A gain compensator compensates for the gain variation of a varactor-tuned voltage tuned oscillator (VCO) in a phase lock loop (PLL). The VCO includes a parallel LC circuit having multiple fixed capacitors that can be switched-in or switched-out of the LC circuit according to a capacitor control signal...http://www.google.de/patents/US7129792?utm_source=gb-gplus-sharePatent US7129792 - Apparatus and method for phase lock loop gain control using unit current sources
