• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.93-99
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• 2016

In this paper, higher order coupler using small size waveguide which applicable for mobile Ku-band multimode monopulse satellite tracking antenna system, has been designed, implemented and tested. Proposed higher order mode coupler adopts a coaxial structure for low profile characteristic considering installation property to mobile satellite terminal system. In addition, by using proposed coupler, extracted tracking error signal pattern has measured and confirmed that required tracking accuracy is satisfied in desired frequency band. In the future, proposed coupler could utilize for multimode monopulse satellite tracking system for high tracking accuracy.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.86-93
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• 2008

The multi-mode terminal modem which is capable of accommodating a variety of wireless communication standards needs versatile arithmetic units for processing a variety of word lengths and wide range of data rates. Since the target hardware is usually designed to meet the required highest performance, it is often wasteful in power consumption especially when low rate data processing cases. Thus, a speed and power adaptability of the arithmetic unit is a desirable feature for the wireless applications. In this paper, we propose a power efficient versatile adder architecture with carry skip logic as a basic building block constructed in hierarchical manner. The validity of the architecture is shown with respect to size, performance, and power efficiency in diverse operating modes.

• Korean Journal of Optics and Photonics
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• v.9 no.1
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• pp.25-30
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• 1998

In this paper, a simple scheme of optical interconnections between M input and N output terminals using mode speckle patterns generated in the mulitmode optical fiber is described. It is shown that fully parallel nonblocking interconnections are accomplished by using properly generated mode speckle patterns as destination codes and dectecting the generated mode speckle patterns separately using M multiplexed Vander Lugt matched filters at each output terminal. The orthogonality condition of mode speckle patterns is investigated by either changing the launching angles or rotating the polarization direction of the beam. Preliminary experiments by use of a 4$\times$4 graded refractive-index multimode fiber coupler whose core diameter was 50 ${\mu}{\textrm}{m}$ were performed to show the feasibility of our scheme.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.1
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• pp.42-48
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• 1988

MM(multimode) PWM(pulse width modulation) Suitable for high performance and harmonic effects minimization of VSI (voltabge source invertetr)-IM (induction motor)drive system is proposed. The approximated optimal, suboptimal and optimal PWM are implemented in the low frequency range, while square wave operation is realized in the hibh frequency range. The pulse width Modulator is capable of generating control signals to a transistorized inverter operating at about 1KHz. All functions except digital comparison have been implemented in softyware making the scheme economical, flexible and reliable. Pulse width modulator is built and tested experimentally. In order to confirm the effectiveness and the reliability of the theoretical proposition, this scheme is applied to 1Hp, Three phase IM. As results, it is concluded that the scheme of MM PWM is superior to other conventional switching scheme through the discussions or analysis carried out on the items such as line-to-line voltage, current and spectrum of current harmonic components observed at the output terminal of inverter, noise level of motor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5B
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• pp.456-477
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• 2006

Due to advances in wireless communication technology and increasing demand for various types of wireless access, cellular, WLAN, and portable internet(such as WiBro and IEEE 802.16) systems are likely to be integrated into a unified wireless access system. This expectation premises the availability of multi-mode handsets and cooperative interworking of heterogenous wireless access networks allied by roaming contracts. Under such environments, a user may lie in the situation where more than one wireless accesses are available at his/her location, and he/she will want to choose the 'best' access among them. In this paper, we define the 'best' access(es) as the access(es) that charges minimum cost while fulfilling the required QoS of wireless access, and address the problem of choosing the optimal set of accesses theoretically by introducing a graph representation of service environment. Two optimal selection algorithms are proposed, which individually consider cases where single or multiple wireless access can be supported by multi-mode handsets.