Tommi Tuovinen

Bio: Tommi Tuovinen is an academic researcher from University of Oulu. The author has contributed to research in topics: Antenna (radio) & Antenna measurement. The author has an hindex of 13, co-authored 46 publications receiving 485 citations.

Digital predistortion of amplitude varying phased array utilising over-the-air combining

Abstract: In this paper, we propose a simple polynomial linearisation technique for nonlinear phased arrays including amplitude control. Due to the large number of antennas and thus power amplifiers in the array, it is inefficient to linearise each power amplifier individually. Therefore, it is demonstrated that the array can be linearised over-the-air using single polynomial. The simulations show that the linearisation is achieved by first linearising the higher driven PAs at the precompression region and then cancelling the compression by the heavily expanding lower driven PAs. The proposed approach offers an alternative way of re-thinking the concept of array linearisation over multiple PAs.

Effect of the antenna-human body distance on the antenna matching in UWB WBAN applications

Abstract: In this paper, the interaction between the ultra wideband (UWB) antenna and human body is considered and demonstrated in the range of 0-30 mm above the body surface, which could be practical operation distance for the on-body antenna. Two different planar UWB antennas (loop and dipole) are used for the examinations. First, the antenna performance in free space (FS) is shown. Then, the effect of the antenna-body distance on the antenna operation is analysed in the terms of the matching, i.e., reflection coefficient S11. Measurements are carried out in the proximity of a real human body while the simulations are run by using the whole body model having a frequency-dependent behaviour. Observations are concluded to commensurate with the antenna field regions and the size of antenna's reactive near-field was satisfied to be an important factor in the evaluation of an acceptable on-body operation. No significant differences between different antennas were observed through investigations. Both antennas perform satisfactory when the distance is high enough. The results of this study are helpful to engineers and designers evaluating antennas for the use in UWB wireless body area network (WBAN) applications.

Analyzing 5G RF System Performance and Relation to Link Budget for Directive MIMO

Abstract: Wideband fifth generation systems utilizing high carrier frequency and multiple-input multiple-output (MIMO) raise major challenges for the system design. Wave propagation and practical hardware tradeoffs at higher frequency ranges provide new boundary conditions for the implementation. This paper addresses system performance boundaries and the analysis method toward multibeam communications at millimeter wave. We combine analysis from antennas and propagation to the radio frequency (RF) transceiver specifications and beamforming requirements. Realistic propagation model and antenna implementation are used to generate beam-specific path gains and provide a wide variety of user scenarios. Using this approach, system level interdependencies and RF performance boundaries can be verified with different antenna configurations in various propagation environments. As an example, we present MIMO link budget analysis targeting 10 Gbits/s for multiple devices in the office scenario at 27 GHz.

Measurement-based on-body path loss modelling for UWB WBAN communications

Abstract: This paper presents a path loss model for an ultra wideband (UWB) wireless body area network (WBAN) on-body communication. The modelling is based on the static frequency domain measurements in an anechoic chamber. The studies are done for several on-body radio channels and with two different UWB antennas (dipole and double loop) for the frequency range of 2-8 GHz. A linear least squares (LS) polynomial data fitting is applied to the post processed measurement data resulting parameters for a path loss model. It is shown that the loop antenna outperforms the dipole antenna in respect to the slope of the attenuation. However, the path loss at the reference distance is higher for the loop. It is also shown that the signal propagation delay in the antenna structures causes error in distance measurement and unless the error is compensated significant differences in the parameters of the path loss model may occur in a WBAN case. Finally, it is observed that by using energy detection notable benefit can be obtained if all propagation paths are considered instead of the first arriving path.

Ultra wideband loop antenna on contact with human body tissues

Abstract: Human body tissues have a strong effect on the antenna operation in wireless body area networks (WBANs). In this study, the authors present the deep investigations of the effect of body tissue thicknesses on the performance of an ultra wideband (UWB) loop antenna by simulations when the antenna is operated on contact with tissues. The planar UWB loop antenna is designed for the examinations, which is targeted to be used in UWB WBAN applications. The effect of tissue thicknesses on the antenna performance is analysed and characterised in the terms of reflection coefficient S 11 , gain and total antenna efficiency, group delay, radiation patterns and specific absorption rate by simulations. A parametric layered human body tissue model with the frequency-dependent behaviour is exploited in the investigations. Further, the reflection coefficient of the presented antenna is measured in the different locations of the author's body. The main aim of these investigations is to demonstrate how the thickness of outermost body tissues affects the antenna performance.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

Abstract: This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

Response to FCC 98-208 notice of inquiry in the matter of revision of part 15 of the commission's rules regarding ultra-wideband transmission systems

Abstract: In general, Micropower Impulse Radar (MIR) depends on Ultra-Wideband (UWB) transmission systems. UWB technology can supply innovative new systems and products that have an obvious value for radar and communications uses. Important applications include bridge-deck inspection systems, ground penetrating radar, mine detection, and precise distance resolution for such things as liquid level measurement. Most of these UWB inspection and measurement methods have some unique qualities, which need to be pursued. Therefore, in considering changes to Part 15 the FCC needs to take into account the unique features of UWB technology. MIR is applicable to two general types of UWB systems: radar systems and communications systems. Currently LLNL and its licensees are focusing on radar or radar type systems. LLNL is evaluating MIR for specialized communication systems. MIR is a relatively low power technology. Therefore, MIR systems seem to have a low potential for causing harmful interference to other users of the spectrum since the transmitted signal is spread over a wide bandwidth, which results in a relatively low spectral power density.

The state-of-the-art wireless body area sensor networks: A survey:

Abstract: Wireless body area sensor network is a sub-field of wireless sensor network. Wireless body area sensor network has come into existence after the development of wireless sensor network reached some ...

Compact EBG-Backed Planar Monopole for BAN Wearable Applications

Abstract: This paper presents a planar monopole backed with a 2 × 1 array of electromagnetic bandgap (EBG) structures. The reflection phase of a single EBG unit cell has been studied and exploited toward efficient radiation of a planar monopole antenna, intended for wearable applications. The shape of the EBG unit cell and the gap between the ground and the EBG layer are adjusted so that the antenna operates at 2.45 GHz. The proposed antenna retains its impedance matching when placed directly upon a living human subject with an impedance bandwidth of 5%, while it exhibits a measured gain of 6.88 dBi. A novel equivalent array model is presented to qualitatively explain the reported radiation mechanism of the EBG-backed monopole. The proposed antenna is fabricated on a 68 × 38 × 1.57 mm 3 board of semiflexible RT/duroid 5880 substrate. Detailed analysis and measurements are presented for various cases when the antenna is subjected to structural deformation and human body loading, and in all cases, the EBG-backed monopole antenna retains its high performance. The reported efficient and robust radiation performance with very low specific absorption rate, compact size, and high gain make the proposed antenna a superior candidate for most wearable applications used for off-body communication.

Beam-Oriented Digital Predistortion for 5G Massive MIMO Hybrid Beamforming Transmitters

Abstract: In this paper, we propose a beam-oriented digital predistortion (BO-DPD) technique for power amplifiers (PAs) in hybrid beamforming massive multiple-input multiple-output (MIMO) transmitters, which can achieve linearization of the transmitted signal in the main beam direction and address the DPD implementation issue in the hybrid beamforming array. In massive MIMO hybrid beamforming transmitters, the conventional DPD to linearize each PA is impractical to implement for that the number of digital chains is less than the number of PAs; however, the BO-DPD can resolve this issue by constructing and linearizing the “virtual” main beam signal rather than single PAs. According to the beamforming weights for array elements, the feedback path combines all PA’s outputs to estimate the main beam signal for DPD processing. In addition, an average estimation method is also presented to broaden the linearized angle range around the main beam direction. A $4 \times 16$ (four subarrays and 16 antennas in each subarray) uniform linear array (ULA) simulation along with a $1 \times 2$ ULA at 2.5 GHz and a $2 \times 2$ ULA at 3.5-GHz experimental tests was performed. The experimental results show that the proposed technique and linearization angle range broadening method achieve up to 15-dB adjacent channel power ratio improvement and 10° linearization angle range in the main beam direction.