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Fully Differential 5-GHz LC-Tank VCOs with Improved Phase Noise and Wide Tuning Range
이자열,이상흥,강진영,박찬우,Seung-Hyeub Oh 한국전자통신연구원 2005 ETRI Journal Vol.27 No.5
In this paper, we propose two LC voltage-controlled oscillators (VCOs) that improve both phase noise and tuning range. With both 1/ƒ induced low-frequency noise and low-frequency thermal noise around DC or around harmonics suppressed significantly by the employment of a current-current negative feedback (CCNF) loop, the phase noise in the CCNF LC VCO has been improved by about 10 dB at 6 MHz offset compared to the conventional LC VCO. The phase noise of the CCNF VCO was measured as -112 dBc/Hz at 6 MHz offset from 5.5 GHz carrier frequency. Also, we present a bandwidth-enhanced LC VCO whose tuning range has been increased about 250 % by connecting the varactor to the bases of the crosscoupled pair. The phase noise of the bandwidth-enhanced LC-tank VCO has been improved by about 6 dB at 6 MHz offset compared to the conventional LC VCO. The phase noise reduction has been achieved because the DCdecoupling capacitor Cc prevents the output commonmode level from modulating the varactor bias point, and the signal power increases in the LC-tank resonator. The bandwidth-enhanced LC VCO represents a 12 % bandwidth and phase noise of -108 dBc/Hz at 6 MHz offset.
Characterization of Bacterial Community Contaminating Floor of A Hot and Dry Sauna
이자열,박두현 대한미생물학회 2012 Journal of Bacteriology and Virology Vol.42 No.4
The purpose of this study was to examine profile of bacteria contaminated in a dry sauna. Bacteria sampled from the floor of the dry sauna (75~80℃) were separated and identified by using a thermal gradient gel electrophoresis (TGGE)technique, and were cultivated using a defined medium at 50℃. Bacteria grown in the defined medium were identified based on 16S-rDNA sequence homology. The band number of DNA separated by TGGE was 15, indicating the species diversity of bacteria contaminating the dry sauna. Seven species of bacteria were successfully cultured on agar plate medium at 50℃, which represented a combination of thermophilic and thermoduric bacteria contaminating the dry sauna. The highest limit temperature for growth of the bacterial isolates was generally 50℃ when cultivated in a defined medium, but was raised to 60℃ when cultivated in a complex medium. Consequently, the bacteria grown at 50~60℃are thermoduric or thermophilic, but others may not be.