jlee
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Dear guys,
I have two questions about flicker noise upconversion of active device (negative transconductance) in LC VCO.
1. For close-in phase noise (1k ~ 100k), it is observed that the noise contribution is dominated by upconverted flicker noise in active device. My question is how can we explain this observation in physical insight? Is it pure AM-PM action by nonlinear cap or harmonic mixing (say 2nd harmonic) ? How to prove that by simulation?
2. In "A 1.5V, 1.7mA 700 MHz CMOS LC Oscillator with no upconverted flicker noise" by K. Hoshino, it is proposed that an inductor inserted at active device source can help to improve close-in phase noise. Why such an inductor can achieve that?
Regards
Jason
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