• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.423-428
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• 2004

The development of a compact and high performance MWIR thermal imaging sensor based on the SOFRADIR 320${\times}$240 element IRCCD detector is described. The sensor has 20 magnification zoom optics with the maximum 40$^{\circ}$${\times}$30$^{\circ}$ of super wide field of view and 7.6 cycles/mrad of resolving power with the operation of attached micro-scanning system. In order to correct nonuniformities of detector arrays, we have proposed a multi-point correction method using defocusing of the optics and we have acquired the highest quality images. The MRTD of our system shows good results below 0.05K at spatial frequency 1 cycles/mrad at narrow field of view. Experimental data and obtained performances are presented and discussed.

• Korean Journal of Optics and Photonics
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• v.22 no.4
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• pp.179-183
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• 2011

An external cavity laser operating at near infrared wavelength is demonstrated by incorporating polymer waveguide Bragg reflectors. 3rd order Bragg grating and oversized rip waveguide structure were designed by using the effective index method and the transmission matrix method. The polymer waveguide was fabricated using polymer materials with refractive indices of 1.462 and 1.435 for the core and the cladding layers, respectively. The external feedback laser with 875-nm Bragg grating exhibits single mode lasing located at 850-nm wavelength with an output power of 0 dBm, a 20-dB bandwidth of 0.2 nm and a side mode suppression ratio of 40 dB.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.494-499
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• 2005

We have demonstrated a fiber short-wavelength filter with a good cut-off property using dissimilar dispersive properties between? a thermally expanded cored fiber and an external medium. Side-polishing is applied to coupling between the fiber and the external medium. The experimental results revealed that the bend edge wavelength can be adjusted by controlling the degree of core expansion. Futhermore, the sharpness of wavelength response? was significantly? improved by employing expanded core fiber instead of a conventional single mode fiber. Tuning range of the band edge wavelength exceeded 400 m based on thermo-optic effect of the external medium.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.10
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• pp.57-62
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• 2009

This study proposes the optimization and numerical analysis of the antenna circuit for antenna design with 13.56 MHz as transmitting wireless power, for calculating the dose radiation exposure to the real time. The 13.56 MHz of the antenna frequency bands is used to the loop antenna which is a induced current for transmitting the power with wireless the reader to the tag. The study compared to the real measurement value as calculating the value of the inductance and capacitance through the numerical analysis for the antenna LC resonance using the theory of the electromagnetic induction method. We tried to search for the resonance point as the voltages of both sides of antenna coil by the scope measures of the peak point, as we tried to be variable the resonance capacitor for the optimization tuning of the antenna circuit and the matching of the antenna port. We convince our research contributes to help the design and application technology of the wireless power transmit system which is received power supply with wireless.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.130-137
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• 2013

This paper presents analog front-end(AFE) circuits for bio-potential measurement. The proposed AFE is composed of IA(instrument amplifier), BPF(band-pass filter), VGA(variable gain amplifier) and SAR(successive approximation register) type ADC. The low gm(LGM) circuits with current division technique and Miller capacitance with high gain amplifier enable IA to implement on-chip AC-coupling without external passive components. Spilt capacitor array with capacitor division technique and asynchronous control make the 12-b ADC with low power consumption and small die area. The total current consumption of proposed AFE is 6.3uA at 1.8V.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.144-149
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• 2017

In this paper, we developed an intelligent and wideband RF-receiver module to represent a high dynamic range and good linearity characteristics up to 650MHz-2700MHz frequency band. and implemented an intelligent digital-RF- distorted signal measuring system for the RF distortion (intermodulation) signals. Broadband RF-receive module was designed to represent the optimized linear parameters of the receiver to meet the low noise and wide dynamic range. The designed intelligent digital-distortion(intermodulation) signal measument system measured by applying the 1MHz IF of third intermodulation signal of DUT and Measured data was recorded by program on the PC monitor with GUI interface. By variable up to 650MHz-2700MHz measured data showed up to -127.8dBc to -138dBc of the distortion (intermodulation) signal. And developed intelligent digital- distortion signal measurement system can be used to measure intermodulation distortion signal of wireless system widely.

• The Journal of the Acoustical Society of Korea
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• v.36 no.4
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• pp.238-246
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• 2017

High frequency ultrasound imaging typically suffers from low sensitivity due to the small aperture of high frequency transducers and shallow imaging depth due to the frequency-dependent attenuation of ultrasound. These limitations should be overcome to obtain high-frequency, high- resolution ultrasound images. One practical solution to the problems is a high-performance signal receiver capable of detecting a very small signal and amplifying the signal with minimal electronic noise addition. This paper reports a recently developed low-noise, wideband ultrasound receiver for high-frequency, high-resolution ultrasound imaging. The developed receiver has an amplification gain of up to 73 dB and a variable amplification gain range of 48 dB over an operating frequency of 80 MHz. Also, it has an amplification gain flatness of ${\pm}1dB$. Due to these high performances, the developed receiver has a signal-to-noise ratio of at least 8.4 dB and a contrast-to-noise ratio of at least 3.7 dB higher than commercial receivers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.11
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• pp.924-927
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• 2017

This paper presents a 6~18 GHz 8-bit true time delay (TTD) circuit. The unit delay circuit is based on m-derived filter with relatively constant group delay. The designed 8-bit TTD is implemented with two single-pole double-throw (SPDT) switches and seven double- pole double-throw (DPDT) switches. The reflection characteristics are improved by using inductors. The designed 8-bit TTD was fabricated using $0.18{\mu}m$ CMOS. The measured delay control range was 250 ps with 1 ps of delay resolution. The measured RMS group delay error was less than 11 ps at 6~18 GHz. The measured input/output return losses are better than 10 dB. The chip consumes zero power at 1.8 V supply. The chip size is $2.36{\times}1.04mm^2$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1774-1781
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• 1997

In this paper, we propose a full digital frequency and phase locked loop for CATV and HDTV receivers adopting VSB modulation. The CATV and HDTV receivers proposed by the Grand-Alliance in USA are ultilizing analog signal processing technology for carrier recovery. By the way, it is not a good architecture for the development of single chip ASIC operating in digital domain. To solve this problem while improving the performance, we first down convert the received r.f. signal to a near baseband signal for a low-rate AD converter and then we use digital signal processing techniques. The proposed system has the frequency pull-in range of -200 KHz +2.50 KHz. Moreover, it has the ability of adaptive loop bandwidth control according to the amount of frequency offset to improve the acquisition time while reducing the phase noise.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.152-159
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• 2005

The method of induction noise reduction can be classified by using passive control or active control method. However, the passive control method has a demerit to reduce the effect of noise reduction to low frequency (below) 500Hz) range and to be limited in a space of the engine room. Whereas, the active control method can overcome the demerit of passive control method. The algorithm of active control is mostly used in LMS (Least-Mean-Square) algorithm because it can obtain the complex transfer function easily in real-time. Especially, Filtered-X LMS (FXLMS) algorithm is applied to an ANC system. However, the convergence performance of LMS algorithm could not match if the FXLMS algorithm is applied to an active control of the induction noise under rapidly accelerated driving conditions. So, in order to solve the problem in this study, the Moving Bandpass Filter(MBPF) was proposed and implemented. The ANC using MBPF for the reduction of the induction noise shows that more noise reduction as 4dB than without MBPF.