• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.223-227
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• 2001

To complement the narrow band characteristics of the microstrip patch antenna, the slot patch antenna was designed for the wide band characteristics. The microstrip slot patch antenna has wide band characteristics when the size of the slots and the feed line shapes are designed accordingly. In this study, various substrates as a epsilon-10, and a epoxy were used to design slot patch antennas. The feed line structure of the circular and square were also designed to have wide band. In the case of slot antennas with the circular patch shapes using epsilon-10 plate 50mm thickness with relative permittivity the 41% bandwidth on the 1.5∼2.28㎓ was shown. When an Epoxy plate 1.Sum thickness with relative permittivity 4.75 is used to construct a circular slot antenna with a square patch form, the frequency band width was obtained 77% as the 1.2∼2.7㎓ frequency range. These results are coincided well with the theoretical results.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1287-1292
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• 2012

In this paper, a dual polarization patch antenna operates at the wide bandwidth of 1.525GHz~1.665GHz was designed and fabricated. To obtain the wide bandwidth and high gain, increased height of air floor from GND was applied, and to get wide band axial ratio and high gain, parasitic patch was applied. The simulation and measurement showed good agreements, the VSWR was less than 1.9 at the frequency bandwidth, the return loss was less than -10dB, and the LHCP(Left Hand Circular Polarization) and RHCP(Right Hand Circular Polarization) isolation was less than -13dB at the frequency bandwidth.

• Journal of the Korean Institute of Navigation
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• v.15 no.1
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• pp.1-9
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• 1991

The coaxial sample holder with 20mm in diameter and the adaptor from type N connector-to-20mm${\phi}$ coaxial tube are designed and manufactured which have been used for designing and measuring the fabricated microwave absorber. In addition, the measure in method of material constants of the microwave absorbers is described, which is focused on minimizing the error due to the sample's shapes, the fitting conditions, etc. After describing the design method of a single-layed microwave absorber, the microwave absorbers for X-band, C-band and S-band RADARs are designed and fabricated, respectively, which are composed of ferrite, carborn, and binder and have good performance. Futhermore, we develop the high performance microwave absorber in extremely wide-band type for RADAR, which is composed of different material and its mixing ratio and which could cover nearly from 4 to 10 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12A
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• pp.951-957
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• 2003

The analysis of RF performance requirement conditions on communication system is critical indicator to predict the performance of system. UWB(Ultra Wide Band) system which the standard is not established yet is difficult to derive the precise system performance requirement condition. Also, there are differences between conventional UWB system and multi-band system about RF performance requirement condition. In this thesis, the differences are analyzed and performance requirement conditions of multi-band UWB system are described on the basis of the differences. Throughput, maximum transmit power, and sensitivity of multi-band UWB system is varied with respect to the number of Sub-Bands. In addition, because of Multi-path effect, if PRF(Pulse Repetition Frequency) is changed, the Multi-path link margin is happened to compensate for Multi-path Energy Loss which is contributed by increasing of the Link Margin. According to Multi-path Margin, the variation of the resistance with respect to sensitivity and interference signal is observed and analyzed through the simulation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.3
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• pp.174-181
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• 2004

In this paper, we review the four receiver architectures and four methods for multi-standard receiver design. Propose reconfigurable RF block can be used for both low-IF and direct conversion architecture. Also, using reconfigurable mixer method, it can be operated at $2{\sim}6$ GHz range for multi-standard receiver. It consists of wideband mixer, filter, and automatic gain control amplifier and to get wide-band operation, $2{\sim}6$ GHz, wide-band mixer use flexible input matching method. Besides, to design multi-standard receiver, LNA bank that support each standard is necessary and it has good performance to compensate the performance of wide-band mixer. Finally, we design and simulate proposed reconfigurable RF block and to prove that it has acceptable performances for various wireless standards, the LNA bank that supports both IEEE 802.11a/b/g and WCDMA is also designed and simulated with it.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.912-918
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• 2001

This paper presents a performance analysis of experimental observations of a uplink smart antenna system operating in a wide-band CDMA environment designed for a WLL (Wireless Local Loop) system. The numerical results shown in this paper have been obtained from practical experiments using commercially developed mobile terminals. The beam pattern provided by the weight vector and the resultant BER (Bit Error Rate) are observed in both indoor and outdoor signal environments. From the experimental observations, it is concluded that the proposed smart antenna system provides significant improvements in receiving both indoor and outdoor signal environments.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.2
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• pp.53-55
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• 2011

The printed wide band monopole antenna having characteristics of dipole by modified coplanar wave guide(CPW) ground plane is presented. We are called a slot-arm printed monopole antenna and investigated the effect of the surface currents of the radiator on ground plane. The proposed antenna is treated as two asymmetric dipoles with the included angle of $90^{\circ}$ degrees which lie along Z-direction symmetrically. It is observed that the effect of the surface currents on the radiation patterns is similar to that of the corresponding dipole. The length and width of the ground plane correspond the radius and length of the dipole respectively. This approach is also valid to general printed monopole antennas. The simulation impedance bandwidth of the proposed antenna the range of 2.4 to 4.6 [GHz] for a voltage stand wave ratio (VSWR)${\leq}$2 and got pick gain of 6 [dBi]. So the proposed antenna is satisfied the requirement of the industry science medical (ISM) band operation.

• Journal of Communications and Networks
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• v.5 no.2
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• pp.167-173
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• 2003

We treat the problem of channel estimation and interference cancellation in multiuser ultra-wide-band (UWB) communication systems over multipath fading channels. The UWB system under consideration employs a random time-hopping impulse radio format. We develop a channel estimation method based on linear weighted algorithm. An iterative channel estimation and interference cancellation scheme is proposed to successively improve the receiver performance. We also consider systems employing multiple transmit and/or receive antennas. For systems with multiple receive antennas, we develop a diversity receiver for the wellseparated antennas. For systems with multiple transmit antennas, we propose to make use of Alamouti’s space-time transmission scheme, and develop the corresponding channel estimation and interference cancellation receiver techniques. Simulation results are provided to demonstrate the performance of various UWB receiver techniques developed in this paper.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.605-608
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• 2006

The recent application of wide band gap oxide semiconductors to transparent thin film transistors (TTFTs) is making a fast and growing (r)evolution on the contemporary solid-state electronics. In this paper we present some of the recent results we have obtained using wide band gap oxide semiconductors, like indium zinc oxide, produced by rf sputtering at room temperature. The devices work in the enhancement mode and exhibit excellent saturation drain currents. On-off ratios above $10^6$ are achieved. The optical transmittance data in the visible range reveals average transmittance higher than 80 %, including the glass substrate. Channel mobilities are also quite respectable, with some devices presenting values around $25\;cm^2/Vs$, even without any annealing or other post deposition improvement processes. The high performances presented by these TTFTs associated to a high electron mobility, at least two orders of magnitude higher than that of conventional amorphous silicon TFTs and a low threshold voltage, opens new doors for applications in flexible, wearable, disposable portable electronics as well as battery-powered applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.977-979
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• 2006

Organic light-emitting diodes (OLEDs) based on the double wide band gap emissive layers in the range of 380 nm to 440 nm are reported. An efficient electroluminescence with a maximum at 400nm was observed at room temperature under a forward bias about 10V. With the wide band gap organic materials for near-ultraviolet emission, the low operating voltage (5V) and high current efficiency (3 cd/A) have been obtained at $2mA/cm^2$