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A 95-dB linear low-power variable gain amplifier
Quoc-Hoang Duong,Quan Le,Chang-Wan Kim,Sang-Gug Lee IEEE 2006 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS PART 1 R Vol.53 No.8
<P>An all-CMOS variable gain amplifier (VGA) that adopts a new approximated exponential equation is presented. The proposed VGA is characterized by a wide range of gain variation, temperature-independence gain characteristic, low-power consumption, small chip size, and controllable dynamic gain range. The two-stage VGA is fabricated in 0.18-mum CMOS technology and shows the maximum gain variation of more than 95 dB and a 90-dB linear range with linearity error of less than plusmn 1 dB. The range of gain variation can be controlled from 68 to 95 dB. The P1dB varies from - 48 to - 17 dBm, and the 3-dB bandwidth is from 32 MHz (at maximum gain of 43 dB) to 1.05 GHz (at minimum gain of - 52 dB). The VGA dissipates less than 3.6 mA from 1.8-V supply while occupying 0.4 mm<SUP>2</SUP> of chip area excluding bondpads</P>
A 0.13 μm CMOS UWB RF Transmitter with an On-Chip T/R Switch
Chang-Wan Kim,Quoc-Hoang Duong,Seung-Sik Lee,Sang-Gug Lee 한국전자통신연구원 2008 ETRI Journal Vol.30 No.4
This paper presents a fully integrated 0.13 μm CMOS MB-OFDM UWB transmitter chain (mode 1). The proposed transmitter consists of a low-pass filter, a variable gain amplifier, a voltage-to-current converter, an I/Q up-mixer, a differential-to-single-ended converter, a driver amplifier, and a transmit/receive (T/R) switch. The proposed T/R switch shows an insertion loss of less than 1.5 dB and a Tx/Rx port isolation of more than 27 dB over a 3 GHz to 5 GHz frequency range. All RF/analog circuits have been designed to achieve high linearity and wide bandwidth. The proposed transmitter is implemented using IBM 0.13 μm CMOS technology. The fabricated transmitter shows a -3 dB bandwidth of 550 MHz at each sub-band center frequency with gain flatness less than 1.5 dB. It also shows a power gain of 0.5 dB, a maximum output power level of 0 dBm, and output IP3 of +9.3 dBm. It consumes a total of 54 mA from a 1.5 V supply.
Trung-Kien Nguyen,Viet-Hoang Le,Quoc-Hoang Duong,Seok-Kyun Han,Sang-Gug Lee,Nak-Seon Seong,Nae-Soo Kim,Cheol-Sig Pyo 한국전자통신연구원 2008 ETRI Journal Vol.30 No.1
This paper presents the experimental results of a lowpower low-cost RF transceiver for the 915 MHz band IEEE 802.15.4b standard. Low power and low cost are achieved by optimizing the transceiver architecture and circuit design techniques. The proposed transceiver shares the analog baseband section for both receive and transmit modes to reduce the silicon area. The RF transceiver consumes 11.2 mA in receive mode and 22.5 mA in transmit mode under a supply voltage of 1.8 V, in which 5 mA of quadrature voltage controlled oscillator is included. The proposed transceiver is implemented in a 0.18 μm CMOS process and occupies 10 mm2 of silicon area.
Kinematic Modeling of Spherical Rolling Robots with a Three-Omnidirectional-Wheel Drive Mechanism
Pham Dinh Ba,Quoc Dong Hoang,Soon-Geul Lee,Thanh Hai Nguyen,Xuan Quang Duong,Boi Chau Tham 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10
The spherical rolling robot (SRR) is an underactuated system with nonholonomic constraints. The proposed drive mechanism for the mobile robot is comprised of three omnidirectional wheels to make the omnidirectional movement of the robot on the floor. The kinematic model of the SRR is derived via nonholonomic constraints. Numerical simulation is analyzed. Results indicate that the robot can track the desired trajectory and maintain its balance stably at the same time.
Thanh-Tung Duonga,Phan Huy Hoang,Luu Thi Nhan,Luong Van Duong,Man Hoai Nam,Le Quoc Tuan 한국물리학회 2019 Current Applied Physics Vol.19 No.11
Large-grain-size and void-free CH3NH3PbI3 films with bilayer structure are fabricated by spin-coating a PbI2 layer onto a mesoporous TiO2 layer and sequentially spraying CH3NH3I (methylammonium iodide, MAI) multilayers. The sprayer is controlled by a homemade three-axis computer numerical control machine; thus, the substrates are coated by successive parallel passes achieved by moving the nozzle. Spray deposition at the optimal spray rate and substrate temperature produces a large-grain-size and void-free methylammonium lead iodide (MAPbI3) bilayer structure. The mesoporous TiO2 layer plays an important role in electron transport by preventing the return of electrons to the perovskite layer and decreasing the contact resistance at the perovskite/ compact TiO2/fluorine tin oxide interface. When the films are incorporated into a solar cell device with a conductive carbon counter electrode, a maximum power conversion efficiency of 10.58% is realised.
Tran Dang Thanh,Phan, T. L.,Phung Quoc Thanh,Hoang Nam Nhat,Duong Anh Tuan,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.6
<P>This paper presents a detailed study on the Co-doping influence on the electrical and magnetotransport properties of La0.7Ca0.3Mn1-xCoxO3(x = 0.09-0.17) prepared by solid-state reaction. Magnetic measurements versus temperature revealed a gradual decrease of the magnetization (M) and Curie temperature (T-C) with increasing Co concentration (x). The T-C values vary from 194 to 159 K as changing x from 0.09 to 0.17, respectively. H/M versus M-2 performances around T-C prove the x = 0.09 sample undergoing a first-order magnetic phase transition (FOMT) while the samples with x >= 0.11 undergo a second-order magnetic phase transition (SOMT). The other with x = 0.10 is considered as a threshold concentration of the FOMT-SOMT transformation. Considering temperature dependences of resistivity, rho(T), in the presence and absence of the magnetic field, the samples (excepting for x = 0.17) exhibit a metal-insulator transition at T (P) = 60-160 K, which shifts toward lower temperatures with increasing x. In the metallic-ferromagnetic region, the rho(T) data are well fitted to a power function rho(T) = rho(0) + rho(2) T-2 + rho(4.5) T-4.5. This indicates electron-electron and electron-magnon scattering processes are dominant at temperatures T < T (P). In addition, the conduction data at temperatures T > theta(D)/2 (theta(D) is the Debye temperature) and T (P) < T < theta(D)/2 obey the small-polaron and variable-range hopping models, respectively. The values of activation energy E-p, and density of states at the Fermi level N(E-F) were accordingly determined. Here, N(E-F) increases while E-p decreases when an external magnetic field is applied. We also have found that N(E-F) increases when materials transfer from the FOMT to the SOMT, and N(E-F) value becomes smallest for the sample having the coexistence of the FOMT and SOMT (i.e., x = 0.10).</P>
Thu Dang Anh Phan,Bao Gia Phung,Tu Thanh Duong,Vu Anh Hoang,Dat Quoc Ngo,Nguyen Dinh The Trinh,Tung Thanh Tran 대한병리학회 2021 Journal of Pathology and Translational Medicine Vol.55 No.2
Background: Langerhans cell histiocytosis (LCH) is more common in children than adults and involves many organs. In children, the BRAF V600E mutation is associated with recurrent and high-risk LCH. Methods: We collected paraffin blocks of 94 pediatric LCH patients to detect BRAF V600E mutation by sequencing. The relationship between BRAF V600E status and clinicopathological parameters were also critically analyzed. Results: BRAF V600E mutation exon 15 was detected in 45 cases (47.9%). Multiple systems LCH showed a significantly higher BRAF V600E mutation rate than a single system (p = .001). No statistical significance was evident for other clinical characteristics such as age, sex, location, risk organs involvement, and CD1a expression. Conclusions: In Vietnamese LCH children, the proportion of BRAF V600E mutational status was relatively high and related to multiple systems.