Browsing by Author "Viikari, Ville"
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Item A 1.5-5-GHz Integrated RF Transmitter Front End for Active Matching of an Antenna Cluster(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-11) Saleem, Ali; Stadius, Kari; Hannula, Jari-Matti; Lehtovuori, Anu; Kosunen, Marko; Viikari, Ville; Ryynänen, Jussi; Department of Electronics and Nanoengineering; Jussi Ryynänen Group; Ville Viikari GroupA recently proposed method for realizing frequency-reconfigurable antennas across a wideband is based on adjusting the feed amplitudes and phases of a multiport antenna. In this article, we demonstrate the feasibility of the method, for the first time, with a conjunction of an integrated RF transmitter and a four-element antenna cluster. The implementation performs on-chip amplitude and phase tuning with supply scaling and delay tuning circuits to tune the antenna cluster without requirement of matching network. The antenna cluster is built with four closely spaced antenna elements implemented on a printed circuit board. The transmitter integrated circuit (IC) is implemented in a 28-nm CMOS process with the chip size of 0.85 mm x 0.95 mm, including pads. The proof-of-concept implementation demonstrates tunability across a wideband from 1.5 to 5 GHz.Item A 2-5.5 GHz Beamsteering Receiver IC With 4-Element Vivaldi Antenna Array(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-09) Zahra, Mahwish; Kempi, Ilia; Haarla, Jaakko; Antonov, Yury; Khonsari, Zahra; Miilunpalo, Toni; Ahmed, Nouman; Inkinen, Juha; Unnikrishnan, Vishnu; Lehtovuori, Anu; Viikari, Ville; Anttila, Lauri; Valkama, Mikko; Kosunen, Marko; Stadius, Kari; Ryynänen, Jussi; Department of Electronics and Nanoengineering; Jussi Ryynänen Group; Ville Viikari Group; Jussi Ryynänen Group; Tampere UniversityIn this article, we present a four-element Vivaldi antenna array and beamsteering receiver IC for the fifth-generation mobile network (5G) new radio (NR). The implemented receiver utilizes a delay-based local-oscillator phase shift technique for accurate beamsteering, and it exhibits 1° to 2.4° phase tuning capability for 2-5 GHz bandwidth accordingly. On-chip delay measurement is performed with pilot signal generation and delay estimation capable of 2-ps accuracy. The IC is fabricated on 28-nm CMOS technology, it occupies an area of 1.4x1.4 mm^2, including bonding pads, and consumes 22.8 mW at 2 GHz for single-receiver path operation. The receiver demonstrates wideband over-the-air reception with the prototype antennas.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 Aalto-1 nanosatelliitin S-kaistan lähetin(2013-06-10) Jussila, Jaakko; Holopainen, Jari; Department of Radio Science and Engineering; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; Viikari, VilleTässä työssä esitellään Aalto-1 satelliitin S-kaistan lähettävän radion suunittelu. Aalto-1 on CubeSat-standardiin perustuva kaukokartoitussatelliitti, jossa on hyötykuormina kolme tieteellistä instrumenttia: korkearesoluutioinen AaSI sepktrikamera, säteilymittari ja plasmajarru. Spektrikamera tuottaa informaatiota jopa useita kymmeniä megatavuja yhden kuvauksen aikana, joten lähettimeltä vaaditaan suurta tiedonsiirtonopeutta. Työssä määritellään vaatimukset, jotka perustuvat CubeSat-satelliittien tehorajoituksiin, avaruusolosuhteiden haasteisiin sekä linkkibudjettisimulaatioihin. Lähetin rakennetaan kaupallisista komponteista, jotka on valittu edellä määritettyjen rajoitteiden perusteella. Lähettimen topologia perustuu Texas Instruments:n CC2500 lähetin-vastaanottimeen, RFMD:n RF5602 tehovahvistimeen ja Texas Instuments:n MSP430 mikro-ohjaimeen. RF-sovituspiirit suunnitellaan käyttäen RF-piirisimulaattoreita ja toteutetaan mikroliuskatekniikalla. Lähettimelle suunniteltiin ensimmäinen prototyyppilevy sekä kehitettiin mikro-ohjaimen ohjelmiston ensimmäinen versio. Prototyypin ensimmäiset funktionaaliset testit osoittavat, että suunniteltu lähettimen rakenne pystyy täyttämään sille asetetut vaatimukset. RF-sovituspiirien testit osoittavat, että sovituspiirien suunnitelmat vaativat jatkokehitystä, jotta lähetin pystyy tuottamaan lähetyksessä tarvittavan tehotason.Item Adjusting radiation pattern of small antennas(2020-02) Lehtovuori, Anu; Luomaniemi, Rasmus; Viikari, Ville; Department of Electronics and NanoengineeringThe antenna clusters have been used to control the impedance properties of the antenna, but they have potential also in radiation pattern reconfigurability. We demonstrate the benefits of multi-feed antennas using a mobile antenna as an example.Item Aligning and tracking a beam steerable millimeter-wave radio link(2015-12-14) Leinonen, Tuomas; Putkonen, Jyri; Sähkötekniikan korkeakoulu; Viikari, VilleIn order to provide high-throughput mobile broadband in a dense urban information society, upcoming cellular networks will finally employ the under-utilized millimeter-wave (mmW) frequencies. The challenging mmW radio environment, however, necessitates massive cell densification with wireless backhauling using very directional links. This thesis investigates how these links between access points may be aligned efficiently, and how alignment reflects the network organization. The work provides a thorough presentation of different high-level aspects and background information required when designing a mmW small cell system. In terms of alignment functionality, both automatic link establishment and proactive tracking are considered. Additionally, the presentation includes an overview of beam steerable antennas, mmW propagation in urban environments, and network organization. The thesis further specifies requirements, proposes possible approaches and compares those with existing implementations. Most of existing mmW beam alignment solutions are intended for short-range indoor communications and do not address the issues in cellular systems. While existing functionality considers only a single link between two devices, efficient design should consider both the entire network and the underlying phenomena. The devices should further exploit the existing network infrastructure, location and orientation information, and the concepts of machine learning. Even though the world has recently seen advancements in the related fields, there is still much work to be done before commercial deployment is possible.Item Ambient Backscattering Transponder with Independently Switchable Rx and Tx Antennas(IEEE, 2019-05-01) Siddiqui, Tauseef; Holopainen, Jari; Viikari, Ville; Department of Electronics and NanoengineeringThis article presents an ambient backscattering transponder with independently beam-switchable receive and transmit antennas. The independently switchable antennas make it possible to collect ambient waves from the direction where they are the strongest and further modulate and redirect the waves toward the receiver possible in a direction other than the ambient source. The transponder consists of patch antennas, circulators, low-power RF switches, and a diode-based modulatorItem Amplifier-Antenna Array Optimization for EIRP by Phase Tuning(2022-04-01) Kutinlahti, Veli-Pekka; Lehtovuori, Anu; Viikari, Ville; Department of Electronics and NanoengineeringIn this paper, we analyse an antenna array fed with element-specific phase shifters and amplifiers. The elements of the array are mutually coupled and the operation of the amplifiers depend on the load impedance presented by the array. We derive a method for maximizing EIRP in a given direction and demonstrate the concept by simulations with 2x2 array fed with element-specific phase shifters and amplifiers at 2.5 GHz. Compared to the reference case, the optimization provides up to 0.7 dB improvement in EIRP in the −3 dB beam steering range.Item Analyzing and Optimizing the EIRP of a Phase-Tunable Amplifier-Antenna Array(IEEE, 2023-01-06) Kutinlahti, Veli-Pekka; Lehtovuori, Anu; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari GroupWe analyze the performance of an amplifier-antenna array by using separately measured amplifier load-pull data and antenna S-parameters and port-specific radiation patterns. We show that the effective isotropic radiated power (EIRP) of the system can be improved by using phase values which differ from progressive phase shift. Maximum EIRP improvement is 1.1 dB in certain steer directions and over 0.5 dB improvement over a large beamsteering range was measured when compared to using the progressive phase-shift envelope.Item Analyzing Radar Cross Section Signatures of Diverse Drone Models at mmWave Frequencies(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-01-01) Semkin, Vasilii; Haarla, Jaakko; Pairon, Thomas; Slezak, Christopher; Rangan, Sundeep; Viikari, Ville; Oestges, Claude; Department of Electronics and Nanoengineering; Ville Viikari Group; Université Catholique de Louvain; New York UniversityIn this work, we present quasi-monostatic Radar Cross Section measurements of different Unmanned Aerial Vehicles at 26-40 GHz. We study the Radar Cross Section signatures of nine different multi-rotor platforms as well as a single Lithium-ion Polymer battery. These results are useful in the design and testing of radar systems which employ millimeter-wave frequencies for superior drone detection. The data shows how radio waves are scattered by drones of various sizes and what impact the primary construction material has on the received Radar Cross Section signatures. Matching our intuition, the measurements confirm that larger drones made of carbon fiber are easier to detect, whereas drones made from plastic and styrofoam materials are less visible to the radar systems. The measurement results are published as an open database, creating an invaluable reference for engineers working on drone detection.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 for Directive Energy Device Against Drones(2019-08-19) Kutinlahti, Veli-Pekka; Holopainen, Jari; Sähkötekniikan korkeakoulu; Viikari, VilleUnmanned aerial vehicles (UAV) have become common in commercial and recreational fields, but also in the hands of criminals. UAVs are used for plural of crimes. Most notably they are used to smuggle contrabands over perimeters, for example to prisons. Presently the industry of neutralizing misused UAVs is growing and testing different methods. Four electromagnetic methods can be distinguished at the moment, which are jamming, spoofing, high-power laser and electromagnetic pulse (EMP). This thesis presents theory on high power microwave (HPM) systems required to design directed EMP system to disable commercial unmanned aerial vehicles and presents a prototype design for high-power circularly polarized directive antenna for the specific purpose. Research of the theory was conducted as a literature review and the design of the antenna was confirmed through electromagnetic simulations on CST Microwave® Studio. Literature review presents basic radiation characteristics of magnetrons, klystrons and backward wave oscillators (BWO), techniques and components for HPM transmission and directive antennas with high power capacity. The different microwave sources are capable of producing microwaves at gigawatt power levels and on frequencies of over 10 GHz. The sole transmission components for HPM are the multitude of different waveguides. The surveyed antennas are the horn antenna, the parabolic antenna, the slotted array waveguide antenna, the helical array antenna and the radial line slotted array (RLSA) antenna. The RLSA was chosen to be designed, because of its low profile. The designed antenna has maximum directivity of 32.8 dB and the system from the magnetron interface to the antenna has a total efficiency of 0.9026=-0.45 dB. The range of the system is estimated to be 130 m with 325 kW input power, within which a commercial UAV is neutralized by the EMP from the antenna.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 Antenna pattern correction techniques at submillimeter wavelengths(Helsinki University of Technology, 2007-04-27) Viikari, Ville; Department of Electrical and Communications Engineering; Sähkö- ja tietoliikennetekniikan osasto; Radio Laboratory; RadiolaboratorioHologram- and reflector-based compact antenna test ranges (CATRs) have shown potential for measurement of large submillimeter wave antennas. However, the measurement accuracy of these ranges needs to be still improved for measuring low side lobe antennas. The measurement accuracy of these ranges can be improved by using antenna pattern correction techniques. Several such techniques have been developed for microwave frequencies but most of them are not directly applicable at submillimeter wavelengths. In this thesis, four antenna pattern correction techniques that are applicable at submillimeter wavelengths are developed: feed scanning based antenna pattern comparison (APC) method, frequency shift method, and two methods that are based on a virtual antenna array. Applicabilities of these methods are studied analytically, and they are verified with simulations and measurements in a hologram-based compact antenna test range at 310 GHz. The feed scanning based APC is applicable for compact antenna test ranges. In this method, the corrected antenna pattern is obtained from the antenna patterns measured with different range feed locations. The antenna pattern of the antenna under test (AUT) is measured at several frequencies in the frequency shift method. This method, which was originally developed for lower frequencies, is now found to be especially applicable for hologram-based CATRs. The method is able to compensate partially a possible non-ideal operation of the hologram, because a hologram is a dispersive element. Virtual array correction techniques are suitable for far-field and compact ranges. In these methods, the antenna pattern of the AUT is measured at several accurately known locations. These measurements form a virtual antenna array at each rotation angle of the AUT. The array factor of each array is modulated such that it has a constant gain towards the desired signal and high attenuation to other directions. Estimates of the antenna pattern of the antenna under test and the angular interference spectrum of the test range are taken into account in the array synthesis. One method uses an alternating projections method for array synthesis, whereas the other method maximizes the signal-to-interference ratio in the measurement. The correction accuracies of the feed scanning APC and frequency shift method are found to be approximately equal to that of the conventional APC. The correction accuracies of the virtual array methods are found to be much better than that of the APC.Item Antenna Pattern Correction Techniques at Submillimeter Wavelengths(2006) Viikari, Ville; Säily, Jussi; Sähkö- ja tietoliikennetekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiItem Antennas for metal-covered handsets(2016-10-27) Kurvinen, Joni; Lehtovuori, Anu; Sähkötekniikan korkeakoulu; Viikari, VilleThis master’s thesis studies the effects of a slotless, continuous metal cover of a mobile terminal on the performance of its antennas. Additionally, LTE MIMO antennas are designed together with GPS and Wi-Fi antennas. The cellular antennas should operate on 704–960MHz and 1.71–2.69 GHz with at least 30% efficiency, and the other antennas at 1.575 GHz, 2.4 GHz, and 5 GHz bands with 40% efficiency. The topic is studied by completing electromagnetic simulations. The used model of the mobile phone is much more accurate than the ones used in earlier studies. The simulations focus on the antenna structures, locations, and sizes, as well as feeding of them. Additionally, matching circuits are investigated, and designed for each antenna. The effect of the metal cover is studied with several test cases, each of which focuses on one parameter, e.g. a dimension, location, or feed of the antenna. The first simulations are done with a simple model, and a concept for the cellular antennas is constructed on the basis of the obtained results. The final simulations are completed, and the antennas optimized with the accurate model. The proposed structure consists of three closely located, strongly coupling elements. The cellular antennas are at distinct ends of the device, and integrated into the side metals. GPS and Wi-Fi antennas are also integrated into the sides, and placed in the area between the ends of the phone. The main challenge due to the metal-cover is obtaining sufficient and wideband matching. Regardless the challenging environment, all the designed antennas fulfill their requirements. Based on the results, achieving a good antenna performance in a metal-covered phone is not impossible.Item Anturidatan lukeminen kaupallisella RFID-lukijalla(2016-08-24) Ojala, Henri; Viikari, Ville; Sähkötekniikan korkeakoulu; Skyttä, JormaRFID:n (radioaaltoihin perustuvan etätunnistuksen) kanssa yhteensopivia anturiratkaisuja kehitetään jatkuvasti. Passiiviset RFID-anturitunnisteet tarjoavat hyvin edullisen tavan jonkin suureen langattomaan mittaamiseen. Anturit eivät tarvitse energiavarastoa kuten paristoa ja ne pienen kokonsa ja langattomuutensa puolesta voidaan sijoittaa haastaviinkin ympäristöihin. Tässä diplomityössä kehitettiin asiakasyritykselle kaupallista UHF RFID-lukijaa käyttävä graafinen tietokonesovellus, joka pystyy lukemaan passiivisten RFID-anturitunnisteiden lähettämää mittaustietoa. Anturit eivät ole minkään standardin mukaisia. Kehitetty Java-sovellus suunniteltiin vain osittain yhteensopivaksi maailmanlaajuisten RFID-standardien kanssa. Sovellus pystyy lukemaan TuntoID-merkkisiä valo- ja voima-anturitunnisteita, sekä kaupallisia RFID-standardien mukaisia Gen2-tunnisteita. Valmis RFID Sensor Tag Reader-niminen sovellus sisälsi käytettyjen tunnisteiden tietokannan, sekä mahdollisuuden sovittaa mitattu suure anturin vastaukseen. Sovelluksen lukunopeus valo- ja voima-anturitunnisteille oli noin 25 signaalinäytettä sekunnissa. Gen2-tunnisteiden lukunopeus oli noin 5 näytettä sekunnissa. Valoanturitunnisteiden lukutarkkuus oli 4 bittiä, voima-anturitunnisteiden 6 bittiä. Lukutarkkuuksia parannettiin keskiarvoistamalla yli 100 peräkkäistä näytettä olettaen, että mittaussignaali muuttuu hitaasti lukunopeuteen verrattuna. Sovelluksen jatkokehitystä varten muodostettiin signaalimalli sovelluskehityksen lomassa tehtyjen mittausten perusteella. Malli huomioi monet luettuun anturiarvoon vaikuttavat tekijät, kuten radiosignaalin saapumiskulman tunnisteeseen nähden, lukijan lähetystehon, lukuetäisyyden sekä punnittavan massan sijainnin voima-anturilla.Item Applying Neural Networks for Predicting Feed Weights of an Antenna Array(2024) Tyrväinen, Juho; Lehtovuori, Anu; Ylä-Oijala, Pasi; Viikari, Ville; Department of Electronics and Nanoengineering; Ville Viikari Group; Department of Electronics and NanoengineeringArtificial neural networks (ANN) are applied to find appropriate phasing for beam steering of patch antenna arrays. To obtain this goal, an ANN is trained using simulated far-field data. Two loss functions are tested and their performance is compared with a uniform and a non-uniform antenna array. The results show that in most cases both tested loss functions perform well, but are not able to find the best solution in all cases.Item Base Station Antenna Array with Calibration Structure(2017-08-28) Haarla, Jaakko; Lehtovuori, Anu; Sähkötekniikan korkeakoulu; Viikari, VilleThe introduction of 5G technologies is pushing most of the research in mobile communications to millimeter waves. However sub-6 GHz frequency range provides excellent wave propagation and also increased capacity due increased usable frequency ranges and should not be ignored. This thesis describes a design process and simulations for a sub-6 GHz indoor picocell base station antenna array with internal calibration network for transceiver self-calibration built around four channel RF transceiver. Antenna type capable of 2 GHz to 6 GHz operation was chosen and designed using EM-simulations. Signal-injection circuitry was also designed using circuit simulator and implemented on a PCB. A 2x2 Vivaldi array was produced that is capable of beam steering with less than or equal to -6 dB active reflection coefficient and greater than or equal to -3 dB total efficiency. Calibration with minimal insertion loss and nearly identical coupling was implemented on the RFIC PCB to form a picocell base station with the antenna array.Item Base station antenna array with calibration structure(2018-01-01) Haarla, Jaakko; Lehtovuori, Anu; Viikari, Ville; Department of Electronics and NanoengineeringThe introduction of 5G technologies is pushing research in mobile communications to millimeter waves. However, sub-6 GHz frequency range as a part of the 5G standard provides excellent wave propagation properties and more capacity due to new usable frequency ranges. This paper introduces a design for picocell base station 2x2 antenna array with integrated signal injection network for transceiver calibration. Operation frequency range is from 2 to 6 GHz. The antenna array with calibration board has better than -6.3 dB active reflection coefficient and efficiency higher than -3 dB. Calibration network provides 29 dB coupling.
