• Journal of electromagnetic engineering and science
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• v.9 no.3
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• pp.146-151
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• 2009

This paper presents a low-loss broadband balun that uses a coplanar waveguide-to-slotline field transformation. It operates over a very wide frequency range and is of compact size since it does not depend on a resonant structure. To analyse imbalance, the coplanar wavelength(CPW) input ground is connected to the CPW output ground through various capacitors to introduce common-mode impedances. As the common-mode impedance increased the imbalance became significantly higher at the higher-frequency band compared with the lower-frequency band. The bias-circuit approach is used to improve the operation bandwidth of the lower-frequency band. The measured results show a passband of 200 MHz to 2 GHz, an insertion loss of less than 0.75 dB, and a size of $20{\times}14\;mm$. The amplitude imbalance is approximately 0.3 dB and the phase imbalance is less than $6^{\circ}$ over the entire operational range.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.7
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• pp.447-452
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• 1987

In this paper, the dependence of piezoelectric properties in the 0-3 composite system of piezoelectric-ceramics polymer materials on particle size of ceramics were investigated. Radial mode and thickness mode of composite were observed similar to single phase of piezoelectric ceramics. The measured values of dielectric constant and dissipation factor were dependent on particle size, which increased with the increasing particle size. the planar coupling factor, thickness coupling factor and thickness frequency constant with the particle size were almost constant, while planar frequency constant increased. The thickness coupling factor decreased with the increasing thickness of specimen. It is found that maximum voltage coeffidient was calculated on the specimen with particle size smallar than 46 ${\mu}m$.

• Journal of Sensor Science and Technology
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• v.14 no.4
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• pp.286-290
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• 2005

We have demonstrated a refractometer for liquid based on a side-polished fiber. The device consists of a side-polished single mode fiber and a rectangular space which plays a role of the multimode planar waveguide when it is infused with a liquid. We presented a simple method to acquire the refractive index of a liquid by use of the spacings of periodic resonance wavelengths of the device. The resolution of the fabricated refractometer was order of $10^{-5}$

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.4
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• pp.53-59
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• 2000

Based on the polarization selectivity of fiber-to-planar waveguide coupler, a novel fiber optic polarizer has been designed and fabricated. The large structural birefringence of a metal-clad planar waveguide enables the polarizer to have wide operating wavelength range. The polymer and gold were used for the guiding layer and cladding layer of the planar waveguide, respectively. The experimental results showed that either TE or TM polarized lightwave could be created by adjusting the thickness of planar waveguide. Operating wavelegth range satisfying more than 16㏈ polarization extinction ratio was 130nm. The average insertion loss of fabricated devices was order of 0.5㏈.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.879-882
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• 2005

This paper shows a method for design of the nano-positioning planar scanner used in the scanning probe microscope. The planar scanner is composed of flexure guides, piezoelectric actuators and feedback sensors. In the design of flexure guides, the Castigliano's theorem was used to find the stiffness of the guide. The motion amplifying mechanism was used in the piezoelectric actuator to achieve a large travel range. We found theoretically the travel range of the total system and verified using the commercial FEM(Finite element method) program. The maximum travel range of the planar scanner is above than 140 $\mu$m. The 3 axis positioning capability was verified by the mode analysis using the FEM program. Moreover, we presented the actual AFM(Atomic Force Microscope) imaging results with up to 2Hz imaging scan rate. Experimental results show that the properties of the proposed planar scanner is well enough to be used in SPM applications like AFM.

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.493-498
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• 2015

Complex acoustic signals can be formed in a water-filled acoustic pulse tube under some exciting conditions. It makes difficult to measure plane-wave reflection coefficient with the pulse tube for low frequency bands. In this study, using COMSOL Multiphysics we show that the tube wall excitation generates complex acoustic field of nonplanar mode as well as planar one. From such field incident or reflected planar mode can be decomposed respectively with a modal decomposition method, two-dimensional Fourier filtering. It makes possible to more accurately determine the plane-wave reflection coefficient of acoustic specimen with time gating.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.489-492
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• 2006

We demonstrate a beat frequency-Switchable dual-mode external cavity laser hybrid integrated on planar lightwave circuit with an FP-LD and a sampled grating as external reflector. The dual-mode external avity laser was able to switch its beat frequency from 132GHz to 406GHz by changing LD current from 50mA to 55mA.

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.248-253
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• 1999

In this paper, we have investigated a fiber type active coupler which utilizes the mode coupling between the side polished single mode optical fiber and the active multimode planar waveguide. The proposed device can be used for not only tunable wavelength filter or optical intensity modulator but also a tool for measuring optical properties of guiding material such as refractive index, birefringence, electro-optic coefficient, and thermo-optic coefficient. We gave designed and optimized a coupler structure using the BPM and fabricated the device using thermo-optic polymer as active planar waveguide overlay. The device showed that insertion loss was less then 0.5 dB, extinction ratio was -13 dB at the resonance wavelength, and the wavelength tunablity due to thermo-optic effect was -1.5 nm/$^{\circ}C$. The active coupler using thermo-optic effect can be used as a wavelength tunable filer, an optical intensity modulator and an optical sensor. pulses that are subsequently compressed by a dispersive optical fiber. Experimental results show that $sech^2$ shape pulses with a pulse width of ~14 ps and a time bandwidth product of ~0.34 are successfully generated at 10 GHz repetition rate. In contrast to other methods, such as higher order soliton compression, this approach does not depend on the optical power and thus shows promise for application to low-power lasers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.767-773
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• 2017

In this paper, we propose a design of Intra prediction angular mode decision for HEVC encoder. Intra prediction coding of HEVC is a method for predicting a current block by referring to samples reconstructed around a current block. Intra prediction supports a total of 35 modes with 1 DC mode, 1 Planar mode, and 33 Angular modes. Intra prediction coding of HEVC works by performing all 35 modes for efficient encoding. However, in order to process all of the 35 modes, the computational complexity and operational time required are high. Therefore, this paper proposes comparing the difference in the value of the original pixel, using an algorithm that determines angular mode efficiently. This new algorithm reduces the Hardware size. The hardware which is proposed was designed using Verilog HDL and was implemented in 65nm technology. Its gate count is 14.9K and operating speed is 2GHz.

• Journal of Sensor Science and Technology
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• v.10 no.3
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• pp.156-162
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• 2001

Novel pressure sensor using the resonance wavelength shift of single mode fiber-to-planar waveguide coupler, was demonstrated. It is found that the resonance wavelength shift due to refractive index variation of polymers by pressure occurs and its sensitivity depends on materials. We adopted symmetric structure of planar waveguide and remove the polarization dependence which is inevitable with side-polished fiber. AZ4562, AZl512 and THB-30 are used as planar waveguide materials and the resonance wavelength shifting by pressure was shown -0.008um/bar, 0.033nm/bar and 0.16nm/bar, respectively.