Browsing by Author "Mallat, Juha"
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Item Alimillimetriaaltoalueen hologrammiin perustuvan kompaktin antennimittauspaikan instrumentointi ja testaus(1999) Säily, Jussi; Mallat, Juha; Sähkö- ja tietoliikennetekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiItem Characterisation and modelling of Schottky and Gunn diodes for mm-wave applications(2006) Kiuru, Tero; Mallat, Juha; Sähkö- ja tietoliikennetekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiTässä diplomityössä on kehitetty sijaiskytkentä kolmelle erilaiselle Schottkysekoitindiodille ja ruuvipakkaukseen integroidulle Gunn-diodille. Sijaiskytkennät on suunniteltu toimimaan kaupallisissa piirisimulaattoreissa. Schottky- ja Gunndiodit on suunniteltu toimimaan millimetriaaltoalueella. Työn ensimmäisessä osassa Schottky-diodin toimintaa ja ominaisuuksia on tutkittu kattavin mittauksin. Sijaiskytkennän komponenttien arvot on saatu teoreettisten laskelmien ja piirisimulaattorin optimointimenetelmien avulla. Sijaiskytkennän toiminta sekoitinpiirissä on osoitettu. Fysikaalinen perusta Schottky-diodin toiminnalle ja kirjallisuuskatsaus Schottky-diodeista on esitetty. Työn jälkimmäisessä osassa on tutkittu pakatun Gunn-diodin taajuusvastetta sähkömagneettisen 3D-simulaattorin avulla. Gunn-diodin pakkauksen reaktiiviset elementit on selvitetty piirisimulaattorin optimointimenetelmien avulla ja sijaiskytkentä pakatulle Gunn-diodille on kehitetty. Gunn-diodien ja Gunnoskillaattoreiden teoreettinen perusta on esitetty.Item Characterization of ferroelectric varactors(2006) Lehkonen, Juha-Pekka; Mallat, Juha; Sähkö- ja tietoliikennetekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiTässä diplomityössä on kehitetty sijaiskytkentä ferrosähköiselle varaktorille. Millimetriaaltoalueelle ulottuvien mittausten avulla varaktorille on tehty sijaiskytkentä, jota voidaan käyttää piirisimulointiohjelmissa. Ferrosähköisyyden teoreettinen perusta on esitetty. Varaktorin karakterisoimiseen tarvittavat fysikaaliset mallit on johdettu. Lisäksi on esitelty joitakin aiemmin valmistettuja piirejä, joissa on käytetty ferrosähköisiä varaktoreja ja vertailtu erilaisia korkeataajuisia viritystekniikoita. Ferrosähköisen varaktorin taajuusvastetta on tutkittu kolmiulotteisella sähkömagneettisella simulaattorilla. Simuloinneista ja mittauksista saatuja tuloksia on vertailtu. Varaktorin sijaiskytkennän komponenttien arvot on johdettu mittaustuloksista käyttämällä piirisimulaattorin optimointimenetelmiä. Mittaustulosten analyysissa on selvinnyt, että lisää mittauksia tarvitsee tehdä.Item Characterization, modeling, and design for applications of waveguide impedance tuners and Schottky diodes at millimeter wavelengths(Aalto University, 2011) Kiuru, Tero; Mallat, Juha; Närhi, Tapani; Radiotieteen ja -tekniikan laitos; Department of Radio Science and Engineering; Sähkötekniikan korkeakoulu; Räisänen, AnttiThis work contributes to two fields of research at millimeter wavelengths: waveguide impedance tuners and Schottky diodes. Three novel impedance tuning devices for frequencies between 75-220 GHz are presented and new modeling and characterization methods applicable to millimeter-wave and THz Schottky diodes are introduced. In addition, the use of waveguide impedance tuners and Schottky diodes is demonstrated in three different applications. Waveguide tuners are used for dielectric material characterization at 75-110 GHz and in a fundamental frequency mixer diode test platform at 183 GHz. Schottky diodes characterized in this work are used in a novel MMIC frequency tripler for 75-140 GHz and in the aforementioned 183 GHz mixer diode test platform. Waveguide impedance tuners are widely used in a variety of applications at millimeter wavelengths, ranging from device matching to load-pull and noise parameter measurements. The three impedance tuners presented in this work are a multiwaveguide-band backshort, waveguide EH-tuner for 140-220 GHz, and a double-stub E-plane tuner for 75-110 GHz. All impedance tuners are based on the dielectric backshort concept, which offers resonance-free operation, low losses, and tuning with higher resolution than is possible with traditional backshorts. For example, at the center frequency of the W-band, 92 GHz, the VSWR of the multiwaveguide-band backshort is larger than 165 for all positions of the backshort and the phase resolution as a function of the backshort movement is 0.0825 (deg)/10 micrometers, which is 10 times more accurate than with a traditional backshort. The Schottky diode is the workhorse in almost all room temperature mixer and frequency multiplier applications at 100-3000 GHz. Design of Schottky-based circuits at these frequencies relies on accurate models for the Schottky diode. In this work, a novel method is presented for simultaneous extraction of Schottky diode series resistance and thermal resistance. The method avoids the inaccuracies inherent in the traditional I-V extraction methods caused by the self-heating of the diode, which can result in too small a value for the extracted series resistance. In addition, a quantitative comparison of low-frequency (1 MHz) and microwave frequency (3-10 GHz) capacitance determination techniques is performed for millimeter-wave and THz Schottky diodes.Item Contactless Terahertz Sensing of Ultrafast Switching in Marx Generator Based on Avalanche Transistors(IEEE, 2022-10-01) Masyukov, Maxim; Vainshtein, Sergey; Mallat, Juha; Taylor, Zachary; Department of Electronics and Nanoengineering; Zachary Taylor Group; Keijo Nikoskinen Group; University of OuluIn this paper, we have studied the temporal evolution of switching for each stage of the Marx generator with picosecond temporal and millimeter spatial resolutions employing terahertz measurements. The Marx circuit utilizes collapsing-field-domain (CFD)-based avalanche switches, which are formed in a bipolar GaAs structure and result in the picosecond speed of powerful carrier generation and electrical switching. The application of the CFD-based avalanche switches emitting mm-wave pulsed radiation in the Marx generator provides a unique opportunity to accurately track the switching instants for each of the circuit stages with a picosecond time precision. The collapsing domains cause the sub-THz pulses radiated by each of the avalanche switches, and the same domains generate the electron-hole plasma thus causing simultaneously the electrical switching. In this work, we report the direct measurements of the switching instants for each of the four stages Marx generator and suggest an interpretation of non-trivial experimental results.Item Design and Realisation of Instrumentation for a 650 GHz Compact Antenna Test Range(2006) Vaaja, Matti; Mallat, Juha; Sähkö- ja tietoliikennetekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiItem Design and Realisation of L-band Frequency Scanning Radiometer(Aalto University, 2010) Vaaja, Matti; Mallat, Juha; Radiotieteen ja -tekniikan laitos; Department of Radio Science and Engineering; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Räisänen, AnttiL-band (1-2 GHz) radiometry has been an ongoing research topic in the Department of Radio Science and Engineering for a number of years. In addition to remote sensing and radioastronomy applications, a radiometer can be used for detecting unwanted radio emissions in a protected frequency band. A frequency scanning radiometer (FIRaL) for detecting radio interference at the frequency interval of 1920 – 1980 MHz is designed and realised in this Licentiate thesis work. The aforementioned frequency band is reserved for mobile communication applications. The theory of radiometry is presented to the necessary extent in order to facilitate the FIRaL radiometer design. The design of the receiver and local oscillator electronics and pyramidal horn antenna is presented. Radiometer performance is studied by measuring the relevant device parameters in laboratory conditions. The feasibility of the radiometer to perform real-world interference surveys is tested by on-site measurements. The realised radiometer receiver input noise temperature is 661 ± 58 K or better. The radiometer is deemed suitable for interference measurements. The preliminary on-site measurements suggests that further measurements are feasible in order to study the extent of radio emissions in the 1920 – 1980 MHz mobile communications band.Item Digitaalinen modulaatio langattomassa tietoliikenteessä(2021-01-14) Autio, Aleksi; Mallat, Juha; Sähkötekniikan korkeakoulu; Turunen, MarkusItem Ferrite Rod Antenna in a Nanosatellite Medium and High Frequency Radio(2016-10-31) Koskimaa, Petri; Mallat, Juha; Kestilä, Antti; Sähkötekniikan korkeakoulu; Kallio, EsaIn this thesis the feasibility of using a ferrite rod antenna as a part of a radio instrument in a nanosatellite was studied. Ferrite rod antennas are used as receiving antennas for amplitude modulation transmissions in the medium and high frequencies. At these frequencies it is possible to study ionospheric properties due to the refraction of radiowaves from different ionospheric layers. The behavior of the antenna was determined from theory and tested using electromagnetic simulation software and measurements. The aluminum body and other metallic structures in the satellite affect the operation of the antenna and its position must be chosen carefully. The results show that ferrite rod antennas can be used for the purpose of receiving medium and high frequency transmissions in an aluminum framed nanosatellite.Item Low-noise local oscillator configurations for millimeter and submillimeter wavelenghts(1997) Säily, Jussi; Mallat, Juha; Sähkö- ja tietoliikennetekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiItem Lyhyen kantaman IoT-radiotekniikat(2017-05-02) Cheung, Tze; Mallat, Juha; Sähkötekniikan korkeakoulu; Turunen, MarkusItem Microstrip lines and passive components in integrated monolithic GaAs microwave circuits(1986) Mallat, Juha; Sähkötekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiItem Mixer test jig for characterisation of Schottky diodes(2008) Dahlberg, Krista; Mallat, Juha; Kiuru, Tero; Radiotieteen ja -tekniikan laitos; Teknillinen korkeakoulu; Helsinki University of Technology; Räisänen, AnttiTässä diplomityössä on suunniteltu ja simuloitu aaltoputki-mikroliuskajohtosiirtymä ja välitaajuussuodatin (IF-suodatin) sekoitintestialustaa varten. Simuloinnin taajuusalue on G-kaista (140-220 GHz) ja suunnittelutaajuus on 183 GHz. Suunnittelu ja simuloinnit on tehty sähkömagneettisella kenttäsimulaattorilla. Aluksi on käyty läpi millimetriaaltoalueen Schottky-diodisekoittimien teoriaa, aaltoputki-mikroliuskajohto siirtymien kirjallisuuskatsaus ja mikroliuskajohto suodattimien teoriaa. Tämän jälkeen on suunniteltu ja simuloitu kaksi aaltoputki-mikroliuskajohto-siirtymää. Ensiksi suunniteltiin ja simuloitiin sondiin perustuva yksinkertainen aalto-putki-mikroliuskajohto siirtymä ja sen jälkeen aaltoputki-mikroliuskajohto-siirtymä WR-5 aaltoputken läpi, jota tullaan käyttämään sekoitintestialustassa. IF-suodatinta tarvitaan estämään radiotaajuisen (RF) signaalin ja paikallisoskillaattori-taajuisen (LO) signaalin pääsyn IF-porttiin. Suunniteltu ja simuloitu suodatin on hammerhead-suodatin. Aaltoputki-mikroliuskajohtosiirtymä ja IF-suodatin on yhdistetty ja simuloitu yhdessä. Aaltoputki-mikroliuskajohtosiirtymälle yhdessä IF-suodattimen kanssa on tehty herkkyysanalyysi, jotta saadaan selville miten herkkä siirtymä on mittojen muutoksille. Lopuksi on simuloitu piirisimulaattorilla aaltoputki-mikroliuskajohtosiirtymä yhdessä IF-suodattimen kanssa osana sekoitinpiiriä kahdella eri diodimallilla.Item Mixer test jig for millimeter wave Schottky diodes(2010) Dahlberg, Krista; Mallat, Juha; Louhi, Jyrki; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Räisänen, AnttiIn this Licentiate's thesis, a mixer test jig for millimetre wave Schottky diodes has been designed, fabricated, and tested. With the mixer test jig different Schottky diodes can be tested and compared in the actual operating environment at the nominal design frequency of 183 GHz. The diode under test is mounted on a substrate and radio frequency (RF) and local oscillator (LO) impedance matching is performed with an integrated low-loss EH-tuner. The structure is simple, and the substrate with the diode can be easily changed. The performance of the mixer test jig is tested with a commercial Schottky diode (VDISC2T6). Single sideband (SSB) conversion loss measurement and noise measurement based determination of double sideband (DSB) conversion loss and mixer DSB noise o temperature are carried out. The measured SSB conversion loss at the signal frequency of. 183 GHz is 7.8 dB and at the image frequency of 181.04 GHz it is 8.5 dB with 2.3 mW LO power at 182.02 GHz. The measured SSB conversion loss at the signal frequency is 6.8 dB, when at the intermediate frequency the matching is optimized with an impedance tuner. In the noise-based measurements a diplexer is needed for LO source noise filtering. The measured DSB conversion loss is 4.9 dB and the mixer DSB noise temperature is 780 K with 2.1 mW LO power at 182.6 GHz with the intermediate frequency of 1.05 GHz. The measured SSB conversion losses are comparable to the best published results of fundamental mixers at 183 GHz. The noise measurement results are slightly worse because the instability of the LO source and the need of noise filtering.Item Ohjelmoitavien järjestelmäpiirien käytännön sovellukset(2021-05-05) Simola, Otto; Mallat, Juha; Sähkötekniikan korkeakoulu; Turunen, MarkusItem Pitkän kantaman IoT-radiotekniikat(2017-04-23) Nettey, Noah; Mallat, Juha; Sähkötekniikan korkeakoulu; Turunen, MarkusItem Pulsed and transient characterization of THz Schottky diodes(2012) Khanal, Subash; Mallat, Juha; Kiuru, Tero; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; Räisänen, AnttiAny non-linear electronic device can be used for the purpose of frequency mixing or multiplication. But when the frequency is very high (in THz band), only few devices can provide acceptable conversion efficiency and low noise performance. GaAs Schottky barrier diodes are preferred and commonly used in heterodyne receivers as a mixing element. However, at higher frequencies the diode size is small which reduces its thermal capability and the self-heating is significant even for small current levels. In this master's thesis different electrical and thermal characterization methods for a diode are reviewed. Limitations of the DC I-V measurement method are identified and a test is carried out to study the feasibility of a new pulsed system for characterization of THz Schottky diodes. The military standard method for thermal impedance testing is studied and suitable modifications to the military standard method are proposed. The transient temperature response of the diode is fitted to an exponential function to extract the junction temperature, thermal impedance and thermal time-constants associated with the internal distribution of thermal resistances and heat capacitances of the diode under test.Item Radiopaikannus satelliittijärjestelmien avulla(2012-12-31) Uotinen, Joonas; Mallat, Juha; Sähkötekniikan korkeakoulu; Turunen, MarkusItem Sis-sekoitinvastaanottimen analyysi ja toteutus(1988) Mallat, Juha; Sähkötekniikan osasto; Teknillinen korkeakoulu; Helsinki University of Technology; Tiuri, MarttiItem Thermal characterization of THz planar Schottky diodes using simulations(2012) Saber, Mohammad Arif; Mallat, Juha; Radiotieteen ja -tekniikan laitos; Sähkötekniikan korkeakoulu; Räisänen, AnttiSchottky diodes are preferred and used in heterodyne receivers as a mixing element. In higher frequencies (THz band) the size of the diode especially the anode junction, becomes very small and causes reduced thermal properties compared to its lower frequency counterparts. Self-heating for these high frequency diodes becomes very significant for even a very small amount of current. In this master's thesis different methods of thermal and electrical characterization have been studied. Also different thermal characteristics like junction temperature, thermal resistance and thermal time constant have been investigated through simulations. COMSOL is the elected software for the simulations. Two commercial diodes have been analyzed and different methods of simulating the thermal properties have been discussed and presented. Also some comparisons with measurement results have been carried out. However, in all these thermal simulations the diode current is kept constant and only DC simulations have been carried out.
