• Journal of IKEEE
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• v.17 no.4
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• pp.484-491
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• 2013

In this paper, we proposed an internal multiband loop embedded monopole antenna for mobile handset that could be used for smart phones. The proposed antenna has a volume of 40 mm(W) ${\times}$ 15 mm(L) ${\times}$ 5 mm(H), ground plane size is 40 mm(W) ${\times}$ 80 mm(L), and covers the GSM900 (Global System for Mobile communications : 880-960 MHz), K-PCS (Korea-Personal Communications Service : 1750-1870 MHz), US-PCS (US Personal Communications Service : 1850-1990 MHz), WCDMA (Wideband Code Division Multiple Access : 1920-2170 MHz), Wibro (2300-2390 MHz), Bluetooth (2400-2483 MHz) and WLAN (Wireless Local Area Network : 2400-2483.5 MHz) bands for VSWR (voltage standing wave ration) less than 3. The proposed loop adding design at middle section of longest branch showed wide impedance bandwidth for the lowest resonance frequency band. The proposed antenna have a lowest resonance frequency band from 738 MHz to 1075 MHz for S11 value of -6dB. A HFSS (High Frequency Structure Simulator) of the Ansys Corporation based on a finite element method is employed to analyze the proposed antenna in the design process and to compare the simulation and experimental results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.10
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• pp.34-40
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• 2001

Ultra Wide Band (UWB) system uses wide band signal, which power spectral density is over all band, It likes as a noise floor, so UWB system can be used without interfering with other communication system. For the first time, we adopted Rayleigh mono pulse antipodal signal which had symmetric characteristic and zero mean. With the power spectral density using stochastic process, we knew that the antipodal signaling scheme removed discrete spectrum and concluded that this had much better spectral suppression, probability of error and data rate than PPM (Pulse Positioning Modulation).

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.3
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• pp.312-318
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• 2016

This paper presents a 2-6 GHz GaN HEMT power amplifier monolithic microwave integrated circuit (MMIC) with bridged-T all-pass filters and output-reactance-compensation shorted stubs using the $0.25{\mu}m$ GaN HEMT foundry process that is developed by WIN Semiconductors, Inc. The bridged-T filter is modified to mitigate the bandwidth degradation of impedance matching due to the inherent channel resistance of the transistor, and the shorted stub with a bypass capacitor minimizes the output reactance of the transistor to ease wideband load impedance matching for maximum output power. The fabricated power amplifier MMIC shows a flat linear gain of 20 dB or more, an average output power of 40.1 dBm and a power-added efficiency of 19-26 % in 2 to 6 GHz, which is very useful in applications such as communication jammers and electronic warfare systems.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.238-246
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• 2011

A 3-5 GHz UWB radar chip in 0.13 ${\mu}m$ CMOS process is presented in this paper. The UWB radar transceiver for surveillance and biometric applications adopts the equivalent time sampling architecture and 4-channel time interleaved samplers to relax the impractical sampling frequency and enhance the overall scanning time. The RF front end (RFFE) includes the wideband LNA and 4-way RF power splitter, and the analog signal processing part consists of the high speed track & hold (T&H) / sample & hold (S&H) and integrator. The interleaved timing clocks are generated using a delay locked loop. The UWB transmitter employs the digitally synthesized topology. The measured NF of RFFE is 9.5 dB in 3-5 GHz. And DLL timing resolution is 50 ps. The measured spectrum of UWB transmitter shows the center frequency within 3-5 GHz satisfying the FCC spectrum mask. The power consumption of receiver and transmitter are 106.5 mW and 57 mW at 1.5 V supply, respectively.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.195-196
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• 2007

Since the digital TV signal band is very wide ($54{\sim}806MHz$), the VCO used in the frequency synthesizer must also have a wide frequency tuning range. Multiple LC VCOs have been used to cover such wide frequency band. However, the chip area increases due to the increased number of integrated inductors. In this paper, a scheme is proposed to cover the full band using only one VCO. The RF VCO block designed using a 0.18um CMOS process consists of a wideband LC VCO, five divide-by-2 circuits and several buffers. The simulation results show that the designed circuit has a phase noise at 10kHz better than -87dBc/Hz throughout the signal band and consumes 10mA from a 1.8V supply.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.12
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• pp.32-37
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• 2000

We proposed to a new method of the aperture coupled microstrip antenna with T-shaped feeding slot. We analyzed method of enhancing the bandwidth of the antenna using FDTD. And the antenna parameters are optimized to get maximum bandwidth. We also calculated the progress process of waves and the distribution of electric field in the time domain. We also calculated return loss, VSWR, input impedance, radiation pattern in the frequency domain by Fourier transforming the time domain results, respectively. It was found that the bandwidth of this antenna changes length and width of the patch, length and width of the slot, length of T-shaped feedline, position of the offset. Measured % bandwidth was 49.2 % in the center frequency 2.5 GHz. These results were in relatively food accordance with calculated values.

• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.7-11
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• 2014

In this paper, we designed resistive MMIC mixer using $0.5{\mu}m$ p-HEMT process. This Mixer is designed to have a similar performance in -4 ~ 4 dBm local oscillator signal power level and to maintain a constant conversion loss and linear performance due to the variation of local signal. In order to have such characteristics, we designed new feedback circuit topology by using FET, and minimized performance change for LO signal power level variation, also obtain MMIC mixer characteristics which is able to apply in wideband. In the design result, When the LO signal power is -4 ~ 4 dBm, there was 6 dB conversion loss and it came up with the excellent result that IIP3 got over 30 dBm in 0.5 ~ 2.6GHz frequency band.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.96-99
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• 2005

As the demand of internet networks using backbone communication systems recently increased, the researches on the high-speed wideband optical communication systems are required. For high-speed optical communication systems, asymmetric sampled grating distributed feedback laser diodes (DFB-LDs) are developed and the reliability of DFB-LDs is examined. The reliability of DFB-LDs is performed by monitoring I-V and L-I characteristics and two degradation phenomena related to the electrical characteristics of LDs are observed during the life tests. The first degradation phenomenon by increasing the reverse current is considered as a formation of leakage current path enough to prevent lasing operation in lateral blocking layer near active region of lasers. The second degradation phenomenon by decreasing the forward current is considered as activation of non-radiative Auger recombination process by thermal energy and the second degradation phenomenon is recovered after the off-test period at room temperature Eventually, evaluating the reliability of DFB LDs can allow us to improved the manufacturability in high-volume manufacturing.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.12
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• pp.7-12
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• 2004

In this paper, CPW wideband distributed amplifier was designed and fabricated using 0.1 $\mum$ InGaAs/InAlAs/GaAs Metamorphic HEMT(High Electron Mobility Transistor). The DC characteristics of MHEMT are 442 mA/mm of drain current density, 409 mS/mm of maximum transconductance. The current gain cut-off frequency(fT) is 140 GHz and the maximum oscillation frequency(fmax) is 447 GHz. The distributed amplifier was designed using 0.1 $\mum$ MHEMT and CPW technology. We designed the structure of CPW curve, tee and cross to analyze the discontinuity characteristics of the CPW line. The MIMIC circuit patterns were optimized electromagnetic field through momentum. The designed distributed amplifier was fabricated using our MIMIC standard process. The measured results show S21 gain of above 6 dB from DC to 45 GHz. Input reflection coefficient S11 of -10 dB, and output reflection coefficient S22 of -7 dB at 45 GHz, respectively. The chip size of the fabricated CPW distributed amplifier is 2.0 mm$\times$l.2 mm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1169-1176
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• 2010

The RF front-end for L1/L2 dual-band Global Positioning System(GPS) receiver is presented in this paper. The RF front-end(down-converter) using low IF architecture consists of a wideband low noise amplifier(LNA), a current mode logic(CML) frequency divider and a I/Q down-conversion mixer with a poly-phase filter for image rejection. The current bleeding technique is used in the LNA and mixer to obtain the high gain and solve the head-room problem. The common drain feedback is adopted for low noise amplifier to achieve the wideband input matching without inductors. The fabricated RF front-end using $0.18{\mu}m$ CMOS process shows a gain of 38 dB for L1 and 41 dB for L2 band. The measured IIP3 is -29 dBm in L1 band and -33 dBm in L2 band, The input return loss is less than -10 dB from 50 MHz to 3 GHz. The measured noise figure(NF) is 3.81 dB for L1 band and 3.71 dB for L2 band. The image rejection ratio is 36.5 dB. The chip size of RF front end is $1.2{\times}1.35mm^2$.