• Journal of Internet of Things and Convergence
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• v.10 no.3
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• pp.1-6
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• 2024

In response to the increasing demand for unrestricted access to diverse services regardless of location, cost-effective and easily deployable Wireless Mesh Network (WMN) solutions have once again captured attention. This paper primarily addresses the implementation challenges of Autonomous Load-balancing Field-based Anycast routing+ (ALFA+) for three-dimensional (3D) WMNs. Subsequently, we evaluate the performance of ALFA+ in an 802.11-based 3D WMN testbed established within a university campus using commercial devices, thus validating the practical viability of ALFA+. While most prior research has relied on performance evaluation through virtual environment simulations, this study distinguishes itself by performance evaluations in a real-world testbed using commercial devices and providing detailed implementation-related information necessary for such evaluations. This approach holds considerable significance in assessing the actual applicability of ALFA+.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.4
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• pp.27-37
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• 2001

The design, fabrication, and an experimental implementation of the strip patch antenna coupled with a H-shaped aperture arc presented in this paper. The proposed antenna has the wide bandwidth, high gain, and low cross-polarization levels. We measured the VSWR, smith chart impedance characteristic, co/cross polarization pattern, gain, and so on. The measured bandwidth of this antenna is 47.1 %. To reduce the back lobe and increase the gain, when the reflector is used, cross polarization level is below -18.2dB at E-plane and below 25.7 dB at H -plane. The maximum gain at 2.05 GHz is also 10.4 dBi and the 3 dB gain bandwidth with center frequency at 2.17 GHz is 24 %, which is the wide bandwidth. This antenna can find applications in mobile communication, wireless LAN, RF communication system, and so on.

• Journal of IKEEE
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• v.27 no.1
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• pp.109-115
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• 2023

In this paper, we design and implement an Ultra-Wide Band (UWB, 3.1~10.6 GHz) antenna with 5G mobile communication (3.42~3.70 GHz) and Wireless Local Area Network (WLAN, 5.15~5.825 GHz) bands rejection characteristics. The proposed antenna consists of a planar radiation patch with two slots. The upper slot contributes to reject 5G mobile communication band and the lower slot contributes to reject WLAN band. The Voltage Standing Wave Ratio (VSWR) values of the proposed antenna show good performances in whole UWB band except for rejection bands based on VSWR 2.0. The proposed UWB antenna was simulated using High Frequency Struture Simulator (HFSS) by Ansoft. The simulated antenna showed dual rejection bands of 3.31~3.92 GHz and 5.04~5.90 GHz in UWB band, and measured antenna showed dual rejection bands of 3.35~3.97 GHz and 5.06~5.97 GHz. The largest VSWR values measured at each rejection band are 13.60 at 3.64 GHz and 10.25 at 5.52 GHz. The measured maximum gain is 5.31 dBi at 10.00 GHz. The lowest gains for the measured antenna at rejection bands are -8.73 dBi at 3.70 GHz and -4.36 dBi at 5.56 GHz.

• ETRI Journal
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• v.31 no.3
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• pp.324-326
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• 2009

We present the design of a compact microstrip lowpass filter with a wide stopband which is up to ten times the cutoff frequency. The filter is based on a coupled-line configuration and shunt open stubs. The open stubs create additional transmission zeros, which are used to extend the stopband of the filter without any additional components or cascaded units. A prototype lowpass filter with a 3 dB cutoff frequency of 0.428 GHz and a 15 dB stopband extended up to 4.77 GHz is fabricated to validate the theoretical predictions.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.661-664
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• 2008

U-Eco City is promoted nation-wide by development of recent IT technology, method of effective countermeasure disasters, which real-time wire/wireless communication network, and 3D-Web GIS shall be connected that massive database, intelligent service be perceived. U&V-City is the four-dimensional future city that actualizes an intelligent daily ubiquitous computing service by embodying 3D-Virtual City, the reproduction of real world U-City while using Digital map, satellite image, VRML(Virtual Reality Modeling Language), which are presentation tool to describe city components and by efficiently catch and cope about nature and human disasters while employing EAI(External Authoring Interface) that provides HTML&JAVA, and interface for efficient removal/process of massive information/service and also by employing GPS/LBS/Navigation in support of the world-wide orientation concept, and RTLS(Real Time Location System).

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2008.10b
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• pp.629-633
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• 2008

Recently, there has been great interest in the application of short-range wireless communication system. In this paper, the miniaturized FM transmitter with low power is developed, and laboratory tests have been carried out. The FM transmitter uses FM radio waves to send sound from any system (MP3, PMP, PDA, MP3 Phone et.) to any nearby radio or stereo system. The transmitter is designed with $2.6cm{\times}2.6cm{\times}2.6cm$ system size. The operating voltage is 3.7 V and used the built-in storage battery. The system can use continuously during 7 hour with once charging. The transmission frequency can select one of 88.1 MHz, 88.3 MHz, or 88.5 MHz in compliance with utility condition. The channel separation ability is 40 dB. The operating temperature is $-10{\sim}+85^{\circ}C$, which use in the industry environment. Consequently, this system sis used conveniently with short distance information transmitter system at the industry field.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.1
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• pp.42-46
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• 2003

In this paper, an MMIC broadband amplifier for wireless communication systems has been developed by using an active feedback method. This active feedback operates at much higher frequencies than a method by a spiral inductor feedback and its size is independent of the inductance value. The MMIC broadband amplifier was designed using a $0.5{\;}{\mutextrm{m}}$ MESFET library. The fabricated chip area was $1.4{\;}mm{\;}{\times}{\;}1.4{\;}mm. Measurement showed a gain of 18 dB with a gain flatness of ${\pm}3$ dB in a 1.5 GHz~3.5 GHz band. The maximum output power and the minimum noise figure were 14 dBm and 2.5 dB in the same band, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.570-572
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• 2012

In this paper, a three-dimensional (3-D) low-loss and wide-band BPF based on low-temperature co-fired ceramic (LTCC) has been presented for mm-wave wireless communication applications. The proposed BPF is designed in a 6-layer LTCC substrate. The double patch resonators are fully integrated into the LTCC dielectrics and vertical via and planar CPW transitions are designed for interconnection between embedded resonators and in/output ports and MMICs, respectively. The designed BPF was fabricated in a 6-layer LTCC dielectric. The fabricated BPF shows a centre frequency (fc) of 53.23 GHz and a 3dB bandwidth of 14.01 % from 49.5 to 56.9 GHz (7.46 GHz). An insertion loss of -1.56 dB at fc and return losses below -10 dB are achieved. Its whole size is $4.7{\times}1.7{\times}0.684mm^3$.

• Journal of IKEEE
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• v.16 no.2
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• pp.69-75
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• 2012

In this paper, microstrip array antenna is proposed for the wireless communication of DSRC(dedicated short range communication) scheme at 5.8GHz, which works as a part of the Navigation terminal. The microstrip patches minimized from a rectangular microstrip antenna with a half wavelength are arrayed to be mounted on the narrow and long area in the top side of the navigation terminal. Besides, the array antenna can limit its own beamwidth to the driving lane and has better directivity. It is simulated to verify the validity of the proposed application. The prototype fabricated has a volume of $18{\times}40{\times}0.8mm^3$. From the measurement, it has circular polarization performance of 4dB axial ratio over 40MHz frequency band. In addition, antenna gain of 6.2dBi and 3dB beamwidth of $70^{\circ}$ at cross section of driving lane have been achieved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2B
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• pp.167-173
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• 2004

This paper reports on the development of a 60㎓ wide bandwidth wireless transceiver using NRD waveguide. We fabricated a wireless transceiver using NRD waveguide, which consists of a 3 dB directional coupler, a bandpass filter, a Gunn oscillator, an ASK modulator, and a Balanced Mixer. The new transceiver is capable of transmitting an output power of 10mW to a distance of more than 1 Km, operating in 60㎓ frequency and bandwidth of 2㎓. The value of BER reached approximately 10 when the transceiver was tested at the 155.52Mbps ATM(OC 3) at the communication distance of 1 km. It demonstrated an impressively stable transmission feature of BER l0$^{6}$ even in the heavy rainfall.