• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.975-983
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• 1998

A duplexer filter operating at 1.9 GHz band for personal communication system is designed and fabricated using $lambada$/4 TEM mode dielectric resonator. The transmitting band pass filter is designed in the type of the elliptic function band rejection filter by 3 dielectric resonators with 5 additional capacitors and 3 inductors. The receiving band pass filter is designed by 3 dielectric resonators with 5 additional capacitors which give additional series resonance. The parameters which are evaluated by design theory are practically applied to the duplexer filter construction and the simulation.

• ETRI Journal
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• v.28 no.4
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• pp.529-532
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• 2006

This letter describes a compact printed helical resonator and its application to a microwave oscillator circuit implemented in coplanar waveguide (CPW) technology. The high quality (Q)-factor and spurious-free characteristic of the resonator contribute to the phase noise reduction and the harmonic suppression of the resulting oscillator circuit, respectively. The designed resonator showed a loaded Q-factor of 180 in a chip area of only 40% of the corresponding miniaturized hairpin resonator without any spurious resonances. The fully planar oscillator incorporated with this resonator showed an additional phase noise reduction of 10.5 dB at a 1 MHz offset and a second harmonic suppression enhancement of 6 dB when compared to those of a conventional CPW oscillator without the planar helical resonator structure.

• Journal of electromagnetic engineering and science
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• v.6 no.3
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• pp.160-164
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• 2006

This paper describes a compact printed helical resonator and its application to a microwave oscillator circuit implemented in coplanar waveguide(CPW) technology. The high Q-factor and spurious-free characteristic of the resonator contribute to the phase noise reduction and the harmonic suppression of the resulting oscillator circuit, respectively. The designed resonator resonating at the frequency of 5.5 GHz showed a loaded Q of 180 in a chip area of only 40 % of the corresponding miniaturized hairpin resonator without any spurious resonances. The fully planar oscillator incorporated with this resonator showed additional phase noise reduction of 10.5 dB at 1 MHz offset and a second harmonic suppression enhancement of 6 dB when compared to those of a conventional CPW oscillator without the planar helical resonator(PHR) structure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.459-468
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• 2014

An additional relationship equation is numerically obtained to increase the accuracy of the conventional equation for obtaining the resonant frequency of a resonator. Although the conventional equation is widely used in industry because of its simplicity, it does not provide enough information on the cavity or the neck of the resonator for noise reduction in a duct. Resonator designers have difficulty implementing resonator design owing to the uncertainty in geometry presented by the well-known formula for determining the resonant frequency. To overcome this problem, this work determines an approximate equation using results of numerical calculation. To this end, shape parameters of the neck and cavity of a resonator are defined, and an equation describing the relationship between them is derived by adjusting the peak frequency in the transmission loss curve of a resonator to its resonant frequency. The application and validity of the derived equation are investigated in a numerical simulation and an acoustic experiment, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.865-868
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• 2005

A Helmholtz resonator is one of noise control elements widely used in many practical applications. The resonator has very high absorption at resonance frequency but the frequency bandwidth is very small. Therefore many kinds of additional resistive screens have been applied to the resonator's neck in order to increase the bandwidth. This paper discusses the absorptive characteristics of a Helmholtz resonator damped by a flexible porous screen in form of wire mesh. First, various experimental results are introduced and studied. Secondly, the effect of the resistive screen is theoretically predicted. It is shown that the distance between the screen and aperture affects on the resonance frequency as well as the absorption of the system.

• Journal of electromagnetic engineering and science
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• v.9 no.3
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• pp.164-173
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• 2009

In this paper, two new circuit structures for European and U.S. ultra-wide band(UWB) bandpass filters(BPFs) with sharp roll-off characteristics are introduced. We show first that the ultra-wide bandpass property is obtained from a $\lambda$/4 open T resonator with a capacitively coupled $\lambda$/4 short-circuited line, which provides two attenuation poles at lower and upper cutoff frequencies. Then, two identical capacitively coupled input/output lines, which can be $\lambda$/4-length open ends or $\lambda$/2-length short ends, with the T-resonator, are adopted to suppress lower and higher frequency components outside of the pass band. There is coupling between the input and output lines providing two additional transmission zeros in the lower and upper transition bands of the filter. Since the coupling between the T-resonator with the $\lambda$/4 short-circuited line and the input/output lines limits the bandwidth of the filter to the European UWB band, both the $\lambda$/4 short-circuited line and the input/output lines are inserted between the two stacked T-resonators for the U.S. UWB band. The filter structures are simulated with ADS and HFSS and realized with low-temperature co-fired ceramic(LTCC) green tape which has the dielectric constant of 7.8. Measurement results agree well with HFSS simulation results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.915-921
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• 2020

Thermoacoustic instability caused by air conditioning in a combustion chamber has emerged as a problem that must be solved to establish a stable combustion system. Thermoacoustic instability is largely divided into primary and secondary acoustic instability. In this study, an experimental study of the effects of heat losses was conducted to investigate the mechanism of secondary acoustic instability. To generate the secondary acoustic instability, a quarter-wavelength resonator with one open end and one closed end was used, and the inside of the resonator was filled with premixed gases. Subsequently, secondary acoustic instability with downward-propagating flames could be realized via thermal expansion on the burnt side. To control heat losses qualitatively, an additional co-axial tube was installed in the resonator with air or nitrogen supply. Therefore, additional diffusion flames can be formed at the top of the resonator depending on the injection of the oxidizer into the co-axial tube when rich premixed flames are used. Consequently, secondary acoustic instability could not be achieved by increasing heat losses to the ambient when the additional diffusion flame was not formed, and the opposite result was obtained with the additional diffusion flame.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.6
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• pp.52-58
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• 2008

In this paper, electrically small square loop antenna with SRR (Split Ring Resonator) cover structure is built and tested. The proposed antenna has very small size, ka = 0.34 by Chu limit. The experimental result shows that the resonant frequency and impedance bandwidth($VSWR{\leq}2$) are 906MHz and 5.8MHz (901.7 - 907.5MHz), respectively. The proposed antenna is matched and designed by equivalent circuit model. The proposed antenna is fabricated simple structure without additional matching network and printed on a Teflon substrate without ground plane. Therefore, it has advantages of low cost, small size, and light weight and will be applied to wireless communication systems where small antennas are required.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.1
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• pp.107-114
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• 2021

In this paper, a planar transistor oscillator for X-band using a newly proposed L-shaped monopole slot resonator is proposed. For planar design, an L-shaped monopole slot with an open-end is used as a resonator for a transistor oscillator. As a result of the simulated design of the resonator in three stages, a high Q value of 1169.84 and a high insertion loss of 49.934 dB were identified. The results of the final design and manufactured oscillator measurements confirmed that the oscillation output is greater than 7 dBm and has good phase noise characteristics of -58 dBc/Hz at 100 kHz offset. The proposed oscillator is planar and has the advantage of being directly applicable to microwave integrated circuit technology. It also has the advantage of being able to reduce its size as it can only be implemented in microstrip form without additional devices such as metal cavities and tuning screws in 3D structures, as in the case of a DRO (dielectric resonance oscillator).

• ETRI Journal
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• v.41 no.2
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• pp.167-175
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• 2019

A wideband dual-polarized antenna coupling cross resonator is proposed for LTE700/GSM850/GSM900 base stations. An additional resonance is introduced to obtain strong coupling between the dipole and resonator. Moreover, the input impedance of the proposed antenna is steadily close to $50{\Omega}$, which results in better impedance matching. Therefore, a wide bandwidth can be achieved with multiresonance. A prototype is fabricated to verify the proposed design. The measured results show that the antenna has a fractional bandwidth of 35.7% from 690 MHz to 990 MHz for ${\mid}S_{11}{\mid}$ < -15 dB. Stable radiation patterns as well as gain are also obtained over the entire operating band. Moreover, a five-element antenna array with an electrical downtilt of $0^{\circ}$to $14^{\circ}$ is developed for modern base station applications. Measurement shows that a wide impedance bandwidth of 34.7% (690 MHz to 980 MHz), stable HPBW (3-dB beamwidth) of $65{\pm}5^{\circ}$, and high gain of $13.8{\pm}0.6dBi$ are achieved with electrical downtilts of $0^{\circ}$, $7^{\circ}$, and $14^{\circ}$.