• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.167-172
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• 2006

In this paper, the 25W power amplifier for UHF band radio transceiver has been designed and realized. The power amplifier was composed of drive, power amplifier and control stages. Feedback topology and coaxial line baluns were used for wide band operation. The VDMOS, which has reliable performance for linearity and efficiency, was used for power device and designed to operate as push-pull amplification at Class AB Bias. The power amplifier designed in such a way was found to show stable AM modulation performance when voice signal was detected at the gate stage, with being designed and realized to meet output specifications of commercial air traffic control transmitter.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.261-264
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• 2005

This paper presents the design of a down-conversion mixer with built-in active balun integrated in a $0.25\;{\mu}m$ pHEMT process. The active balun consists of series-connected common-gate FET and common-source FET. The designed balun achieved broadband characteristics by optimizing gate-width and bias condition for the reduction in parasitic effect. From DC to more than 6GHz, the active balun shows the phase error of less than 3 degree and the gain error of less than 0.4 dB. A single-balanced down-conversion mixer with built-in broadband active balun has been designed with optimum width, load resistor and bias for conversion gain and without any matching component for broadband operating. The designed mixer whose size of including on-chip bias circuit is $1\;mm{\times}1\;mm$ shows the conversion gain of better than 7 dB from 2 GHz to 6 GHz and $P_{1dB}$ of -10 dBm at 5.8 GHz

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.129-135
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• 2010

In this paper, we propose and demonstrate a new four-port BPSK direct conversion receiver based on $0.18\;{\mu}m$ CMOS technology for K-band applications. The proposed direct conversion receiver is composed of two active combiners, an lumped LC balun, two power detectors and an analog decode. The designed direct conversion receiver is successfully demodulated BPSK signal with 40 Mbps in the K-band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.9
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• pp.879-885
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• 2014

In this paper, we designed and fabricated wideband 3-axis isotropic antenna for the Electro-Magnetic Fields(EMFs) measurement. Each part of proposed 3-axis antenna has isotropic characteristics and arbitrary axis of proposed 3-axis antenna could be selectable using RF switch. Also, a resistor was inserted in each axis of proposed 3-axis antenna for improving antenna gain and noise suppression characteristics, and port impedance of each dipole antenna were matched by balun. For the performance verification of antenna, GTEM Cell which generates standard electromagnetic field was used for the derivation of antenna factor and receiver sensitivity. As a result, fabricated 3-axis isotropic antenna has receiver sensitivity of 0.12~4.2 mV/m and typical VSWR of 3.3:1 within a wide operation frequency range from 0.03 MHz to 3 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1318-1323
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• 2010

A lot of demand for parts of millimeter wave band, as would be expected 57~63 GHz band down conversion mixer was designed and fabricated using IHP 0.25 um SiGe process. Designed and fabricated mixer was double balanced type and located reduced 3D balun at RF port and buffer amplifier at outport for suppression LO signal and conversion gain. Fabricated mixer measured conversion gain of 13.8 dB, $P1dB_{in}$ -17 dBm and 88 mA of current consumption characteristics, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1206-1211
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• 2006

In this paper, a Balun-BPF with the balun and BPF characteristics is proposed by using dual-mode ring resonator of $1{\lambda}$. We obtained the property of balun with the phase imbalance by symmetrically placing each output of ring resonator. The dual mode has been made by impedance difference between input and output lines. The fabricated Balun-BPF shows bandwidth of 40 MHz and insertion loss of 2.4 dB at a center frequency of 2.45 GHz. It shows the phase imbalance of $180{\sim}184$ degree and the magnitude imbalance of within 1 dB. The measured frequency responses agree well with simulated ones.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.227-231
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• 2004

A MMIC (Monolithic Microwave Integrated Circuit) mixer chip using the schottky diode of InGaAs/CaAs p-HEMT process has been developed for receiver down converter of Ka-band. A different approach of MMIC mixer structure is applied for reducing the chip size by the exchange of ports between IF and LO. This MMIC covers with RF (30.6∼31.0㎓)and IF (20.8∼21.2㎓). According to the on-wafer measurement, the MMIC mixer with miniature size of 3.0mm1.5mm demonstrates conversion loss below 7.8㏈, LO-to-RF isolation above 27㏈, LO-to-IF isolation above 19㏈ and RF-to-IF isolation above 39㏈, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1414-1416
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• 2016

In this paper, a SWB (Super-WideBand) dipole antenna with self-complementary structure is proposed for signal intelligence. The proposed antenna consists of a self-complementary dipole antenna and a tapered balun for balanced feeding. The measured -10 dB reflection bandwidth of the proposed antenna is more than 28:1 (0.73-20 GHz) and 3 dB axial ratio bandwidth is 3.25:1 (1.91-6.22 GHz) with RHCP (Right Hand Circular Polarization) at +z direction. The measured radiation patterns are omni-directional in lower frequency band and bi-directional in higher frequency band. The measured peak gain within -10 dB reflection bandwidth varies from 2.83 dBi to 7.66 dBi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.257-267
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• 2015

This paper presents a ultra-wideband sinuous antenna that operates in a whole frequency range (0.824~5.85 GHz) of Cellular/GSM-800, GSM900, ISM, GPS, DCS/GSM1800, PCS/GSM1900, WCDMA/UMTS/IMT2000, WiBro, WLAN and WiMax. The proposed antenna, which is composed of two sinuous arms, is designed as a self-complementary structure in order to have frequency-independent characteristics. It also uses a wideband balun of Klopfenstein taper structure to match to $50{\Omega}$. Experimental results show that the -10 dB return loss bandwidth of the proposed antenna is 5.24 GHz that ranges from 0.76 to 6 GHz, which covers all the frequency bands of the various wireless services. Within the entire operating frequency range, the measured radiation patterns in both E-plane and H-plane show nearly constant bidirectional broadside beams and the maximum antenna gain is measured to fall between 2.32~6.01 dBi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.806-812
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• 2009

In this paper, the omnidirectional circularly polarized(CP) antenna using arc-shaped mushroom structure with curved branch is proposed. To obtain a vertical polarization and an omnidirectional radiation pattern, the CP antenna uses zeroth-order resonance(ZOR) mode of composite right and left handed(CRLH) transmission line. The horizontal polarization is achieved by the curved branches. Also, the spacing between curved branch and arc-shaped mushroom structure gives the $90^{\circ}$ phase difference between vortical and horizontal polarization. The proposed antenna, therefore, has an omnidirectional CP radiation pattern In the azimuthal plane. The electrical size of the proposed antenna is reduced by 38%, compared with that of the previously presented omnidirectional CP antenna. In addition, the CP antenna is simply designed without $90^{\circ}$ phase shifter and dual feed line. The proposed antenna uses a Bazooka balun for good impedance matching and radiation pattern. To improve 3 dB axial ratio in XY plane, the designed antenna is optimized. After optimization, the measured 3 dB axial ratio in XY plane is observed in $86{\sim}282^{\circ}$.