• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.4
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• pp.282-285
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• 2019

A 100-nm gate-length metamorphic high electron mobility transistor(mHEMT) with a T-shaped gate was fabricated using a two-step gate recess and characterized for DC and microwave performance. The mHEMT device exhibited DC output characteristics having drain current($I_{dss}$), an extrinsic transconductance($g_m$) of 1,090 mS/mm and a threshold voltage($V_{th}$) of -0.65 V. The $f_T$ and $f_{max}$ obtained for the 100-nm mHEMT device were 190 and 260 GHz, respectively. The developed mHEMT will be applied in fabricating W-band monolithic microwave integrated circuits(MMICs).

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2070-2078
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• 2014

In this work, the frequency response of gate-all-around (GAA) Ge/GaAs heterojunction tunneling field-effect transistor (TFET) with hetero-gate-dielectric (HGD) and pnpn channel doping profile has been analysed by technology computer-aided design (TCAD) device-circuit mixed-mode simulations, with comparison studies among ppn, pnpn, and HGD pnpn TFET devices. By recursive tracing of voltage transfer curves (VTCs) of a common-source (CS) amplifier based on the HGD pnpn TFET, the operation point (Q-point) was obtained at $V_{DS}=1V$, where the maximum available output swing was acquired without waveform distortion. The slope of VTC of the amplifier was 9.21 V/V (19.4 dB), which mainly resulted from the ponderable direct-current (DC) characteristics of HGD pnpn TFET. Along with the DC performances, frequency response with a small-signal voltage of 10 mV has been closely investigated in terms of voltage gain ($A_v$), unit-gain frequency ($f_{unity}$), and cut-off frequency ($f_T$). The Ge/GaAs HGD pnpn TFET demonstrated $A_v=19.4dB$, $f_{unity}=10THz$, $f_T=0.487$ THz and $f_{max}=18THz$.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.16-19
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• 2000

DC and low frequency noise characteristics of InGaP/InGaAs pseudomorphic HEMTs (p-HEMTs) grown by compound source MBE are investigated for temperature range of 150K to 370K. Equivalent input noise spectra( $S_{iv}$ ) were measured as a function of frequency and temperature. $S_{iv}$ was measured to be 3.4 $\times$ 10$^{-12}$ $V^2$/ Hz at 1kHz for 1.3 X 50${\mu}{\textrm}{m}$$^2$InGaP/InGaAs p-HEMT at room temperature. Measurements of the low-frequency noise spectra of the p-HEMT as a function of temperature show that the trap with an activation energy level around 0.589 eV is a dominant trap that accounts for the low-frequency noise behavior of the device. The normalized extrinsic gm frequency dispersion of the p-HEMT. was as low as 2.5％ at room temperature, indicating that the device has well-behaved low-frequency noise characteristics. Sub-micron (0.25 $\times$ 50${\mu}{\textrm}{m}$$^2$) gate p-HEMT showed $f_{T}$ and $f_{max}$ of 40GHz and 108GHz, respectively.y.y.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.402-408
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• 2017

In this paper, we analyzed the frequency characteristics of hexagonal spiral thin-film inductor based on non-contact AC coupling for wireless signal transmission. We compared and analyzed the frequency characteristics of the rectangular spiral inductor and the hexagonal spiral inductor according to the number of turns, the line width and the line spacing of the conductor. Hexagonal spiral inductor has more number of turns to has the same inductance as rectangular spiral inductor, but the overall length of the conductors is shortened. This reduces the self inductance and increases the mutual inductance so that the overall inductance can have the same value. Also, since the overall length of the conductor is shortened and the magnetic resistance is reduced, the quality factor and the self-resonant frequency performance can be secured. The proposed hexagonal spiral thin-film inductor has the inductance of 3.54nH at 2GHz, the quality factor of max 14.00 at 5.0GHz and the self-resonant frequency at about 11.3GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.78-83
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• 2014

This paper suggest an effective idea to implement an low area multi-mode one dimension transform block of HEVC(High Efficiency Video Coding). The time consuming multiplier path is designed to operate on low frequency. Normal multipliers dealing with variable operands are replaced with smaller constant multipliers which do the product with constant coefficient and variable only using shifters and adders. This scheme increases total multiplier counts but entire areas are reduced owing to smaller area of constant multiplier. Idle cycles caused by doubled multipliers enable to use multi-cycle paths on the cycle eating multiplier data path. Operating frequency is lowered by multi-cycle path but total throughput is maintained. This structure is implemented with TSMC 0.18 CMOS process library, and operated on 186MHz frequency to process a 4k($3840{\times}2160$) image. Max operating frequency is 300MHz.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.623-624
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• 2006

In this paper, we introduce the design and fabrication of V-band power amplifier MMIC with excellent gain-flatness for IEEE 802.15.3c WPAN system. The V-band power amplifier was designed using ETRI' $0.12{\mu}m$ PHEMT process. The PHEMT shows a peak transconductance ($G_{m,peak}$) of 500 mS/mm, a threshold voltage of -1.2 V, and a drain saturation current of 49 mA for 2 fingers and $100{\mu}m$ total gate width (2f100) at $V_{ds}$=2 V. The RF characteristics of the PHEMT show a cutoff frequency, $f_T$, of 97 GHz, and a maximum oscillation frequency, $f_{max}$, of 166 GHz. The gains of the each stages of the amplifier were modified to have broadband characteristics of input/output matching for first and fourth stages and get more gains of edge regions of operating frequency range for second and third stages in order to make the gain-flatness of the amplifier excellently for wide band. The performances of the fabricated 60 GHz power amplifier MMIC are operating frequency of $56.25{\sim}62.25\;GHz$, bandwidth of 6 GHz, small signal gain ($S_{21}$) of $16.5{\sim}17.2\;dB$, gain flatness of 0.7 dB, an input reflection coefficient ($S_{11}$) of $-16{\sim}-9\;dB$, output reflection coefficient ($S_{22}$) of $-16{\sim}-4\;dB$ and output power ($P_{out}$) of 13 dBm. The chip size of the amplifier MMIC was $3.7{\times}1.4mm^2$.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.1
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• pp.11-17
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• 2013

A design method to achieve multiple band-rejection characteristics in a wideband circular slot antenna is presented. First, a wideband circular slot antenna fed by a coplanar waveguide is designed to operate in the frequency range between 2.3 and 11GHz, which covers WLAN, WiBro, WiMAX, and UWB frequency bands. Next, resonant frequency variations of rejection bands are examined with respect to different slot locations and lengths when slots are inserted on the ground conductor and the circular patch of the antenna. When arc-shaped slots are placed close to the circular transition from a feeding part, multiple notch bands are obtained. In this case, a half of the guided wavelength of the first notch band corresponds to the slot length and other notch bands are integer-multiple of the first band. Single notch band can be obtained when the slot is located off the transition part. Based on this study, a wideband circular slot antenna with five band-rejection frequency bands at 2.45, 3.5, 4.9, 7.35, and 9.8GHz is designed and fabricated. The first arc-shaped slots are located in the ground conductor close to the circular transition from a feeding part to generate notch bands at 2.45, 4.9, 7.35, and 9.8GHz, while the second slot for 3.73 GHz is placed on top side in the circular patch. The proposed design method is validated by good agreement between the simulated and measured results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1167-1176
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• 2009

In This Paper, we introduce an efficient IFFT design technique named for transmitter of OFDM (Orthogonal Frequency Division Multiplexing) system. In OFDM system, a cyclic prefix is inserted in forepart of OFDM symbol to prevent ICI(Inter-channel Interference) and ISI (Inter-symbol Interference). Attaching cyclic prefix causes delay in storing and copying IFFT result. The proposed IFFT removes this delay because its output is cyclic shifted by the length of cyclic prefix. So we can make a complete OFDM symbol by just copying the forepart of IFFT output to the end. In many cases, the length of cyclic prefix is 1/2n of FFT size, and this IFFT does not require additional hardware complexity and it does not cause any performance degradation.

• The Mathematical Education
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• v.49 no.1
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• pp.111-118
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• 2010

This paper attempts to establish a scoring system for the originality in evaluation of mathematical creativity. The scoring system is composed of three categories; fluency, flexibility and originality. In this paper, we proposed an evaluation method for originality as following based on relative frequency and standard normal distribution. (1) Fluency: It is judged on the basis of the number of correct answers a student made. If several correct answers are given for a single category, then its maximum score is set to 5 points. (2) Flexibility: We examined how many categories the students' responses can be classified into. If at most 15 answers are allowed for each question, the maximum score of flexibility is 15 points. (3) Originality: Originality score is given if a student made some original response that other students did not show. That is, it reflects relative rarity. The originality is measured according to the following steps: Step 1: Analyze the frequency of how many students made an answer to the response type categorized at low level, and calculate the relative frequency p of each category. Step 2: Find the originality point os for each response, that is, os = max{0,z} where z satisfies P(Z > z) = p with standard normal distributed random variable Z. For example, - p is greater than 0.5: 0 point - p is 0.1587: 1 point - p is 0.0228: 2 points - p is 0.0013: 3 points Step 3: Assign the one's originality score to the sum of originality point for each response. Remark. There is no upper limit of originality score.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1297-1307
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• 2009

The purpose of this paper is to propose a detection algorithm and a tracking algorithm based on silent time using MB-OFDM UWB(Multi-Band Orthogonal Frequency Division Multiplexing Ultra Wide Band) receiver in order to satisfy DAA(Detect And Avoid) regulation of Korea to permit UWB in 3.1~4.8 GHz. In DAA regulation of Korea, if UWB device receives a signal more than -80 dBm/MHz from the victim system during UWB operation, the UWB system should avoid the collision within 2 sec. In this paper, we proposed the detection algorithm to detect the victim signal received by －80 dBm/MHz for the avoidance process that changes the operating UWB frequency to other UWB frequency and the subcarrier tracking algorithm to follow up the subcarrier positions of the victim signal for the tonenulling avoidance process that decreases the TX power of subcarriers occupied by the victim signal by -70 dBm/MHz. The performance of the detection algorithm and the tracking algorithm suggested in this paper is verified in simulation results considering various conditions.