Digitally controlled oscillator using semiconductor capacitance elements

Claim 1

A circuit for switching the frequency of an oscillator in discrete steps to up to 2n different values directly in response to n control voltages representing an n digit binary word, where n is an integer greater than 1, comprising in combination: in the tuned circuit of said oscillator, n networks which continuously remain in the tuned circuit, said networks connected essentially in parallel with each other, each network containing a voltage controlled semiconductor capacitance element, each such element capable of assuming one capacitance value in response to a control voltage in a first relatively large range extending to VL, a second capacitance value in response to a control voltage in a second relatively large range beginning at VH, where the region VL to VH between these two ranges is relatively small and where VL and VH are voltages where each of said elements one capacitance value is proportional to a different power of two and the corresponding second capacitance value is a fixed multiple greater than one times said one capacitance value; means for applying to each such element a different one of said n control voltages, where each control voltage is at one of two binary levels, one level in said first range and the other level in said second range; and means for decoupling each network from the remaining networks whereby the application of a control voltage to a particular network will not affect the capacitance of the remaining networks.