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Journal Article
Fully Differential 5-GHz LC-Tank VCOs with Improved Phase Noise and Wide Tuning Range
- Authors
- Ja Yol Lee, Chan Woo Park, Sang Heung Lee, Jin Young Kang, Seung Hyeub Oh
- Issue Date
- 2005-10
- Citation
- ETRI Journal, v.27, no.5, pp.473-483
- ISSN
- 1225-6463
- Publisher
- 한국전자통신연구원 (ETRI)
- Language
- English
- Type
- Journal Article
- Abstract
- In this paper, we propose two LC voltage-controlled oscillators (VCOs) that improve both phase noise and tuning range. With both 1/f 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 cross-coupled 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 DC-decoupling capacitor Cc prevents the output common-mode 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.
- KSP Keywords
- 5 GHz, 6 MHz, Carrier frequency, Cross-coupled pair, Fully differential, LC tank, LC voltage controlled oscillator(LC-VCO), Low frequency noise, Negative feedback, Noise reduction(NR), Thermal noise