• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.2
• /
• pp.50-55
• /
• 2012

Fabry-Perot (FP) resonator antennas with scan capabilities are described in this paper. The proposed antennas, excited by a thinned array, not only achieve higher directivities but also improve suppression of sidelobes relative to that of the thin array alone. Compared to the conventional microstrip patch array, the directivity enhancement and suppression of sidelobe level were achieved by increase of the aperture size of the proposed Fabry-Perot resonator antenna.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2003.11a
• /
• pp.487-491
• /
• 2003

Design procedure of corrugated horn antenna for mm-wave frequency range is presented, and hybrid condition in horn is calculated. Balanced hybrid mode should be converted in the horn from TE11 mode by the proper corrugation dimensions which size are available to be fabricated under the mm-wave short wavelength condition. In this paper, corrugate profiles which satisfy both hybrid condition and fabrication possibility are obtained.. By cylindrical mode theory, the electromagnetic fields both inside hem and corrugation are delivered. Propagation characteristics in hem is calculated by the mode impedance matching method with boundary conditions, and radiation fields are obtained by the Kirchhoff-Hyugen principle to the hem aperture fields. A mm-wave corrugated horn operates on 85 - 115GHz is designed and fabricated, and results of measurement are also shown.

• Journal of Sensor Science and Technology
• /
• v.16 no.4
• /
• pp.247-253
• /
• 2007

Low power consumption sensor network platform (sensor node) for sensor networking with IEEE 802.15.4 protocol was fabricated. The sensor node used ceramic bar type antenna for increasing RF signal performance and decreasing PCB size occupied by antenna. The communication range of the fabricated sensor node was about $20{\sim}30$ m in open environment with 915 MHz frequency bandwidth and well supported by Tiny OS. The sensor node have good connectivity with various external devices by RS-232, I2C, analogue and digital expansion board, hence, this sensor node can be applied to various applications in wireless sensor network and ubiquitous sensor network.

• Journal of electromagnetic engineering and science
• /
• v.13 no.2
• /
• pp.104-112
• /
• 2013

A novel miniaturized artificial magnetic conductor (AMC) is proposed for dual-band operation. An AMC unit cell that employs four slots in the metallic patch is used to achieve miniaturization as well as easy control of the second/first resonant frequency ratio, which can be varied from 1.5 to 3.26 by simply changing the slot shape for a given metallic patch size. A dual-band antenna composed of a wideband monopole suspended over the proposed AMC surface is designed and tested to validate this approach. The measurements result in a satisfactory and good matching condition for the dual-band antenna.

• Proceedings of the IEEK Conference
• /
• 2007.07a
• /
• pp.183-184
• /
• 2007

As the mobile communication service is widely used, the demand for wireless repeaters is rapidly increasing because of the easiness of extending service areas. But wireless repeaters has a problem that the output of the transmit antenna is partially fed back to the receive antenna, which results in feedback interference. In this paper, we investigate the performance of adaptive variable step-size NLMS-based algorithms for cancelling the interference signals in the W-CDMA system under time-varying multipath channels. The criteria for comparison are tracking capability, convergence speed, and complexity.

• Journal of Communications and Networks
• /
• v.9 no.2
• /
• pp.141-149
• /
• 2007

Multiple-input multiple-output (MIMO) transmit pre-coding/beamforming can significantly improve system spectral efficiency. However, several obstacles prevent precoding from wide deployment in early wireless networks: The significant feedback overhead, performance degradation due to feedback delay, and the large storage requirement at the mobile devices. In this paper, we propose a precoding method that addresses these issues. In this approach, only 3 or 6 bits feedback is needed to select a precoding matrix from a codebook. There are fifteen codebooks, each corresponding to a unique combination of antenna configuration (up to 4 antennas) and codebook size. Small codebooks are prestored and large codebooks are efficiently computed from the prestored codebook, modified Hochwald method and Householder reflection. Finally, the feedback delay is compensated by channel prediction. The scheme is validated by simulations and we have observed significant gains comparing to space-time coding and antenna selection. This solution was adopted as a part of the IEEE 802.16e specification in 2005.

• Journal of electromagnetic engineering and science
• /
• v.17 no.2
• /
• pp.51-56
• /
• 2017

This study proposes a modeling process of equivalent terrains to reduce the computational load and time of a full-wave electromagnetic (EM) simulation. To verify the suitability of the proposed process, an original terrain model with a size of $3m{\times}3m$ is equivalently quantized based on the minimum range resolution of a radar, and the radar image of the quantized model is compared with that of the original model. The results confirm that the simulation time can be reduced from 407 hours to 162 hours without a significant distortion of the radar images, and an average estimation error of the quantized model (20.4 mm) is similar to that of the original model (20.3 mm).

• Journal of Electrical Engineering and Technology
• /
• v.9 no.3
• /
• pp.997-1001
• /
• 2014

In this paper, the interference in small MIMO antennas having two identical composite right- and left-handed transmission-line(CRLH-TL)-based radiating elements is remarkably decreased. The radiating element has the broadside-capacitive coupling as well as slots to be equivalent to the CRLH-TL to prevent the size from increasing for an LTE high band. The suspended line bridging the two radiating elements is optimized to lower the interference between them down to -23 dB, while the overall MIMO antenna system is compact and its antenna performance is acceptable. The design is tested for 2.5 GHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.465-466
• /
• 2007

In electrode-less lamp, The key point in creating an efficient light source based on RF discharge is to minimize the RF power loss in the RF coupler which for Anderson's type of RF lamp is due to losses in the ferrite core. This loss depends on the particular ferrite material, its size, geometry, frequency in this kind of inductive lamp shows that the correct choice of discharge current has a crucial effect on the core loss. In this study, we measured Ferrite temperature in normal state, then analyzed electrical and optical characteristics according to ferrite shape. We were able to know that was ferrite of the antenna had relate closely with temperature and luminous of the lamp. Also we appraised temperature and electrical, optical properties during turn on the lamp.

• Journal of the Korea Society of Computer and Information
• /
• v.24 no.7
• /
• pp.71-78
• /
• 2019

This paper describes a design for a RF receiver to receive satellite digital audio service. The RF receiver designed in this study is a planar structure that is easy to install on the rooftop of a car and is compact in size. In addition, it can be applied to certain commercial models because it has low noise and high gain characteristics. The impedance bandwidth of antenna is 17.8%(415MHz), and the axial ratio is below 3dB as good properties for the bandwidth of 40MHz which is a satellite digital audio service band. Also, it had a broad radiation beamwidth of $95.41^{\circ}$ in H-plane and $117.45^{\circ}$ in E-plane. From the results of the field test of satellite digital audio service reception for the RF receiver, it demonstrated good C/N rate(10.2dB).