• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.770-773
• /
• 2004

The transmission loss coefficient is very important acoustic property in parallel with absorption and acoustic impedance categorizing the acoustical materials, which can control the acoustical problems. At the same time, the transmission loss coefficient is a key parameter to choose the optimum material for the analysis of acoustical characteristics of material using SEA(Statistical Energy Analysis). In this paper, the acoustic transmission loss measurement system using 4-microphone TL tube is applied to the exhaust system, which is one of the most important acoustic control parameters in a car, based on the idea calculating the full transfer matrix. The theoretical background and measurement system are introduced, and finally the measurement results are verified.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.7
• /
• pp.718-724
• /
• 2008

A flexible structure submerged in acoustic fluid is affected by its surrounding fluid. In this case, the coupling effects between structures and surrounding fluid have an effect on the submerged structure as external force and change impedance of acoustic domain. Therefore, the coupling effects by its surrounding fluid complicatedly change the characteristics of a submerged structure such as natural frequencies and damping coefficients. In this paper, using the analytic modal equation of a spherical shell surrounded by water and air, the complex changes of damping coefficients and natural frequencies of submerged structures are studied for various external acoustic fluid and structures.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.5
• /
• pp.81-86
• /
• 2011

In this paper, fractal microstrip patch antenna in a semicircle, by designing a multi-resonant antenna was improved by bandwidth issues, including the IEEE 802.11 wireless LAN and IEEE802.16e-band mobile WiMax specification both of which can contain non-directional antenna design and measured characteristics of the antenna for multi-resonant resonant frequency, impedance matching, radiation pattern, brilliantly polarity and multiple independent frequencies that can be controlled to meet the three semicircular wireless communications by inserting fractal patch antenna was designed.

• Proceedings of the IEEK Conference
• /
• 2001.06a
• /
• pp.401-404
• /
• 2001

We designed and fabricated symmetrical partially shorted MSAs for 850 MHz band on various Copper-clad Laminates substrates, where the width of the radiation patch is identical with that of the ground plane and the radiation patch is partially shorted to the ground plane. The resonant frequency, return loss and input impedance due to the permittivity(2.5, 3.5, 10.0) and thickness(0.76~1.57 mm, 6 types) were measured by reducing the PSW (Partially Shorted Width) to 0 mm. As a result, good characterized antennas with average 11% reduced resonant length and return loss 7.288~29.445 dB were obtained when the total PSW was in the range of 70% of radiated patch width, compared to the conventional λ/4 MSA.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.30A no.5
• /
• pp.36-44
• /
• 1993

In this paper, a simple design method is represented for a contiguous-band waveguide manifold diplexer which employs a half-wavelength line at the input port of the singly terminated bandpass filterand has resonant-slot coupled E-plane T-junctions. This design method is based on the fact that the input impedance characteristics of the singly terminated bandpass filter are approximately unchanged when a resonant slot and a half-wavelength line at the input port of the filter are employed. This design method is also applicable to the design of the multiplexer. A contiguous-band waveguide manifold diplexer using the post coupled cavity filters is designed, constructed, and tested. The computed and experimental results show the validity of the theory.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2003.11a
• /
• pp.273-277
• /
• 2003

This paper presents a structure of the Wilkinson power divider that can suppress the 9ea harmonic output. The power divider consists of ${\lambda}/4n$ open stubs, which are located at the $3{\lambda}/4$ branches and parallel connection of resistor which shunts the output ports. Experimental results show that this power divider suppresses from 1st to 9th harmonic components to less than -37dB, while maintaining the characteristics of a conventional Wilkinson power divider; featuring an equal power split, a simultaneous impedance matching at all ports and a good isolation between output ports. these results agree quite well with the simulation results.

• 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.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2003.11a
• /
• pp.343-346
• /
• 2003

A new structure to design low pass filters (LPFs) is presented rho proposed structure has the etched shape of Quad-Spiral DGS(Defected Ground Structure) on microstrip transmission lines. By extracting the equivalent circuit elements of unit Quad-Spiral DGS, LPFs are designed easily. The equivalent circuit of Quad-Spiral DGS consists of a step impedance resonator and lumped elements. The proposed LPF provided steep rejection characteristics with 5-poles. Experimental results show excellent agreements with circuit simulation results in wide band and the validity of our circuit modeling for LPF design. The result shows another possibility of Quad Spiral DGS for microwave devices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.6
• /
• pp.581-585
• /
• 2013

A technique to expand the operating impedance bandwidth of a microstrip patch antenna is presented. The antenna is fed by a truncated T-shaped microstrip line on the ground plane with the rectangular slot. The proposed microstrip patch antenna offers wide bandwidth characteristics with the rectangular slot which has optimized size and position on the ground plane. The simulation result shows a fractional bandwidth of 127.8 %(0.65 to 2.95 GHz) at VSWR 2:1.

• Proceedings of the KIEE Conference
• /
• 1996.07c
• /
• pp.1407-1408
• /
• 1996

The development of MCFC is going to the second stage of development and recent studies have been focusing on long-term durability of cell component. Systematic investigation on corrosion behavior of Fe-based alloys has been done in (62+38) mol % (Li+K) $CO_3$ melt at 923K by using steady-state polarization and electrochemical impedance spectroscopy method. It was found that the corrosion current t of these Fe-based alloys decreased with increasing Cr, Al content.