I havent read the paper. BUT
Quote:It stated that sharing the nmos bias node (drain nodes of the two LCVCO current source), it can improve amplitude mismatch and improve phase noise Pnoise.
Quadrature LC VCO comprises of two LC VCOs operating at 90 degrees phase diff.
The Drain of the TCS nmos is pulled up twice in one Period of Oscillation in a Single LC VCO. i.e. TCS Node has a major harmonic at 2*fosc.
If you connect the TCS nodes of two LC-VCOs, then if your QVCO is exactly symmetric, & ignoring higherr-order non-linearities,
the 2f fluctuation due to 1st VCO is out of phase to the 2f fluctuation due to the 2nd.
Hence, they should cancel & result in an improvement in Phase Noise.
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Mayank.
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LC QVCO with shared bias node (Read 1508 times)