• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.672-679
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• 1999

This paper describes the design method of active bandpass filters which employ active impedance inverters. Several authors have reported active bandpass filters. However, the functional description of the active blocks in the filters have not been throughly studied. In this paper, the active inverter block of the bandpass filter has is analyzed in the view point of filter design. The designed 3-pole bandwidth filter has its insertion gain of 24 dB at the center frequency of 865 MHz with 75 MHz bandwidth. The noise figure of the active bandpass filter is less than 2.5 dB within its passband.

• The Journal of Natural Sciences
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• v.8 no.1
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• pp.27-32
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• 1995

Magnetic Resonance Imaging anti-solenoid probes have been constructed for the internal imaging. Signal-to-noise ratios of the images acquired by the anti-solenoid probes were compared with those obtained by commercial probes such as a head coil and a body coil. In terms of the internal imaging, the anti-solenoid probes, constructed in the present study, was performed better than the conventional commercial probes. Also, RF(radio-frequency)-field maps produced by the anti-solenoid probes have been simulated using computers. The possibility of human internal imaging using the anti-solenoid probes has been discussed as well.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.10
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• pp.971-978
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• 2013

This work presents a W band frequency synthesizer which is composed of 26 GHz VCO, Phase Locked Loop and frequency tripler using 65 nm RF CMOS process. Frequency tuning range of 26 GHz VCO covers the band from 22.8~26.8 GHz and final output frequency of the tripler is from 74 to 75.6 GHz. The fabricated frequency synthesizer consumes 75.6 mW and its phase noise is -75 dBc/Hz at 1 MHz offset, -101 dBc/Hz 10 MHz offset respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.948-958
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• 2010

Human body signals collected by the MRI system are very weak, such that they may be easily affected by either external noise or system instability while being imaged. Therefore, this paper analyzes the nonuniformity caused by a design of the RF receiving coil in a low-magnetic-field MRI system, and proposes an efficient method to improve the image uniformity. In this paper, a method for acquiring 3D bias volume data by using phantom data among various methods for correcting such nonuniformity in MRI image is proposed, such that it is possible to correct various-sized images. It is shown by simulations that images obtained by various imaging methods can be effectively corrected using single bias data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.959-966
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• 2010

Quantitative ultrasound analysis provides fundamental information of various ultrasound parameters using spectral information of the short-gated radiofrequency(RF) data. Therefore, accurate extraction of spectral information from backscattered RF signal is crucial for further analysis of medical ultrasound parameters. In this paper, we propose two techniques for calculating a more accurate power spectrum which are based on the phase-compensation using the normalized cross-correlation to minimize estimation errors due to phase variations, and the weighted averaging technique to maximize the signal-to-noise ratio(SNR). The simulation results demonstrate that the proposed method estimates better results with 10% smaller estimation variances compared to the conventional methods.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1957-1959
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• 2000

The PD measurement method is very useful to detect insulation degradation. Recently, the HFPD(High Frequency Partial Discharge) measurement testing is widely used in partial discharge measurement of HV machines because HFPD measurement testing receives less influence of external noise and has a merit of good sensitivity. Therefore it is very useful method compare to previous conventional PD testing method and effective diagnosis method in power transformer that requires in-service diagnosis. But partial discharges have very complex characteristics of discharge pattern so it is required continuous research to development of precise analysis method. In this study, simulated transformer is manufactured and HFPD occurred from simulated transformer is measured with broad band antenna and active-line RF measurement system in real time, the degradation grade of transformer is analyzed through produced patterns in simulated transformer according to applied voltages. Also the PD pattern which was measured with EMC analyzer and RF measurement system is compared.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.42-47
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• 2001

Analyzing the ECG signal, we can find heart disease, for example, arrhythmia and myocardial infarction, etc. Particularly, detecting arrhythmia is more important, because serious arrhythmia can take away the life from patients within ten minutes. In this paper, we would like to introduce the signal processing for ECG analysis and the device made for wireless communication of ECG data. In the signal processing, the wavelet transform decomposes the ECG signal into high and low frequency components using wavelet function. Recomposing the high frequency bands including QRS complex, we can detect QRS complex and eliminate the noise from the original ECG signal. To recognize the ECG signal pattern, we adopted the polynomial approximation partially and statistical method. The ECG signal is divided into small parts based on QRS complex, and then, each part is approximated to the polynomials. Comparing the approximated ECG pattern with the database, we can detect and classify the heart disease. The ECG detection device consists of amplifier, filters, A/D converter and RF module. After amplification and filtering, the ECG signal is fed through the A/D converter to be digitalized. The digital ECG data is transmitted to the personal computer through the RF transceiver module and serial port.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.764-768
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• 2002

In this paper, a double balanced gilbert cell MMIC mixer was realized in Tachyonics SiGe HBT technology. The fabricated mixer has 17 dB conversion gain, 9.8 dB noise figure, -4.2 dBm output 1 dB compression point, -27 dBc RF to IF isolation, and the good input, output matching characteristics. It draws 10 mA from a 3 V supply. The simulation and the measured results are closer to each other, which confirms accuracy of the model library and reliability of the process.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.173-176
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• 2005

본 연구는 2005. 7. 1 시행 공포된 전파법 시행령 개정안 내용 중 전력선통신설비의 주파수 대역이 9kHz${\sim}$450kHz에서 그 상한선 범위가 30MHz까지 확대 시행됨과 관련하여 전력선통신설비가 단파대 무선통신에 혼신을 야기할 수 있음에 따라 그 영향여부를 평가하는 방법을 제시하고 향후 전력선통신설비를 운용함에 있어서 단파대 무선통신에 영향을 회피하기 위한 대책방안을 제안하는데 있다. 전력선통신의 운용주파수 확대와 관련하여 정보통신부 전파연구소에서 전력선통신이 단파대 무선통신의 혼신여부에 대하여 측정 관찰해 왔으며 그 간섭정도를 판단하기 위해 노력해 왔다. 본 연구에서는 전파수신기, 신호발생기 및 SINAD(Signal to Noise and Distortion) Meter를 사용한 측정방법을 제시하고 있으며 이는 무선(RF : Radio Frequency) 환경에 적합한 측정방법으로 기존의 EMC(electromagnetic compatibility) 환경에 의한 한계를 극복할 수 있다. 또한, 본 연구에서는 전력선통신설비가 단파대 해상이동통신에 영향을 최소화하기 위하여 보호구역을 설정 또는 해당 주파수에 대하여 운용금지하는 방안을 제시함으로써 무선통신환경을 보호하는데 그 목적이 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.4
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• pp.367-370
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• 2004

We fabricated SiGe BiCMOS devices, which are important for ultra high speed RF IC chips, by employing $0.35\mu{m}$ CMOS process. To meet with the requirement of low noise level with linear base leakage current at low VBE region, we try to minimize polysilicon/ silicon interface traps by optimizing capping silicon thickness and EDR(emitter drive-in RTA) temperature. We employed $200\AA$and $300\AA$-thick capping silicon, and varied the EDR process condition at temperature of $900-1000^\circ{C}$, and time of 0-30 sec at a given capping silicon thickness. We investigated current gain behavior at each process condition. We suggest that optimum EDR process condition would be $975^\circ{C}$-30 sec with $300\AA$-thick capping silicon for proposed $0.35\mu{m}$-SiGe HBT devices.