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A Wideband On-Chip Directional Coupler Using a Negative Capacitance Circuit
Doan, Nhut-Tan,Lai, Ngoc-Duy-Hien,Kim, Hyoungsoo,Yoon, Sang-Woong IEEE 2019 IEEE transactions on microwave theory and techniqu Vol.67 No.1
<P>We propose a wideband lumped element directional coupler using lossy negative capacitance (NCAP). NCAP provides a broadband resonance effect combined with passive inductors and capacitors in a circuit, enabling the coupler to exhibit wideband directivity performance. In addition, a 3-dB loss in the NCAP enhanced the bandwidth at the expense of the transmission gain, which decreased by only 0.3 dB. The proposed coupler was implemented in the IBM 7RF 180-nm CMOS technology. The size of the core chip is <TEX>$1180\,\,\mu \text {m} \times 570\,\,\mu \text{m}$</TEX>. The designed NCAP provides a capacitance of −13 pF using a supply voltage of 2.7 V and a current of 9.6 mA. The coupling was designed to be −10 dB at the center frequency of 1 GHz. The bandwidth was defined by the frequency range, which exhibited a directivity of more than 30 dB. The S-parameter measurements showed an absolute bandwidth ranging from 0.86 to 1.12 GHz, and a fractional bandwidth of 26%. In the bandwidth, the coupling had a 0.5-dB variation, the transmission loss was smaller than 2.14 dB, and the noise figures were 1.8–2.5 dB.</P>
Tan Luong Van,Trong Huan Nguyen,Nhut Minh Ho,Xuan Nam Doan,Thanh Hai Nguyen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a control strategy of the voltage compensation based on a nine switch converter (NSC) to enhance a low-voltage ride-through (LVRT) capability for a doubly fed induction generator (DFIG) wind turbine system. The nine switch converter connected to a stator-side of the DFIG can enable to compensate the voltage response of the system during the grid faults. For series voltage source converter (VSC), a control algorithm consisting of dual voltage controllers is implemented for the two sequence components in the dq synchronous reference frame. As for shunt voltage source converter (VSC), a control algorithm is carried out in the dq reference frame and incorporates both an inner current control loop and an outer voltage control loop. The effectiveness of the proposed methods is verified by the simulation results for the 2 [MW]-DFIG wind turbine system under unbalanced grid voltage conditions.
Retrodirective RF System for Wireless Power Transfer
Wan-Su Kim,Nhut-Tan Doan,Tan-Binh Ngo,Sang-Woong Yoon 대한전자공학회 2019 대한전자공학회 학술대회 Vol.2019 No.6
This paper presents the overall wireless power transfer RF system with circulator for phase conjugating Retro-directive array (RDA). This work consists of two main parts. The former presents the Retrodirective System & Feed-forward-Cancellation (FFC) part while focus on beam of 1 x 4 RDA system & the improved transmitter (Tx) to receiver (Rx) isolation. The latter includes design of integrated circuits for power amplifier and drive amplifier. This system operates with Tx frequency of 2.4 GHz and Rx frequency of 2.5 GHz. The beamforming accuracy and minimum sensitivity of the RF system depends on the Tx-Rx isolation characteristic of the circulator. Hence, to enhance the isolation, FFC technique is incorporated. The isolation performance at 2.4 GHz and 2.5 GHz is improved by 18 dB and 21 dB, respectively, in this work.
A Broadband On-chip Power Divider up to W-band with Three-dimensional Three-coupled Lines
Trung-Sinh Dang,Nhut-Tan Doan,Byung-Sung Kim,Nam-Yoon Kim,Chang-Woo Kim,Sang-Woong Yoon 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.1
A state-of-the-art broadband on-chip power divider in millimeter-wave up to 103 GHz is presented. The power divider employs novel three-dimensional (3-D) three-coupled lines to achieve the desired mode impedances for an extremely wideband characteristic. The power divider was implemented in TSMC 180 nm RF CMOS IC technology with six metal layers. Measurements show the absolute bandwidth from 11 to 103 GHz with matching conditions of all of the ports and isolation between two outputs of less than -10 dB. The fractional bandwidth is 161.4%. The insertion loss is between 1.2 and 7.9 dB across the overall bandwidth. The core size of the power divider is 0.18 mm × 0.68 mm.