calven303
Member level 3
hi!
how to reduce the harmonic coupling of the varactor to the control voltage.the control voltage in my pll oscillates because the 2nd harmonic coupling of the varactor.and the peak-to-peak value is related to the loop filter capacitance,and it can even achieves to 20mv.the larger the capacitance of the loop filter ,the smaller the peak-to-peak value.i guess the reason is that the impedance from the control node to gnd is small if the capacitance is large. many papers talk about how to reduce the noise,but few papers refer to the harmonic coupling.is there a range of peak-to-peak value that we can accept.please give me some explanations.thanks a lot
best regards
how to reduce the harmonic coupling of the varactor to the control voltage.the control voltage in my pll oscillates because the 2nd harmonic coupling of the varactor.and the peak-to-peak value is related to the loop filter capacitance,and it can even achieves to 20mv.the larger the capacitance of the loop filter ,the smaller the peak-to-peak value.i guess the reason is that the impedance from the control node to gnd is small if the capacitance is large. many papers talk about how to reduce the noise,but few papers refer to the harmonic coupling.is there a range of peak-to-peak value that we can accept.please give me some explanations.thanks a lot
best regards