Browsing by Author "Ala-Laurinaho, Juha"
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- 5G antenna challenges and opportunities
A4 Artikkeli konferenssijulkaisussa(2019-08-01) Viikari, Ville; Luomaniemi, Rasmus; Ala-Laurinaho, Juha; Kurvinen, Joni; Kahkonen, Henri; Lehtovuori, Anu; Leino, MikkoAntenna 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. - 650 GHz imaging as alignment verification for millimeter wave corneal reflectometry
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(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, ZacharyA 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. - Antenna Array Based on 3D-printed Plastic BoR Elements Coated with Conductive Paint
A4 Artikkeli konferenssijulkaisussa(2023) Kuosmanen, Matti; Ala-Laurinaho, Juha; Holopainen, Jari; Viikari, VilleThe 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. - Antenna measurements at millimeter wavelengths - Overview
A4 Artikkeli konferenssijulkaisussa(2018-01-01) Räisänen, Antti V.; Zheng, Jianfang; Ala-Laurinaho, Juha; Viikari, VilleTesting 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. - Antennivahvistuksen määrittäminen lähikenttämittauksissa
Sähkötekniikan korkeakoulu | Bachelor's thesis(2017-12-04) Pälli, Samu-Ville - Beam Optimization for 28 GHz Phased Array Utilizing Measurement Data
A4 Artikkeli konferenssijulkaisussa(2020-03) Leino, Mikko K.; Bergman, Jan; Ala-Laurinaho, Juha; Viikari, VilleThis 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. - Beam steerable 26 – 30 GHz antenna for a fifth generation cellular base station
Sähkötekniikan korkeakoulu | Master's thesis(2016-06-13) Montoya Moreno, Resti - Beam-Reconfigurable Antenna Based on Vector Modulator and Rotman Lens on LTCC
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021) Karki, Sabin Kumar; Varonen, Mikko; Kaunisto, Mikko; Rantala, Arto; Lahti, Markku; Lamminen, Antti; Holmberg, Jan; Kantanen, Mikko; Ala-Laurinaho, Juha; Viikari, VilleA 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°. - Beam-steerable E-band lens antenna for 5G backhaul link
Sähkötekniikan korkeakoulu | Master's thesis(2016-10-31) Karki, Sabin - Calibration Alignment Sensitivity in Corneal Terahertz Imaging
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(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, ZacharyImproving 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%). - Calibration of a Two-Port Millimeter-wave Quasioptical Measurement System
A4 Artikkeli konferenssijulkaisussa(2024) Masyukov, Maxim; Tamminen, Aleksi; Nefedova, Irina; Ala-Laurinaho, Juha; Palli, Samu Ville; Generalov, Andrey; Taylor, ZacharyA quasioptical setup based on a Gaussian beam telescope system has been created to analyze the room-temperature and cryogenic millimeter-wave S-parameters of materials and devices for astronomical instrumentation, simulated and tested. The room temperature tests were performed in the WR-3.4 (220-330 GHz) frequency range after completing the thru-reflect-line calibration with a set of custom calibration standards. The system capabilities have been tested during the characterization of the planar devices and materials. - Capacitively-Loaded Feed Line to Improve mm-Wave and Sub-6 GHz Antenna Co-Existence
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2020) Kurvinen, Joni; Montoya Moreno, Resti; Lehtovuori, Anu; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; van Wonterghem, Jari; Viikari, VilleThe 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. - Characterization of Skin Permittivity for Human Fingers by Open-ended Waveguide at Sub-THz
A4 Artikkeli konferenssijulkaisussa(2024-09-26) Xue, Bing; Haneda, Katsuyuki; Icheln, Clemens; Ala-Laurinaho, JuhaThis paper proposes a method for characterizing the complex permittivity of the human finger skin based on an open-ended waveguide covered with a thin dielectric sheet at sub-terahertz frequencies. The measurement system is initially analyzed through full-wave simulations with a detailed finger model. Next, the model is simplified by replacing the finger with an infinite sheet of human skin to calculate the forward electromagnetic problem related to the permittivity characterization. Following this, a radial basis network is employed to train the inverse problem solver. Finally, the complex permittivities of finger skins are characterized for 10 volunteers. The variations in complex relative permittivity across different individuals and skin regions are analyzed, revealing a deviation of < 2 for both the real and imaginary parts of permittivity across 140 to 220 GHz. Repeated measurements at the same location on the finger demonstrate good repeatability with a relative estimation uncertainty < ± 1.4%. - Co-Designed Handset Antennas with Wide Angular mm-Wave Coverage and LTE MIMO
A4 Artikkeli konferenssijulkaisussa(2019-11-25) Kurvinen, Joni; Kähkönen, Henri; Lehtovuori, Anu; Ala-Laurinaho, Juha; Viikari, VilleThe 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. - Co-Designed mm-Wave and LTE Handset Antennas
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-03) Kurvinen, Joni; Kahkonen, Henri; Lehtovuori, Anu; Ala-Laurinaho, Juha; Viikari, VilleFifth 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. - Comparison of additively manufactured and machined antenna array performance at Ka band
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-01) Kahkonen, Henri; Proper, Sebastian; Ala-Laurinaho, Juha; Viikari, VilleAdditive 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. - Comparison of Additively Manufactured Dual-Polarized Probe Antennas at Ku-Band
A4 Artikkeli konferenssijulkaisussa(2023) Karki, Sabin Kumar; Ala-Laurinaho, Juha; Viikari, VilleThis 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. - Kahden vaiheenpalautusalgoritmin vertailu alimillimetriaaltoalueella
Helsinki University of Technology | Master's thesis(2004) Lerber, Annakaisa vonDiplomityössä 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. - Complex Permittivity Characterization of Low-Loss Dielectric Slabs at Sub-THz
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-10-14) Xue, Bing; Haneda, Katsuyuki; Icheln, Clemens; Ala-Laurinaho, Juha; Tuomela, JuhaThis paper presents a novel low-complexity method to characterize the permittivities of low-loss dielectric slabs at millimeter-wave and sub-terahertz bands. The method assumes plane-wave illumination of the material under test and utilizes reflected fields on two air-material interfaces, resolved through a sufficiently wide-band measurement. Unlike conventional methods, it does not need a reference measurement using a metal plate and a back metal plate. The applicability of the method is discussed. The misalignment of a reference plane and the effects of the gap between the back metal and the material under test are analyzed for published reflected-field based methods to show the advantages of the method. Finally, the proposed method is applied to estimate the permittivities of both plexiglass with 30 mm thickness and nylon with 21 mm thickness across 140-210 GHz and compared against the free-space transmission method, showing good agreement. The proposed method is suitable for permittivity characterization of low-loss materials when a wide-band plane-wave measurement is possible. - Connected Dipole Antenna Cluster of Enhanced Spherical Coverage CDF for mm-Wave Applications
A4 Artikkeli konferenssijulkaisussa(2023) Chen, Quangang; Ala-Laurinaho, Juha; Khripkov, Alexander; Ilvonen, Janne; Moreno, Resti Montoya; Viikari, VilleIn 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.