Jong-Hyuk Lim

A Reconfigurable PIFA Using a Switchable PIN-Diode and a Fine-Tuning Varactor for USPCS/WCDMA/m-WiMAX/WLAN

A reconfigurable planar inverted-F antenna using a switchable PIN-diode and a fine-tuning varactor is presented for mobile communication applications. Selection of operating modes is achieved by switching the PIN-diode between radiators and tuning the varactor on an antennas shorting line. Mode I, with the PIN-diode off and tuning the varactor, operates for USPCS (1.85-1.99 GHz), WCDMA (1.92-2.18 GHz), and WLAN (5.15-5.825 GHz). As a result, the varactor used to achieve frequency fine-tuning does not need a DC bias circuit and can expand the bandwidth without increasing the physical size. Mode II, with the PIN diode on and the fixed 0-V varactor, operates for USPCS and m-WiMAX (3.4-3.6 GHz). To optimize the antenna structure, a parametric analysis is performed by sweeping the length and width of the radiators. Furthermore, equivalent models of a PIN diode and a varactor are presented for accurate prediction of antenna performances which are also analyzed by varying diode parameters. All simulated results are confirmed with measured data. The peak gains show 2.84, 2.81, 1.25, and 1.49 dBi at USPCS, WCDMA, m-WiMAX, and WLAN, respectively.

Simultaneous Frequency and Isolation Reconfigurable MIMO PIFA Using PIN Diodes

A reconfigurable multiple input multiple output (MIMO) planar inverted-F antenna (PIFA) is presented for three worldwide m-WiMAX bands: 2.3-2.4 GHz, 2.5-2.7 GHz, and 3.4-3.6 GHz. In order to achieve low mutual coupling, i.e., high isolation, a band-notched quarter-wave slot line on the ground plane is used between the two reconfigurable antennas. Two PIN-diodes are appropriately located on the slot line in order to electrically control the slot length. By adjusting both the PIN-diode biases for the reconfigurable antennas and the reconfigurable isolation slot, the proposed antenna simultaneously obtains the operating frequency and isolation reconfigurability for the three operating bands. A parametric analysis is performed to investigate optimized slot lengths for the three operation modes. All of the simulated results are confirmed with measurements. Measured isolation performance of greater than 30 dB improves the radiation efficiency, diversity gain, and channel capacity for all operating frequencies.

Reconfigurable antenna for Korean WIBRO and DMB systems

This paper presents a novel reconfigurable antenna to achieve the frequency diversity. The proposed reconfigurable antenna can select a Korean wireless broadband Internet (WIBRO) over 2300 - 2400 MHz or Korean digital multimedia broadcasting (DMB) over 2605 - 2655 MHz band, using PIN-diode on and off. Slits are inserted on the patch to increase an electrical length and PIN-diodes are allocated on the slits to switch them. Therefore the antenna has size reduction and control operating bands. The measured bandwidth has SO MHz at the WIBRO band and 70 MHz at the DMB band. The antenna gain is obtained from 0.2 dBi to 2.2 dBi.

Fan Noise Reduction of a Vehicle BSG Motor

In this study, we studied fan noise reduction of a vehicle BSG (belt driven starter & generator) motor. The noise levels and frequency spectra of the BSG motor were measured experimentally. Based on these results, the blade passing frequency (BPF) generated by the fan was proven to be the main noise source of the BSG motor. In order to reduce the fan noise, design parameters of the fan were selected and noise analysis was performed through simulation. Using the design of experiments, the influence of the design parameters on the noise was analyzed and the fan design to reduce the fan noise was performed. Finally, the improved fan was manufactured and the noise test was performed. The noise level of the BSG motor with the improved fan was evaluated by comparison with the noise level of the existing BSG motor.

A Mode Sorting Method Using the MAC of a Rotor-bearing System

ABSTRACT This paper presents a sorting method of mode vectors and natural frequencies about a rotor-journal bearing system. The rotor is solved by the finite element method, the bearing stiffness and damping coefficient are solved by the finite difference method. At any rotation speed section through the ei-genvalue analysis of the system, mode vectors and natural frequencies not sorted are confirmed via the Campbell diagram and the MAC(modal assurance criterion). To sort mode vectors and natural frequencies of the section, a mode sorting method is presented through a method of rearranging the MAC of the mode vectors. Finally, the mode vectors and the natural frequencies are sorted by using the presented method, these are verified through the MAC. * 기 호 설 명 B : 베어링 감쇠 c : 베어링 간극 D : 베어링 직경 h : 베어링 유막두께 K : 베어링 강성 p : 유막압력 R : 베어링 반경 W : 축하중λ : 고유진동수 : 유막점성계수Ω : 회전속도ψ : 모드벡터 M : 질량행렬 G : 자이로스코픽 행렬 K : 강성행렬 1. 서 론 현대 기술이 발전함에 따라 산업체에서 사용되는 대부분의 대형 회전기계들은 고속 운전에 따른 고출력, 경량화 그리고 경제적 차원에서의 설계비용 절감을 목표로 하고 있다. 이러한 이유로 고속운전에 따른 고출력 및 경량화의 목표달성을 위해 설계단계에서의 회전축계 시스템의 정확한 동특성 해석이 요구되고 있다.대형 회전축계 시스템의 개선된 설계를 위해 회전축(rotor)과 그것을 지지하는 저널베어링에 대한

Small antennas combining multiple bands with MIMO techniques

A small PIFA using multi-band, wide-band, high-isolation MIMO techniques, covering GSM900/DCS/PCS/UMTS/WLAN operational bands, has been demonstrated using both simulations and measurements. In order to achieve the wide bandwidth required for DCS/PCS/UMTS services, a resonator and a meander shorting line were adopted. In addition, a modified neutralization link was incorporated to obtain the high isolation characteristic necessary for a MIMO WLAN service. Simulations and measurements demonstrated very similar results for S-parameters, ECC, and radiation patterns. In addition, Good diversity characteristics for the WLNA band are also achieved. Therefore, the proposed antenna combining a multi-band antenna with MIMO antennas will be useful for future mobile handset applications.

Patterned Helical DVB-T Antenna With an Open Stub and a Matching Network

A miniaturized embedded digital video broadcasting-terrestrial (DVB-T) antenna with a patterned helical structure is proposed for mobile broadcasting. An open stub and a matching network are used in order to achieve a compact size and a wide bandwidth, respectively. The antenna has a volume of 58.83.29 mm3, which is small enough for use in mobile handsets. The measured results satisfy the DVB-T bandwidth requirements from 174 to 230 MHz and show omnidirectional radiation patterns with antenna gains ranging from -21 to -11 dBi.

Frequency-Diversity Patch Antenna for WiBro and Satellite-DMB

This letter presents a reconfigurable antenna with a microstrip patch that uses PIN-diode connections on slits to achieve frequency diversity. By switching the diodes on or off, a surface current path on the antenna is changed, which effectively results in shifting the operating frequency. Thus the antenna can select both WiBro and DMB bands.

A microwave modeling of multilayered chip inductors

In this paper a new microwave equivalent-circuit making use of mathematical analysis is presented for multilayer chip inductors. Parasitic effects are introduced by turns of conductors in the multilayer chip inductor especially at microwaves and create an intricate equivalent-circuit reduced into a new equivalent-circuit confirmed with mathematical analysis. The proposed equivalent-circuit is confirmed with measurement from 2.7 to 8.2 nH on a Teflon substrate up to 13 GHz.