| Adel Barakat | Last modified date：2024.04.02 |
Assistant Professor /
Department of I&E Visionaries /
Faculty of Information Science and Electrical Engineering
Papers
| 1. | Adel Barakat, Ramesh K. Pokharel, Low-Pass Filtering Admittance Inverter for High Out-of-Band Rejection Millimeter-Wave On-Chip BPF, IEEE Transactions on Circuits and Systems II: Express Briefs, 10.1109/TCSII.2023.3283532, 70, 11, 3963-3967, 2023.11. |
| 2. | Samundra K. Thapa, Ramesh K. Pokharel, Adel Barakat, Ruibing Dong, Shuhei Amakawa, Shinsuke Hara, Issei Watanabe, Akifumi Kasamatsu, Implementation of SIW Cavity in Commercial CMOS Technology for Sub-Terahertz Band Applications, IEEE MTT-S International Microwave Symposium Digest, 10.1109/IMS37964.2023.10188161, 2023-June, 493-496, 2023.06, For sub-terahertz band applications, two compact and low-loss on-chip substrate integrated waveguide (SIW) cavities are designed in CMOS technology. Compact size cavity is achieved by utilizing the folded ridge structure in the quarter mode SIW (QMSIW) structure which is loaded with complementary split-ring resonators (CSRRs). Two prototypes of the proposed QMSIW cavities with and without CSRR are fabricated in 1P6M CMOS technology. From the measurement, both cavities present return losses higher than 27 dB and external Q-factors higher than 140. The proposed work shows that even at such high frequencies, compact and low-loss SIWs can be fabricated in commercial CMOS technology and opens a window to utilizing such cavities for other low-loss components such as oscillators, on-chip bandpass filters and on-chip antennas for sub-terahertz band applications.. |
| 3. | Babita Gyawali, Samundra Kumar Thapa, Mohamed Aboualalaa, Adel Barakat, Ramesh Kumar Pokharel, Frequency Switching Dual Power Band Rectifier with Load-Modulation Technique, 2023 IEEE Wireless Power Technology Conference and Expo, WPTCE 2023 - Proceedings, 10.1109/WPTCE56855.2023.10216256, 2023.06, The frequency switching dual power band rectifier is proposed to achieve both low-power and high-power applications from a single circuit. Two different operating frequencies f1 = 900 MHz and f2 = 2.4 GHz are selected for low-power and high-power applications, respectively. The proposed rectifier fulfills stable operation at two levels of input power by making frequency switching. The Schottky diodes HSMS 2850 and HSMS 2860 are selected for f1 and f2, respectively, based on their performance with respect to the input power. Instead of conventional lumped inductors, defected ground structure (DGS)-based inductors are employed in matching circuits. For maximum RF-to-dc conversion efficiency in both low and high-power conditions, two different optimal loads are required, which is achieved from the load-modulation technique by using Bipolar Junction Transistor (BJT). The measurement result of the proposed rectifier shows more than 50% conversion efficiency for the power range -18 dB to 2 dBm and 8 dBm to 20 dBm with circuit size of 35 mm × 30 mm.. |
| 4. | Adel Barakat, Mohd Khairi Bin Zulkalnain, Ramesh Pokharel, Comparator-less ASK-PWM CDR Circuit for Forward Data Communication Over A Single Channel Wireless Power and Data Transfer System, 2023 IEEE Wireless Power Technology Conference and Expo, WPTCE 2023 - Proceedings, 10.1109/WPTCE56855.2023.10215978, 2023.06, In this work, a new clock and data recovery (CDR) scheme is proposed for amplitude shift keying (ASK) with pulse width modulation (PWM) encoding. Such a technique can fully recover the clock as well as the encoded data without the need for any comparator. The clock is recovered by passing the ASK-PWM encoded data to the frequency divider and frequency multiplier. Then, the data sampler can recover the data by sampling the ASK-PWM modulated data using a delayed version of the recovered clock with no additional processing. This technique is intended for a data transfer system over an inductively coupled wireless power transfer system (WPT) system for biomedical implants where the data will modulate the power carrier without the need for a dedicated data channel. A prototype example implementation of the CDR scheme on a 180 nm Complementary-Metal-Oxide-Semiconductor (CMOS) technology with a data rate of 2 Mbps is provided as a proof-of-concept. This CDR prototype has an area of 8000 μm2 and consumes a power of 129 microwatts from a 1.4 Voltage dc supply.. |
| 5. | Ramesh K. Pokharel, Tomoki Fukuda, Samundra K. Thapa, Adel Barakat, Ruibing Dong, Shinsuke Hara, Issei Watanabe, Akifumi Kasamatsu, 200 GHz-band Low-loss Half-Mode SIW CMOS Interconnects and Transmission Lines for Sub-Terahertz Frequency Band Applications, IEEE MTT-S International Microwave Symposium Digest, 10.1109/IMS37964.2023.10188034, 2023-June, 497-500, 2023.06, Low-loss half-mode substrate integrated waveguide (HMSIW)-based interconnects and transmission lines are designed and implemented in Complementary Metal-Oxide Semiconductor (CMOS) technology. In HMSIW interconnects, complementary split ring resonators (CSRR) whose self-resonance is much higher than the cut-off frequency of the SIW are etched on, due to which matching is improved. By controlling the parameters of the CSRRs, the losses due to microstrip to SIW transition are substantially improved, and no extra external matching circuit is required. A prototype was fabricated in 1P6M CMOS technology and tested. The measured cut-off frequency of the proposed HMSIW transmission line is 110 GHz, and the measured attenuation constant at frequencies of 175-220 GHz is less than 1.4 dB/mm. This work confirms a significant performance improvement of the CMOS interconnects in the sub-terahertz frequency band.. |
| 6. | Xin Jiang, Ramesh K. Pokharel, Adel Barakat, Kuniaki Yoshitomi, Hybrid SRR-Based Stacked Metamaterial for Miniaturized Dual-Band Wireless Power Transfer System, IEEE Transactions on Antennas and Propagation, 10.1109/TAP.2023.3262977, 2023.06. |
| 7. | Ramesh K. Pokharel, Adel Barakat, 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.. |
| 8. | Samundra K. Thapa, Baichuan Chen, Adel Barakat, Kuniaki Yoshitomi, Ramesh K. Pokharel, Miniaturized Slot-Loaded SIW Resonator and Its Application to C-band Low Phase Noise Oscillator, 2020 50th European Microwave Conference, EuMC 2020, 10.23919/EuMC48046.2021.9338129, 161-164, 2021.01, This paper presents a C-band low phase noise oscillator using small size low-profile substrate integrated waveguide (SIW) resonator for RF applications. A compact 6 GHz SIW resonator size is possible by introducing ?g/4 resonating slots. A size reduction of 29.87% is achieved while maintaining the quality factor. Also, the impedance of the SIW resonator is controlled by appropriate selection of the location of these introduced slots; which advantages for the conjugate matching between SIW resonator and the active device and removes the need of matching circuit between them. Then, a C-band oscillator prototype utilizing the proposed compact SIW resonator is designed, fabricated and measured. The measured results shows a phase noise of -122.11 dBc/Hz at 1 MHz offset with an output power of -4.2 dBm at 5.96 GHz oscillation frequency.. |
| 9. | Xin Jiang, Fairus Tahar, Takashi Miyamotol, Adel Barakat, Kuniaki Yoshitomi, Ramesh K. Pokharel, Design of three layers-stacked metasurface and its application to compact dual-band WPT system, 2021 IEEE Wireless Power Transfer Conference, WPTC 2021, 10.1109/WPTC51349.2021.9458177, 2021.06, This paper proposes a three-layers stack metasurface first, and then employed it to a compact double-band wireless power transfer (WPT) system. For the proposed dual-band WPT system, the metasurface exhibits the wide-band characteristic of the negative-near-zero permeability from 222 MHz to 889 MHz, where the transmission efficiency improves significantly at longer WPT distance at the lower band. Only a unit cell is stacked in three layers so that the size of the proposed metasurface has significantly reduced compared to a conventional metasurface where several unit cells are arranged in 1-D topology. The size of the proposed WPT system and the metasurface is 15 x15 mm and 20 x20 mm, respectively. Also, capacitors with the value of 0.1pF are etched on the gaps of the metasurface. The measured efficiencies' improvement ratios are 1.13 at 390 MHz in the air, where the WPT distance is significantly improved from 19 mm to 23 mm.. |
| 10. | Xin Jiang, Ramesh K. Pokharel, Adel Barakat, Kuniaki Yoshitomi, Wideband Stacked Metamaterial for a Compact and Efficient Dual-band Wireless Power Transfer, IEEE MTT-S International Microwave Symposium Digest, 10.1109/IMS37962.2022.9865455, 2022-June, 198-201, 2022.06, A novel wideband stacked metamaterial is proposed for a dual-band wireless power transfer (WPT) system. Firstly, two types of split-ring resonators (SRRs) of different self-resonance frequencies are proposed. Then we sandwiched each type of the unit cell. Consequently, the proposed metamaterial exhibits wideband near-zero characteristics on both the real part and imaginary part of the permeability. Also, compared with conventional 1-D metamaterial [2], the proposed metamaterial can significantly empower both bands simultaneously of the dual-band WPT system. An experiment shows that the proposed metamaterial of size (20 mm x 20 mm 5.468 mm) has improved the efficiencies of both bands from 18.6%, 22.9% to 51.8% and 47.8%, respectively, at a wireless power transfer distance of 20 mm.. |
| 11. | Samundra K. Thapa, Ramesh K. Pokharel, Baichuan Chen, Adel Barakat, On-Chip Millimeter-Wave DGS Based Bandstop Filter in 0.18-μm CMOS Process, IEEE Transactions on Circuits and Systems II: Express Briefs, 10.1109/TCSII.2022.3158995, 69, 6, 2732-2736, 2022.06, Defected Ground Structure (DGS) based on-chip bandstop filter (BSF) design is proposed for millimeter-wave applications. In the proposed structure, a capacitively loaded T-shape resonator is embedded in the original DGS resonator, which forms two high quality ( ${Q}$ -) factor small loop resonators. Moreover, this structure, in combination with the feedline and series capacitor, independently realizes the position of two transmission poles: one at each side of the parallel resonance without increasing the layout size. The proposed BSF presents a sharp scattering (S-) parameter response due to the appearance of two transmission poles. As a result, the loaded ${Q}$ -factor and negative group delay of the BSF are improved. The prototype of the proposed BSF is fabricated in 0.18- $mu ext{m}$ Complementary Metal-Oxide-Semiconductor (CMOS) process and measured. The measurement result shows a return loss of 1.78 dB at 53.2 GHz center stopband frequency with the negative group delay of 161 pS. The measurement results also agree well with the electromagnetic simulation results. Without pads, the active area of the prototyped BSF is only 0.024 mm2.. |
| 12. | Samundra K. Thapa, Ramesh K. Pokharel, Baichuan Chen, Tomoki Fukuda, Adel Barakat, Millimeter-Wave High Q-factor Sixteenth Mode SIW Cavity Resonator Implemented in 0.18-μm CMOS Technology, IEEE MTT-S International Microwave Symposium Digest, 10.1109/IMS37962.2022.9865522, 2022-June, 560-563, 2022.06, Millimeter-wave miniaturized Substrate Integrated Waveguide (SIW) cavity resonator is proposed in 0.18-μm CMOS technology. Miniaturization of the SIW cavity resonator is achieved first by taking 1/16thparts of the standard SIW and employing folded ridge structure. Later this folded ridge sixteenth mode SIW cavity is inductively loaded by a complementary split-ring resonator, which provides internal matching within the cavity resonator. This improved matching enhances the return loss, the external Q-factor, and ultimately, the loaded Q-factor of the proposed cavity resonator. At 60 GHz resonance frequency, the fabricated prototype of the proposed cavity resonator presents a measured reflection coefficient of -33.42 dB, with the external Q- factor 112. Moreover, the active area of the fabricated cavity without measuring pads is only 0.019 mm2.. |
| 13. | S. Alshhawy, Adel Barakat, Ramesh K. Pokharel, Kuniaki Yoshitomi, Low Magnetic Loss Metamaterial Based Miniaturized WPT System for Biomedical Implants, IEEE MTT-S International Microwave Symposium Digest, 10.1109/IMS37962.2022.9865438, 2022-June, 275-278, 2022.06, We propose a low magnetic loss multi-ring resonator (MRR) metamaterial. Then, we utilize this MRR metamaterial in a stacked configuration as the WPT transmitter (TX) for a miniaturized receiver (RX) embedded in biomedical tissue. A prototype is fabricated, and the measurement shows an efficiency of 51% at 50 MHz when the TX/RX separation distance is 9 mm. The TX/RX sizes are 20 mm × 20 mm and 7 mm × 7 mm, respectively. Hence, the proposed system has a figure-of- merit of 0.42, which is a significant improvement over the previously reported WPT systems. Also, the simulated specific absorption rate is within the recommended level when the input power is 21 dBm.. |
| 14. | Omar Z. Alngar, Adel Barakat, Ramesh K. Pokharel, High PAE CMOS Power Amplifier With 44.4% FBW Using Superimposed Dual-Band Configuration and DGS Inductors, IEEE Microwave and Wireless Components Letters, 10.1109/LMWC.2022.3189347, 2022.07, A two-stage 180-nm CMOS wideband (14–22 GHz) power amplifier (PA) with a superimposed staggered technique and defected-ground-structure (DGS) inductors is introduced, where a wideband peaking main stage is designed at the center frequency; then, a superimposed dual-band (SDB) driver stage is proposed to obtain the optimally flat gain response over the whole bandwidth (BW). Also, DGS inductors are used to enhance the power added efficiency (PAE) of the implemented PA by decreasing the matching circuits’ insertion losses. The proposed PA achieved a power gain of 12 dB at a total chip area of 0.564 mm |
| 15. | Omar Z. Alngar, Adel Barakat, Ramesh K. Pokharel, Capacitive Feedbacked Cold-Phase Compensator Analog Pre-Distorter and PAE Enhancer for K-Band CMOS PAs, IEEE Transactions on Circuits and Systems I: Regular Papers, 10.1109/TCSI.2022.3205367, 2022.09, A K-band two-stage power amplifier (PA) with capacitive-feedbacked cold-phase compensator (cold-PC) linearizer and power-added-efficiency (PAE) enhancer is introduced in 180-nm CMOS technology. This cold-PC consists of two parts. First, a cold-FET analog pre-distorter (APD) with a new capacitive-feedbacked technique is proposed to improve the linear behavior of the PA by enhancing the corresponding APD’s compensation slope. The proposed implementation has a reduced insertion loss and a minimal chip area overhead. Second, a low-pass two-tunable inductive and capacitive PC is proposed to solve the phase shift problem at intermediate nodes that would enhance the PAE of the stacked-transistors configuration. The implemented PA achieves, at 23.5-GHz, a maximum measured PAE of 21.2%, output power at the 1-dB compression point (OP |
| 16. | Omar Z. Alngar, Adel Barakat, Ramesh K. Pokharel, A High PAE Stacked K-band Power Amplifier Using π-Phase Compensation Technique, RFIT 2022 - 2022 IEEE International Symposium on Radio-Frequency Integration Technology, 10.1109/RFIT54256.2022.9882403, 42-44, 2022.08, A three-Tunable low-pass π-phase compensator technique is proposed and employed in a K-band CMOS power amplifier (PA) to solve the phase shift problem at intermediate nodes of stacked transistor configurations (STCs). Also, it reduces the effects of harmonic signals that in turns, enhances the overall power added efficiency (PAE) of the PA. The PA consists of two stages i.e. driver and main stages, designed using 2-STCs in 180-nm CMOS technology. The fabricated PA achieved a power gain of 12.8 dB at 23 GHz, a maximum PAE of 18.3%, an output power of 1 dB compression point left(mathrm{P}{1 mathrm{~dB } } ight) of 14.1 1 dBm, and saturated output power left(mathrm{P}{ ext {sat } } ight) of 16.0 dBm while it consumes chip area of 0.604 mm2 including pads.. |
| 17. | Baichuan Chen; Samundra K. Thapa; Adel Barakat; Ramesh K. Pokharel, A W-Band Compact Substrate Integrated Waveguide Bandpass Filter With Defected Ground Structure in CMOS Technology, IEEE Transactions on Circuits and Systems II: Express Briefs , 10.1109/TCSII.2021.3123655, 69, 3, 889-893, 2022.03, [URL], This brief proposes the first on-chip bandpass filter (BPF) based on substrate integrated waveguide (SIW) for W-band applications. Slot-loaded, folded ridge and quarter mode technology is used to reduce the cavity size. The coupling characteristic of two folded ridged quarter mode substrate integrated waveguide (QMSIW) cavities implemented in CMOS technology is investigated. A simplified equivalent lumped-element circuit model of the proposed wide-band BPF approach is provided and applied to study the coupling characteristic of slot-loaded folded ridged QMSIW cavity. Then, a novel coupling method using a defected ground structure is proposed to realize a proper coupling intensity for BPF design. Finally, the proposed BPF design is implemented in a commercial complementary metal-oxide-semiconductor (CMOS) technology, fabricated, and measured. The active size of the proposed cavity resonator is only 405 μm×185μm ( 0.22λg×0.1λg ), and the measured insertion loss ( |S21 | ) is 3.15 dB with a central frequency of 85.5 GHz.. |
| 18. | Shimaa Alshhawy; Adel Barakat; Kuniaki Yoshitomi; Ramesh K. Pokharel, Compact and Efficient WPT System to Embedded Receiver in Biological Tissues Using Cooperative DGS Resonators, IEEE Transactions on Circuits and Systems II: Express Briefs, 10.1109/TCSII.2021.3123954, 69, 3, 869 -873, 2022.03, [URL], This brief presents a compact and efficient resonance-shift insensitive wireless power transfer (WPT) system. This is possible by using a small electrical length defected ground structure (DGS) resonator, which is found effective against the resonance-shift phenomenon resulted from the higher permittivity of the tissue. Tissue has two undesired effects on a WPT system: (i) reduced coupled quality factor, and (ii) self-resonance shifting that leads to mismatch loss. So, the efficiency of a WPT system degrades in a tissue environment. Then, using the small electrical length DGS, we build a WPT transmitter (TX) using three cooperative DGS resonators to mitigate both issues. The fabricated prototype operates at 49 MHz in the air and tissue. This shows no change in operating frequency when the same receiver (Rx) is kept in the air or embedded inside tissues, which proves the effectiveness of the proposed cooperative DGS-WPT system against the resonance shift. The measured efficiency is 62% when the RX is embedded inside the tissue and is 68% in the air.. |
| 19. | Samundra K. Thapa; Ramesh K. Pokharel; Baichuan Chen; Adel Barakat, On-Chip Millimeter-Wave DGS Based Bandstop Filter in 0.18-μm CMOS Process , IEEE Transactions on Circuits and Systems II: Express Briefs, 10.1109/TCSII.2022.3158995, 69, 6, 2732 -2736, 2022.06, [URL], Defected Ground Structure (DGS) based on-chip bandstop filter (BSF) design is proposed for millimeter-wave applications. In the proposed structure, a capacitively loaded T-shape resonator is embedded in the original DGS resonator, which forms two high quality ( Q -) factor small loop resonators. Moreover, this structure, in combination with the feedline and series capacitor, independently realizes the position of two transmission poles: one at each side of the parallel resonance without increasing the layout size. The proposed BSF presents a sharp scattering (S-) parameter response due to the appearance of two transmission poles. As a result, the loaded Q -factor and negative group delay of the BSF are improved. The prototype of the proposed BSF is fabricated in 0.18- μm Complementary Metal-Oxide-Semiconductor (CMOS) process and measured. The measurement result shows a return loss of 1.78 dB at 53.2 GHz center stopband frequency with the negative group delay of 161 pS. The measurement results also agree well with the electromagnetic simulation results. Without pads, the active area of the prototyped BSF is only 0.024 mm2.. |
| 20. | Baichuan Chen; Ramesh K. Pokharel; Samundra K. Thapa; Nusrat Jahan; Adel Barakat, Design of 50-GHz Low Phase Noise VCO Employing Two-Branches DGS Resonator in 0.18- μm CMOS Technology, IEEE Microwave and Wireless Components Letters, https://doi.org/10.1109/LMWC.2022.3171405, 2022.05, [URL], This letter presents a V-band low phase noise voltage-controlled oscillator (VCO) design using a novel integrated two-branches defected ground structure (DGS) resonator in 0.18-μm complementary metal-oxide-semiconductor (CMOS) technology. The proposed DGS resonator is realized in the top metal layer (M6) which has not only a higher quality factor than its predecessors but is also effective to reduce the length of interconnects. The measured carrier frequency and phase noise are 49 GHz and -122.05 dBc/Hz (-102.58 dBc/Hz) at 10-MHz (1-MHz) offset frequencies, respectively. The VCO core consumes 5.5 mW of dc power from the dc supply, which results in a figure of merit (FoM) of -189 dBc/Hz. The proposed VCO using the two-branches DGS resonator may give an alternative low-cost solution for designing a high-performance VCO or frequency synthesizer at V-band and beyond.. |
| 21. | , [URL]. |
| 22. | Baichuan Chen, Samundra K. Thapa, Adel Barakat, Ramesh K. Pokharel, A W-Band 0.01 mm2 Cavity Resonator Employing Slot-Loaded Shielded Folded Ridged Quarter-Mode in CMOS Technology, IEEE Microwave and Wireless Components Letters, 10.1109/LMWC.2021.3122149, 32, 2, 113-116, 2022.02, [URL], This letter proposes a W -band compact cavity resonator for future applications of on-chip bandpass filters (BPFs), oscillators, phase shifters, and so on. To mitigate the leakage from the open sides of a folded ridged quarter-mode substrate integrated waveguide (SIW) cavity, shielding structures made of vias are employed. Two parallel inductive slots are etched on the top metal layer for further size reduction. Later, the one-port cavity is converted to a two-port cavity resonator and utilized in the design of W -band BPF. The proposed design is implemented in a commercial complementary metal-oxide-semiconductor (CMOS) technology, fabricated, and measured. The active size of the proposed cavity resonator is only 99 mu text{m},,boldsymbol {times },,99,,mu text{m} ( 0.054 boldsymbol {lambda }-{mathbf {g } },,{ boldsymbol {times } },,0.054{} boldsymbol {lambda }-{mathbf {g } } ), and the measured insertion loss ( vert S-{21}vert ) is 2.26 dB.. |
| 23. | Nusrat Jahan, Adel Barakat, Ramesh K. Pokharel, Design of Low Phase Noise VCO Considering C/L Ratio of LC Resonator in 0.18-μm CMOS Technology , IEEE Transactions on Circuits and Systems II: Express Briefs, 10.1109/TCSII.2021.3079309, 68, 12, 3513-3517, 2021.05, [URL], A voltage-controlled oscillator (VCO) is usually designed by maximizing the quality (Q-) factor of the LC-tank resonator to realize a low phase noise. For the same frequency, the ratio of C/L affects the loaded Q-factor (QL) and then phase noise of the VCO. This affect has not been considered so far in the design of VCO because the conventional on-chip spiral inductor cannot be optimized for C/L ratio. This brief first investigates the effects of C/L ratio on the phase noise, and a design methodology for optimized C/L ratio using defected ground structure (DGS) resonator is presented. Then, the resonators were further evaluated based on LgL-product simulation for a fixed Ibias. Employing the proposed resonator, a very low phase noise KUband VCO is designed and implemented in 0.18-lm CMOS technology. The measurement result shows that the proposed VCO has a phase noise of -110.77 dBc/Hz at 1 MHz offset of 17.5 GHz carrier frequency and a frequency tuning range of 8.7%. The VCO consumes 2.3 mW power, which results in a figure of merit (FoM) of -191.95 dB.. |
| 24. | Adel Barakat, Ramesh K. Pokharel, Shimaa Alshhawy, Kuniaki Yoshitomi, Shigeo Kawasaki, High isolation simultaneous wireless power and information transfer system using coexisting DGS resonators and Figure-8 Inductors, IEEE MTT-S International Microwave Symposium Digest, 10.1109/IMS30576.2020.9223866, 2020-August, 1172-1175, 2020.08, For the first time, we propose a combination of coupled defected ground structure (DGS) resonators for wireless power transfer and coupled Figure-8 inductors for information transfer. This combination allows the realization of a simultaneous compact wireless power and information transfer (WPIT). Each set of the DGS resonators and the Figure-8 inductors are located on the same plane. However, they show negligible coupling due to the coupling cancellation mechanism of the Figure-8 inductors. Hence, high isolation can be achieved between the power and information channels. A prototype is fabricated for operation at 50 MHz and 100 MHz. The overall area of the TX/RX is 30 mm × 30 mm and are separated by 14 mm. The measured efficiencies are 78% and 76% at 50 MHz and 100 MHz, respectively, and the isolation is more than 34 dB.. |
| 25. | Samundra K. Thapa, Baichuan Chen, Adel Barakat, Kuniaki Yoshitomi, Ramesh K. Pokharel, 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.. |
| 26. | 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, 2021.02, 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 imes15 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.. |
| 27. | Barakat, Adel; Yoshitomi, Kuniaki; Pokharel, Ramesh K., 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. |
| 28. | Elsaidy, Elsayed; Barakat, Adel; Abdel-Rahman, Adel B.; Allam, Ahmed; Pokharel, Ramesh K., Ultracompact CMOS 60-GHz Tapped-Line Combline BPF With Two Transmission Zeros Using Defected Ground Structures, IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY, 10.1109/TCPMT.2018.2861411, 8, 9, 1642-1649, 2018.09. |
| 29. | Nusrat Jahan, Siti Amalina Enche Ab Rahim, Hamed Mosalam, Adel Barakat, Takana Kaho, Ramesh K. Pokharel,, 22-GHz-Band Oscillator Using Integrated H-Shape Defected Ground Structure Resonator in 0.18-mu m CMOS Technology, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, 10.1109/LMWC.2018.2801031, 28, 3, 233-235, 2018.03, A novel 22-GHz-band oscillator using an integrated defected ground structure (DGS) resonator is presented for quasimillimeter waveband applications. The DGS is etched on the first metal layer (M1) below a 50-Ω microstrip line on the top metal layer (M6) of 0.18-μm one-poly six-metal (1P6M) complementary metal-oxide-semiconductor (CMOS) technology. The proposed oscillator is fabricated using 0.18-μm CMOS technology, and the measured carrier frequency and phase noise are 22.88 GHz and -129.21 dBc/Hz (-108.05 dBc/Hz) at 10-MHz (1 MHz) offset frequency, respectively. The power dissipation is 6 mW that results in a figure of merit to be -188.8 dB. As the DGS resonator could be designed at any high frequency, it may give an alternative design approach of high performance voltage controlled oscillator and frequency synthesizers at K-band and beyond, thus alleviates the problem of self-resonance that a spiral inductor usually encounters at higher frequency.. |
| 30. | 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, 10.1109/TCSII.2017.2740401, 64, 12, 1372-1376, 2017.12, 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).. |
| 31. | Fairus Tahar, Redzuan Saad, Adel Barakat, Ramesh Kumar Pokharel, 1.06 FoM and Compact Wireless Power Transfer System Using Rectangular Defected Ground Structure Resonators, IEEE Microwave and Wireless Components Letters, 10.1109/LMWC.2017.2750032, 27, 11, 1025-1025, 2017.11, [URL], This letter proposes a wireless power transfer (WPT) system using coplanar waveguide fed rectangular defected ground structure (DGS) resonators. One of the advantages of rectangular DGS resonator is that it has higher quality (Q-) and coupling (K-) factor compared to the H-shape or semi-H-shape DGS resonators. When two DGS resonators are coupled back-to-back, it transforms to a bandpass filter with tight coupling, resulting in the transfer of power wirelessly. The fabricated WPT system of size 35.8 mm×20 mm achieves, for the first time, a figure of merit of more than one at a WPT distance from 40 to 44 mm.. |
| 32. | Anwer S. Abd El-Hameed, Adel Barakat, Adel B. Abdel-Rahman, Ahmed Allam, Ramesh Kumar Pokharel, Ultracompact 60-GHz CMOS BPF Employing Broadside-Coupled Open-Loop Resonators, IEEE Microwave and Wireless Components Letters, 27, 9, 818-820, 2017.09, [URL], This letter presents a 60-GHz ultracompact on-chip bandpass filter (BPF). The designed filter is based on a unique structure, which consists of two overlapped broadside-coupled open-loop resonators, achieving a high level of miniaturization. Moreover, each resonator is loaded by a metal-insulator-metal capacitor to get further miniaturization. Defected ground structure pattern is constructed under the filter structure to enhance the insertion loss (IL). This BPF is designed and fabricated using a standard 0.18-μm complementary metal-oxide-semiconductor technology for millimeter-wave applications. The fabricated BPF chip size is 240 × 225 μm2 including pads. The measured results agree well with the simulation ones and show that the BPF has an IL of 3.3 dB at 59.5-GHz center frequency, and a bandwidth of 12.9 GHz.. |
| 33. | Nusrat Jahan, Siti Amalina Enche Ab Rahim, Adel Barakat, Takana Kaho, Ramesh Kumar Pokharel, Design and Application of Virtual Inductance of Square-Shaped Defected Ground Structure in 0.18- μm CMOS Technology, IEEE Journal of the Electron Devices Society, 10.1109/JEDS.2017.2728686, 5, 5, 2168-6734, 2017.07, [URL], This paper investigates a possibility of application of a virtual inductor realized by an integrated defected ground structure (DGS) to design a front-end circuit in CMOS technology. Two types of DGS are analyzed and found that the inductance realized by a square-shaped DGS achieves smaller size and higher quality factor than an H-shaped DGS. Then, a 15-GHz low phase noise voltage-controlled oscillator (VCO) employing the proposed square-shaped DGS in 0.18-μm 1P6M CMOS technology is designed. The fabricated VCO operates from 15.2 to 16.12 GHz and consumes 5-mW power. The measured phase noise is -132.08 dBc/Hz at 10-MHz offset frequency, and this results in the figure of merit (FoM) and FoM taking account of the area to be 189.1 and 199.9 dB, respectively.. |
| 34. | Adel Barakat, Ahmed Allam, Hala Elsadek, Adel B. Abdel-Rahman, Ramesh Kumar Pokharel, Americ Bisognin, Cyril Luxey, 60 GHz CMOS Circular Patch Antenna on Chip, Microwave Journal, 60, 2, 90-100, 2017.02. |
| 35. | Sherif Hekal, Adel B. Abdel-Rahman, Hongting Jia, Ahmed Allam, Adel Barakat, Ramesh Kumar Pokharel, A Novel Technique for Compact Size Wireless Power Transfer Applications Using Defected Ground Structures, IEEE Transactions on Microwave Theory and Techniques, http://dx.doi.org/10.1109/TMTT.2016.2618919, 65, 1, 591-599, 2017.02, [URL], This paper presents a novel technique for high efficiency and compact size wireless power transfer (WPT) systems. These systems are based on coupled defected ground structure (DGS) resonators. Two types of DGSs (H-shape and semi-H-shape) are proposed. The semi-H-shaped DGS realizes larger inductance value, and this results in higher WPT efficiency. Instead of using an inductive-fed resonant coupling, we propose capacitive-fed resonant coupling, which reduces the design complexity and enhances the efficiency further. The DGS resonator of both the systems is loaded by chip capacitors for miniaturization. An equivalent circuit using approximate quasi-static modeling is extracted. An analytical design procedure is developed to calculate the optimum design parameters for the proposed WPT systems. The optimized structures are fabricated and measured. The simulation and measurement results are in good agreement. The proposed semi-H-shaped DGS WPT system has a peak efficiency of 73% at a transmission distance of 25 mm. In turn, the figure of merit becomes the highest among the WPT systems proposed so far.. |
| 36. | Adel Barakat, Sherif Hekal, Ramesh K. Pokharel, Simple design approach for asymmetric resonant inductive coupled WPT systems using J-inverters, Asia-Pacific Microwave Conference Proceedings, APMC, 10.1109/APMC.2016.7931382, 2017.05, This paper presents a simple and precise design method for asymmetric resonant inductive coupled wireless power transfer (WPT) systems without the involvement of circuit or electromagnetic (EM) simulators. The design method is based on the generalized second-order band-pass filter (BPF). First, the values of the BPF's J-inverters are computed based on the mutual coupling between the transmitter (TX) and the receiver (RX). Then, the required components are extracted from the J-inverters values. We achieved good agreements between the analytical design procedure, the circuit and the EM simulations, and the measurements. The measured efficiency is 75% at a transmission distance of 38 mm, and the sizes of the TX and RX are 50×50 mm2 and 30×30 mm2, respectively.. |
| 37. | Sherif Hekal, Adel B. Abdel-Rahman, Ahemd Allam, Hongting Jia, Adel Barakat, Ramesh Kumar Pokharel, Asymmetric Wireless Power Transfer Systems Using Coupled DGS Resonators, IEICE Electronics Express, http://doi.org/10.1587/elex.13.20160591, 13, 21, 20160591, 2016.11, [URL], his paper presents a new design for wireless power transfer (WPT) systems using asymmetric structures for the transmitter (TX) and the receiver (RX), and the TX/RX are constructed using spiral-strips defected ground structure (DGS) resonators. The proposed spiral-strips DGS resonator overcome the problem of low self-inductance that encountered by H-shape DGS resonator in [1, 2], so that the proposed WPT system that employs the proposed spiral-strips DGS resonators has better efficiency and higher power transmission distance. Design methodology of the proposed WPT system are formulated and fabricated. The measurement results show a WPT efficiency of 78% at a transmission distance of 40 mm with the TX and RX areas of 50 x 50 mm2 and 30 x 30 mm2, respectively.. |
| 38. | Sherif Hekal, Adel B. Abdel-Rahman, Hongting Jia, Ahmed Allam, Adel Barakat, Takano Kaho, Ramesh Kumar Pokharel, Compact Wireless Power Transfer System Using Defected Ground Bandstop Filters, IEEE Microwave and Wireless Components Letters, 10.1109/LMWC.2016.2601300, 26, 10, 2016.10, [URL], This letter presents a new design for wireless power transfer (WPT) applications using two coupled bandstop filters (BSF). The stopband is created by etching a defected structure on the ground plane, and the power is transferred through electromagnetic (EM) resonant coupling when the two BSFs are coupled back to back. An equivalent circuit model of the proposed WPT system is extracted. Verification of the proposed design is performed through a good agreement between the EM simulation, circuit simulation, and measurement results. The proposed system achieves a measured WPT efficiency of 68.5% at a transmission distance of 50 mm using a compact size (40 x 40mm²). This results in a figure of merit of the proposed system to be 0.856 and the ratio of transmission distance/lateral size is 1.25 that is the highest among the WPT systems proposed so far using planar structures.. |
| 39. | Nessim Mahmoud, Adel Barakat, Adel B. Abdel-Rahman, Ahmed Allam, Ramesh Kumar Pokharel, Compact Size On-Chip 60 GHz H-Shaped Resonator BPF, IEEE Microwave and Wireless Components Letters, 10.1109/LMWC.2016.2597219, 26, 9, 681-683, 2016.09, [URL], In this letter, we propose a compact size, small insertion loss 60 GHz on-chip H-shaped resonator bandpass filter (BPF) using 0.18 μm standard CMOS technology. The BPF Size is miniaturized by loading the H-shaped resonator with metal-insulator-metal capacitors at its ends. Besides, two defected ground structure cells are etched under the coupled lines to improve the filter insertion loss. Furthermore, selectivity is enhanced by loading the center of the H-shaped resonator with two unsymmetrical meander line stubs generating two transmission zeroes at 50 and 70 GHz. The fabricated BPF chip size is 240×650 μm2. The measured insertion loss and fractional bandwidth are 2.5 dB at 60 GHz and 21%, respectively.. |
| 40. | Siti Amalina Enche Ab Bahim, Adel Barakat, Ramesh Kumar Pokharel, Improving the Quality Factor of Inductor in Si-Substrate by Introducing Fully Depleted PN-junctions, Research Reports on Information Science and Electrical Engineering of Kyushu University, 21, 2, 45-48, 2016.07, [URL], This paper presents a novel technique to improve the quality factor (Q-factor) of a standard inductor in Si-substrate without post-processing. The proposed method employs a distributed grid of N-well in the Psubstrate beneath the inductor. This will create a layer of PN junctions. The width of the N-well is chosen wisely so that full depletion occurs in every PN junction, forming a large depleted area which has high resistivity, thus reduces the substrate loss and increases Q-factor of the inductor. An example of the proposed idea is illustrated using a 1nH inductor in 0.18 mm CMOS technology. In this paper, High-Frequency Simulation Structure (HFSS)1) based on finite element method is used for simulation. As expected, the electromagnetic (EM) simulation shows that the total equivalent resistance of the inductor decreases, resulting in the improvement of its Q-factor by 9%. Finally, the improved inductor is used to design a 5GHz cross-coupled CMOS LC oscillator, which results in an improvement of 2.1dBc/Hz of phase noise at 10 kHz offset frequency.. |
| 41. | A. Barakat, R. Pokharel, T. Kaho, 60 GHz on-chip mixed coupled BPF with H-shaped defected ground structures, Electronics Letters, 10.1049/el.2015.4465, 52, 7, 533-535, 2016.04, A 60 GHz miniaturised, low loss on-chip bandpass filter (BPF) based on open-loop resonators is presented. Overlapping of the BPF's resonators leads to miniaturisation and introduces a mixed coupling con-figuration. Moreover, its resonators are folded to minimise the size and the insertion loss (IL). H-shaped defected ground structures are also used to reduce IL and to improve the out of band rejection. The measured IL, return loss, centre frequency, and bandwidth are 2.85 dB, 18 dB, 59 GHz and 15.5 GHz with a chip size of 368 × 262 μm2 including pads.. |
| 42. | Adel Barakat, Muhammad Hanif, Ramesh Kumar Pokharel, Miniaturized Low loss 60GHz CMOS Mixed Coupled BPF with Patterned Ground shield, Microwave and Optical Technology letters, 10.1002/mop.29650, 58, 3, 697-699, 2016.03, [URL], This letter presents a miniaturized low loss mixed coupled on-chip band-pass filter using overlapped open loop ring resonators and using patterned ground shields. The fabricated prototype shows an insertion loss of 3.7 dB, a return loss > 20 dB, a bandwidth of 13 GHz, and a chip size of 700 μm × 450 μm. . |
| 43. | Adel Barakat, Ramesh Kumar Pokharel, Takana Kaho, 60 GHz on-chip mixed coupled BPF with H-shaped defected ground structures, Electronics Letters, 10.1049/el.2015.4465, 2016.03, [URL], This letter presents a 60 GHz miniaturized, low loss on-chip bandpass filter (BPF) based on open-loop resonators (OLR). Overlapping of the BPF’s resonators leads to miniaturization and introduces a mixed coupling configuration. Moreover, its resonators are folded to minimize the size and the insertion loss. H-shaped defected ground structures are also used to reduce insertion loss and to improve the out of band rejection. The measured insertion loss, return loss, centre frequency, and bandwidth are 2.85 dB, 18 dB, 59 GHz and 15.5 GHz with a chip size of 368 × 262 um2 including pads.. |
| 44. | Adel Barakat, Ahmed Allam, Hala Elsadek, Adel Abdelrahman, Ramesh Kumar Pokharel, Takana Kaho, Improved gain 60 GHz CMOS antenna with N-well grid, IEICE Electronics Express, 10.1587/elex.13.20151115, 13, 5, 2016.03, [URL], This paper presents a novel technique to enhance Antenna-on-Chip (AoC) gain by introducing a high resistivity layer below it. Instead of using the costly ion implantation method to increase resistivity, the N-well that is available in the standard CMOS process is used. A distributed grid structure of N-well on P-type substrate is designed such that the P and N-type semiconductors are fully depleted forming a layer with high resistivity. By an electromagnetic simulation, the using depletion layers enhance the antenna gain and radiation efficiency without increasing the occupied area. The simulated and measured |S11| are in fair agreement. The measured gain is –1.5 dBi at 66 GHz.. |
| 45. | Adel Barakat, Muhammad Hanif, Ramesh K. Pokharel, Miniaturized low loss 60 GHz CMOS mixed coupled BPF with patterned ground shield, Microwave and Optical Technology Letters, 10.1002/mop.29650, 58, 3, 697-699, 2016.03, This letter presents a miniaturized low loss mixed coupled on-chip band-pass filter using overlapped open loop ring resonators and using patterned ground shields. The fabricated prototype shows an insertion loss of 3.7 dB, a return loss > 20 dB, a bandwidth of 13 GHz, and a chip size of 700 μm × 450 μm.. |
| 46. | Adel Barakat, Ahmed Allam, Hala Elsadek, Adel B. Abdel-Rahman, Ramesh K. Pokharel, Takana Kaho, Improved gain 60GHz CMOS antenna with N-well grid, IEICE Electronics Express, 10.1587/elex.13.20151115, 13, 5, 2016.02, This paper presents a novel technique to enhance Antenna-on- Chip gain by introducing a high resistivity layer below it. Instead of using the costly ion implantation method to increase resistivity, the N-well that is available in the standard CMOS process is used. A distributed grid structure of N-well on P-type substrate is designed such that the P and N semiconductors types are fully depleted forming a layer with high resistivity. By an electromagnetic simulation, the using depletion layers enhance the antenna gain and radiation efficiency without increasing the occupied area. The simulated and measured |S11| are in fair agreement. The measured gain is −1.5 dBi at 66 GHz.. |
| 47. | Anwer S.Abd El-Hameed, Adel Barakat, Adel B. Abdel-Rahman, Ahmed Allam, Ramesh K. Pokharel, A60-GHz double-Y balun-fed on-chip Vivaldi antenna with improved gain, Proceedings of the International Conference on Microelectronics, ICM, 10.1109/ICM.2015.7438050, 2016-March, 307-310, 2016.03, A60-GHz double-Y balun-fed exponential tapered slot Vivaldi antenna-on-chip (AOC) is designed using standard 0.18μm six metal-layer CMOS technology. A double-Y balun feeding structure is used to make transition from coplanar to slot line. Three methods are developed for improving antenna radiation properties. First, an impeding longitudinal rectangular slits on the backed edge of the Vivaldi antenna are used to enhance the gain. Second, loading circular metal-strips are used as additional director into the slot area of Vivaldi antenna on M6. Finally, a planar arc reflector is used to inhibit the back lobe, contributing to the enhancement of gain and efficiency. The overall antenna size is very compact and equal to 700um × 940μm. The influence of the antenna position on the radiation properties is also studied. The proposed antenna offers a simulated peak gain and a radiation efficiency of-1.9 dBi and 24%, respectively.. |
| 48. | Nessim Mahmoud, Anwer S.Abd El-Hameed, Adel Barakat, Adel B. Abdel-Rahman, Ahmed Allam, Ramesh K. Pokharel, Performance enhancement of 0.18μm CMOS on chip bandpass filters using H-shaped parasitic element, Proceedings of the International Conference on Microelectronics, ICM, 10.1109/ICM.2015.7438049, 2016-March, 303-306, 2016.03, A design of an improved open loop resonator on-chip bandpass filter for 60 GHz millimeter-wave applications using 0.18 μm CMOS technology is presented. The proposed on-chip BPF employs H-shaped parasitic structure inserted between two open loop coupled resonator. The adoption of a two open loop coupled resonators BPF and the utilization of two transmissions zero located at 48 and 80 GHz permit a compact size and high selectivity of the BPF. In addition, the parasitic H-shaped structure increases the capacitance between the two resonators, which enables a further reduction of the physical length of the filter and enhances the coupling between the resonators which improve the filter insertion loss. The proposed BPF has a center frequency of 60 GHz, an insertion loss of-2 dB, a 3dB band width of 13 GHz, and a core size 160 × 480 μm2 with total chip size 680 × 280 μm2 (including bonding pads).. |
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