• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.1
• /
• pp.37-43
• /
• 2001

In this paper, we designed a linear power amplifier considering its delay characteristics fur wideband operation. The power amplifier has the gain of 37 dB and is designed in 3-stage typ with 1W output power. The error amplifier has the gain of 55 dB and is designed in 4-stage typ. And directional coupler and power divider are designed. Vector modulator is used to adjust magnitude and phase of signal. A linear power amplifier, that is assembled with each modules, is designed considering the delay characteristics for 2.11~2.2 GHz. Its C/I3 ratio has been improved by B5 dB for bandwidth of 30 MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.6 s.121
• /
• pp.674-679
• /
• 2007

In this paper, the size of the dual-mode microstrip ring resonator is reduced by adding four open stubs, and bandpass filters having 100 MHz bandwidth are designed at the center frequency of 2 GHz. The size of the ring resonator can be controlled by varying the capacitance of the stubs, and the bandpass filter can be designed in two cases, which are two combinations of the stubs. Two bandpass filters are designed and fabricated by using the two-stage bandpass filter circuit model of the proposed structure, and the measured results show good agreement with the simulated results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.2
• /
• pp.99-108
• /
• 2018

This paper presents a design study of a solid state power oscillator to replace the conventional magnetron. The operational conditions of a single-stage 300 W LDMOS power amplifier were fully characterized. The power module consisted of two amplifiers connected in parallel. A delay-line feedback loop was designed for self-oscillation. A phase shifter was inserted in the delay-line feedback loop for adjusting the round-trip phase. Experiments performed using the power oscillator showed an output power of 800 W and a DC-RF conversion efficiency of 58 % at 2.327 GHz. The measured results were in good agreement with those predicted by numerical simulations.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.2 no.2
• /
• pp.37-43
• /
• 2009

In this study, multi-channel digital hearing aid algorithm for low power system is proposed. First, MDCT(Modified Discrete Cosine Transform) method converts time domain of input speech signal into frequency domain of it. Output signal from MDCT makes a group about each channel, and then each channel signal adjusts a gain using LCF(Loudness Compensation Function) table depending on hearing loss of an auditory person. Finally, compensation signal is composed by TDAC and IMDCT. Its all of process make progress 16-bit fixed-point operation. We use fast-MDCT instead of MDCT for reducing system complexity and previously computed tables instead of log computation for estimating a gain. This algorithm evaluate through computer simulation.

• KIPS Transactions on Computer and Communication Systems
• /
• v.5 no.5
• /
• pp.103-108
• /
• 2016

In this paper, we propose a resource allocation scheme that guarantees transmission rate for each mobile stations by mitigating interference between a base station-to-mobile station link and a relay station-to-mobile station link. Specifically, we dynamically adjust the boundary between access zone and relay zone using signal to interference plus noise ratio. Moreover, we cluster the mobile stations under sever interference and manage the channel quality of these mobile stations by allocating additional radio resource. Our simulation results show that the proposed scheme can improve the efficiency of radio resources and ensure fairness among mobile stations.

• Korean Journal of Optics and Photonics
• /
• v.9 no.4
• /
• pp.270-273
• /
• 1998

We have demonstrated the wavelength tunable ultrashort pulse fiber ring laser proposed the novel method for measuring the cavity loss from relaxation oscillation frequency and the pump power. To suppress the polarization instability the laser cavity is configured with polarization maintaining fibers and to control the center wavelength a 2.4 nm bandwidth tunable wavelength filter was inserted in the cavity. The laser has 8 picosecond pulse width, 10 GHz repetition rate and 1.2 mW average power in 1530-1560 nm operation range.

• Journal of Korea Multimedia Society
• /
• v.6 no.2
• /
• pp.319-324
• /
• 2003

In this paper, a new wideband tunable analog element for multimedia system is proposed. The proposed active element is composed of the complementary cascode circuit which can extend transconductance of an element. Therefore, the unity gain frequency which is determined transconductance is increased than that of the conventional element. And then these results are verified by the 0.22$\mu\textrm{m}$ CMOS n-well parameter simulation. As a result, the gam and the unity gam frequency are 42dB and 200MHz on 2V supply voltage. And power dissipation of the designed element is 0.32mW.

• Journal of Korea Multimedia Society
• /
• v.14 no.5
• /
• pp.650-657
• /
• 2011

This paper proposes a novel bit allocation algorithm for H.264 scalable extension(SE) based on a human visual system (HVS) to improve the coding efficiency. The proposed algorithm is consist of two stages: visual weighting model and visual weighting-based bit allocation algorithm. In the first stage, the visual weighting for each macroblock (MB) is analyzed according to the region of interests. Then the adaptation of the visual weighting into the bit allocation routine for each quality layer is performed for improving the visual quality. In the simulation results, it is observed that the proposed scheme can improve the subjective and objective video quality in the same bit rate, compared to the previous scalable video coding in H.264.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.644-647
• /
• 2004

RF 시스템에서 발룬(Balun)은 회로기판과 집적회로 사이의 임피던스 매칭에 사용되는 소자로서, 전력의 균등한 분배와 함께 180도 위상차를 만드는 역할을 하는 주요 회로부품이다. 시스템의 요구사양에 따라 balanced 임피던스가 $50\Omega$인 소자뿐만 아니라, 25 또는 100, $200\Omega$인 소자들도 많이 사용되는데, 대부분의 계측기가 $50\Omega$을 I/O 임피던스로 설정하고 있어, balanced 임피던스가 $50\Omega$이 아닌 경우 특성을 측정하기 위해서는 별도의 지그설계가 필요하다. 본 연구에서는 중심주파수가 900MHz이고, balanced 임피던스가 $100\Omega$이며, LTCC 모듈 내에 내장되는 임베디드 발룬의 최적 평가를 위한 PCB 측정지그의 구조에 대하여 설계 및 시뮬레이션을 실시하고, 이에 따라 제작된 지그를 시뮬레이션 결과와 비교하였다. 지그를 구성하는 마이크로스트림의 임피던스를 조절함으로써 유효한 측정주파수범위를 넓힐 수 있었으며, 제작된 지그는 설계치에 거의 근접한 전송특성을 나타내었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.10a
• /
• pp.137-140
• /
• 2004

Oscillating heat release associated with periodic vortex-flame interaction was investigated experimentally. Turbulent jet flames were stabilized with recirculating hot products in a dump combustor, and large-scale periodic vortices were imposed into the jet flame by acoustic forcing. Forcing frequencies and operating parameters were adjusted to simulate unstable combustor operation in practical combustors. The objectives were to characterize vortex-heat release interaction that leads to unwanted heat release fluctuations and to identify the proper fuel injection pattern that could be used for actively suppressing such fluctuations. Phase-resolved CH* chemiluminescence and schlieren images were used as diagnostic tools. The results were compared at corresponding phases of vortex shedding cycle.