Visjnoe
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Dear all,
I'm evaluating a 1.8GHz VCO with a 4bit capacitor bank for coarse frequency tuning. Typically, for a given frequency channel, the PLL that includes this VCO can obtain lock for three neighbouring capacitor bank settings i, i+1 and i+2.
I notice quite a significant phase noise variation (~ +/2 dB) between the lowest (i) and highest band (i+2) for each frequency channel.
I know that the VCO phase noise varies in general versus this capacitor bank setting since it influences the Q of the tank, but normally the Q of the tank will not vary a lot for neighbouring bank settings (differing only in 1 LSB)....
Any insights on the mechanism causing this variation are welcome.
Regards
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