Patent ID: 7298225

Claim:
A symmetrical voltage controlled oscillator (VCO) system comprising: a frequency tuning circuit containing one or more varactors for receiving a predetermined tuning signal and a frequency tuning bias signal for altering capacitances of the varactors; a modulation circuit coupled in parallel with the frequency tuning circuit containing one or more varactors for modulating one or more outputs, wherein the modulation circuit further includes: a first capacitor and a second capacitor coupled in series and to a first output and a second output that is complementary to the first output on their first ends respectively; and a first resistor and a second resistor coupled in series with and between the first and second capacitors with a mid point between the first and second resistors coupled to ground; and a core circuit coupled in a parallel with the frequency tuning circuit and the modulation circuit for providing an oscillation mechanism, wherein the core circuit further includes: at least one PMOS cross-coupled transistor structure having at least a pair of cross-coupled PMOS transistors with sources thereof coupled to a power source; and at least one NMOS cross-coupled transistor structure having at least a pair of cross-coupled NMOS transistors with sources thereof coupled to an electrical ground, wherein circuit elements of the VCO system are symmetrically arranged and the varactors are tuned to deliver the outputs at an output frequency.