• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.10
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• pp.1189-1195
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• 2007

We design and fabricate, in this parer, a triple band folded monopole antenna for the folder type mobile phone handset that can be served GSM/DCS/USPCS mobile phone system. Antenna structure is modified meander shape which is obtained both extension of antenna physical length for GSM band and same directional multi-currents flowing on the antenna conductor surface for DCS/USPCS band. This antenna has as good performances as high radiation resistance and gain increment, and would be applied to mobile phone handset that is not able to be performed by internal antenna. By measurement, fabricated antenna by the press process shows under VSWR 3:1 at closed folder state and 2:1 at opened folder state over whole GSM/DCS/USPCS band, and has maximum gain as -0.02 dBi for GSM, +0.2 dBi for DCS, +0.78 dBi for USPCS band with almost omnidirectional H-plane radiation pattern.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3C
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• pp.323-330
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• 2007

Performance indicators such as output SNR, SIR, SINR for rectangular smart antennas in CDMA basestations have been derived. Simulations have been carried out to find the rectangular smart antenna performance while varying the input SNR, number of antenna elements, and the interferers' spatial distributions. Simplified Conjugate Gradient Method was chosen as the underlying beam forming algorithm. It has been shown that the performance of a rectangular smart antenna is similar to that of the linear one having the same number of elements when the interferers are randomly distributed over the whole azimuth angle range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.5
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• pp.713-721
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• 2001

In this paper, parasitic patches gap-coupled microstrip antenna and stacked microstrip patch antenna combined with parallel coupled lines, which are a kind of wideband impedance matching network, are proposed to get the wider bandwidth. The iterative method using a distributed network is proposed to design the parallel coupled lines as a wideband impedance matching network. Measurements show that the proposed antennas provide wider bandwidths ~1.6 times and ~1.5 times those of conventional parasitic gap-coupled microstrip patch antenna and stacked microstrip patch antenna. In addition, measured radiation patterns show no serious variation of radiation patterns though the parallel coupled lines is added. The antenna gain is, however, lowered about 1 dB and 0.5 dB by the coupling loss in the parallel coupled lines.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1096-1104
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• 2006

In this paper, the broadband antenna for the combined base station of Cellular/PCS/IMT-2000/Wibro and S-DMB services is designed and the proposed antenna allows having sufficient coverage for each service band. In order to get the broadband impedance matching, the tapered sections are applied on the both terminus of hi-conical respectively. The design parameter is calculated and simulated by using FDTD method. As a result, the measured bandwidth of the proposed antenna is $0.79GHz{\sim}2.93GHz$ and the gain is distributed from 5.5 dBi up to 8.19 dBi.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.456-462
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• 2011

This paper investigates the outage behavior of peak interference power limited cognitive radio (CR) networks with multiple transmit antennas. In CR-multi-input single-output (MISO) channel, the total transmit power is distributed over the transmitantennas. First, we use the orthogonal space-time codes (STC) to achieve the transmit diversity at CR-receiver (rx) and investigate the effect of the power distribution on the interference power received at the primary-receiver (P-rx). Then, we investigate the transmit antenna selection (TAS) scheme in which the CR system selects the best transmit antenna and allocates all the power to the selected best antenna. Two transmit antenna selection strategies are proposed depending on if feedback channel is available or not. We derive the closed form expressions of outage probability and outage capacity of all schemes with arbitrary number of transmit-antennas. We show that the proposed schemes significantly improve the outage capacity over the single antenna systems in Rayleigh fading environment. We also show that TAS based scheme outperforms the STC based scheme when peak interference power constraint is imposed on the P-rx only if a feedback channel from CR-rx to CR-transmitter is available.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.1
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• pp.191-210
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• 2011

Topology management, which includes neighbor discovery, tracking and updating, is a key area that need to be dealt with appropriately to increase network performance. The use of directional antenna in Wireless Mesh Networks is beneficial in constructing backbone networks viewing the properties of directional antenna. The backbone links must be robust to obtain better network performance. In this paper, a simple yet effective topology protocol is presented that performs well compared to its predecessors. Our protocol constructs the topology with the constraints in the number of links per node. The full topology is constructed in two phases. The resultant topology is termed as Web-topology. The topology formed is robust, efficient, and scalable.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.4
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• pp.309-314
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• 2013

This paper dealt with the radiated electromagnetic wave detection of partial discharge (PD) in oil for insulation diagnostics of oil-immersed transformers. Three types of electrode system were fabricated to simulate the insulation defects that could occur in oil-immersed transformers. Frequency components of radiated electromagnetic wave in oil was measured by broadband bi-conical antennas of 300 MHz~2 GHz and a spectrum analyzer of 9 kHz~3 GHz. Frequency component of electromagnetic waves from PD in oil were highly distributed at 500 MHz. From the result, a narrow-band monopole antenna with the center frequency of 500 MHz was fabricated. We could detect PD signal in insulation oil without an influence of external noise by a measurement system which consists of the prototype monopole antenna, a LNA (Low Noise Amplifier), an oscilloscope and a spectrum analyzer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.4
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• pp.747-752
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• 2009

In this paper, the MIMO(Multi-Input Multi-Output) channel characteristics for Rx antenna spacing are described in the real environment, which has LOS(Ling of Sight) and NLOS (Won-Line of Sight). We developed $2\times2$ MIMO channel measurement system at 2.3GHz Wibro Band. MIMO antenna evaluation parameters such as received power, channel capacity and spatial correlation are evaluated for standard dipole antenna with 0.25, 0.5, 0.75 and 1.0 wavelength spacing at 2-position for LOS and 4-position for NLOS. The spatial correlation is distributed more than 0.9 in most LOS case which might be intricate to operate MIMO communication. MIMO antenna design need to be focused on getting spatial diversity and reducing spatial correlation in LOS case.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.8
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• pp.474-480
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• 2014

In this paper, we propose a study for the next generation terrestrial broadcasting technology based on SFN(Single Frequency Networks), which applies multiple receiving antenna to improve receiving performance of cloud transmission system. By applying multiple receiving antenna, the received broadcast signals at the boundary of different SFN broadcasting area could be modelled by distributed MIMO system. Due to the interference cancellation effect of the MIMO detector, the proposed scheme could suppress the adjacent area interference more efficiently compared to the single receiving antenna case. Simulation results show that receiving performance can be improved dramatically in overlapping area of SFN by applying multiple antenna receivers in cloud transmission system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.891-897
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• 2018

In this paper, we propose a blind estimation scheme for the antenna spacing of nonuniform linear array MIMO radar using distributed electronic sensors based on ESPRIT. We present a blind method to separate orthogonal waveforms of a MIMO radar based on the antenna spacing estimation. The estimated orthogonal waveforms of a MIMO radar can be used for disabling opponent MIMO radars.