Dr. Marko Sonkki M.Sc, Ph.D

Vol: 63 Pages: 2813-2819 Year: 2023 Publisher: IEEE

Abstract: This communication presents a wideband, dual-polarized Vivaldi antenna or tapered slot antenna with over a decade (10.7:1) of bandwidth. The dual-polarized antenna structure is achieved by inserting two orthogonal Vivaldi antennas in a cross-shaped form without a galvanic contact. The measured -10 dB impedance bandwidth (S 11 ) is approximately from 0.7 up to 7.30 GHz, corresponding to a 166% relative frequency bandwidth. The isolation (S 21 ) between the antenna ports is better than 30 dB, and the measured maximum gain is 3.8-11.2 dB at the aforementioned frequency bandwidth. Orthogonal polarizations have the same maximum gain within the 0.7-3.6 GHz band and a slight variation up from 3.6 GHz. The cross-polarization discrimination (XPD) is better than 19 dB across the measured 0.7-6.0 GHz frequency bandwidth, and better than 25 dB up to 4.5 GHz. The measured results are compared with the numerical ones in terms of S-parameters, maximum gain, and XPD.

Vol: 64 Pages: 5020-5029 Year: 2019 Publisher: IEEE

Abstract: This paper provides some design guidelines for the excitation of broadband slotted planar antennas, addressing key issues such as coupling, symmetries, and multiple feeding. The theory of characteristic modes (CMs) is used to identify the collection of current modes that exist on these structures, dealing with a valuable understanding of the radiating mechanisms and allowing a more controlled design process. Modal analysis of a circular aperture cut on a finite square ground plane is presented in order to demonstrate that an optimum choice of the feeding mechanism can be made according to the current distribution of the desired modes. Based on the information yielded by this modal analysis, a capacitive-coupled dual-feed circular aperture antenna is presented. This antenna takes advantage of the symmetries of the characteristic currents by making use of multiple feeding, in order to excite only some particular modes. The usage of commonly-fed and differentially-fed configurations enables an increased control of the excitation of modes in the structure. CM analysis of the antenna including the feeding structures is presented, showing the influence of the feeding lines in the performance of this type of antenna. A prototype of the antenna has been fabricated and measured. Simulated and measured results are presented, being in good agreement.

Vol: 40 Pages:89-100 Year:2018 Publisher: ETRI Journal

Abstract: Millimeter wave communication is one of the main disruptive technologies in upcoming 5G mobile networks. One of the first candidate applications, which will be commercially ready by 2020, is wireless backhaul links or wireless last-mile communication. This paper provides an analysis of this use case from radio engineering and implementation perspectives. Furthermore, preliminary experimental results are shown for a proof-of-concept wireless backhaul solution developed within the EU-KR 5GCHAMPION project, which will be showcased during the 2018 Winter Olympic Games in Korea. In this paper, we verify system-level calculations and a theoretical link budget analysis with conductive and radiated over-the-air measurements. The results indicate that the implemented radio solution is able to achieve the target key performance indicator, namely, a 2.5 Gbps data rate on average, over a range of up to 200 m.

Vol: 19 Pages:90 Year:2018 Publisher: MDPI

Abstract: The number of IoT (Internet of Things) devices is predicted to increase dramatically in the years to come and their manufacturing and maintenance, including both commercial and ecological aspects associated with these, are gaining substantial attention. One of the effective ways of addressing both these issues at a time is the energy-neutral systems, which operate with the energy harvested from their environment. To address the major problem of this system, namely the low reliability, in the current paper, we develop and study the utility of a system powered solely with the wireless power transfer (WPT) over a radio frequency (RF) channel. In the article, we propose a methodology for developing and implementing a real-life IoT application based on RF WPT. We employ the proposed methodology to develop a WPT-powered solution to sense the temperature and the angular velocity in the rotating industrial environment. First, we discuss the key trade-offs arising when selecting and developing the new components for a WPT system. Then, we present and detail our solutions and describe the results of their evaluations. Finally, we instrument and evaluate the complete system, proving that it is capable of meeting all the design goals and requirements. The results reported in this paper can be of interest to the practitioners, for whom they provide a step-by-step methodology of WPT application development with a practical example. In addition, these results may be valuable for analysts, as they demonstrate many practical interrelations and effects specific to real-life WPT applications.

Vol: 7 Pages:149026-149038 Year:2019 Publisher: IEEE

Abstract: A new antenna structure is presented in this paper. The antenna is operating at the Ultra-Wideband (UWB) band, 3.75-4.25 GHz, defined originally in the Body Area Networks (BAN) part of the IEEE 802.15.6 standard. The antenna size is 89 mm × 60 × 21 mm. The antenna is a directive with a measured gain of 8 dBi at 4 GHz center frequency. Since the proposed antenna is designed to meet the aspects of a receiving antenna for wireless capsule endoscopy localization, the antenna behavior in close proximity to a human body, in particular the small intestine area, is performed. To this end, initial on-body simulations were carried out by means of a tissue-layer model emulating the dielectric properties of the human body tissues at 4 GHz center frequency. This was followed by voxel model investigations. The human body's impact on the antenna characteristics was analyzed first, followed by the examination of the power flow propagation inside the tissues. These analyses are consistent in evaluating the antenna's ability to communicate with a capsule placed at the small intestine. Later, the antenna free-space propagation was assessed and validated by measurements. These results are followed by a measured on-body investigation conducted on male and female persons. Simulation results were obtained by CST Microwave Studio. Results were confirmed by measurements, conducted in an anechoic chamber at the University of Oulu, Finland. The results were measured in the frequency domain and later post-processed to a time domain. Consequently, measured results converge to the simulation ones. It is concluded that the antenna could be used for Wireless Capsule Endoscopy communications with UWB signaling complying with IEEE 802.15.6 standard.

Vol: 5 Pages:1-10 Year:2018 Publisher: IEEE

Abstract: The paper presents simulated and measured results of a large millimeter-wave antenna array, designed by keeping mind the particular interests for proof of concepts in 5G demonstrations in the South Korean Winter Olympics 2018. The array consists of 16 (2x8) unit cells, each having four (2x2) linearly polarized patch elements exited with the same amplitude and phase. The desired -10 dB impedance bandwidth for the array is from 25.65 GHz to 27.50 GHz, and the proposed structure achieves lower than -30 dB mutual coupling between the unit cells. The presented simulation and measurement results show a good match with each other, as well as with the specifications. The radiation pattern is measured element by element at 27 GHz, and the results are summed in post-processing to perform the array factor. Sidelobe levels are 15 dB below the maximum gain, whereas the measured maximum gain is around 20 dB as the numerical results predicted 21.5 dB.

Vol: 20 Pages:431-432 Year:2020 Publisher: Springer International Publishing

Abstract: A novel UWB antenna working in the 805.15.6 low-UWB region is proposed in this chapter. The antenna is targeted for Wireless Capsule Endoscopy (WCE) localization. Simulation results show that the antenna performs well at 4 GHz with a 500 MHz bandwidth which is compliant with the IEEE 802.15.6 standard for Body Area Networks (BAN). A preliminary study on the single antenna performance is presented first, followed by the introduction of the box-shaped cavity version of the antenna structure. Both types of antenna are directional with high gain. To investigate WCE applications, the cavity antenna in proximity of a multi-layer model emulating human body tissue properties at 4 GHz was also simulated.

Vol: 71 Pages:2908-2921 Year:2023 Publisher: IEEE

Abstract: This article presents a dual-band, dual-polarized antenna operating from 24 up to 40 GHz at 5G new radio (NR) millimeter-wave (mm-Wave) Frequency Range 2 (FR2) bands. A novel stacking arrangement of ring patches is proposed to achieve wide dual-band operation with stable gain. Two pairs of stacked ring patches operating at lower (24.25–29.5 GHz) and upper (37–40 GHz) FR2 bands are alternately integrated at four metal layers. The antenna offers a sharp roll-off and a filter-like response with radiation nulls between the operating bands due to the stacking configuration. The antenna is aperture-coupled and stripline-fed, and it conforms to the antenna-in-package (AiP) requirements. The proposed single antenna element and a

Vol: 7 Pages:74670-74682 Year:2019 Publisher: IEEE

Abstract: This paper presents a comprehensive study on the impact of sternotomy wires on the characteristics of ultra-wideband (UWB) radio propagation channels in the human chest area. The study is conducted using two simulation models: a planar layer model and a three-dimensional elliptical layer model. The study includes antennas designed for on-body and in-body communications. Furthermore, the measured data and propagation path calculations are presented to verify the simulation results. The main purpose is to show how the steel wires affect the on-body channel characteristics and in-body propagation within the tissues when the monitoring antennas are located in close vicinity of the human body. The study is conducted by evaluating: 1) channel characteristics in both frequency and time domains; 2) 2D power flow figures; and 3) Poynting vector values. Furthermore, the impact of the fat layer thickness on the visibility of sternotomy wires is studied. Moreover, the impact of sternotomy wires is studied for the case of the recently operated patient, for which the sternotomy wires are on the sternum bone surface, as well as for the case where the sternotomy wires are embedded into the sternum bone. It is found that sternotomy wires have a clear impact on the channel. The strength of the impact depends on the antenna types used by the monitoring devices, the thickness of the fat layer in the sternum area, and whether the sternotomy wires are on the sternum surface or whether they have already been embedded in the sternum as it happens with time.

Vol: 2 Pages:285-301 Year:2021 Publisher: MDPI

Abstract: This paper describes the development and evaluation of an on-body flexible antenna designed for an in-body application, as well as on-body communications at ISM and UWB frequency bands. The evaluation is performed via electromagnetic simulations using the Dassault Simulia CST Studio Suite. A planar tissue layer model, as well as a human voxel model from the human abdominal area, are used to study the antenna characteristics next to human tissues. Power flow analysis is presented to understand the power flow on the body surface as well as within the tissues. Simulation results show that this wearable flexible antenna is suitable for in-body communications in the intestinal area, e.g., for capsule endoscopy, in the industrial, scientific, and medical (ISM) band, and at lower ultra-wideband (UWB). At higher frequencies, the antenna is suitable for on-body communications as well as in-body communications with lower propagation depth requirements. Additionally, an antenna prototype has been prepared and the antenna performance is verified with several on-body measurements. The measurement results show a good match with the simulation results. The novelty of the proposed antenna is its compact size and flexible substrate material, which makes it feasible and practical for several different medical diagnosis and monitoring applications.