Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Kuniaki Yoshitomi Last modified date:2021.06.04

Professor / Education Collaboration Department / Department of I&E Visionaries / Faculty of Information Science and Electrical Engineering

1. Ramesh K. Pokharel, Adel Barakat1, Shimaa Alshhawy, Kuniaki Yoshitomi, Costas Sarris, Wireless power transfer system rigid to tissue characteristics using metamaterial inspired geometry for biomedical implant applications, Scientific Reports, 10.1038/s41598-021-84333-3, 11, 1, 2021.03, Conventional resonant inductive coupling wireless power transfer (WPT) systems encounter performance degradation while energizing biomedical implants. This degradation results from the dielectric and conductive characteristics of the tissue, which cause increased radiation and conduction losses, respectively. Moreover, the proximity of a resonator to the high permittivity tissue causes a change in its operating frequency if misalignment occurs. In this report, we propose a metamaterial inspired geometry with near-zero permeability property to overcome these mentioned problems. This metamaterial inspired geometry is stacked split ring resonator metamaterial fed by a driving inductive loop and acts as a WPT transmitter for an in-tissue implanted WPT receiver. The presented demonstrations have confirmed that the proposed metamaterial inspired WPT system outperforms the conventional one. Also, the resonance frequency of the proposed metamaterial inspired TX is negligibly affected by the tissue characteristics, which is of great interest from the design and operation prospects. Furthermore, the proposed WPT system can be used with more than twice the input power of the conventional one while complying with the safety regulations of electromagnetic waves exposure..
2. Thapa S.K., Chen B., Barakat A., Yoshitomi K., Pokharel R.K., X-Band Feedback Type Miniaturized Oscillator Design with Low Phase Noise Based on Eighth Mode SIW Bandpass Filter, IEEE Microwave and Wireless Components Letters, 10.1109/LMWC.2021.3064602, 31, 5, 485-488, 2021.05, A standard substrate integrated waveguide (SIW)-based bandpass filter (BPF) suffers from bulkiness that limits its application in the implementation of compact size low phase noise oscillator. Instead, in this letter, an eighth mode SIW (EMSIW) resonator-based BPF is utilized to realize a miniaturized low phase noise oscillator for X -band applications. Additionally, an equivalent circuit model of EMSIW-BPF is presented. A compact feedback-type oscillator prototype using EMSIW-BPF is designed and fabricated for the first time with a circuit area of just 1092 mm2. The experimental results of the prototype show a phase noise of -126.13 dBc/Hz at 1 MHz offset from 9.97 GHz oscillation frequency with an output power of 3.17 dBm..
3. Mohamed Aboualalaa, Islam Mansour, Adel Barakat, Kuniaki Yoshitomi, Ramesh K. Pokharel, Improvement of Magnetic Field for Near-Field WPT System Using Two Concentric Open-Loop Spiral Resonators, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, 10.1109/LMWC.2020.3016136, 30, 10, 993-996, 2020.08, This letter introduces two concentric open-loop spiral resonators (OLSRs) that are used to improve magnetic field for nonradiative wireless power transfer (WPT) systems. OLSRs are fed through metal–insulator–metal (MIM) capacitive coupling using a 50-Ω microstrip transmission line. First, a single OLSR is designed and implemented for WPT, then two OLSRs are used instead of a single OLSR to emphasize the surface current on the spiral resonators. Therefore, it helps to intensify the electromagnetic field in order to get a high transmission distance or higher efficiency. The proposed WPT system operates at 438.5 MHz with a measured power transfer efficiency (PTE) of 70.8% at a transmission distance of 31 mm and a design area of 576 mm2. An equivalent circuit of the proposed WPT system is presented as a heuristic approach to show the electrical behavior of the WPT system..
4. Adel Barakat, Shimaa Alshhawy, Kuniaki Yoshitomi, Ramesh K. Pokharel, Simultaneous Wireless Power and Information Transfer Using Coupled Co-Existing Defected Ground Structure Resonators, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—II: EXPRESS BRIEFS, 10.1109/TCSII.2020.3016385, 68, 2, 632-636, 2020.08, In this brief, we realize a simultaneous wireless power and information transfer (WPIT) system using co-existing coupled defected ground structure (DGS) resonators. First, co-existing DGS resonators are utilized in the design of simultaneous band stop filter (BSF) responses. Then, coupling two sets of co-existing DGS-BSFs achieves simultaneous WPIT. The DGS resonators have spiral elliptical-shape and share the same ground plane. The coupling characteristics are studied to improve the kQ-product of power carrier and reduce the cross-coupling with the Information carrier. A prototype is fabricated having a size 30 mm × 15 mm for both transmitter (TX) and receiver (RX). The separation between TX and RX is 15 mm. At this separation, the measured efficiencies are 71% and 66% at 49.6 MHz and 149 MHz, respectively, and the isolation between the power channel TX and the information channel RX is 39 dB at 49.6 MHz..
5. Shimaa Alshhawy, Adel Barakat, Kuniaki Yoshitomi, Ramesh K. Pokharel, Separation-Misalignment Insensitive WPT System Using Two-Plane Printed Inductors, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, 10.1109/LMWC.2019.2935621 , 29, 10, 683-686, 2019.10, This letter presents a separation-misalignment insensitive wireless power transfer (WPT) system. This insensitivity is possible by minimizing the variation of mutual inductance. The transmitter (TX) of the proposed WPT system uses a two-plane printed inductor, and the receiver (RX) is a single-plane one. The TX encloses the RX to achieve minimal mutual inductance variations. Hence, the lost mutual inductance due to the misalignment between the RX and one of the TX inductors is compensated by getting close to/moving away from the other TX inductor. Furthermore, admittance inversion and compensation networks are designed to compensate for the remaining variations. Then, we design and fabricate a prototype at 50 MHz. Each TX inductor has an area of 50 mm × 50 mm and an initial separation of 30 mm from the 25 mm×25 mm RX. The measured efficiency ranges between 72.5% and 80.5% for the separation of ±20 mm from the initial position..
6. Adel Barakat, Kuniaki Yoshitomi, Ramesh K. Pokharel, Design and Implementation of Dual-Mode Inductors for Dual-Band Wireless Power Transfer Systems, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—II: EXPRESS BRIEFS, 10.1109/LMWC.2019.2935621, 66, 8, 1287-1291, 2019.08, We propose a dual-band wireless power transfer (WPT) system employing a dual-mode inductor. The dual-mode inductor is possible through enforcing a self-resonance condition by loading an inductor in series by a tank circuit. In return, two distinct resonances are achieved, simultaneously, utilizing a single compensation capacitor as the inductance of the dual-mode inductor appears with a smaller value after its self-resonance. Also, by maintaining the same mutual coupling, the coupling coefficient becomes larger at the higher resonance, which allows for the employment of the same source/load admittance inversion network to achieve maximum power transfer at both of the operating frequency bands, concurrently. We verify the operation by fabricating a dual-band WPT system, which shows measured efficiencies of 70% and 69% at 90.3 MHz and 138.8 MHz, correspondingly. The size of the WPT system is 50 × 50 mm and has a transfer distance of 40 mm..
7. L.S. Yang , L. Yang , Y.A. Zhu , Kuniaki Yoshitomi , Haruichi Kanaya, Polarization reconfigurable slot antenna for 5.8 GHz wireless applications, AEU - International Journal of Electronics and Communications, 10.1016/j.aeue.2019.01.022, 101, 27-32, 2019.03, A CPW-fed circular polarization reconfigurable antenna is proposed in this paper. The antenna consists of two symmetrically placed inverted L-shaped slots. By using a T-type bias device to change the bias states of two PIN diodes which connect the two slots with the feed port respectively, right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) can be realized accordingly. For both states, the measured −10 dB impedance bandwidth is 5.78–5.96 GHz, while the measured 3 dB axial ratio bandwidth is 5.64–5.91 GHz (4.7%), both the
bandwidths can cover the 5.8 GHz ISM band. By using floating ground and reflector board to enhance the front to back ratio of the antenna, 6.84 dBi measured gain can be realized at 5.8 GHz..
8. Adel Barakat, Kuniaki Yoshitomi, Ramesh K. Pokharel, Design Approach for Efficient Wireless Power Transfer Systems During Lateral Misalignment, IEEE Transactions on Microwave Theory and Techniques, 10.1109/TMTT.2018.2852661, 66, 9, 4170-4177, 2018.09, This paper methodizes efficiency improvement during lateral misalignment for the wireless power transfer (WPT) system using two coupled semielliptic defected ground structure (DGS) resonators. We design the WPT system using a scaled value of the available mutual coupling between the resonators at perfect alignment. This scaled mutual coupling value enforces over-coupling regime, and the WPT efficiency is lower than the peak one. Then, during lateral misalignment, WPT efficiency improves until it peaks at critical coupling. Next, with further misalignment, the efficiency drops as the system enters loose coupling regime. The proposed method consists of two steps. First, we derive an analytical approach to determine the scaled mutual coupling value for efficiency design during lateral misalignment, and second, we improve the maximum obtainable efficiency by careful designing of the DGS structures’ profile. We verify the proposed method by implementing the WPT system at 300 MHz, which shows a peak efficiency of 80% for a size Do× Do = 40×40 mm2 with a transfer distance d = Do. During misalignment, the efficiency is higher than 50% for a lateral shift up to ±0.75 Do..
9. Hany A. Atallah, Adel B. Abdel-Rahman, Yoshitomi Kuniaki, Ramesh Kumar Pokharel, Design of compact frequency agile filter-antenna using reconfigurable ring resonator bandpass filter for future cognitive radios, International Journal of Microwave and Wireless Technologies, DOI: 10.1017/S1759078717001556, 10, 4, 487-496, 2018.05, In this paper, a new miniaturized frequency agile filter-antenna with a wide reconfigurable frequency band is proposed for interweave cognitive radios (CRs). A tunable bandpass filter (BPF) composed of a symmetrical ring resonator is cascaded to the feed line of an ultra-wideband planar antenna. The structure of the proposed ring resonator BPF is simple and compact so that the total size of the proposed filter-antenna is smaller than that of a conventional system made of a separate antenna and BPF. The reconfigurability of the proposed filter-antenna is achieved by changing the operating frequency of the BPF by loading the ring resonator with a single varactor diode at its center. The fabricated prototype has successfully achieved a wide operational bandwidth of 1.43 GHz which covers continuous narrow bands from 4.65 to 6.08 GHz. Moreover, the operating tunable narrow bands have stable radiation characteristics. Good agreement bet een measurement and simulation results is demonstrated..
10. Hany A. Atallah, Adel B. Abdel-Rahman, Yoshitomi Kuniaki, Ramesh Kumar Pokharel, CPW-Fed UWB antenna with sharp and high rejection multiple notched bands using stub loaded meander line resonator, International Journal of Electronics and Communications (AEU), 83, 22-31, 2018.01, This paper presents a CPW-fed UWB filter-antenna with sharp and high rejection multiple band notches for band-notched UWB communication applications. The band notch operation is achieved by employing a sharp bandstop filter (BSF) with multiple reject bands using only one element meander line resonator at the bottom layer through theoretical calculations and parametric studies. The adjustment of the notched bands is successfully accomplished by loading the meander line with open ended stubs to modify the harmonic frequencies to the desired bands. The structure of the proposed BSF is simple and compact so that the proposed filter-antenna is achieved with the same size of the reference UWB antenna without an extra area. Measurement results show that the proposed filter-antenna has two notches at the WiMAX systems operating in the 5.8 GHz (5.725?5.85 GHz) and at the international telecommunication union (ITU) operating in the 8.2 GHz (8.025?8.4 GHz). Also, it has sharp rejection characteristics at the edges of the federal communication commission (FCC) band for UWB communications. The experimental measurements are in good agreement with theoretical and simulation results for the BSF and the filterantenna. Moreover, the filter-antenna exhibits stable omnidirectional radiation patterns except at the notched bands..
11. Fairus Tahar, Adel Barakat, Redzuan Saad, Kuniaki Yoshitomi, Ramesh K. Pokharel, Dual-Band Defected Ground Structures Wireless Power Transfer System With Independent External and Inter-Resonator Coupling, IEEE Transactions on Circuits and Systems II: Express Briefs, DOI: 10.1109/TCSII.2017.2740401, 64, 12, 1372-1376, 2017.08, This brief proposes a design methodology based on the admittance (J-) inverters for a dual-band wireless power transfer (WPT) system that employs two cascaded circulars defected ground structure (DGS) resonators with different capacitive loading to guarantee distinct resonances. A single microstrip line excites the two DGSs, and when two DGS resonators are coupled back to back, it transforms to a dual band pass filter leading to WPT at both bands. Each of the DGS resonators has independent coupling. Thus, the realized J-Inverters are designed independently. Also, we employ a single stub for the matching. This stub appears with a different length according to the operating frequency; hence, an independent external coupling is achieved at both frequencies. A compact size of 30 mm × 15 mm is fabricated achieving a WPT efficiency of more than 71% at a power transfer distance of 16 mm for both bands (0.3 and 0.7 GHz)..
12. 岩井 郁也, Yoshitomi Kuniaki, Haruichi Kanaya, Miniaturized high-band UWB array antenna, Microwave and Optical Technology Letters, 10.1002/mop.30599, 59, 7, 1651-1655, 2017.05, High-band ultra-wide band (UWB) miniaturized array antenna with coplanar wave guide (CPW) feed line is presented. Antenna element is composed of monopole antenna with truncated ground plane. Both antenna layer and ground pattern are placed on the top of the substrate. It is suitable for the miniaturized wireless devices such as three dimensional integrations or stacking of the multi layer. To obtain the wide band and flat gain characteristic, rectangular notches are inserted on the antenna layer, and optimized the current flow and antenna impedance. For array antenna, by changing the length of the CPW feed line, the antenna gain is suitable in the wide band which is 7–10.4 GHz (23 dB bandwidth). The total antenna size of the two array antenna is 16 mm 3 11.5 mm 30.418 mm. Simulated gain is 3.8 dB..
13. Hany A. Atallah, Adel B. Abdel-Rahman, Yoshitomi Kuniaki, Ramesh Kumar Pokharel, Reconfigurable Band-Notched Slot Antenna Using Short Circuited Quarter Wavelength Microstrip Resonators, Progress In Electromagnetics Research C, 68, 119-127, 2016.10, In this paper, a CPW feed ultrawideband (UWB) slot antenna with a single reconfigurable notched band is proposed for overlay cognitive radio (CR) systems. The proposed antenna utilizes two symmetrical short circuited quarter wavelength resonators at the top layer and close to the ground to create a single notch. The switching reconfiguration is achieved by changing the length of resonators to prevent the interference to the primary users that are operating in the wireless local area network (WLAN) band at 5.725–5.825 GHz and the international telecommunication union (ITU) band at 8.05–8.4GHz. The center frequency of the notched band can be tuned by selecting the length of the resonators, which is achieved by employing two ideal switches. Moreover, the proposed antenna has been fabricated and tested. The experimental data confirmed that the proposed design can selectively have a band notch over the two existent desired bands..
14. Hany A. Atallah, Adel B. Abdel-Rahman, Yoshitomi Kuniaki, Ramesh Kumar Pokharel, Mutual Coupling Reduction in MIMO Patch Antenna Array Using Complementary Split Ring Resonators Defected Ground Structure, Applied Computational Electromagnetics Society Journal, 31, 7, 737-743, 2016.07, In this paper, complementary split ring resonators (CSRRs) defected ground structure (DGS) is introduced to suppress surface waves and to reduce the mutual coupling between E-plane coupled two elements of a microstrip patch MIMO antenna array. The CSRRs-DGS is easily etched on the ground plane between the array elements. The CSRRs-based DGS acts as a bandstop filter between the array elements and operates in the same desired frequency band of the array at 9.2 GHz. Significant reduction of the electromagnetic (EM) mutual coupling is achieved between array elements with a reduced edge-to-edge spacing of 7.5 mm (0.22 ?o). Experimental results show that more than 30 dB isolation between the array elements is obtained using an array of CSRR-based DGS. Moreover, the antenna array parameters are successfully optimized with a numerical experimentation technique using a 3D full-wave EM simulator. The design of the proposed array is fabricated and measured for verification purposes. The proposed design has been simulated and validated experimentally. Good agreement is found between the simulated and the measured data..
15. Chai Eu Guan, Yoshitomi Kuniaki, Haruichi Kanaya, Derivation of the Optimum Distance between Periodically Spaced Vias for Leakage Suppression at S-band, MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, 10.1002/mop.29776, 58, 5, 1257-1260, 2016.05, In this letter, the optimum center-to-center separation between vias in the conductor-backed coplanar waveguide (CBCPW) is presented for leakage suppression in the dielectric region. Leakage mechanism at high frequencies associated with surface wave or parallelplate mode were widely studied in the past. In this work, antenna arrays have been used to compare leakage in CPW and CBCPW feed network at S-band. By using identical antenna elements, CPW-fed slot dipole antenna array has been compared against CBCPW-fed slot dipole antenna array with a ground via fence. Instead of using shorting pins with minimum nonzero gap, optimum center-to-center separation distance between vias has been derived from the bandgap phenomenon. Approximately 20% of total loss across the frequency range of interest in CPW feed network obtained from the comparison of the CPW-fed antenna array against the CBCPW-fed antenna array can be attributed to unwanted leakage in the dielectric substrate..
16. Hany A. Atallah, Adel B. Abdel-Rahman, Yoshitomi Kuniaki, Ramesh Kumar Pokharel, Design of Dual Band-Notched CPW-Fed UWB Planar Monopole Antenna Using Microstrip Resonators, Progress In Electromagnetics Research Letters, 59, 51-56, 2016.03, In this letter, a new coplanar waveguide (CPW) fed ultra-wideband (UWB) planar monopole antenna with dual band-reject characteristics is proposed. Two resonators of different lengths are employed at the bottom layer to create two notches at the frequency.
17. Hany A. Atallah, Adel B. Abdel-Rahman, Yoshitomi Kuniaki, Ramesh Kumar Pokharel, Tunable Band-Notched CPW-Fed UWB Monopole Antenna Using Capacitively Loaded Microstrip Resonator for Cognitive Radio Applications, Progress In Electromagnetics Research C, 62, 109-117, 2016.02, In this paper, a new compact coplanar waveguide (CPW) ultrawideband (UWB) antenna with an electronically tunable notched band is proposed for an overlay onto cognitive radio (CR) systems. The proposed antenna utilized a rectangular microstrip resonator in.
18. Lingsheng Yang, Yongan Zhu, Yoshitomi Kuniaki, CPW-Fed Reconfigurable Clover-Shaped Antenna with Switchable Circular Polarization, Progress In Electromagnetics Research C, 60, 147-156, 2016.01, In this paper, a CPW-fed reconfigurable clover-shaped antenna with switchable circular polarization is proposed. This antenna consists of a clover-shaped patch, four p-i-n diodes, and two pairs of quarter-circular-rings. By electrically controlling the fo.
19. Lingsheng Yang, Tao Li, Feng Wang, Yoshitomi Kuniaki, Compact Tri-Bans MIMO Antenna for LTE/GSM Mobile Handset Application, IEICE Transaction on Communications, E99-B, 1, 177-185, 2016.01, A tri-band Multiple-input-multiple-output (MIMO) antenna system for LTE 700, LTE2500 and GSM 1800/1900 mobile handset application is presented. The whole system consists of four identical 3-D IFAs (inverted F antenna) folded on FR4 cuboids. Without any sp.
20. Hideharu Yoshioka, Lingsheng Yang, Emad Tamman, Yoshitomi Kuniaki, A highly compact dual-band WLAN/UWB monopole antenna, IEICE Electronics Express, 9, 3, 160-164, 2012.02.
21. Lingsheng Yang, Kuniaki Yoshitomi, A compact circular corner monopole antenna for UWB application, Microwave and Optical Technology Letters, 5, 4, 147-150, 2012.01.
22. Lingsheng Yang, Kuniaki Yoshitomi, Design of a dual-band antenna with L-shaped stub, IEICE Electronics Express, 8, 22, 1887-1891, 2011.11.
23. L. Lolit Kumar Singh, Bhaskar Gupta, Partha P. Sarkar, Kuniaki Yoshitomi, and Kiyotoshi Yasumoto, Cross Slot Multifrequency Patch Antennas, MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Vol.5, No.6, pp.390-395, 2010.03.
24. L. Lolit Kumar Singh, Bhaskar Gupta, Partha P Sarkar, Kiyotoshi Yasumoto and Kunikai Yoshitomi, L-Shaped Slot Broadband Single Layer Rectangular Patch Antennas, International Journal of Microwave and Technology, vol. 5, no. 6, 390-395, Vol.5, No.6, pp.390-395, 2010.11.
25. K. Yoshitomi, A study on the excitation and the input impedance of an antenna, Asian Journal of Physics, Vol. 19, No. 2, 2009, 2009.05.
26. L. Lolit Kumar Singh, B. Gupta, K. Yoshitomi, and K. Yasumoto, New single layer wideband rectangular patch antenna, Asian Journal of Physics, Vol. 19, No. 2, 2009, 2009.05.
27. Kosei Moriyama and Kuniaki Yoshitomi, Apartment Electrical Wiring: A Cause of Extremely Low Frequency Magnetic Field Exposure in Residential Areas, Bioelectromagnetics, 10.1002/bem.20099, 26, 3, 238-241, vol.26, pp.238-241, 2005.04.
28. Kosei Moriyama, Hiroyuki Sato, Kenji Tanaka, Yoshiyuki Nakashima, and Kuniaki Yoshitomi, Extremely Low Frequency Magnetic Fields Originating from Equipment Used for Assisted Reproduction, Umbilical Cord and Peripheral Blood Stem Cell Transplantation, Transfusion, and Hemodialysis, Bioelectromagnetics, 10.1002/bem.20071, 26, 1, 69-73, vol.26, pp.69-73, 2005.01.
29. Hongting Jia, Kiyotoshi Yasumoto and Kuniaki Yoshitomi, Analysis of Rectangular-Groove Waveguides Using the Fourier Transform Technique, Microwave and Optical Technology Letters, 10.1002/mop.20148, 41, 5, 388-392, Volume 41, Number 5, pp.388-392, 2004.06.
30. Measurement and reduction of power frequency magnetic fields in a residential area

K. Yoshitomi

The Transactions of the Institute of Electronics, Information and Communication Engineers B.
31. Measurement of RF noise in a magnetic sheild with a developed monopole antenna -- Effect of RF noise on FLL operation of dc-SQUID sensors --

K. Tashiro, I. Sasada, K. Yoshitomia and K. Kazami

Transactions of the Magnetics Society of Japan.
32. H.Jia, K.Yoshitomi, and K.Yasumoto, Rigorous analysis of E-/H-plane junctions in rectangular waveguides using Fourier transform technique, Progress In Electromagnetics Research, PIER, Vol.PIER21, pp.273--292, 1998.01.
33. K.Yasumoto and K.Yoshitomi, Efficient calculation of lattice sums for free-space periodic Green's function, IEEE Transactions on Antennas and Propagation, 10.1109/8.777130, 47, 6, 1050-1055, Vol.47, No.6, pp.1050 -- 1055, 1999.06.
34. K.Yoshitomi, Radiation from a slot in an impedance surface, IEEE Transactions on Antennas and Propagation, 10.1109/8.954925, 49, 10, 1370-1376, Vol.49, No.10, pp.1370-1376, 2001.10.
35. H.Jia, K.Yoshitomi, and K.Yasumoto, Rigorous analysis of rectangular waveguide junctions by Fourier transform technique, Progress In Electromagnetics Research, PIER, Vol.20, pp.263--282, 1998.01.