by one skilled in the art that the ratio of the capacitances can be varied according to a desired or target application example applications are cordless phones and bluetooth operating in the 2 4 ghz ism band the cordless phones use fsk with a 500 khz deviation for a number of reasons the vcos for such phones are often run at twice the frequency ie 4 8 ghz if it is assumed that an oscillator has a typical nominal gain of k vco 500 mhz v with respect to v tune and 5 mhz v with respect to v mod and v data of u2212 0 1v then n is approximately 90 to 70 if no other capacitors are present in the example then n might be 100 however in practice n would typically need to be adjusted downwards to compensate for oscillator parasitic capacitance in practice a precise value for n would be found by simulation bluetooth uses about a 150 khz deviation therefore given the same assumptions above n would take values in the range of about 300 to 233 furthermore the magnitudes of the controlling voltages can also be selected according to a desired variation in capacitance one skilled in the art appreciates that a 2 1 capacitance variation for a 1v change in v tune can be achieved using mos varactors such a relatively large capacitance variation with respect to v tune is desirable to compensate for at least one of tolerances on l and c and also to allow different frequencies channels to be realised that is to achieve a desired numbers of channels having an appropriate channel spacing it will be appreciated that such a 2 1 change in capacitance for a relatively small controlling voltage compares favourably with.