[article-cris] Sähkötekniikan korkeakoulu / ELEC

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A 0.35-to-2.6GHz multilevel outphasing transmitter with a digital interpolating phase modulator enabling up to 400MHz instantaneous bandwidth
(2017-03-02) Kosunen, Marko; Lemberg, Jerry; Martelius, Mikko; Roverato, Enrico; Nieminen, Tero; Englund, Mikko; Stadius, Kari; Anttila, Lauri; Pallonen, Jorma; Valkama, Mikko; Ryynänen, Jussi; Department of Electronics and Nanoengineering; Department of Micro and Nanosciences; Jussi Ryynänen Group; Nokia; Tampere University of Technology
Advanced wireless radio standards set stringent requirements on the bandwidth, frequency range and reconfigurability of base-station transmitters. Recently, the outphasing concept has shown promise of wide bandwidth while taking advantage of process scaling with extensive exploitation of rail-to-rail signaling. Recent outphasing transmitter designs have often focused on power-amplifier (PA) and power-combiner implementations while omitting the phase modulator [1,2]. Moreover, previously reported transmitters with integrated digital phase modulators have only shown bandwidths up to 40MHz [3,4], although 133MHz has been demonstrated at 10GHz carrier frequency utilizing phase modulators based on conventional IQ-DACs [5]. Thus, digital-intensive outphasing transmitters capable of modulation with hundreds of MHz bandwidth at existing cellular frequency bands have not yet been published. To address the aforementioned challenge, this paper introduces a multilevel outphasing transmitter with four amplitude levels, including the first prototype implementation based on the digital interpolating phase modulator concept [6]. The transmitter is targeted for 5G picocell base stations and has been verified to operate with instantaneous bandwidth up to 400MHz. In addition, the developed phase modulator eliminates the need for complex on-chip frequency synthesizers by introducing digital carrier frequency generation, demonstrated between 0.35 and 2.6GHz, while utilizing a single 1.8GHz reference clock.
A 0.39–3.56-μW Wide-Dynamic-Range Universal Multi-Sensor Interface Circuit
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020-10-15) Moayer, Mohammad Mehdi; Salomaa, Jarno; Halonen, Kari; Department of Electronics and Nanoengineering; Kari Halonen Group
This paper presents an ultra-low-power, widedynamic- range interface circuit for capacitive and resistive sensors. The circuit is implemented as a switched-capacitor circuit using programmable capacitors to achieve high configurability. The circuit was fabricated using a CMOS 0.18 μm process. Different types of capacitive and resistive sensors were measured using the interface to demonstrate its support for multi-sensor systems with an ultra-low-power budget. Experimental results show that the circuit is able to interface various sensors within the overall capacitance range of 0.6–550 pF and resistance range of 3.7–5100 k , while consuming only 0.39–3.56 μW from a 1.2 V supply. A proximity, gesture, and touch-sensing system is also developed consisting of the designed interface circuit and a sensor element that is able to detect the displacement of an object up to 15 cm from the sensing electrodes consuming only 0.83 μW from a 1.2 V supply.
A 0.6–4.0 GHz RF-Resampling Beamforming Receiver with Frequency-Scaling True-Time-Delays up to Three Carrier Cycles
(IEEE, 2020) Spoof, Kalle; Zahra, Mahwish; Unnikrishnan, Vishnu; Stadius, Kari; Kosunen, Marko; Ryynänen, Jussi; Department of Electronics and Nanoengineering; Jussi Ryynänen Group
True-time-delays (TTDs) enable wideband analog and hybrid beamforming by mitigating the beam squint problem. This letter reports a TTD beamforming receiver supporting delays up to three carrier-frequency cycles. The implementation is the first published work in which the delays scale with the carrier frequency. The scaling enables TTDs for large arrays at low-GHz frequencies where long delays are required due to \lambda _{c}/2 antenna spacing. The delays are implemented through delayed resampling of a passive mixer's discrete-time output. Driving the mixers with pulse-skipped local oscillator (LO) signals allows the delay range to exceed one carrier cycle. A polyphase receiver structure prevents aliasing of noise and unwanted tones caused by LO pulse-skipping. Our prototype implementation demonstrates squint-free beamforming for an-800 MHz instantaneous RF bandwidth. The proposed TTD is efficient for large arrays since the power consumption per antenna is only 5-13-mW across the 0.6-4.0-GHz frequency range. The prototype was implemented in 28-nm FD-SOI CMOS, and the die area including bonding pads is only 1.2 mm2.
A 1.5-1.9-GHz all-digital tri-phasing transmitter with an integrated multilevel class-D power amplifier achieving 100-MHz RF bandwidth
(Institute of Electrical and Electronics Engineers, 2019-06-01) Lemberg, Jerry; Martelius, Mikko; Roverato, Enrico; Antonov, Yury; Nieminen, Tero; Stadius, Kari; Anttila, Lauri; Valkama, Mikko; Kosunen, Marko; Ryynänen, Jussi; Department of Electronics and Nanoengineering; Jussi Ryynänen Group; Tampere University
We present a prototype RF transmitter with an integrated multilevel class-D power amplifier (PA), implemented in 28-nm CMOS. The transmitter utilizes tri-phasing modulation, which combines three constant-envelope phase-modulated signals with coarse amplitude modulation in the PA. This new architecture achieves the back-off efficiency of multilevel outphasing, without linearity-degrading discontinuities in the RF output waveform. Because all signal processing is performed in the time domain up to the PA, the entire system is implemented with digital circuits and structures, thus also enabling the use of synthesis and place-and-route CAD tools for the RF front end. The effectiveness of the digital tri-phasing concept is supported by extensive measurement results. Improved wideband performance is validated through the transmission of orthogonal frequency-division multiplexing (OFDM) bandwidths up to 100 MHz. Enhanced reconfigurability is demonstrated with non-contiguous carrier aggregation and digital carrier generation between 1.5 and 1.9 GHz without a frequency synthesizer. For a 20-MHz 256-QAM OFDM signal at 3.5% error vector magnitude (EVM), the transmitter achieves 22.6-dBm output power and 14.6% PA efficiency. Thanks to the high linearity enabled by tri-phasing, no digital predistortion is needed for the PA.
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 Group
A 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.
A 100–750 MS/s 11-Bit Time-to-Digital Converter With Cyclic-Coupled Ring Oscillator
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2021-03-24) Jarvinen, Okko; Unnikrishnan, Vishnu; Siddiqui, Waqas; Korhonen, Teuvo; Koli, Kimmo; Stadius, Kari; Kosunen, Marko; Ryynanen, Jussi; Department of Electronics and Nanoengineering; Jussi Ryynänen Group; Department of Electronics and Nanoengineering; Huawei Technologies
This paper presents the first measured cyclic-coupled ring oscillator (CCRO) time-to-digital converter (TDC). The CCRO realizes a robust true time-domain delay interpolation with sub-gate-delay resolution. The architecture employs real-time quantization to reduce conversion time and hence maximize bandwidth. Furthermore, the CCRO phase progression is encoded with a bubble error suppression logic, thereby building resilience to delay mismatches from circuit/layout imperfections. The prototype circuit implemented in a 28 nm CMOS process demonstrates a combination of high resolution and high sample rate over wide range of sample rates. The TDC achieves its peak figure-of-merit (FoM) of 0.051 pJ/conv.-step at 100 MS/s while delivering 8.38-bit linear resolution and 15.4 ps time resolution, operating from a 0.55 V supply. The TDC demonstrates the highest reported linear resolution of 9.29 bits among converters operating above 100 MS/s, at 125 MS/s and 0.9 V supply, while achieving 4.4 ps time resolution and 0.16 pJ/conv.-step FoM. Further, the real-time quantizing architecture allows fast operation up to 750 MS/s, where the TDC delivers 6-bit linear resolution and 0.48 pJ/conv.-step FoM operating from 0.9 V supply.
152 fs nanotube-mode-locked thulium-doped all-fiber laser
(2016-07-04) Wang, Jinzhang; Liang, Xiaoyan; Hu, Guohua; Zheng, Zhijian; Lin, Shenghua; Ouyang, Deqin; Wu, Xu; Yan, Peiguang; Ruan, Shuangchen; Sun, Zhipei; Hasan, Tawfique; Department of Micro and Nanosciences; Zhipei Sun Group; Shenzhen University; University of Cambridge
Ultrafast fiber lasers with broad bandwidth and short pulse duration have a variety of applications, such as ultrafast time-resolved spectroscopy and supercontinuum generation. We report a simple and compact all-fiber thulium-doped femtosecond laser mode-locked by carbon nanotubes. The oscillator operates in slightly normal cavity dispersion at 0.055 ps 2, and delivers 152 fs pulses with 52.8 nm bandwidth and 0.19 nJ pulse energy. This is the shortest pulse duration and the widest spectral width demonstrated from Tm-doped all-fiber lasers based on 1 or 2 dimensional nanomaterials, underscoring their growing potential as versatile saturable absorber materials.
A 180-nW static power UWB IR transmitter front-end for energy harvesting applications
(2017-09-28) Haapala, Tuomas; Pulkkinen, Mika; Salomaa, Jarno; Halonen, Kari; Department of Electronics and Nanoengineering; Kari Halonen Group
This paper presents a versatile, FCC compliant ultra-wideband impulse radio transmitter front-end (TFE) that performs well at a wide range of pulse repetition rates up to 105 MHz. The TFE delivers 2.2 pJ pulses with 6.7 % efficiency at 3.8 GHz center frequency. The leakage power is 180 nW from a 1.2 V supply. The TFE operates robustly with a variety of power sources, including a 6.5 cm2 photovoltaic array in office illumination. Along with the low static power consumption level, this feature makes the TFE suitable for energy harvesting applications. The TFE is fabricated in a 180 nm CMOS process.
180° rotations in the polarization angle for blazars
(EDP SCIENCES, 2020-04-21) Cohen, M.H.; Savolainen, Tuomas; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group; California Institute of Technology
Rotations of the electric vector position angle (EVPA) in blazars are often close to an integral multiple of 180°. There are many examples of this in the literature, and we strengthen the evidence by showing that, in the RoboPol monitoring program, nπ rotations occur more frequently than otherwise expected by chance. We explain this using a model consisting of two polarized emission components: a “jet” that is constant in time and a “burst” that is variable. The EVPA of the combination is EVPAjet at both the beginning and the end of the burst, so the net rotation across the burst must be nπ. Several examples of this model are analyzed on the Stokes plane, where the winding number for the Stokes vector of the combination gives the value of n. The main conclusion is that the EVPA rotation can be much larger than the physical rotation of the emission region around the axis of the jet, but this requires the EVPAs of the jet and the burst to be nearly orthogonal. Shock-in-jet calculations can provide a physical model for our toy model and in addition they automatically give the required orthogonality. The model is illustrated with data from the literature on OJ 287. We suggest that the large rapid EVPA rotation seen in OJ 287 might be a phase effect and not representative of a physical rotation.
An 18–28 GHz dual-mode down-converter IC for 5G applications
(Springer, 2024-02) Naghavi, Saeed; Ryynänen, Kaisa; Zahra, Mahwish; Korsman, Aleksi; Stadius, Kari; Kosunen, Marko; Unnikrishnan, Vishnu; Anttila, Lauri; Valkama, Mikko; Ryynänen, Jussi; Department of Electronics and Nanoengineering; Jussi Ryynänen Group; Department of Electronics and Nanoengineering; Tampere University
Emerging spectrum trends require a higher integration of 5G New Radio Frequency Range 1 (FR1) and Frequency Range 2 (FR2) bands to enhance the availability of spectrum and spectrum-sharing opportunities. To enable the reception of both FR1 and FR2 bands in a seamless hardware entity, we propose combining homodyne and heterodyne architectures. This necessitates the incorporation of a down-converter module that transfers the incoming signals from FR2 bands down to FR1, ensuring compatibility with an FR1 direct-conversion receiver (DCR) for the final signal reception. The primary focus of this paper is the design and implementation of the required integrated down-converter. The module includes an integrated balun, a low-noise amplifier (LNA) with a bypass mode, a dual-mode mixer, and an intermediate frequency (IF) amplifier. The introduced bypass mode helps to further elevate the linearity performance compared to the nominal mode. The bypass mode is designed for joint communication and sensing operation to avoid the compression of the receiver. This work also incorporates a local oscillator (LO) signal distribution network with phase tuning elements using a mixed-signal approach. The circuit is implemented in a 22-nm CMOS process, and the active die area is 0.6 mm 2 . The measurements demonstrate that the implemented chip can efficiently perform the required frequency conversion over a wide frequency range of 18–28 GHz. Conversion gain of 4.5–7.5 dB, noise figure of 15–19.7 dB, 1 dB compression point (IP1dB) of − 16 to − 10 dBm, and input third-order intercept point (IIP3) of − 5 to 0 dBm are achieved. The measured IP1 dB and IIP3 for the bypass mode are +0.5 to +4.5 dBm and +8.5 to +10 dBm, respectively.
A 2 GS/s 9-bit Time-Interleaved SAR ADC with Overlapping Conversion Steps
(2022) Tenhunen, Miikka; Spoof, Kalle; Unnikrishnan, Vishnu; Stadius, Kari; Kosunen, Marko; Ryynanen, Jussi; Department of Electronics and Nanoengineering; Jussi Ryynänen Group; Department of Electronics and Nanoengineering; Tampere University
This paper presents a wideband 8-way time-interleaved (TI) 9-bit successive approximation register (SAR) analog-to-digital converter (ADC) with overlapping conversion steps that improve the speed of operation. The ADC generates its clocks using a synchronous counter based circuit which reduces the SAR delay. A common-mode reference based split capacitor array digital-to-analog converter (DAC) is implemented that achieves high speed and low power consumption. Simulation results are presented for the ADC designed in a 22 nm CMOS process. The TI ADC achieves at least 7.7 ENOB at 2 GS/s and consumes a total of 19.8 mW from 0.8 V supplies, resulting in 47.6 fF/conv-step. The single ADC achieves 8.34 ENOB at 250 MS/s, consuming 1.43 mW in total and 17.7 fF/conv-step.
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 University
In 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.
2-D magnetomechanical transient simulation of a motor with a bar breakage
(2017) Climente-Alarcon, Vicente; Arkkio, Antero; Antonino-Daviu, Jose A.; Department of Electrical Engineering and Automation; Polytechnic University of Valencia
The analysis of the vibration response of electrical machines has importance in noise prediction and more recently, fault diagnosis. This work presents a strongly coupled 2-D magnetomechanical simulation of an induction machine under heavy operational conditions: a direct-on-line startup. Both healthy and broken bar states are simulated in a time span long enough to allow the detailed study of the varying frequency components. The results yield, in addition to the usual electrical and magnetic quantities, electromagnetic induced vibration components in the stator. A comparison with current and vibration experimental data is also performed.
2-D Magnetomechanical Transient Study of a Motor Suffering a Bar Breakage
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018) Climente-Alarcon, Vicente; Arkkio, Antero; Antonino-Daviu, Jose; Department of Electrical Engineering and Automation; Polytechnic University of Valencia
The analysis of the vibration response of electrical machines has importance in noise prediction and more recently, diagnosis of electrical faults, especially in the industrial environment, where it is a well-known technique. This work assesses the performance of a strongly coupled 2-D magnetomechanical approach, as directly available in multiphysics software, for the simulation of an induction machine under heavy operational conditions: a direct-on-line startup. Both healthy and broken bar states are simulated in a time span long enough to allow the detailed study of the varying frequency components. The results yield, in addition to the usual electrical and magnetic quantities, electromagnetic-induced vibration components in the stator. A comparison with current and vibration experimental data is also performed showing a good agreement with variable frequency components and certain limitations concerning their amplitude.
A 20-60GHz Digitally Controlled Composite Oscillator for 5G
(2018) Antonov, Yury; Tormanen, Markus; Ryynänen, Jussi; Pärssinen, Aarno; Stadius, Kari; Department of Electronics and Nanoengineering; Jussi Ryynänen Group; Lund University; University of Oulu
This paper describes a frequency generator supporting over-an-octave tuning range for 5G receiver front-end. Generator is built by composition of smaller-range oscillators multiplexed to the common output that drives a downconversion mixer. Simulated in 28nm CMOS with full physical device models the composite oscillator exhibits a frequency tuning range from 21.5 to 60.7GHz (95.3%) dissipating less then 25.8mW from a 0.9V supply. As a result, it achieves −184dBc/Hz FOM TR.
2006 May-July major radio flare episodes in Cygnus X-3: spectrotiming analysis of the X-ray data
(2013) Koljonen, K.I.I.; McCollough, M.L.; Hannikainen, D.C.; Droulans, R.
The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
(2015) , MAGIC Collaboration; , VERITAS Collaboration; Metsähovi Radio Observatory; Department of Radio Science and Engineering; Anne Lähteenmäki Group
Aims: We perform an extensive characterization of the broadbandemission of Mrk 421, as well as its temporal evolution, during thenon-flaring (low) state. The high brightness and nearby location (z =0.031) of Mrk 421 make it an excellent laboratory to study blazaremission. The goal is to learn about the physical processes responsiblefor the typical emission of Mrk 421, which might also be extended toother blazars that are located farther away and hence are more difficultto study. Methods: We performed a 4.5-month multi-instrumentcampaign on Mrk 421 between January 2009 and June 2009, which includedVLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple,among other instruments and collaborations. This extensive radio tovery-high-energy (VHE; E> 100 GeV) γ-ray dataset providesexcellent temporal and energy coverage, which allows detailed studies ofthe evolution of the broadband spectral energy distribution. Results: Mrk421 was found in its typical (non-flaring) activity state,with a VHE flux of about half that of the Crab Nebula, yet the lightcurves show significant variability at all wavelengths, the highestvariability being in the X-rays. We determined the power spectraldensities (PSD) at most wavelengths and found that all PSDs can bedescribed by power-laws without a break, and with indices consistentwith pink/red-noise behavior. We observed a harder-when-brighterbehavior in the X-ray spectra and measured a positive correlationbetween VHE and X-ray fluxes with zero time lag. Such characteristicshave been reported many times during flaring activity, but here they arereported for the first time in the non-flaring state. We also observedan overall anti-correlation between optical/UV and X-rays extending overthe duration of the campaign. Conclusions: Theharder-when-brighter behavior in the X-ray spectra and the measuredpositive X-ray/VHE correlation during the 2009 multi-wavelength campaignsuggests that the physical processes dominating the emission duringnon-flaring states have similarities with those occurring during flaringactivity. In particular, this observation supports leptonic scenarios asbeing responsible for the emission of Mrk 421 during non-flaringactivity. Such a temporally extended X-ray/VHE correlation is not drivenby any single flaring event, and hence is difficult to explain withinthe standard hadronic scenarios. The highest variability is observed inthe X-ray band, which, within the one-zone synchrotron self-Comptonscenario, indicates that the electron energy distribution is mostvariable at the highest energies.Appendix A is available in electronic form at http://www.aanda.orgThecomplete data set shown in Fig. 1 is only available at the CDS viaanonymous ftp to http://cdsarc.u-strasbg.fr(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A126
220-240-GHz High-Gain Phase Shifter Chain and Power Amplifier for Scalable Large Phased-Arrays
(IEEE, 2023) Najmussadat, Md; Ahamed, Raju; Varonen, Mikko; Parveg, Dristy; Kantanen, Mikko; Halonen, Kari A.I.; Department of Electronics and Nanoengineering; VTT Technical Research Centre of Finland; Department of Electronics and Nanoengineering
This paper focuses on the design aspects of the key components for a scalable phased-array system over the 200 GHz frequency range. A high-gain phase shifter chain for 220 to 240 GHz frequency range and a high-gain power amplifier (PA) with a high output power are designed in a 0.13-μm SiGe BiCMOS technology. The phase shifter chain includes a low-noise amplifier (LNA), a vector modulator phase shifter (PS), and a gain-enhancing amplifier. The LNA is a five-stage cascode design. The vector modulator core is realized by two variable gain amplifiers based on the Gilbert cell architecture. A four-stage cascode design is used for the gain-enhancing amplifier. The phase shifter chain shows a measured gain of 18 dB at 230 GHz with a 360° phase tuning range and more than 10 dB of gain control. The chip achieves a minimum measured noise figure of 11.5 dB at 230 GHz and shows a wideband noise characteristic. The complete phase shifter chain chip consumes a dc power of 153 mW and occupies a 1.41 mm2 area.A high-power PA that is critical for a large phased-array system is designed. This paper presents a unique 4-way power combining technique utilizing a differential quadrature coupler. The realized balanced PA occupies an area of 0.67 mm2 and shows a measured peak gain of 21 dB at 244 GHz. The PA consumes 819 mW of dc power and delivers a maximum saturated output power (Psat) of 7.1 dBm at 244 GHz and more than 4.3 dBm of Psat from 230 to 255 GHz.
22nd international conference on digital audio effects DAFx 2019 (2-6 september 2019, Birmingham, United Kingdom)
(Springer International Publishing AG, 2020-02-01) Stables, Ryan; Hockman, Jason; Välimäki, Vesa; Fontana, Federico; Birmingham City University; Dept Signal Process and Acoust; University of Udine
This meeting report gives an overview of the DAFx 2019 conference held in September 2019 at Birmingham City University, Birmingham, UK. The conference had the same theme as this special issue: digital audio effects. In total, 51 papers were presented at DAFx 2019 either in oral or in poster sessions. The conference had 157 delegates, almost half from industry and the rest from universities around the world. As the number of submissions and participants remains sufficiently high, it is planned that the DAFx conference series will be continued every autumn.
25 years of spectral UV measurements at Sodankylä, Finland
(2016-04-22) Lakkala, Kaisa; Anu, Heikkilä,; Kärhä, Petri; I., Ialongo,; Karppinen, Tomi; Karhu, Juha; Lindfors, Anders V.; Meinander, Outi; Dept Signal Process and Acoust; Finnish Meteorological Institute

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