstrip patch arrays are used as the radiating elements. The beam-switching array is designed on the LTCC substrate to operate at 71-76 GHz. In this work, the feasibility of implementing a beam-switching network with a vector modulator (VM) integrated circuit as switching element is studied for the first time. The measured radiation pattern of the beam-switching array with the VM is in line with the simulated radiation pattern. The measured peak realized gain of the beam port 1, 2, 3, and 4 with 3-dB backoff gain of the VM are 17, 17, 17.8, 16.9 dBi at 75 GHz, respectively. In addition, the work demonstrates the possibility of beam-reconfigurability in beam-switching array by simultaneous excitation of the beam ports in optimum phase using the VM. The simultaneous excitation of the adjacent two ports, 1-2, 2-3, and 3-4, steer the beam towards -19°, 0°, and 19°, respectively, which improves the beam cross-over level. With various combinations of simultaneous excitation, the half power beam-width of the beam-switching array is varied from 17.8° to 75°.Item Beam-steerable E-band lens antenna for 5G backhaul link(2016-10-31) Karki, Sabin; Ala-Laurinaho, Juha; Sähkötekniikan korkeakoulu; Viikari, VilleItem Calibration Alignment Sensitivity in Corneal Terahertz Imaging(Multidisciplinary Digital Publishing Institute (MDPI), 2022-05-01) Zarrinkhat, Faezeh; Baggio, Mariangela; Lamberg, Joel; Tamminen, Aleksi; Nefedova, Irina; Ala-Laurinaho, Juha; Khaled, Elsayed E.M.; Rius, Juan M.; Romeu, Jordi; Taylor, Zachary; Department of Electronics and Nanoengineering; Zachary Taylor Group; Ville Viikari Group; Department of Electronics and Nanoengineering; Assiut University; BarcelonaTechImproving the longitudinal modes coupling in layered spherical structure contributes significantly to corneal terahertz sensing, which plays a crucial role in the early diagnosis of cornea dystrophies. Using a steel sphere to calibrate reflection from the cornea sample assists in enhancing the resolution of longitudinal modes. The requirement and challenges toward applying the calibration sphere are introduced and addressed. Six corneas with different properties are spotted to study the effect of perturbations in the calibration sphere in a frequency range from 100 GHz to 600 GHz. A particle-swarm optimization algorithm is employed to quantify corneal characteristics considering cases of accurately calibrated and perturbed calibrated scenarios. For the first case, the study is carried out with signal-to-noise values of 40 dB, 50 dB and 60 dB at waveguide bands WR-5.1, WR-3.4, and WR-2.2. As expected, better estimation is achieved in high-SNR cases. Furthermore, the lower waveguide band is revealed as the most proper band for the assessment of corneal features. For perturbed cases, the analysis is continued for the noise level of 60 dB in the three waveguide bands. Consequently, the error in the estimation of corneal properties rises significantly (around 30%).Item Capacitively-Loaded Feed Line to Improve mm-Wave and Sub-6 GHz Antenna Co-Existence(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020) Kurvinen, Joni; Montoya Moreno, Resti; Lehtovuori, Anu; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; van Wonterghem, Jari; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari Group; Huawei TechnologiesThe co-existence of millimeter-wave (mm-wave) and sub-6GHz antennas in a smartphone presents many performance-limiting aspects. When both antennas are attached to the metal frame, the feed lines of the mm-wave antennas might short-circuit the sub-6GHz antennas, and thus, may significantly affect their performance. This paper presents a method to design feed lines that function as transmission lines at mm-wave frequencies but correspond to open circuits at sub-6GHz. This study determines, in theory, the smallest achievable capacitive loading with different line types and experimentally validates the approach. The capacitive loading due to the feed line is small enough to maintain the sub-6GHz performance. At the mm-wave band, the insertion loss of the line is 1dB with a measured reflection coefficient below −10dB. The introduced common-mode capacitive load of the feed line on the sub-6GHz antennas corresponds to 0.19pF capacitance.Item Co-Designed Handset Antennas with Wide Angular mm-Wave Coverage and LTE MIMO(2019-11-25) Kurvinen, Joni; Kähkönen, Henri; Lehtovuori, Anu; Ala-Laurinaho, Juha; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari GroupThe co-existence of mm-wave and LTE antennas in modern handsets is yet an unsolved challenge in the phone industry and antenna research community. The different antenna types merged together in a shared volume easily hinder each other's performance. This paper extends the work published recently, showing how high-gain mm-wave antennas at 28 GHz can be incorporated in the same volume with LTE MIMO antennas. The results show that with small compromises a decent performance can be achieved at both mm-wave and LTE bands.Item Co-Designed mm-Wave and LTE Handset Antennas(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019-03) Kurvinen, Joni; Kahkonen, Henri; Lehtovuori, Anu; Ala-Laurinaho, Juha; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari GroupFifth generation mobile networks will introduce several new frequencies for short-range high-capacity communications. Future handsets must also support current frequency bands for backwards compatibility and long-range communications. This paper presents a proof-of-concept solution for co-designed millimeter-wave and LTE antennas in a metal-rimmed handset. The design shows that both antenna types can be accommodated within the volume and be integrated into the same structure. Presented antennas operate at 700–960 MHz, 1710–2690 MHz, and 25–30 GHz. Simulations and measurements suggest the system can be designed in such a way that the millimeter-wave antenna does not hinder the low band performance. LTE antennas generally reach over 60% total efficiency while the millimeterwave module has a peak gain of 7 dBi with measurementverified beam-steering capability. The proposed design proves that 5G mm-wave antennas can be embedded to 4G systems without greatly sacrificing display size or sub-6 GHz antenna performance.Item Comparison of additively manufactured and machined antenna array performance at Ka band(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-01) Kahkonen, Henri; Proper, Sebastian; Ala-Laurinaho, Juha; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari Group; RISE BioeconomyAdditive manufacturing (AM) is a rapidly developing field, which potentially decreases the manufacturing costs and enables increasingly complex antenna shapes. Metal-based AM might be particularly useful for manufacturing antennas at millimeter-wave (mm-wave) range, because these antennas are physically small enough making AM cost efficient, and manufacturing accuracy could still suffice for good electrical performance. In this letter, two additively manufactured and identical machined fully metallic Ka-band Vivaldi antenna arrays are compared. The manufactured antenna arrays are compared using RF measurements to conclude the feasibility of AM for manufacturing antenna arrays at mm-wave frequencies. Comparison of the measured radiation patterns and realized gains of each of the antenna arrays between 26 and 40 GHz shows close to identical radiation patterns for all the arrays. A loss in realized gain of 0.5-1.5 dB is observed in the AM arrays when compared to the machined array due to the used materials and the surface roughness.Item Comparison of Additively Manufactured Dual-Polarized Probe Antennas at Ku-Band(2023) Karki, Sabin Kumar; Ala-Laurinaho, Juha; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari GroupThis paper presents a comparison between two additively manufactured dual-polarized open-ended waveguide probe antennas. The probe antenna design covers the up-link and down-link frequencies of satellite communications at Ku-band (10.7 - 14.5 GHz), and it could be used for fast ground-station antenna measurements. The used fabrication processes are the fused filament fabrication (FFF) followed by the metallization with conductive paint and the direct metal printing using binder-jet process. The measured performance of the manufactured prototypes agrees well with the simulated performance in the design frequency range. The slight dimensional deviations from the design values increase the low-frequency coupling and reflection coefficients compared to the simulations. To decrease the coupling between polarizations, a horn-type waveguide opening is introduced.Item Comparison of two phase retrieval algorithms at sub-millimeter wavelengths(2004) Lerber, Annakaisa von; Ala-Laurinaho, Juha; Sähkö- ja tietoliikennetekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiDiplomityössä on tutkittu mahdollisuutta käyttää iteratiivisia vaiheenpalautusalgoritmeja alimillimetriaaltoalueen antennimittauksissa. Työhän on valittu kaksi alan kirjallisuudessa esitettyä algoritmia ja ne on kirjoitettu Matlabin ohjauskielellä vertailua varten. Valitut algoritmit ovat Kalifornian yliopiston (UCLA) tutkimusryhmän iteratiiviseen Fourier-menetelmään perustuva tasolta-tasolle-diffraktioalgoritmi (PPD) ja Napolin sekä Salernon yliopistojen tutkimusryhmän käyttämä konjugaattigradienttialgoritmi (CGM). Algoritmit laskevat sähkökentän amplitudin sekä vaiheen antennin apetuurissa kahden amplitudi- tai intensiteettitasomittauksen perusteella. Molemmat mittaustasot sijaitsevat antennin lähikentässä tietyn etäisyyden päässä toisistaan. Lisäinformaationa PPD-algoritmi tarvitsee antennin apertuurin koon. Algoritmeja on vertailtu toisiinsa mallinnetun esimerkkikentän avulla 310 GHz:n taajuudella antennin apertuurin ollessa neliskulmainen ja kooltaan 40 lambda x 40 lambda. Algoritmien vertailussa on tutkittu niiden suppenevuutta, kahden mittaustason välimatkan merkitystä algoritmien suorituskykyyn sekä kohinan, näytteenottovälin kasvattamisen ja näytteenottoantennin paikkavirheiden vaikutusta. PPD-algoritmin havaittiin suppenevan nopeasti ja saavuttavan hyviä tuloksia tilanteissa, jossa seuraavat kriteerit täyttyivät: 1) mittaustasojen välisen etäisyyden tuli olla riittävä, 2) näytteenottovälin tuli olla <=lambda/2 ja 3) kohina ja mittausvirheet eivät saaneet olla liian merkittäviä. CGM-algoritmi havaittiin suppenevuudeltaan huomattavasti PPD-algoritmia hitaammaksi, mutta kestävämmäksi erilaisille muutoksille mittauksissa. CGM-algoritmin hitaus johtuu kulma-alueen vaiheittaisesta kasvattamisesta, joka estää iteraatiotuloksen ajautumisen paikalliseen minimiin globaalin ratkaisun sijasta. Diplomityötä varten mitattiin kaksi y-suuntaista leikkausta 310 GHz:n taajuudella hologrammiin perustuvassa kompaktin mittauspaikan hiljaisessa alueessa. Mittauksissa haluttiin selvittää algoritmien soveltuvuutta hiljaisen alueen analysointiin. Hologrammin halkaisija on 0,6 m ja yhdensuuntaiset mittaustasot sijaitsivat 1,8 m:n ja 2,02 m:n päässä hologrammista. Algoritmit eivät pystyneet laskemaan vaihetta oikein amplitudimittausten perusteella, sillä yksiulotteinen tasoaaltohajotelma ei pysty riittävällä tarkkuudella mallintamaan todellista kaksiulotteisesta hologrammista säteilevää kenttää.Item Connected Dipole Antenna Cluster of Enhanced Spherical Coverage CDF for mm-Wave Applications(2023) Chen, Quangang; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; Moreno, Resti Montoya; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari Group; Huawei TechnologiesIn this paper, we present an antenna cluster concept operating in millimeter-wave (mm-Wave) frequency bands for 5G applications. Unlike conventional arrays made up of identical elements, a cluster array is constructed using non-identical dipoles with high coupling that are placed in a 2-mm wide slot. The cumulative distribution function (CDF) of the spherical coverage gain is used to evaluate the beam-forming capability. High coverage gain over a wide band can be achieved by adjusting the amplitudes and phases of excitation vector. To further enhance the spherical coverage, reactive elements are loaded into the gaps between adjacent dipoles. These reactive elements are selected from a pre-defined database using genetic algorithm-based optimization. The proposed connected dipole cluster demonstrates hemispherical coverage gains greater than 4 dB in the low band (24 to 29.5 GHz) and greater than 6 dB in the high band (37.5 to 43.5 GHz) at the 50%-tile CDF.Item Crack Stop as a Coupling Element Between an IC Chip and Antenna(2024) Bergman, Jan H.S.; Ryynänen, Kaisa; Ala-Laurinaho, Juha; Stadius, Kari; Ryynänen, Jussi; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari Group; Jussi Ryynänen Group; Department of Electronics and NanoengineeringMillimeter-wave antenna arrays place integrated transceiver chips and antennas in close proximity to each other. As a result, the presence of the chip will affect the performance of the system significantly, with the metallic structures within the chip being a source for structural resonances. A transition which utilizes one of these metallic structures, the crack stop, as a coupling element is presented. The proposed design allows a non-galvanic connection between the IC chip and the antenna. The performance of the transition is analyzed through simulations, and is shown to reach above-70-percent power transmission between 42.3 GHz and 62 GHz, covering the majority of V-band.Item Cross polarization and aberrations with Dragonian and equivalent off-axis parabolic mirrors for beam collimation in THz imaging systems(SPIE, 2022) Rezapoor, Pouyan; Tamminen, Aleksi; Ala-Laurinaho, Juha; Dabironezare, Shahab Oddin; Llombart, Nuria; Taylor, Zachary; Department of Electronics and Nanoengineering; Wikner, DA; Robertson, DA; Zachary Taylor Group; Ville Viikari Group; Delft University of TechnologyThe relative benefits of an offset Dragonian reflector compared to equivalent off-axis parabolic (OAP) mirrors for feeding collimated beam to a scanned beam imaging system are investigated. Physical-optics simulation of the Dragonian are performed at 500 GHz. The input is a Gaussian beam with a frequency dependent waist radius fit to the output of a standard Pickett-Potter horn. The collimated output beam properties are characterized, including cross-polarization, beam waist radius, Gaussicity, and M-squared parameter. Next, by sweeping the parameters of an OAP reflector (parent focal length and incidence angle) in the physical-optics simulations, we find the geometry in which the properties of the output beam best match the Dragonian geometry. This reflector is found to be an OAP with 108.22 mm parent focal length and 30. incidence angle. An additional OAP reflector is also considered in these simulations, which is the most often used 90. OAP. The parent focal length is 56.95 mm for this mirror, so that we have a similar beam waist radius in the detector plane. Finally, physical optics simulations reveal that the Dragonian geometry produces much smaller cross-polarization in the detector plane (-23 dB at the beam waist) in comparison with OAP reflector (being -14 dB and -8 dB for 30 degrees and 90 degrees off-axis mirrors, respectively). The 30. OAP reflector is able to produce similar beam quality in terms of phase variation, Gaussicity, and beam waist radius at the detector plane.Item Cross polarization in swept beam THz imaging systems using off-axis parabolic mirrors(2022) Rezapoor, Pouyan; Tamminen, Aleksi; Nefedova, Irina; Ala-Laurinaho, Juha; Llombart, Nuria; Rodilla, Helena; Stake, Jan; Taylor, Zachary; Department of Electronics and Nanoengineering; Zachary Taylor Group; Ville Viikari Group; Delft University of Technology; Chalmers University of TechnologyThe optical behavior of a terahertz imaging system employing a train of four identical off-axis parabolic mirrors with oblique incidence angle illumination is investigated in this work. The aperture filling and aberrations of a single off-axis parabolic mirror when illuminated by a Gaussian terahertz beam at its focus point is measured and simulated. The amplitude of E-field in transverse electric (TE) and transverse magnetic (TM) polarizations at target plane reveals a significant cross polarization, even when there is zero cross polarization at the source beam, amplitude of which is ∼ 33% of TE polarization. The investigation of the E-field on the detector plane reveals that this ratio is ∼ 1.5% at the detector plane, and the cross polarized E-field at the target plane is rotated back to co polarization. Although its amplitude is negligible, the TM distribution at detector plane is bimodal and tilted about the optical axis.
