temperature drift of VCO

as the temp increase the propertise of the FET diferent like the capacitance and the current and so on , and this will make the oscillator change in freq

also the varactor will be affected

khouly

thanks khouly, but I think the inductor makes more contribution on temp drift, isn't it?

yeah also the inductor will drift with temperature will also affect the oscillation frequency

khouly

The capacitor also has a temperature coefficient. If you are using discrete parts, then you can probably buy a negative temperature coefficient (NTC) capacitor that roughly cancels out the inductor's typically positive temperature coefficient.