• Journal of KIEE
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• v.11 no.1
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• pp.62-68
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• 2001

In this paper it is proposed an advanced modified sliding mode control of a rotor field oriented control of induction motor. The application of this unconventional control has very good results, such as disturbance rejection and nice dynamic properties. Stability can be guaranteed even in the worst situation. A conventional "sliding mode" controller is characterised by fast switching control signal, which causes the chattering of the drive system. To overcome this problem, a modified law is used, by introducing a hysteresis band and a continuous control, which modifies the conventional law. The control is accomplished with dual TMS320C44 floating-point digital signal processor. The validity of the proposed method was verified by experiment on the propulsion system simulator, used for the development of Korean High-Speed Railway Train(KHSRT).in(KHSRT).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.1-6
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• 2011

By incorporating a polarization-diversity loop configuration (PDLC), we have demonstrated inline conversion between transmission and reflection spectra of a fiber Bragg grating (FBG) without reconfiguration of the fiber filter structure. The proposed apparatus consists of a polarization beam splitter, an FBG, and two quarter-wave plates (QWP's). The inline conversion operation between transmission and reflection spectra of the FBG was performed by proper adjustment of QWP's within the proposed filter. The band rejection ratio and side-mode suppression ratio in transmission and reflection modes of the fabricated filter were measured as ~17.0[dB] and ~16.4[dB], respectively.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.2 s.25
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• pp.77-86
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• 2006

Usually, a tracking-gate of the tracker is used to track the target radar signal in the active ECM system. In this paper, we propose the feed-back tracking-gate filtering method. The designed method applies a tracking-gate of the tacker to the ECM system's receiver as a rejection or pass filter selected by the receiver's purpose, and the specific target signals can be passed or rejected though this tracking-gate filter. Thus, the number of input signals within the receiver's search band is minimized owing to this filter except the target signals. In conclusion, the EW equipment's reaction time can be reduced and the error value about the target signals can be lower than the previous methods'.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.761-770
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• 1997

Narrowband signals can be treated like a single tone interference at the receiver which demodulates wideband signals spectrum overlaid at the same frequency band. In this paper, the single tone interference is effectively suppressed by the use of a multicarrier DPSK direct-sequence(DS) spread spectrum(SS) with maximal-ratio(MR) combining instead of notch filter, which is hard to implement. A noncoherent DPSK system is considered because it is more realizable and does not require any complicate phase tracking, compared with a single carrier system subject to a constraint system bandwidth, and their performance comparisons are validated through simulation. We also propose a suboptimal-ratio(SR) combining which yields uniform and tight low bound on the performance of the MR combining, and then system parameters re optimized by theoretically evaluating the low bound, since an exact analysis appears intractable.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.325-331
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• 2002

In this paper, surface acoustic wave(SAW) bandpass filters using slanted finger interdigital electrode transducers(IDTs) are investigated. The slanted finger IDTs are used to design SAW filters with good shape factor, a flat passband, and good out-of-band rejection characteristic. For the filter design, input-output IDT structure was simulated with modified impulse model; uniform-withdrawal weighting IDTs, withdrawal-withdrawal weighting IDTs. SAW filters of uniform-withdrawal weighting IDTs structure were designed and fabricated on $128^{\circ}LiNbO_3$ piezoelectric substrates. Implemented SAW filter has a fractional bandwidth of 30%, center frequency of 70MHz and shape factor of $1.12\pm0.01$.

• ETRI Journal
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• v.26 no.3
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• pp.229-240
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• 2004

This paper reports on our development of a dual-mode transceiver for a CMOS high-rate Bluetooth system-onchip solution. The transceiver includes most of the radio building blocks such as an active complex filter, a Gaussian frequency shift keying (GFSK) demodulator, a variable gain amplifier (VGA), a dc offset cancellation circuit, a quadrature local oscillator (LO) generator, and an RF front-end. It is designed for both the normal-rate Bluetooth with an instantaneous bit rate of 1 Mb/s and the high-rate Bluetooth of up to 12 Mb/s. The receiver employs a dualconversion combined with a baseband dual-path architecture for resolving many problems such as flicker noise, dc offset, and power consumption of the dual-mode system. The transceiver requires none of the external image-rejection and intermediate frequency (IF) channel filters by using an LO of 1.6 GHz and the fifth order onchip filters. The chip is fabricated on a $6.5-mm^{2}$ die using a standard $0.25-{\mu}m$ CMOS technology. Experimental results show an in-band image-rejection ratio of 40 dB, an IIP3 of -5 dBm, and a sensitivity of -77 dBm for the Bluetooth mode when the losses from the external components are compensated. It consumes 42 mA in receive ${\pi}/4-diffrential$ quadrature phase-shift keying $({\pi}/4-DQPSK)$ mode of 8 Mb/s, 35 mA in receive GFSK mode of 1 Mb/s, and 32 mA in transmit mode from a 2.5-V supply. These results indicate that the architecture and circuits are adaptable to the implementation of a low-cost, multi-mode, high-speed wireless personal area network.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1193-1200
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• 2008

This paper describes a developed 5Watt power amplifier module fer mobile communication system using Gallium Nitride (GaN) devices. Three amplification stages such as pre-amplifier, driver amplifier, and power amplifier have been fabricated and measured separately in advance for incorporating the total power amplifier module and estimating the performances. In addition, a defected ground structure is combined with the output stage of the power amplifier module for improving harmonic rejection and adjacent channel power (ACP) characteristics. The measured performances of the GaN power amplifier module include 58dB,min of gain, 37dBm,min of output power, 50dBc,min of harmonic rejection, 35dBc,min of IMD3 for 2-tone input, and 35dBc,min of ACP at 2.1GHz frequency band.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.91-98
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• 2013

Magnetic sensor chip for measuring bio-magnetism is implemented in $0.18{\mu}m$ CMOS technology. The magnetic sensor chip consists of a small-sized high inductance coil sensor and an instrumentation amplifier (IA). High inductance coil sensor with suitable sensitivity and bandwidth for measurement of bio-magnetic signal is designed using electromagnetic field simulation. Low gm operational transconductance amplifier (OTA) using transconductance reduction techniques is designed for on-chip solution. Output signal sensitivity of magnetic sensor chip is $3.25fT/{\mu}V$ and reference noise of 21.1fT/${\surd}$Hz. Proposed IA is designed along with band pass filters(BPF) to reduce magnetic signal noise by using current feedback techniques. Proposed IA achieves a common mode rejection ratio of 117.5dB while the input noise referred is kept below $0.87{\mu}V$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1462-1469
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• 2008

This paper proposes the design method based on the Composite Right/Left-Handed(CRLH) structure to miniaturize and enhance the rejection performance in the stopband of the bandpass filter for a VHF band($169{\sim}211\;MHz$). For realization, we used the 0-th order resonance point of the CRLH and the simple theory of Inverter as coupling. The proposed technique is validated by the performance predictions and experiments, (Insertion loss <2 dB, $S_{11}$< -15 dB, suppression of up to the 3rd harmonic) and it is found out that the suggested method enables the size reduction of around 60 % from the conventional filters such as the parallel edge coupled type.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.118-125
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• 2007

Harmonic band of bandpass filter(BPF) is suppressed using coupled mushroom structure. Between double positive (DPS) transmission line such as microstrip and double negative(DNG) transmission line such as one dimensional mushroom structure, strong coupling broadly arises in the cross range of dispersion curves of isolated microstrip and mushroom structure because of complex propagation constant in the cross range. Strong coupling inhibits wave propagation, so that this kind of structure can be utilized as bandstop filter(BSF). This BSF utilizes coupled transmission line instead of coupled resonator, resulting in broad bandwidth(>30 %), shan-rejection, and high rejection level. The strong coupling between DPS and DNG transmissionline makes it possible shorten coupling length, resulting in compact size. In this paper, parallel coupled BSF having center frequency of 4 GHz and 3 dB fractional bandwidth of 40 % is designed and utilized to suppressed spurious mode of two bandpass filters.