Patent ID: 7259638

Claim:
A voltage controlled oscillator, comprising: a resonance tank circuit comprising an inductor and a variable capacity diode; and an amplificationn circuit that performs oscillating and amplification at a resonance frequency of the resonance tank circuit, and changes a control voltage to the variable capacity diode to change an oscillation frequency, wherein the resonance tank circuit is provided with a capacity band switching circuit to selectively add a capacity to change an oscillation frequency band, and a current band switching circuit to feed an appropriate driving current to the amplification circuit, with respect to the oscillation frequency band selected by the capacity band switching circuit; wherein the capacity added by the capacity band switch circuit is determined such that an upper bound frequency in a certain oscillation frequency band connects with a lower bound frequency in a following oscillation frequency band by a frequency axis, and wherein the capacity band switch circuit has at least two capacities and a switch inserted in series with the capacity and each capacity value of the at least two capacities increases one by one by a multiple of two.