• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.3 s.357
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• pp.92-97
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• 2007

Switching mode amplifiers have been studied widely for use at microwave frequency range, and the class E amplifier which is a type of switching mode amplifier offers very high efficiency approaching 100%. In this paper, 2.4GHz microwave class E amplifier with 66% power added efficiency (PAE) and 17.6dBm output has been linearized for use at wireless LAN transmitter, and digital predistortion technique with look up table is applied. With -3dBm input power of wireless LAN, measured output spectrum can meet the required IEEE 802.11g standard spectrum mask, and the digital predistortion output spectrum has been improved by 5dB of ACPR at 20MHz offset from center frequency.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.4
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• pp.549-554
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• 2017

In this paper, we studied the design and fabrication of $2{\times}2$ microstrip array antenna at around 5 GHz band.. To improve of frequency properties of antenna, feed microstrip patch antenna was simulated by HFSS(High Frequency Structure Simulator). A $2{\times}2$ array antenna was designed and fabricated by photolithograph on an FR4 substrate (dielectric constant of 4.4 and thickness of 1.6 mm). The fabricated $2{\times}2$ array antenna showed a center frequency, the minimum return loss and bandwidth were 5.3 GHz, -24dB, and 390MHz, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.4
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• pp.121-126
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• 2010

Regarding HEMP has been studied as few thousand of paper by major nuclear bomb holding countries with USA for the self protection against nuclear bomb attract. Major HEMP protection facilities are consist of the shielding, filtering, grounding and high voltage protection circuits. Shielding room construction required a highest cost among the key protective facilities. Most of a theoretical formulas listed on the paper and related books has a little correlations in the certain frequency band between the theoretical formulas and field measuring results. For the reasons we proposed the advanced new theoretical formulas and developed the computer simulation S/W as enough as apply to the cost effective shielding room design for HEMP considering the various structural constants.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1115-1122
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• 2003

In this paper we fabricated microchip antenna operating in bluetooth frequency bands(2.402∼2.480GHz). The antenna has a size of about 54mm${\times}419mm${\times}40.8mm, giving a total bluetooth PCB for support and chip of about 11mm${\times}44mm${\times}41.6mm. Bandwidth of the designed and fabricated chip antenna for bruetooth is 10.71 % at the resonated frequency of 2.45GHz and the resonant frequency and bandwidth versus change of any arbitrary feed point is observed. also, E-plane and H-plane in the Measured radiation pattern characteristic of chip antenna is compared and analyzed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.23-30
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• 2010

In this paper, a design for the 900MHz bandwidth RFID reader antenna with circular polarization is proposed and experimentally investigated. The 900MHz bandwidth RFID reader antenna is proposed as a simple radiator with loading capacitor to generate LHCP(Left Hand Circular Polarization). Also, the design and fabrication of antenna has the returnloss of -32.28dB at the center frequency of 1010MHz and Bandwidth of 12.5% at 905Hz~1030MHz. Proposed LHCP antenna of maximum gain is 6dBi and satisfy axial ratio based on 2. From the measured result, axial ratios based on 2 are observed at the operating frequencies. The proposed antenna is suitable for RFID applications in wireless communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.587-596
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• 2005

In this paper, we propose an OFDMA/CDM-based cellular system, which accommodates multiple users in frequency-domain and multiplexes user data with frequency-domain spreading. The proposed system utilizes random codes to discriminate cells and adopts the pre-equalization to enhance the performance. For cellular applications, a number of pre-equalization techniques are compared and an efficient power allocation scheme is suggested with a transmit power constraint. Especially, the validity of OFDMA/CDM based cellular system is investigated, by comparing the performance for varying the number of multiplexed data symbols at different locations. Finally the pre/post-equalization is proposed to reduce the performance degradation caused by time delay.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.1
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• pp.7-11
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• 2004

In this paper, the wideband microstrip patch antennas for the Personal communications Service (PCS : 1750∼1870 MHz) and International Mobile Telecommunications-2000 (IMT-2000 : 1920∼2170 MHz) dual band are studied. Experimental and simulation results on the dual band antenna are presented. Simulation results are in good agreement with measurements. The experimental and simulation results confirm the wideband characteristics of the antenna. The studied antenna satisfied the wideband characteristics that are required characteristics for above 420 MHz impedance bandwidth for the PCS and IMT-2000 dual band antenna. In this paper, through the designing of a dual band antenna, we have presented the availability for PCS ＆ IMT-2000 base station antenna. An impedance bandwidth of 33% (VSWR<1.5, 650 GHz) and a maximum gain of 7dB can be achieved. The radiation pattern is stable across the passband.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.32-43
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• 1999

In this paper, the transformed QMSA to load a capacitor without limitation of the electric force on QMSA(Quarter-wavelength Microstrip Antenna) is designed. Bandwidth of the designed and manufactured antenna is 5.7% at the resonant frequency of 2.0 GHz and the resonant frequency and bandwidth versus change of any arbitrary feed point is observed. Since the size of wide slot width between the left and right parallel plate to load a capacitor is very wide bandwidth, will be suitable for very wide bandwidth communication. The radiation pattern characteristics of the designed antenna based on the dipole structure and the aperture structure analysis method. As calculation results, relative backward radation is - 5 dB.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.128-132
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• 2017

In this thesis, a BPF(band-pass filter) at the center frequency of 2.14GHz, and bandwidth of 20MHz is designed and implemented using high Q dielectric resonators with ${\varepsilon}_r=38$. The DR(dielectric resonator) is resonated by $TE_{01{\delta}}$-mode and it has a hole in the center of DR. The BPF consists of 6-poles dielectric resonators and the characteristic of elliptic function is obtained by non-adjacent coupling. It has the average insertion loss of 0.97dB and the return loss over 25dB in its passband. In this thesis, the frequency selectivity is more improved by the coupling characteristics between non-adjacent resonators than that of dielectric resonator filters with a Chebyshev response.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.84-89
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• 1994

A tunable pulsed dye laser was operated in a single longitudinal mode by injection locking with a cw ring dye laser. A doubled Nd:YAG laser was used as the pumping source. Phase sensitive detection technique was applied to maintain the required match between the master laser frequency and the slave resonator cavity length. The fluctuation of the center frequency of the pulsed laser was < 10 MHz, and the pulse duration (FWHM) was 6 ns. The linewidth measured by scanning confocal interferometer was 130 MHz. When pumped by 50 mJ of the doubled Nd:YAG laser, the output energy of the pulsed dye laser was 2 mJ and the peak power was 330 kW. 30 kW.