• ETRI Journal
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• 제41권2호
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• pp.145-159
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• 2019

To reduce the number of radio frequency (RF) chains in multiple input multiple output (MIMO) systems, generalized spatial modulation (GSM) techniques have been proposed in the literature. In this paper, we propose a zero-forcing (ZF)-based detector, which performs an initial pruning of the search tree that will be considered as the initial condition in a sphere decoding (SD) algorithm. The proposed method significantly reduces the computational complexity of GSM systems while achieving a near maximum likelihood (ML) performance. We analyze the performance of the proposed method and provide an analytic performance difference between the proposed method and the ML detector. Simulation results show that the performance of the proposed method is very close to that of the ML detector, while achieving a significant computational complexity reduction in comparison with the conventional SD method, in terms of the number of visited nodes. We also present some simulations to assess the accuracy of our theoretical results.

• Journal of the Korean Physical Society
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• 제80권
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• pp.640-646
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• 2022

Hybrid PET/MRI is a useful imaging system that can improve diagnostic accuracy by providing both functional and anatomical information. However, the combination of PET and MRI can lead to mutual interference, which can degrade the performances of both imaging systems. One of the methods that is capable of preserving the performance of both modalities is to apply RF shielding to PET detectors and electronics. The purpose of this study was to propose a new RF shielding method using Au-plated conductive fabric (PCF) tape that could not only minimize RF interference and eddy current, but that could also be applied to complex PET gantry and detector module structures more easily than thin Cu foils, which have been widely used as a shielding material for hybrid PET/MRI systems. To evaluate the performance of the proposed new RF shielding method, the effects of the two RF shield materials (Cu and Au) on the B1 + field generated by the RF head coil were estimated using a computer simulation method. The effects of the Au PCF tape and Cu foil on the homogeneity and SNR of the MR image were also experimentally evaluated using a commercial 3-T MRI. The uniformity of the B1 + field map was slightly decreased by the use of Cu and Au RF shields. The deterioration in the MR image quality caused by the Au PCF tape was less than that caused by Cu foil. The simulation and experimental results indicate that Au PCF tape can serve as an alternative shielding material that reduces RF interference and eddy current for hybrid PET/MRI systems.

• JSTS:Journal of Semiconductor Technology and Science
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• 제8권4호
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• pp.277-282
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• 2008

A fully integrated inductorless CMOS impulse radio ultra-wideband (IR-UWB) receiver is implemented using $0.18\;{\mu}m$ CMOS technology for 3-5 GHz application. The UWB receiver adopts the non-coherent architecture, which removes the complexity of RF architecture and reduces power consumption. The receiver consists of inductorless differential three stage LNA, envelope detector, variable gain amplifier (VGA), and comparator. The measured sensitivity is -70 dBm in the condition of 5 Mbps and BER of $10^{-3}$. The receiver chip size is only $1.8\;mm\;{\times}\;0.9\;mm$. The consumed current is 15 mA with 1.8 V supply.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.223-228
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• 2009

We propose an on-line machine learning approach for object recognition, where new images are continuously added and the recognition decision is made without delay. Random forest (RF) classifier has been extensively used as a generative model for classification and regression applications. We extend this technique for the task of building incremental component-based detector. First we employ object descriptor model based on bag of covariance matrices, to represent an object region then run our on-line RF learner to select object descriptors and to learn an object classifier. Experiments of the object recognition are provided to verify the effectiveness of the proposed approach. Results demonstrate that the propose model yields in object recognition performance comparable to the benchmark standard RF, AdaBoost, and SVM classifiers.

• Journal of Semiconductor Engineering
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• 제3권1호
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• pp.154-160
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• 2022

In this paper, we design a DC-DC boost converter with RF noise immunity to supply a stable positive output voltage for OLED displays. For RF noise immunity, an input voltage variation reduction circuit (IVVRC) is adopted to ensure display quality by reducing the undershoot and overshoot of output voltage. The boost converter for a positive voltage Vpos operates in the SPWM-PWM dual mode and has a dead-time controller using a dead-time detector, resulting in increased power efficiency. A chip was fabricated using a 0.18 um BCDMOS process. Measurement results show that power efficiency is 30% ~ 76% for load current range from 1 mA to 100 mA. The boost converter with the IVVRC has an overshoot of 6 mV and undershoot of 4 mV compared to a boost converter without that circuit with 18 mV and 20 mV, respectively.

• 한국전기전자재료학회논문지
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• 제20권10호
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• pp.883-888
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• 2007

Investigation of improving the properties of UV detector which uses the wide bandgap of ZnO are under active progress. The present study focused on the design and fabrication of i-ZnO/p-inversion $layer/n^--Si$ Epi. which is characterized with very thin p-type inversion layer for UV detectors. The i-ZnO thin film for achieving p-inversion layer which was grown by RF sputtering at $450^{\circ}C$ and then annealed at $400^{\circ}C$ in $O_2$ gas for 20 min shows good intrinsic properties. High (0002) peak intensity of the i-ZnO film is shown on XRD spectrum and it is confirmed by XPS analysis that the ratio of Zn : O of the i-ZnO film is nearly 1 : 1. Measurement shows high transmission of 79.5 % in UV range (< 400 nm) for the i-ZnO film. Measurement of $V_r-I_{ph}$ shows high UV photo-current of 1.2 mA under the reverse bias of 30 V.

• 한국전자파학회논문지
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• 제21권3호
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• pp.278-284
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• 2010

본 논문에서는 저잡음 증폭기와 무바이어스 쇼트키 다이오드를 사용하여 W-Band에서 동작하는 밀리미터파 다이오드 검출기를 설계, 제작하였다. 향상된 감도 특성을 얻기 위해 다이오드 검출기는 검출기와 저잡음 증폭기로 구성된다. 저잡음 증폭기단은 발진을 제거하기 위해, 높은 저지 대역 특성을 갖도록 설계된 하우징에 저잡음 증폭기 MMIC 칩을 사용해 제작한다. 다이오드 검출기단은 단순한 구조를 사용하기 위해 무바이어스 쇼트기 다이오드를 사용하고, 저잡음 증폭기단과의 연결을 용이하도록 하기 위해 평면형으로 설계한다. 설계 및 제작된 W-band 검출기는 입력 전력 -45~-20 dBm의 변화에 대하여 20~500 mV의 출력 전압을 얻었다. 본 검출기는 수동 밀리미터파 영상 시스템에 적용할 수 있다.

• 한국전자파학회논문지
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• 제18권4호
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• pp.379-388
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• 2007

본 논문에서는 사람의 생체 신호를 감지하기 위해 1.6 GHz 단일 채널 도플러 센서와 아날로그 및 디지털 신호 처리부로 구성되어 있는 실시간 호흡 및 심장 박동 감지기를 개발하였다. 도플러 센서의 RF Front End는 발진기, 믹서, 저잡음 증폭기, 브랜치-라인 하이브리드, 그리고 패치 안테나로 구성되어 있다. 센서에 사용된 브랜치-라인 하이브리드는 기존의 하이브리드에 비해 40 % 정도 크기를 줄이면서도 상당히 유사한 성능을 가지도록 인공 전송 선로(artificial transmission line)를 사용하였다. 아날로그 신호처리부는 2차 Sallen-Key 능동 필터를 사용하여 제작되었고 디지털 신호 처리부는 LabVIEW를 사용하여 컴퓨터상에서 구현되었다. 개발된 시스템은 최대 50 cm 거리에서 사람의 호흡과 심장 박동을 측정함으로써 성능을 검증하였다.

• 한국항행학회논문지
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• 제20권6호
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• pp.556-561
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• 2016

논문은 ISM 밴드 응용분야에 사용되는 13.35 MHz, 5 kW RF 제너레이터의 구현에 대한 내용이다. 이 제너레이터의 구성은 드라이브증폭기와 LDMOS 1.25 kW 트랜지스터를 클래스 AB 푸쉬풀 증폭기로 구현한 모듈을 바탕으로 4개의 모듈을 윌킨슨 형태의 전송선로 변환기를 이용하여 결합하는 구조를 갖고 있다. 이 제너레이터는 선형성보다는 높은 출력과 효율을 얻는 것이 중요하며, 트랜지스터에서 발생하는 열은 워터 쿨링에 의한 수냉식 방법을 선택하여 외부로 배출하였다. 또한, 결합기와 저역통과 필터의 결합 그리고 출력 및 반사 신호를 검출하는 보호회로를 삽입하였다. 이렇게 구현된 RF 제너레이터는 포화 전력레벨 5.33 kW 출력에서 79 %의 효율을 얻었다.

• Journal of Biosystems Engineering
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• 제24권3호
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• pp.235-242
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• 1999

This study was conducted to develop a grain moisture meter using microwave free space transmission technique at X-band frequency. The 10.5GHz microwave oscillator using a dielectric resonator was designed and fabricated to transmit electromagnetic wave through standard horn antenna to a sample holder with the wetted Hwasung and Chuchung rough rice(12.00∼26.25%). To detect the output voltage of transmitted wave from receiving horn antenna, the detector was composed of shottkey diode and RF impedance matching circuit. The regression model for measurement of grain moisture content was developed. Its correlation coefficient and standard error of prediction (SEP) were found to be 0.9882 and 0.657 respectively between measure and predicted moisture contents.