• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.12
• /
• pp.1367-1374
• /
• 2008

A new high-gain Fabry-$P{\acute{e}}rot$ cavity antenna for wireless broadband internet(Wibro) base station antennas, which is covered with metamaterial superstrate presenting simultaneous negative values of permittivity and permeability, is proposed. To facilitate the fabrication process using the printed circuit board(PCB) technology of today, a new planar-type metamaterial superstrate is designed, which shows negative and low positive values of a refractive index near the Wibro service frequency band. And the principle of antenna gain enhancement is analyzed from the two different view points of effectively low refractive index and of the Fabry-$P{\acute{e}}rot$ resonance condition. Single square patch antenna is used as a feeder. The separation distance is determined by considering the reflection phases of the metamaterial superstrate and the substrate satisfying Fabry-$P{\acute{e}}rot$ resonance condition, respectively. Comparison between the prediction and the measurement shows good agreement, which verifies the validity of our design approach.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.10
• /
• pp.1171-1179
• /
• 2012

In this study, we consider a dynamic positioning system (DPS) design problem that can be extended to many application fields. Toward this end, tracking and positioning control problems are discussed. In particular, we design a tracking control system that incorporates an observer based on the 2-DOF servo system design approach in order to obtain the desired state information. In the case of observer design, a weighted $H_{\infty}$ error bound approach for a state estimator is considered. Based on an algebraic Riccati equation (inequality) approach, a necessary and sufficient condition for the existence of a full-order estimator that satisfies the weighted $H_{\infty}$ error bound is introduced. The condition for the existence of the estimator is denoted by a linear matrix inequality (LMI) that yields an optimized solution and the observer gain.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.24 no.6
• /
• pp.628-633
• /
• 2014

This paper proposes a performance improvement method of the conventional double talk detection method which can operate before convergence of the echo canceller. The proposed method estimates the coefficients of the linear predictive coding(LPC) filter by using the primary input signal. The time-varying threshold for double talk detection is determined based on the LPC filter gain of the primary input signal level. The proposed method can reduce not only false detection rate which means wrong detection of single talk as double talk but also double talk detection delay. Computer simulation was performed using a long-term real speech signals. It is shown that the proposed method improves the conventional method in terms of lowering the false detection rate and shortening the detection delay.

• Korean Journal of Optics and Photonics
• /
• v.33 no.3
• /
• pp.99-105
• /
• 2022

We have evaluated the performance of an all-optical automatic gain-controlled (AGC) erbium-doped fiber amplifier (EDFA) to suppress the optical signal fluctuation induced by atmospheric turbulence in terrestrial free-space optical communication systems. In our measurements, the input power into the EDFA was set to be -30 dBm and -10 dBm to operate the amplifier in the small-signal and saturation regions, respectively. The fluctuations in the optical signal were emulated with an acousto-optic modulator driven with a sinusoidal voltage. From the measured results, we have found that an all-optical AGC EDFA could suppress the optical signal fluctuation effectively, as long as the EDFA operated in the small-signal region with a high feedback amplified spontaneous emission (ASE) power.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.40 no.9
• /
• pp.673-684
• /
• 2003

A degenerated differential pair has been widely used as a standard topology for digitally programmable CMOS VGAs. A variable degeneration resistor has been implemented using a resistor string or R-2R ladder with MOSFET switches. However, in the VGAs using these conventional methods, low-voltage and high-speed operation is very hard to achieve due to the dc voltage drop over the degeneration resistor. To overcome this problem a new variable degeneration resistor is proposed where the dc voltage drop is almost removed. Using the proposed gain control scheme, a low-voltage and high-speed CMOS VGA is designed. HSPICE simulation results using a 0.25${\mu}{\textrm}{m}$ CMOS process parameters show that the designed VGA provides a 3dB bandwidth of 360MHz and a 80dB gain control range in 2dB step. Gain errors are less than 0.4dB at 200MHz and less than l.4dB at 300MHz. The designed circuit consumes 10.8mA from a 2.5V supply and its die area is 1190${\mu}{\textrm}{m}$${\times}$360${\mu}{\textrm}{m}$.

• The Korean Journal of Air & Space Law and Policy
• /
• v.35 no.1
• /
• pp.63-101
• /
• 2020

'Flight safety zone' means a zone that the Minister of National Defense designates under Articles 4 and 6 of the Protection of Military Bases and Installations Act (hereinafter 'PMBIA') for the safety of flight during takeoff and landing of military aircrafts. The purpose of flight safety zone is to contribute to the national security by providing necessary measures for the protection of military bases and installations and smooth conduct of military operations. In this case, when the state set and used the flight safety zone, the landowner claimed restitution of unjust enrichment against the country. This article is an analysis based on the existing legal theory regarding the legitimacy of plaintiff's claim, and the summary of the discussion is as follows. A person who without any legal ground derives a benefit from the property or services of another and thereby causes loss to the latter shall be bound to return such benefit (Article 741 of the Civil Act). Since the subject matter is an infringing profit, the defendant must prove that he has a legitimate right to retain the profit. The State reserves the right to use over the land designated as a flight safety zone in accordance with legitimate procedures established by the PMBIA for the safe takeoff and landing of military aircrafts. Therefore, it cannot be said that the State gained an unjust enrichment equivalent to the rent over the land without legal cause. Expropriation, use or restriction of private property from public necessity and compensation therefor shall be governed by Act: provided, that in such a case, just compensation shall be paid (Article 23 (1) of the Constitution of The Republic of KOREA). Since there is not any provision in the PMBIA for loss compensation for the case where a flight safety zone is set over land as in this case, next question would be whether or not it is unconstitutional. Even if it is designated as a flight safety zone and the use and profits of the land are limited, the justification of the purpose of the flight safety zone system, the appropriateness of the means, the minimization of infringement, and the balance of legal interests are still recognized; thus just not having any loss compensation clause does not make the act unconstitutional. In conclusion, plaintiff's claim for loss compensation based on the 'Act on Acquisition of and Compensation for land, etc. for Public Works Projects', which has no provision for loss compensation due to public limits, is unjust.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2005.05a
• /
• pp.119-124
• /
• 2005

순로구분 자동화 시스템이 상용화를 앞두게 됨에 따라 실제 순로구분기의 운영계획을 비롯한 자동화 방안 등에 대한 연구가 활발히 진행되고 있다. 또한 순로구분기의 유형의 결정과 운영 방식을 고려한 자동화 효과를 분석하여 실제로 어느 정도의 경제적 효익이 발생할 수 있는가에 대한 청사진이 제시되어야 할 필요성이 있다. 그러나, 이제까지 순로구분의 자동화와 순로구분 시스템의 효율적인 운영을 위한 사업의 타당한 당위성이나 최적의 사업 및 운영에 대한 목표 등의 구체적인 모델링이 없었으며, 이러한 모델링을 위한 분석체계가 미흡했던 것이 사실이다. 이에 본 연구는 순로구분의 자동화 효과에 대한 경제성을 인건비 절감을 통하여 분석하고, 우편물량과 순로구분기 유형, 운영 일정에 대한 시나리오를 설정하여 각각 소요되는 자동화 비용을 분석하고, 현재의 수작업 순로구분에 비하여 경제적인 이득이 얼마나 발생하는가에 대하여 분석한다. 본 연구는 학술적으로는 순로구분 자동화라는 새로운 시스템이 도입됨에 따라 설정되는 정성적인 변수들을 계량화하여 이를 경제성 분석에 반영함으로써 상호 배타적인 투자안에 대한 결론을 도출하려고 노력하였다. 또한 우편업무 개선을 위한 실무적 측면에서는 순로구분기의 도입과 시스템이 실제로 상용화되는 과정에 따라 구체화되는 여러 요인에 따라서 요구되는 의사결정을 위한 기초 자료로써 활용될 수 있다.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.12 no.3
• /
• pp.258-266
• /
• 2007

When the magnetic levitation system(MAGLEV) initially rise, The MAGLEV has a weak point that is very large variation of the electric current. In this paper, The author applied the multi-loop-control to stably control the magnetic levitation system(MAGLEV). The gains of the control algorithm were selected based on pole locations formulated from a prototype Bessel transfer function model. The design incorporate tradeoffs in DC-to-DC converter hard-ware para-meters and pole locations. In order to confirm the superiority of the proposed pole selection md controller, MATLAB simulation and experiment results are presented.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.42 no.5 s.335
• /
• pp.55-62
• /
• 2005

In this paper, we propose an efficient symbol detection algorithm for space-frequency OFDM (SF-OFDM) transmit diversity scheme and present the implementation results of the SF-OFDM WLAN baseband processor with the proposed algorithm. When the number of sub-carriers in SF-OFDM scheme is small, the interference between adjacent sub-carriers may be generated. The proposed algorithm eliminates this interference in a parallel manner and obtains a considerable performance improvement over the conventional detection algorithm. The bit error rate (BER) performance of the proposed detection algorithm is evaluated by the simulation. In the case of 2 transmit and 2 receive antennas, at $BER=10^{-4}$ the proposed algorithm obtains about 3 dB gain over the conventional detection algorithm. The packet error rate (PER), link throughput, and coverage performance of the SF-OFDM WLAN with the proposed detection algorithm are also estimated. For the target throughput at $80\%$ of the peak data rate, the SF-OFDM WLAN achieves the average SNR gain of about 5.95 dB and the average coverage gain of 3.98 meter. The SF-OFDM WLAN baseband processor with the proposed algorithm was designed in a hardware description language and synthesized to gate-level circuits using 0.18um 1.8V CMOS standard cell library. With the division-free architecture, the total logic gate count for the processor is 945K. The real-time operation is verified and evaluated using a FPGA test system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.12
• /
• pp.1167-1172
• /
• 2013

This paper presents a X-band doppler radar with high conversion gain using a self-oscillating-mixer(SOM) that oscillation and frequency mixing is realized at the same time. To improve phase noise of the SOM oscillator, a ${\lambda}/2$ slotted square patch resonator(SSPR) was proposed, which shows high Q-factor of 175.4 and the 50 % reduced circuit area compared to the conventional resonator. To implement the low power system, low biasing voltage of 1.7 V was supplied. To enhance the conversion gain of the SOM, bias circuit is configured near the pinch-off region of transistor, and the conversion gain was optimized. The output power of the proposed SOM was -3.16 dBm at 10.65 GHz. A high conversion gain of 9.48 dB was obtained whereas DC Power consumption is relatively low about 7.65 mW. The phase noise is -90.91 dBc/Hz at 100 kHz offset. The figure-of-merit(FOM) of the proposed SOM was measured as -181.8 dBc/Hz, which is supplier to other SOMs by more than about 7 dB.